Adding example source to support MCJIT/Kaleidoscope blog posts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186854 91177308-0d34-0410-b5e6-96231b3b80d8

20 files changed, 9374 insertions, 0 deletions

diff --git a/examples/Kaleidoscope/MCJIT/README.txt b/examples/Kaleidoscope/MCJIT/README.txt
new file mode 100644
index 0000000000..ba742645ac
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/README.txt
@@ -0,0 +1,12 @@
+//===----------------------------------------------------------------------===/
+//                          Kaleidoscope with MCJIT
+//===----------------------------------------------------------------------===//
+
+The files in this directory are meant to accompany a series of blog posts
+that describe the process of porting the Kaleidoscope tutorial to use the MCJIT
+execution engine instead of the older JIT engine.
+
+When the blog posts are ready this file will be updated with links to the posts.
+
+These directories contain Makefiles that allow the code to be built in a
+standalone manner, independent of the larger LLVM build infrastructure.
\ No newline at end of file
diff --git a/examples/Kaleidoscope/MCJIT/cached/Makefile b/examples/Kaleidoscope/MCJIT/cached/Makefile
new file mode 100644
index 0000000000..dde39a75d7
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/cached/Makefile
@@ -0,0 +1,11 @@
+all: toy-mcjit toy-jit toy-ir-gen
+
+toy-mcjit : toy.cpp
+	clang++ toy.cpp -g -O3 -rdynamic -fno-rtti `llvm-config --cppflags --ldflags --libs core mcjit native irreader` -o toy-mcjit
+
+toy-jit : toy-jit.cpp
+	clang++ toy-jit.cpp -g -O3 -rdynamic -fno-rtti `llvm-config --cppflags --ldflags --libs core jit native irreader` -o toy-jit
+
+# This is a special build for the purpose of converting Kaleidoscope input to an IR file
+toy-ir-gen : toy-jit.cpp
+	clang++ toy-jit.cpp -g -O3 -rdynamic -fno-rtti -DDUMP_FINAL_MODULE `llvm-config --cppflags --ldflags --libs core jit native irreader` -o toy-ir-gen
diff --git a/examples/Kaleidoscope/MCJIT/cached/README.txt b/examples/Kaleidoscope/MCJIT/cached/README.txt
new file mode 100644
index 0000000000..6acaf057f2
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/cached/README.txt
@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===/
+//                          Kaleidoscope with MCJIT
+//===----------------------------------------------------------------------===//
+
+The files in this directory are meant to accompany the first in a series of
+three blog posts that describe the process of porting the Kaleidoscope tutorial
+to use the MCJIT execution engine instead of the older JIT engine.
+
+When the blog post is ready this file will be updated with a link to the post.
+
+The source code in this directory demonstrates the third version of the
+program, now modified to accept an input IR file on the command line and,
+optionally, to use a basic caching mechanism to store generated object images.
+
+The toy-jit.cpp file contains a version of the original JIT-based source code
+that has been modified to support the input IR file command line option.
+
+This directory contain a Makefile that allow the code to be built in a
+standalone manner, independent of the larger LLVM build infrastructure. To build
+the program you will need to have 'clang++' and 'llvm-config' in your path. If
+you attempt to build using the LLVM 3.3 release, some minor modifications will
+be required.
+
+This directory also contains a Python script that may be used to generate random
+input for the program and test scripts to capture data for rough performance
+comparisons.  Another Python script will split generated input files into
+definitions and function calls for the purpose of testing the IR input and
+caching facilities.
\ No newline at end of file
diff --git a/examples/Kaleidoscope/MCJIT/cached/genk-timing.py b/examples/Kaleidoscope/MCJIT/cached/genk-timing.py
new file mode 100644
index 0000000000..96dd6db5da
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/cached/genk-timing.py
@@ -0,0 +1,219 @@
+#!/usr/bin/env python
+
+import sys
+import random
+
+class TimingScriptGenerator:
+    """Used to generate a bash script which will invoke the toy and time it"""
+    def __init__(self, scriptname, outputname):
+        self.timeFile = outputname
+        self.shfile = open(scriptname, 'w')
+        self.shfile.write("echo \"\" > %s\n" % self.timeFile)
+
+    def writeTimingCall(self, filename, numFuncs, funcsCalled, totalCalls):
+        """Echo some comments and invoke both versions of toy"""
+        rootname = filename
+        if '.' in filename:
+            rootname = filename[:filename.rfind('.')]
+        self.shfile.write("echo \"%s: Calls %d of %d functions, %d total\" >> %s\n" % (filename, funcsCalled, numFuncs, totalCalls, self.timeFile))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy-mcjit < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (filename, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With JIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy-jit < %s > %s-jit.out 2> %s-jit.err\n" % (filename, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+
+class KScriptGenerator:
+    """Used to generate random Kaleidoscope code"""
+    def __init__(self, filename):
+        self.kfile = open(filename, 'w')
+        self.nextFuncNum = 1
+        self.lastFuncNum = None
+        self.callWeighting = 0.1
+        # A mapping of calls within functions with no duplicates
+        self.calledFunctionTable = {}
+        # A list of function calls which will actually be executed
+        self.calledFunctions = []
+        # A comprehensive mapping of calls within functions
+        # used for computing the total number of calls
+        self.comprehensiveCalledFunctionTable = {}
+        self.totalCallsExecuted = 0
+
+    def updateTotalCallCount(self, callee):
+        # Count this call
+        self.totalCallsExecuted += 1
+        # Then count all the functions it calls
+        if callee in self.comprehensiveCalledFunctionTable:
+            for child in self.comprehensiveCalledFunctionTable[callee]:
+                self.updateTotalCallCount(child)
+
+    def updateFunctionCallMap(self, caller, callee):
+        """Maintains a map of functions that are called from other functions"""
+        if not caller in self.calledFunctionTable:
+            self.calledFunctionTable[caller] = []
+        if not callee in self.calledFunctionTable[caller]:
+            self.calledFunctionTable[caller].append(callee)
+        if not caller in self.comprehensiveCalledFunctionTable:
+            self.comprehensiveCalledFunctionTable[caller] = []
+        self.comprehensiveCalledFunctionTable[caller].append(callee)
+
+    def updateCalledFunctionList(self, callee):
+        """Maintains a list of functions that will actually be called"""
+        # Update the total call count
+        self.updateTotalCallCount(callee)
+        # If this function is already in the list, don't do anything else
+        if callee in self.calledFunctions:
+            return
+        # Add this function to the list of those that will be called.
+        self.calledFunctions.append(callee)
+        # If this function calls other functions, add them too
+        if callee in self.calledFunctionTable:
+            for subCallee in self.calledFunctionTable[callee]:
+                self.updateCalledFunctionList(subCallee)
+
+    def setCallWeighting(self, weight):
+        """ Sets the probably of generating a function call"""
+        self.callWeighting = weight
+
+    def writeln(self, line):
+        self.kfile.write(line + '\n')
+
+    def writeComment(self, comment):
+        self.writeln('# ' + comment)
+
+    def writeEmptyLine(self):
+        self.writeln("")
+
+    def writePredefinedFunctions(self):
+        self.writeComment("Define ':' for sequencing: as a low-precedence operator that ignores operands")
+        self.writeComment("and just returns the RHS.")
+        self.writeln("def binary : 1 (x y) y;")
+        self.writeEmptyLine()
+        self.writeComment("Helper functions defined within toy")
+        self.writeln("extern putchard(x);")
+        self.writeln("extern printd(d);")
+        self.writeln("extern printlf();")
+        self.writeEmptyLine()
+        self.writeComment("Print the result of a function call")
+        self.writeln("def printresult(N Result)")
+        self.writeln("  # 'result('")
+        self.writeln("  putchard(114) : putchard(101) : putchard(115) : putchard(117) : putchard(108) : putchard(116) : putchard(40) :")
+        self.writeln("  printd(N) :");
+        self.writeln("  # ') = '")
+        self.writeln("  putchard(41) : putchard(32) : putchard(61) : putchard(32) :")
+        self.writeln("  printd(Result) :");
+        self.writeln("  printlf();")
+        self.writeEmptyLine()
+
+    def writeRandomOperation(self, LValue, LHS, RHS):
+        shouldCallFunc = (self.lastFuncNum > 2 and random.random() < self.callWeighting)
+        if shouldCallFunc:
+            funcToCall = random.randrange(1, self.lastFuncNum - 1)
+            self.updateFunctionCallMap(self.lastFuncNum, funcToCall)
+            self.writeln("  %s = func%d(%s, %s) :" % (LValue, funcToCall, LHS, RHS))
+        else:
+            possibleOperations = ["+", "-", "*", "/"]
+            operation = random.choice(possibleOperations)
+            if operation == "-":
+                # Don't let our intermediate value become zero
+                # This is complicated by the fact that '<' is our only comparison operator
+                self.writeln("  if %s < %s then" % (LHS, RHS))
+                self.writeln("    %s = %s %s %s" % (LValue, LHS, operation, RHS))
+                self.writeln("  else if %s < %s then" % (RHS, LHS))
+                self.writeln("    %s = %s %s %s" % (LValue, LHS, operation, RHS))
+                self.writeln("  else")
+                self.writeln("    %s = %s %s %f :" % (LValue, LHS, operation, random.uniform(1, 100)))
+            else:
+                self.writeln("  %s = %s %s %s :" % (LValue, LHS, operation, RHS))
+
+    def getNextFuncNum(self):
+        result = self.nextFuncNum
+        self.nextFuncNum += 1
+        self.lastFuncNum = result
+        return result
+
+    def writeFunction(self, elements):
+        funcNum = self.getNextFuncNum()
+        self.writeComment("Auto-generated function number %d" % funcNum)
+        self.writeln("def func%d(X Y)" % funcNum)
+        self.writeln("  var temp1 = X,")
+        self.writeln("      temp2 = Y,")
+        self.writeln("      temp3 in")
+        # Initialize the variable names to be rotated
+        first = "temp3"
+        second = "temp1"
+        third = "temp2"
+        # Write some random operations
+        for i in range(elements):
+            self.writeRandomOperation(first, second, third)
+            # Rotate the variables
+            temp = first
+            first = second
+            second = third
+            third = temp
+        self.writeln("  " + third + ";")
+        self.writeEmptyLine()
+
+    def writeFunctionCall(self):
+        self.writeComment("Call the last function")
+        arg1 = random.uniform(1, 100)
+        arg2 = random.uniform(1, 100)
+        self.writeln("printresult(%d, func%d(%f, %f) )" % (self.lastFuncNum, self.lastFuncNum, arg1, arg2))
+        self.writeEmptyLine()
+        self.updateCalledFunctionList(self.lastFuncNum)
+
+    def writeFinalFunctionCounts(self):
+        self.writeComment("Called %d of %d functions" % (len(self.calledFunctions), self.lastFuncNum))
+
+def generateKScript(filename, numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting, timingScript):
+    """ Generate a random Kaleidoscope script based on the given parameters """
+    print "Generating " + filename
+    print("  %d functions, %d elements per function, %d functions between execution" %
+          (numFuncs, elementsPerFunc, funcsBetweenExec))
+    print("  Call weighting = %f" % callWeighting)
+    script = KScriptGenerator(filename)
+    script.setCallWeighting(callWeighting)
+    script.writeComment("===========================================================================")
+    script.writeComment("Auto-generated script")
+    script.writeComment("  %d functions, %d elements per function, %d functions between execution"
+                         % (numFuncs, elementsPerFunc, funcsBetweenExec))
+    script.writeComment("  call weighting = %f" % callWeighting)
+    script.writeComment("===========================================================================")
+    script.writeEmptyLine()
+    script.writePredefinedFunctions()
+    funcsSinceLastExec = 0
+    for i in range(numFuncs):
+        script.writeFunction(elementsPerFunc)
+        funcsSinceLastExec += 1
+        if funcsSinceLastExec == funcsBetweenExec:
+            script.writeFunctionCall()
+            funcsSinceLastExec = 0
+    # Always end with a function call
+    if funcsSinceLastExec > 0:
+        script.writeFunctionCall()
+    script.writeEmptyLine()
+    script.writeFinalFunctionCounts()
+    funcsCalled = len(script.calledFunctions)
+    print "  Called %d of %d functions, %d total" % (funcsCalled, numFuncs, script.totalCallsExecuted)
+    timingScript.writeTimingCall(filename, numFuncs, funcsCalled, script.totalCallsExecuted)
+
+# Execution begins here
+random.seed()
+
+timingScript = TimingScriptGenerator("time-toy.sh", "timing-data.txt")
+
+dataSets = [(5000, 3,  50, 0.50), (5000, 10, 100, 0.10), (5000, 10, 5, 0.10), (5000, 10, 1, 0.0),
+            (1000, 3,  10, 0.50), (1000, 10, 100, 0.10), (1000, 10, 5, 0.10), (1000, 10, 1, 0.0),
+            ( 200, 3,   2, 0.50), ( 200, 10,  40, 0.10), ( 200, 10, 2, 0.10), ( 200, 10, 1, 0.0)]
+
+# Generate the code
+for (numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting) in dataSets:
+    filename = "test-%d-%d-%d-%d.k" % (numFuncs, elementsPerFunc, funcsBetweenExec, int(callWeighting * 100))
+    generateKScript(filename, numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting, timingScript)
+print "All done!"
diff --git a/examples/Kaleidoscope/MCJIT/cached/split-lib.py b/examples/Kaleidoscope/MCJIT/cached/split-lib.py
new file mode 100644
index 0000000000..5cdcc6d46c
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/cached/split-lib.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+
+class TimingScriptGenerator:
+    """Used to generate a bash script which will invoke the toy and time it"""
+    def __init__(self, scriptname, outputname):
+        self.shfile = open(scriptname, 'w')
+        self.timeFile = outputname
+        self.shfile.write("echo \"\" > %s\n" % self.timeFile)
+
+    def writeTimingCall(self, irname, callname):
+        """Echo some comments and invoke both versions of toy"""
+        rootname = irname
+        if '.' in irname:
+            rootname = irname[:irname.rfind('.')]
+        self.shfile.write("echo \"%s: Calls %s\" >> %s\n" % (callname, irname, self.timeFile))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy-mcjit -use-object-cache -input-IR=%s < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (irname, callname, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT again\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy-mcjit -use-object-cache -input-IR=%s < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (irname, callname, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With JIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy-jit -input-IR=%s < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (irname, callname, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+
+class LibScriptGenerator:
+    """Used to generate a bash script which will convert Kaleidoscope files to IR"""
+    def __init__(self, filename):
+        self.shfile = open(filename, 'w')
+
+    def writeLibGenCall(self, libname, irname):
+        self.shfile.write("./toy-ir-gen < %s 2> %s\n" % (libname, irname))
+
+def splitScript(inputname, libGenScript, timingScript):
+  rootname = inputname[:-2]
+  libname = rootname + "-lib.k"
+  irname = rootname + "-lib.ir"
+  callname = rootname + "-call.k"
+  infile = open(inputname, "r")
+  libfile = open(libname, "w")
+  callfile = open(callname, "w")
+  print "Splitting %s into %s and %s" % (inputname, callname, libname)
+  for line in infile:
+    if not line.startswith("#"):
+      if line.startswith("print"):
+        callfile.write(line)
+      else:
+        libfile.write(line)
+  libGenScript.writeLibGenCall(libname, irname)
+  timingScript.writeTimingCall(irname, callname)
+
+# Execution begins here
+libGenScript = LibScriptGenerator("make-libs.sh")
+timingScript = TimingScriptGenerator("time-lib.sh", "lib-timing.txt")
+
+script_list = ["test-5000-3-50-50.k", "test-5000-10-100-10.k", "test-5000-10-5-10.k", "test-5000-10-1-0.k", 
+               "test-1000-3-10-50.k", "test-1000-10-100-10.k", "test-1000-10-5-10.k", "test-1000-10-1-0.k",
+               "test-200-3-2-50.k", "test-200-10-40-10.k", "test-200-10-2-10.k", "test-200-10-1-0.k"]
+
+for script in script_list:
+  splitScript(script, libGenScript, timingScript)
+print "All done!"
diff --git a/examples/Kaleidoscope/MCJIT/cached/toy-jit.cpp b/examples/Kaleidoscope/MCJIT/cached/toy-jit.cpp
new file mode 100644
index 0000000000..2539025aa2
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/cached/toy-jit.cpp
@@ -0,0 +1,1207 @@
+#define MINIMAL_STDERR_OUTPUT
+
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/JIT.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IRReader/IRReader.h"
+#include "llvm/PassManager.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Transforms/Scalar.h"
+#include <cstdio>
+#include <map>
+#include <string>
+#include <vector>
+
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Command-line options
+//===----------------------------------------------------------------------===//
+
+namespace {
+  cl::opt<std::string>
+  InputIR("input-IR",
+              cl::desc("Specify the name of an IR file to load for function definitions"),
+              cl::value_desc("input IR file name"));
+} // namespace
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+  tok_eof = -1,
+
+  // commands
+  tok_def = -2, tok_extern = -3,
+
+  // primary
+  tok_identifier = -4, tok_number = -5,
+  
+  // control
+  tok_if = -6, tok_then = -7, tok_else = -8,
+  tok_for = -9, tok_in = -10,
+  
+  // operators
+  tok_binary = -11, tok_unary = -12,
+  
+  // var definition
+  tok_var = -13
+};
+
+static std::string IdentifierStr;  // Filled in if tok_identifier
+static double NumVal;              // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+  static int LastChar = ' ';
+
+  // Skip any whitespace.
+  while (isspace(LastChar))
+    LastChar = getchar();
+
+  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+    IdentifierStr = LastChar;
+    while (isalnum((LastChar = getchar())))
+      IdentifierStr += LastChar;
+
+    if (IdentifierStr == "def") return tok_def;
+    if (IdentifierStr == "extern") return tok_extern;
+    if (IdentifierStr == "if") return tok_if;
+    if (IdentifierStr == "then") return tok_then;
+    if (IdentifierStr == "else") return tok_else;
+    if (IdentifierStr == "for") return tok_for;
+    if (IdentifierStr == "in") return tok_in;
+    if (IdentifierStr == "binary") return tok_binary;
+    if (IdentifierStr == "unary") return tok_unary;
+    if (IdentifierStr == "var") return tok_var;
+    return tok_identifier;
+  }
+
+  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
+    std::string NumStr;
+    do {
+      NumStr += LastChar;
+      LastChar = getchar();
+    } while (isdigit(LastChar) || LastChar == '.');
+
+    NumVal = strtod(NumStr.c_str(), 0);
+    return tok_number;
+  }
+
+  if (LastChar == '#') {
+    // Comment until end of line.
+    do LastChar = getchar();
+    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
+    
+    if (LastChar != EOF)
+      return gettok();
+  }
+  
+  // Check for end of file.  Don't eat the EOF.
+  if (LastChar == EOF)
+    return tok_eof;
+
+  // Otherwise, just return the character as its ascii value.
+  int ThisChar = LastChar;
+  LastChar = getchar();
+  return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+/// ExprAST - Base class for all expression nodes.
+class ExprAST {
+public:
+  virtual ~ExprAST() {}
+  virtual Value *Codegen() = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+class NumberExprAST : public ExprAST {
+  double Val;
+public:
+  NumberExprAST(double val) : Val(val) {}
+  virtual Value *Codegen();
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+class VariableExprAST : public ExprAST {
+  std::string Name;
+public:
+  VariableExprAST(const std::string &name) : Name(name) {}
+  const std::string &getName() const { return Name; }
+  virtual Value *Codegen();
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+  char Opcode;
+  ExprAST *Operand;
+public:
+  UnaryExprAST(char opcode, ExprAST *operand) 
+    : Opcode(opcode), Operand(operand) {}
+  virtual Value *Codegen();
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+class BinaryExprAST : public ExprAST {
+  char Op;
+  ExprAST *LHS, *RHS;
+public:
+  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) 
+    : Op(op), LHS(lhs), RHS(rhs) {}
+  virtual Value *Codegen();
+};
+
+/// CallExprAST - Expression class for function calls.
+class CallExprAST : public ExprAST {
+  std::string Callee;
+  std::vector<ExprAST*> Args;
+public:
+  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
+    : Callee(callee), Args(args) {}
+  virtual Value *Codegen();
+};
+
+/// IfExprAST - Expression class for if/then/else.
+class IfExprAST : public ExprAST {
+  ExprAST *Cond, *Then, *Else;
+public:
+  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
+  : Cond(cond), Then(then), Else(_else) {}
+  virtual Value *Codegen();
+};
+
+/// ForExprAST - Expression class for for/in.
+class ForExprAST : public ExprAST {
+  std::string VarName;
+  ExprAST *Start, *End, *Step, *Body;
+public:
+  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
+             ExprAST *step, ExprAST *body)
+    : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+  virtual Value *Codegen();
+};
+
+/// VarExprAST - Expression class for var/in
+class VarExprAST : public ExprAST {
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+  ExprAST *Body;
+public:
+  VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
+             ExprAST *body)
+  : VarNames(varnames), Body(body) {}
+  
+  virtual Value *Codegen();
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+class PrototypeAST {
+  std::string Name;
+  std::vector<std::string> Args;
+  bool isOperator;
+  unsigned Precedence;  // Precedence if a binary op.
+public:
+  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
+               bool isoperator = false, unsigned prec = 0)
+  : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
+  
+  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
+  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
+  
+  char getOperatorName() const {
+    assert(isUnaryOp() || isBinaryOp());
+    return Name[Name.size()-1];
+  }
+  
+  unsigned getBinaryPrecedence() const { return Precedence; }
+  
+  Function *Codegen();
+  
+  void CreateArgumentAllocas(Function *F);
+};
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+  PrototypeAST *Proto;
+  ExprAST *Body;
+public:
+  FunctionAST(PrototypeAST *proto, ExprAST *body)
+    : Proto(proto), Body(body) {}
+  
+  Function *Codegen();
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
+/// token the parser is looking at.  getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+  return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+  if (!isascii(CurTok))
+    return -1;
+  
+  // Make sure it's a declared binop.
+  int TokPrec = BinopPrecedence[CurTok];
+  if (TokPrec <= 0) return -1;
+  return TokPrec;
+}
+
+/// Error* - These are little helper functions for error handling.
+ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
+PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
+FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
+
+static ExprAST *ParseExpression();
+
+/// identifierexpr
+///   ::= identifier
+///   ::= identifier '(' expression* ')'
+static ExprAST *ParseIdentifierExpr() {
+  std::string IdName = IdentifierStr;
+  
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '(') // Simple variable ref.
+    return new VariableExprAST(IdName);
+  
+  // Call.
+  getNextToken();  // eat (
+  std::vector<ExprAST*> Args;
+  if (CurTok != ')') {
+    while (1) {
+      ExprAST *Arg = ParseExpression();
+      if (!Arg) return 0;
+      Args.push_back(Arg);
+
+      if (CurTok == ')') break;
+
+      if (CurTok != ',')
+        return Error("Expected ')' or ',' in argument list");
+      getNextToken();
+    }
+  }
+
+  // Eat the ')'.
+  getNextToken();
+  
+  return new CallExprAST(IdName, Args);
+}
+
+/// numberexpr ::= number
+static ExprAST *ParseNumberExpr() {
+  ExprAST *Result = new NumberExprAST(NumVal);
+  getNextToken(); // consume the number
+  return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static ExprAST *ParseParenExpr() {
+  getNextToken();  // eat (.
+  ExprAST *V = ParseExpression();
+  if (!V) return 0;
+  
+  if (CurTok != ')')
+    return Error("expected ')'");
+  getNextToken();  // eat ).
+  return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static ExprAST *ParseIfExpr() {
+  getNextToken();  // eat the if.
+  
+  // condition.
+  ExprAST *Cond = ParseExpression();
+  if (!Cond) return 0;
+  
+  if (CurTok != tok_then)
+    return Error("expected then");
+  getNextToken();  // eat the then
+  
+  ExprAST *Then = ParseExpression();
+  if (Then == 0) return 0;
+  
+  if (CurTok != tok_else)
+    return Error("expected else");
+  
+  getNextToken();
+  
+  ExprAST *Else = ParseExpression();
+  if (!Else) return 0;
+  
+  return new IfExprAST(Cond, Then, Else);
+}
+
+/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
+static ExprAST *ParseForExpr() {
+  getNextToken();  // eat the for.
+
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after for");
+  
+  std::string IdName = IdentifierStr;
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '=')
+    return Error("expected '=' after for");
+  getNextToken();  // eat '='.
+  
+  
+  ExprAST *Start = ParseExpression();
+  if (Start == 0) return 0;
+  if (CurTok != ',')
+    return Error("expected ',' after for start value");
+  getNextToken();
+  
+  ExprAST *End = ParseExpression();
+  if (End == 0) return 0;
+  
+  // The step value is optional.
+  ExprAST *Step = 0;
+  if (CurTok == ',') {
+    getNextToken();
+    Step = ParseExpression();
+    if (Step == 0) return 0;
+  }
+  
+  if (CurTok != tok_in)
+    return Error("expected 'in' after for");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+
+  return new ForExprAST(IdName, Start, End, Step, Body);
+}
+
+/// varexpr ::= 'var' identifier ('=' expression)? 
+//                    (',' identifier ('=' expression)?)* 'in' expression
+static ExprAST *ParseVarExpr() {
+  getNextToken();  // eat the var.
+
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+
+  // At least one variable name is required.
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after var");
+  
+  while (1) {
+    std::string Name = IdentifierStr;
+    getNextToken();  // eat identifier.
+
+    // Read the optional initializer.
+    ExprAST *Init = 0;
+    if (CurTok == '=') {
+      getNextToken(); // eat the '='.
+      
+      Init = ParseExpression();
+      if (Init == 0) return 0;
+    }
+    
+    VarNames.push_back(std::make_pair(Name, Init));
+    
+    // End of var list, exit loop.
+    if (CurTok != ',') break;
+    getNextToken(); // eat the ','.
+    
+    if (CurTok != tok_identifier)
+      return Error("expected identifier list after var");
+  }
+  
+  // At this point, we have to have 'in'.
+  if (CurTok != tok_in)
+    return Error("expected 'in' keyword after 'var'");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+  
+  return new VarExprAST(VarNames, Body);
+}
+
+/// primary
+///   ::= identifierexpr
+///   ::= numberexpr
+///   ::= parenexpr
+///   ::= ifexpr
+///   ::= forexpr
+///   ::= varexpr
+static ExprAST *ParsePrimary() {
+  switch (CurTok) {
+  default: return Error("unknown token when expecting an expression");
+  case tok_identifier: return ParseIdentifierExpr();
+  case tok_number:     return ParseNumberExpr();
+  case '(':            return ParseParenExpr();
+  case tok_if:         return ParseIfExpr();
+  case tok_for:        return ParseForExpr();
+  case tok_var:        return ParseVarExpr();
+  }
+}
+
+/// unary
+///   ::= primary
+///   ::= '!' unary
+static ExprAST *ParseUnary() {
+  // If the current token is not an operator, it must be a primary expr.
+  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+    return ParsePrimary();
+  
+  // If this is a unary operator, read it.
+  int Opc = CurTok;
+  getNextToken();
+  if (ExprAST *Operand = ParseUnary())
+    return new UnaryExprAST(Opc, Operand);
+  return 0;
+}
+
+/// binoprhs
+///   ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+  // If this is a binop, find its precedence.
+  while (1) {
+    int TokPrec = GetTokPrecedence();
+    
+    // If this is a binop that binds at least as tightly as the current binop,
+    // consume it, otherwise we are done.
+    if (TokPrec < ExprPrec)
+      return LHS;
+    
+    // Okay, we know this is a binop.
+    int BinOp = CurTok;
+    getNextToken();  // eat binop
+    
+    // Parse the unary expression after the binary operator.
+    ExprAST *RHS = ParseUnary();
+    if (!RHS) return 0;
+    
+    // If BinOp binds less tightly with RHS than the operator after RHS, let
+    // the pending operator take RHS as its LHS.
+    int NextPrec = GetTokPrecedence();
+    if (TokPrec < NextPrec) {
+      RHS = ParseBinOpRHS(TokPrec+1, RHS);
+      if (RHS == 0) return 0;
+    }
+    
+    // Merge LHS/RHS.
+    LHS = new BinaryExprAST(BinOp, LHS, RHS);
+  }
+}
+
+/// expression
+///   ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+  ExprAST *LHS = ParseUnary();
+  if (!LHS) return 0;
+  
+  return ParseBinOpRHS(0, LHS);
+}
+
+/// prototype
+///   ::= id '(' id* ')'
+///   ::= binary LETTER number? (id, id)
+///   ::= unary LETTER (id)
+static PrototypeAST *ParsePrototype() {
+  std::string FnName;
+  
+  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+  unsigned BinaryPrecedence = 30;
+  
+  switch (CurTok) {
+  default:
+    return ErrorP("Expected function name in prototype");
+  case tok_identifier:
+    FnName = IdentifierStr;
+    Kind = 0;
+    getNextToken();
+    break;
+  case tok_unary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected unary operator");
+    FnName = "unary";
+    FnName += (char)CurTok;
+    Kind = 1;
+    getNextToken();
+    break;
+  case tok_binary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected binary operator");
+    FnName = "binary";
+    FnName += (char)CurTok;
+    Kind = 2;
+    getNextToken();
+    
+    // Read the precedence if present.
+    if (CurTok == tok_number) {
+      if (NumVal < 1 || NumVal > 100)
+        return ErrorP("Invalid precedecnce: must be 1..100");
+      BinaryPrecedence = (unsigned)NumVal;
+      getNextToken();
+    }
+    break;
+  }
+  
+  if (CurTok != '(')
+    return ErrorP("Expected '(' in prototype");
+  
+  std::vector<std::string> ArgNames;
+  while (getNextToken() == tok_identifier)
+    ArgNames.push_back(IdentifierStr);
+  if (CurTok != ')')
+    return ErrorP("Expected ')' in prototype");
+  
+  // success.
+  getNextToken();  // eat ')'.
+  
+  // Verify right number of names for operator.
+  if (Kind && ArgNames.size() != Kind)
+    return ErrorP("Invalid number of operands for operator");
+  
+  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static FunctionAST *ParseDefinition() {
+  getNextToken();  // eat def.
+  PrototypeAST *Proto = ParsePrototype();
+  if (Proto == 0) return 0;
+
+  if (ExprAST *E = ParseExpression())
+    return new FunctionAST(Proto, E);
+  return 0;
+}
+
+/// toplevelexpr ::= expression
+static FunctionAST *ParseTopLevelExpr() {
+  if (ExprAST *E = ParseExpression()) {
+    // Make an anonymous proto.
+    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
+    return new FunctionAST(Proto, E);
+  }
+  return 0;
+}
+
+/// external ::= 'extern' prototype
+static PrototypeAST *ParseExtern() {
+  getNextToken();  // eat extern.
+  return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+static Module *TheModule;
+static FunctionPassManager *TheFPM;
+static IRBuilder<> Builder(getGlobalContext());
+static std::map<std::string, AllocaInst*> NamedValues;
+
+Value *ErrorV(const char *Str) { Error(Str); return 0; }
+
+/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
+/// the function.  This is used for mutable variables etc.
+static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
+                                          const std::string &VarName) {
+  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
+                 TheFunction->getEntryBlock().begin());
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+                           VarName.c_str());
+}
+
+Value *NumberExprAST::Codegen() {
+  return ConstantFP::get(getGlobalContext(), APFloat(Val));
+}
+
+Value *VariableExprAST::Codegen() {
+  // Look this variable up in the function.
+  Value *V = NamedValues[Name];
+  if (V == 0) return ErrorV("Unknown variable name");
+
+  // Load the value.
+  return Builder.CreateLoad(V, Name.c_str());
+}
+
+Value *UnaryExprAST::Codegen() {
+  Value *OperandV = Operand->Codegen();
+  if (OperandV == 0) return 0;
+#ifdef USE_MCJIT
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
+#else
+  Function *F = TheModule->getFunction(std::string("unary")+Opcode);
+#endif
+  if (F == 0)
+    return ErrorV("Unknown unary operator");
+  
+  return Builder.CreateCall(F, OperandV, "unop");
+}
+
+Value *BinaryExprAST::Codegen() {
+  // Special case '=' because we don't want to emit the LHS as an expression.
+  if (Op == '=') {
+    // Assignment requires the LHS to be an identifier.
+    // For now, I'm building without RTTI because LLVM builds that way by
+    // default and so we need to build that way to use the command line supprt.
+    // If you build LLVM with RTTI this can be changed back to a dynamic_cast.
+    VariableExprAST *LHSE = reinterpret_cast<VariableExprAST*>(LHS);
+    if (!LHSE)
+      return ErrorV("destination of '=' must be a variable");
+    // Codegen the RHS.
+    Value *Val = RHS->Codegen();
+    if (Val == 0) return 0;
+
+    // Look up the name.
+    Value *Variable = NamedValues[LHSE->getName()];
+    if (Variable == 0) return ErrorV("Unknown variable name");
+
+    Builder.CreateStore(Val, Variable);
+    return Val;
+  }
+  
+  Value *L = LHS->Codegen();
+  Value *R = RHS->Codegen();
+  if (L == 0 || R == 0) return 0;
+  
+  switch (Op) {
+  case '+': return Builder.CreateFAdd(L, R, "addtmp");
+  case '-': return Builder.CreateFSub(L, R, "subtmp");
+  case '*': return Builder.CreateFMul(L, R, "multmp");
+  case '/': return Builder.CreateFDiv(L, R, "divtmp");
+  case '<':
+    L = Builder.CreateFCmpULT(L, R, "cmptmp");
+    // Convert bool 0/1 to double 0.0 or 1.0
+    return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+                                "booltmp");
+  default: break;
+  }
+  
+  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+  // a call to it.
+  Function *F = TheModule->getFunction(std::string("binary")+Op);
+  assert(F && "binary operator not found!");
+  
+  Value *Ops[] = { L, R };
+  return Builder.CreateCall(F, Ops, "binop");
+}
+
+Value *CallExprAST::Codegen() {
+  // Look up the name in the global module table.
+  Function *CalleeF = TheModule->getFunction(Callee);
+  if (CalleeF == 0) {
+    char error_str[64];
+    sprintf(error_str, "Unknown function referenced %s", Callee.c_str()); 
+    return ErrorV(error_str);
+  }
+  
+  // If argument mismatch error.
+  if (CalleeF->arg_size() != Args.size())
+    return ErrorV("Incorrect # arguments passed");
+
+  std::vector<Value*> ArgsV;
+  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+    ArgsV.push_back(Args[i]->Codegen());
+    if (ArgsV.back() == 0) return 0;
+  }
+  
+  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
+}
+
+Value *IfExprAST::Codegen() {
+  Value *CondV = Cond->Codegen();
+  if (CondV == 0) return 0;
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  CondV = Builder.CreateFCmpONE(CondV, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                "ifcond");
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+  
+  // Create blocks for the then and else cases.  Insert the 'then' block at the
+  // end of the function.
+  BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
+  BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
+  BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
+  
+  Builder.CreateCondBr(CondV, ThenBB, ElseBB);
+  
+  // Emit then value.
+  Builder.SetInsertPoint(ThenBB);
+  
+  Value *ThenV = Then->Codegen();
+  if (ThenV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+  ThenBB = Builder.GetInsertBlock();
+  
+  // Emit else block.
+  TheFunction->getBasicBlockList().push_back(ElseBB);
+  Builder.SetInsertPoint(ElseBB);
+  
+  Value *ElseV = Else->Codegen();
+  if (ElseV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+  ElseBB = Builder.GetInsertBlock();
+  
+  // Emit merge block.
+  TheFunction->getBasicBlockList().push_back(MergeBB);
+  Builder.SetInsertPoint(MergeBB);
+  PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
+                                  "iftmp");
+  
+  PN->addIncoming(ThenV, ThenBB);
+  PN->addIncoming(ElseV, ElseBB);
+  return PN;
+}
+
+Value *ForExprAST::Codegen() {
+  // Output this as:
+  //   var = alloca double
+  //   ...
+  //   start = startexpr
+  //   store start -> var
+  //   goto loop
+  // loop: 
+  //   ...
+  //   bodyexpr
+  //   ...
+  // loopend:
+  //   step = stepexpr
+  //   endcond = endexpr
+  //
+  //   curvar = load var
+  //   nextvar = curvar + step
+  //   store nextvar -> var
+  //   br endcond, loop, endloop
+  // outloop:
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Create an alloca for the variable in the entry block.
+  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+  
+  // Emit the start code first, without 'variable' in scope.
+  Value *StartVal = Start->Codegen();
+  if (StartVal == 0) return 0;
+  
+  // Store the value into the alloca.
+  Builder.CreateStore(StartVal, Alloca);
+  
+  // Make the new basic block for the loop header, inserting after current
+  // block.
+  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+  
+  // Insert an explicit fall through from the current block to the LoopBB.
+  Builder.CreateBr(LoopBB);
+
+  // Start insertion in LoopBB.
+  Builder.SetInsertPoint(LoopBB);
+  
+  // Within the loop, the variable is defined equal to the PHI node.  If it
+  // shadows an existing variable, we have to restore it, so save it now.
+  AllocaInst *OldVal = NamedValues[VarName];
+  NamedValues[VarName] = Alloca;
+  
+  // Emit the body of the loop.  This, like any other expr, can change the
+  // current BB.  Note that we ignore the value computed by the body, but don't
+  // allow an error.
+  if (Body->Codegen() == 0)
+    return 0;
+  
+  // Emit the step value.
+  Value *StepVal;
+  if (Step) {
+    StepVal = Step->Codegen();
+    if (StepVal == 0) return 0;
+  } else {
+    // If not specified, use 1.0.
+    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
+  }
+  
+  // Compute the end condition.
+  Value *EndCond = End->Codegen();
+  if (EndCond == 0) return EndCond;
+  
+  // Reload, increment, and restore the alloca.  This handles the case where
+  // the body of the loop mutates the variable.
+  Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
+  Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
+  Builder.CreateStore(NextVar, Alloca);
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  EndCond = Builder.CreateFCmpONE(EndCond, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                  "loopcond");
+  
+  // Create the "after loop" block and insert it.
+  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+  
+  // Insert the conditional branch into the end of LoopEndBB.
+  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
+  
+  // Any new code will be inserted in AfterBB.
+  Builder.SetInsertPoint(AfterBB);
+  
+  // Restore the unshadowed variable.
+  if (OldVal)
+    NamedValues[VarName] = OldVal;
+  else
+    NamedValues.erase(VarName);
+
+  
+  // for expr always returns 0.0.
+  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
+}
+
+Value *VarExprAST::Codegen() {
+  std::vector<AllocaInst *> OldBindings;
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Register all variables and emit their initializer.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
+    const std::string &VarName = VarNames[i].first;
+    ExprAST *Init = VarNames[i].second;
+    
+    // Emit the initializer before adding the variable to scope, this prevents
+    // the initializer from referencing the variable itself, and permits stuff
+    // like this:
+    //  var a = 1 in
+    //    var a = a in ...   # refers to outer 'a'.
+    Value *InitVal;
+    if (Init) {
+      InitVal = Init->Codegen();
+      if (InitVal == 0) return 0;
+    } else { // If not specified, use 0.0.
+      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
+    }
+    
+    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+    Builder.CreateStore(InitVal, Alloca);
+
+    // Remember the old variable binding so that we can restore the binding when
+    // we unrecurse.
+    OldBindings.push_back(NamedValues[VarName]);
+    
+    // Remember this binding.
+    NamedValues[VarName] = Alloca;
+  }
+  
+  // Codegen the body, now that all vars are in scope.
+  Value *BodyVal = Body->Codegen();
+  if (BodyVal == 0) return 0;
+  
+  // Pop all our variables from scope.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
+    NamedValues[VarNames[i].first] = OldBindings[i];
+
+  // Return the body computation.
+  return BodyVal;
+}
+
+Function *PrototypeAST::Codegen() {
+  // Make the function type:  double(double,double) etc.
+  std::vector<Type*> Doubles(Args.size(), 
+                             Type::getDoubleTy(getGlobalContext()));
+  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+                                       Doubles, false);
+
+  Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
+  // If F conflicted, there was already something named 'Name'.  If it has a
+  // body, don't allow redefinition or reextern.
+  if (F->getName() != Name) {
+    // Delete the one we just made and get the existing one.
+    F->eraseFromParent();
+    F = TheModule->getFunction(Name);
+    // If F already has a body, reject this.
+    if (!F->empty()) {
+      ErrorF("redefinition of function");
+      return 0;
+    }
+    // If F took a different number of args, reject.
+    if (F->arg_size() != Args.size()) {
+      ErrorF("redefinition of function with different # args");
+      return 0;
+    }
+  }
+
+  // Set names for all arguments.
+  unsigned Idx = 0;
+  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+       ++AI, ++Idx)
+    AI->setName(Args[Idx]);
+    
+  return F;
+}
+
+/// CreateArgumentAllocas - Create an alloca for each argument and register the
+/// argument in the symbol table so that references to it will succeed.
+void PrototypeAST::CreateArgumentAllocas(Function *F) {
+  Function::arg_iterator AI = F->arg_begin();
+  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
+    // Create an alloca for this variable.
+    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
+
+    // Store the initial value into the alloca.
+    Builder.CreateStore(AI, Alloca);
+
+    // Add arguments to variable symbol table.
+    NamedValues[Args[Idx]] = Alloca;
+  }
+}
+
+Function *FunctionAST::Codegen() {
+  NamedValues.clear();
+  
+  Function *TheFunction = Proto->Codegen();
+  if (TheFunction == 0)
+    return 0;
+
+  // If this is an operator, install it.
+  if (Proto->isBinaryOp())
+    BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
+
+  // Create a new basic block to start insertion into.
+  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+  Builder.SetInsertPoint(BB);
+  
+  // Add all arguments to the symbol table and create their allocas.
+  Proto->CreateArgumentAllocas(TheFunction);
+
+  if (Value *RetVal = Body->Codegen()) {
+    // Finish off the function.
+    Builder.CreateRet(RetVal);
+
+    // Validate the generated code, checking for consistency.
+    verifyFunction(*TheFunction);
+
+    // Optimize the function.
+    TheFPM->run(*TheFunction);
+
+    return TheFunction;
+  }
+  
+  // Error reading body, remove function.
+  TheFunction->eraseFromParent();
+
+  if (Proto->isBinaryOp())
+    BinopPrecedence.erase(Proto->getOperatorName());
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static ExecutionEngine *TheExecutionEngine;
+
+static void HandleDefinition() {
+  if (FunctionAST *F = ParseDefinition()) {
+    if (Function *LF = F->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read function definition:");
+      LF->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleExtern() {
+  if (PrototypeAST *P = ParseExtern()) {
+    if (Function *F = P->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read extern: ");
+      F->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleTopLevelExpression() {
+  // Evaluate a top-level expression into an anonymous function.
+  if (FunctionAST *F = ParseTopLevelExpr()) {
+    if (Function *LF = F->Codegen()) {
+      // JIT the function, returning a function pointer.
+      void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
+      // Cast it to the right type (takes no arguments, returns a double) so we
+      // can call it as a native function.
+      double (*FP)() = (double (*)())(intptr_t)FPtr;
+#ifdef MINIMAL_STDERR_OUTPUT
+      FP();
+#else
+      fprintf(stderr, "Evaluated to %f\n", FP());
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+  while (1) {
+#ifndef MINIMAL_STDERR_OUTPUT
+    fprintf(stderr, "ready> ");
+#endif
+    switch (CurTok) {
+    case tok_eof:    return;
+    case ';':        getNextToken(); break;  // ignore top-level semicolons.
+    case tok_def:    HandleDefinition(); break;
+    case tok_extern: HandleExtern(); break;
+    default:         HandleTopLevelExpression(); break;
+    }
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C" 
+double putchard(double X) {
+  putchar((char)X);
+  return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C" 
+double printd(double X) {
+  printf("%f", X);
+  return 0;
+}
+
+extern "C" 
+double printlf() {
+  printf("\n");
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Command line input file handlers
+//===----------------------------------------------------------------------===//
+
+Module* parseInputIR(std::string InputFile) {
+  SMDiagnostic Err;
+  Module *M = ParseIRFile(InputFile, Err, getGlobalContext());
+  if (!M) {
+    Err.print("IR parsing failed: ", errs());
+    return NULL;
+  }
+
+  return M;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main(int argc, char **argv) {
+  InitializeNativeTarget();
+  LLVMContext &Context = getGlobalContext();
+
+  cl::ParseCommandLineOptions(argc, argv,
+                              "Kaleidoscope example program\n");
+
+  // Install standard binary operators.
+  // 1 is lowest precedence.
+  BinopPrecedence['='] = 2;
+  BinopPrecedence['<'] = 10;
+  BinopPrecedence['+'] = 20;
+  BinopPrecedence['-'] = 20;
+  BinopPrecedence['/'] = 40;
+  BinopPrecedence['*'] = 40;  // highest.
+
+  // Make the module, which holds all the code.
+  if (!InputIR.empty()) {
+    TheModule = parseInputIR(InputIR);
+  } else {
+    TheModule = new Module("my cool jit", Context);
+  }
+
+  // Create the JIT.  This takes ownership of the module.
+  std::string ErrStr;
+  TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create();
+  if (!TheExecutionEngine) {
+    fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
+    exit(1);
+  }
+
+  FunctionPassManager OurFPM(TheModule);
+
+  // Set up the optimizer pipeline.  Start with registering info about how the
+  // target lays out data structures.
+  OurFPM.add(new DataLayout(*TheExecutionEngine->getDataLayout()));
+  // Provide basic AliasAnalysis support for GVN.
+  OurFPM.add(createBasicAliasAnalysisPass());
+  // Promote allocas to registers.
+  OurFPM.add(createPromoteMemoryToRegisterPass());
+  // Do simple "peephole" optimizations and bit-twiddling optzns.
+  OurFPM.add(createInstructionCombiningPass());
+  // Reassociate expressions.
+  OurFPM.add(createReassociatePass());
+  // Eliminate Common SubExpressions.
+  OurFPM.add(createGVNPass());
+  // Simplify the control flow graph (deleting unreachable blocks, etc).
+  OurFPM.add(createCFGSimplificationPass());
+
+  OurFPM.doInitialization();
+
+  // Set the global so the code gen can use this.
+  TheFPM = &OurFPM;
+
+  // Prime the first token.
+#ifndef MINIMAL_STDERR_OUTPUT
+  fprintf(stderr, "ready> ");
+#endif
+  getNextToken();
+
+  // Run the main "interpreter loop" now.
+  MainLoop();
+
+  // Print out all of the generated code.
+  TheFPM = 0;
+#if !defined(MINIMAL_STDERR_OUTPUT) || defined(DUMP_FINAL_MODULE)
+  TheModule->dump();
+#endif
+  return 0;
+}
diff --git a/examples/Kaleidoscope/MCJIT/cached/toy.cpp b/examples/Kaleidoscope/MCJIT/cached/toy.cpp
new file mode 100644
index 0000000000..6c8e38b13f
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/cached/toy.cpp
@@ -0,0 +1,1551 @@
+#define MINIMAL_STDERR_OUTPUT
+
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/MCJIT.h"
+#include "llvm/ExecutionEngine/ObjectCache.h"
+#include "llvm/ExecutionEngine/SectionMemoryManager.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IRReader/IRReader.h"
+#include "llvm/PassManager.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Transforms/Scalar.h"
+#include <cstdio>
+#include <map>
+#include <string>
+#include <vector>
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Command-line options
+//===----------------------------------------------------------------------===//
+
+cl::opt<std::string>
+InputIR("input-IR",
+        cl::desc("Specify the name of an IR file to load for function definitions"),
+        cl::value_desc("input IR file name"));
+
+cl::opt<bool> 
+UseObjectCache("use-object-cache", 
+               cl::desc("Enable use of the MCJIT object caching"),
+               cl::init(false));
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+  tok_eof = -1,
+
+  // commands
+  tok_def = -2, tok_extern = -3,
+
+  // primary
+  tok_identifier = -4, tok_number = -5,
+  
+  // control
+  tok_if = -6, tok_then = -7, tok_else = -8,
+  tok_for = -9, tok_in = -10,
+  
+  // operators
+  tok_binary = -11, tok_unary = -12,
+  
+  // var definition
+  tok_var = -13
+};
+
+static std::string IdentifierStr;  // Filled in if tok_identifier
+static double NumVal;              // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+  static int LastChar = ' ';
+
+  // Skip any whitespace.
+  while (isspace(LastChar))
+    LastChar = getchar();
+
+  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+    IdentifierStr = LastChar;
+    while (isalnum((LastChar = getchar())))
+      IdentifierStr += LastChar;
+
+    if (IdentifierStr == "def") return tok_def;
+    if (IdentifierStr == "extern") return tok_extern;
+    if (IdentifierStr == "if") return tok_if;
+    if (IdentifierStr == "then") return tok_then;
+    if (IdentifierStr == "else") return tok_else;
+    if (IdentifierStr == "for") return tok_for;
+    if (IdentifierStr == "in") return tok_in;
+    if (IdentifierStr == "binary") return tok_binary;
+    if (IdentifierStr == "unary") return tok_unary;
+    if (IdentifierStr == "var") return tok_var;
+    return tok_identifier;
+  }
+
+  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
+    std::string NumStr;
+    do {
+      NumStr += LastChar;
+      LastChar = getchar();
+    } while (isdigit(LastChar) || LastChar == '.');
+
+    NumVal = strtod(NumStr.c_str(), 0);
+    return tok_number;
+  }
+
+  if (LastChar == '#') {
+    // Comment until end of line.
+    do LastChar = getchar();
+    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
+    
+    if (LastChar != EOF)
+      return gettok();
+  }
+  
+  // Check for end of file.  Don't eat the EOF.
+  if (LastChar == EOF)
+    return tok_eof;
+
+  // Otherwise, just return the character as its ascii value.
+  int ThisChar = LastChar;
+  LastChar = getchar();
+  return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+/// ExprAST - Base class for all expression nodes.
+class ExprAST {
+public:
+  virtual ~ExprAST() {}
+  virtual Value *Codegen() = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+class NumberExprAST : public ExprAST {
+  double Val;
+public:
+  NumberExprAST(double val) : Val(val) {}
+  virtual Value *Codegen();
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+class VariableExprAST : public ExprAST {
+  std::string Name;
+public:
+  VariableExprAST(const std::string &name) : Name(name) {}
+  const std::string &getName() const { return Name; }
+  virtual Value *Codegen();
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+  char Opcode;
+  ExprAST *Operand;
+public:
+  UnaryExprAST(char opcode, ExprAST *operand) 
+    : Opcode(opcode), Operand(operand) {}
+  virtual Value *Codegen();
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+class BinaryExprAST : public ExprAST {
+  char Op;
+  ExprAST *LHS, *RHS;
+public:
+  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) 
+    : Op(op), LHS(lhs), RHS(rhs) {}
+  virtual Value *Codegen();
+};
+
+/// CallExprAST - Expression class for function calls.
+class CallExprAST : public ExprAST {
+  std::string Callee;
+  std::vector<ExprAST*> Args;
+public:
+  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
+    : Callee(callee), Args(args) {}
+  virtual Value *Codegen();
+};
+
+/// IfExprAST - Expression class for if/then/else.
+class IfExprAST : public ExprAST {
+  ExprAST *Cond, *Then, *Else;
+public:
+  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
+  : Cond(cond), Then(then), Else(_else) {}
+  virtual Value *Codegen();
+};
+
+/// ForExprAST - Expression class for for/in.
+class ForExprAST : public ExprAST {
+  std::string VarName;
+  ExprAST *Start, *End, *Step, *Body;
+public:
+  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
+             ExprAST *step, ExprAST *body)
+    : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+  virtual Value *Codegen();
+};
+
+/// VarExprAST - Expression class for var/in
+class VarExprAST : public ExprAST {
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+  ExprAST *Body;
+public:
+  VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
+             ExprAST *body)
+  : VarNames(varnames), Body(body) {}
+  
+  virtual Value *Codegen();
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+class PrototypeAST {
+  std::string Name;
+  std::vector<std::string> Args;
+  bool isOperator;
+  unsigned Precedence;  // Precedence if a binary op.
+public:
+  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
+               bool isoperator = false, unsigned prec = 0)
+  : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
+  
+  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
+  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
+  
+  char getOperatorName() const {
+    assert(isUnaryOp() || isBinaryOp());
+    return Name[Name.size()-1];
+  }
+  
+  unsigned getBinaryPrecedence() const { return Precedence; }
+  
+  Function *Codegen();
+  
+  void CreateArgumentAllocas(Function *F);
+};
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+  PrototypeAST *Proto;
+  ExprAST *Body;
+public:
+  FunctionAST(PrototypeAST *proto, ExprAST *body)
+    : Proto(proto), Body(body) {}
+  
+  Function *Codegen();
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
+/// token the parser is looking at.  getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+  return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+  if (!isascii(CurTok))
+    return -1;
+  
+  // Make sure it's a declared binop.
+  int TokPrec = BinopPrecedence[CurTok];
+  if (TokPrec <= 0) return -1;
+  return TokPrec;
+}
+
+/// Error* - These are little helper functions for error handling.
+ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
+PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
+FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
+
+static ExprAST *ParseExpression();
+
+/// identifierexpr
+///   ::= identifier
+///   ::= identifier '(' expression* ')'
+static ExprAST *ParseIdentifierExpr() {
+  std::string IdName = IdentifierStr;
+  
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '(') // Simple variable ref.
+    return new VariableExprAST(IdName);
+  
+  // Call.
+  getNextToken();  // eat (
+  std::vector<ExprAST*> Args;
+  if (CurTok != ')') {
+    while (1) {
+      ExprAST *Arg = ParseExpression();
+      if (!Arg) return 0;
+      Args.push_back(Arg);
+
+      if (CurTok == ')') break;
+
+      if (CurTok != ',')
+        return Error("Expected ')' or ',' in argument list");
+      getNextToken();
+    }
+  }
+
+  // Eat the ')'.
+  getNextToken();
+  
+  return new CallExprAST(IdName, Args);
+}
+
+/// numberexpr ::= number
+static ExprAST *ParseNumberExpr() {
+  ExprAST *Result = new NumberExprAST(NumVal);
+  getNextToken(); // consume the number
+  return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static ExprAST *ParseParenExpr() {
+  getNextToken();  // eat (.
+  ExprAST *V = ParseExpression();
+  if (!V) return 0;
+  
+  if (CurTok != ')')
+    return Error("expected ')'");
+  getNextToken();  // eat ).
+  return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static ExprAST *ParseIfExpr() {
+  getNextToken();  // eat the if.
+  
+  // condition.
+  ExprAST *Cond = ParseExpression();
+  if (!Cond) return 0;
+  
+  if (CurTok != tok_then)
+    return Error("expected then");
+  getNextToken();  // eat the then
+  
+  ExprAST *Then = ParseExpression();
+  if (Then == 0) return 0;
+  
+  if (CurTok != tok_else)
+    return Error("expected else");
+  
+  getNextToken();
+  
+  ExprAST *Else = ParseExpression();
+  if (!Else) return 0;
+  
+  return new IfExprAST(Cond, Then, Else);
+}
+
+/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
+static ExprAST *ParseForExpr() {
+  getNextToken();  // eat the for.
+
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after for");
+  
+  std::string IdName = IdentifierStr;
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '=')
+    return Error("expected '=' after for");
+  getNextToken();  // eat '='.
+  
+  
+  ExprAST *Start = ParseExpression();
+  if (Start == 0) return 0;
+  if (CurTok != ',')
+    return Error("expected ',' after for start value");
+  getNextToken();
+  
+  ExprAST *End = ParseExpression();
+  if (End == 0) return 0;
+  
+  // The step value is optional.
+  ExprAST *Step = 0;
+  if (CurTok == ',') {
+    getNextToken();
+    Step = ParseExpression();
+    if (Step == 0) return 0;
+  }
+  
+  if (CurTok != tok_in)
+    return Error("expected 'in' after for");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+
+  return new ForExprAST(IdName, Start, End, Step, Body);
+}
+
+/// varexpr ::= 'var' identifier ('=' expression)? 
+//                    (',' identifier ('=' expression)?)* 'in' expression
+static ExprAST *ParseVarExpr() {
+  getNextToken();  // eat the var.
+
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+
+  // At least one variable name is required.
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after var");
+  
+  while (1) {
+    std::string Name = IdentifierStr;
+    getNextToken();  // eat identifier.
+
+    // Read the optional initializer.
+    ExprAST *Init = 0;
+    if (CurTok == '=') {
+      getNextToken(); // eat the '='.
+      
+      Init = ParseExpression();
+      if (Init == 0) return 0;
+    }
+    
+    VarNames.push_back(std::make_pair(Name, Init));
+    
+    // End of var list, exit loop.
+    if (CurTok != ',') break;
+    getNextToken(); // eat the ','.
+    
+    if (CurTok != tok_identifier)
+      return Error("expected identifier list after var");
+  }
+  
+  // At this point, we have to have 'in'.
+  if (CurTok != tok_in)
+    return Error("expected 'in' keyword after 'var'");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+  
+  return new VarExprAST(VarNames, Body);
+}
+
+/// primary
+///   ::= identifierexpr
+///   ::= numberexpr
+///   ::= parenexpr
+///   ::= ifexpr
+///   ::= forexpr
+///   ::= varexpr
+static ExprAST *ParsePrimary() {
+  switch (CurTok) {
+  default: return Error("unknown token when expecting an expression");
+  case tok_identifier: return ParseIdentifierExpr();
+  case tok_number:     return ParseNumberExpr();
+  case '(':            return ParseParenExpr();
+  case tok_if:         return ParseIfExpr();
+  case tok_for:        return ParseForExpr();
+  case tok_var:        return ParseVarExpr();
+  }
+}
+
+/// unary
+///   ::= primary
+///   ::= '!' unary
+static ExprAST *ParseUnary() {
+  // If the current token is not an operator, it must be a primary expr.
+  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+    return ParsePrimary();
+  
+  // If this is a unary operator, read it.
+  int Opc = CurTok;
+  getNextToken();
+  if (ExprAST *Operand = ParseUnary())
+    return new UnaryExprAST(Opc, Operand);
+  return 0;
+}
+
+/// binoprhs
+///   ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+  // If this is a binop, find its precedence.
+  while (1) {
+    int TokPrec = GetTokPrecedence();
+    
+    // If this is a binop that binds at least as tightly as the current binop,
+    // consume it, otherwise we are done.
+    if (TokPrec < ExprPrec)
+      return LHS;
+    
+    // Okay, we know this is a binop.
+    int BinOp = CurTok;
+    getNextToken();  // eat binop
+    
+    // Parse the unary expression after the binary operator.
+    ExprAST *RHS = ParseUnary();
+    if (!RHS) return 0;
+    
+    // If BinOp binds less tightly with RHS than the operator after RHS, let
+    // the pending operator take RHS as its LHS.
+    int NextPrec = GetTokPrecedence();
+    if (TokPrec < NextPrec) {
+      RHS = ParseBinOpRHS(TokPrec+1, RHS);
+      if (RHS == 0) return 0;
+    }
+    
+    // Merge LHS/RHS.
+    LHS = new BinaryExprAST(BinOp, LHS, RHS);
+  }
+}
+
+/// expression
+///   ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+  ExprAST *LHS = ParseUnary();
+  if (!LHS) return 0;
+  
+  return ParseBinOpRHS(0, LHS);
+}
+
+/// prototype
+///   ::= id '(' id* ')'
+///   ::= binary LETTER number? (id, id)
+///   ::= unary LETTER (id)
+static PrototypeAST *ParsePrototype() {
+  std::string FnName;
+  
+  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+  unsigned BinaryPrecedence = 30;
+  
+  switch (CurTok) {
+  default:
+    return ErrorP("Expected function name in prototype");
+  case tok_identifier:
+    FnName = IdentifierStr;
+    Kind = 0;
+    getNextToken();
+    break;
+  case tok_unary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected unary operator");
+    FnName = "unary";
+    FnName += (char)CurTok;
+    Kind = 1;
+    getNextToken();
+    break;
+  case tok_binary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected binary operator");
+    FnName = "binary";
+    FnName += (char)CurTok;
+    Kind = 2;
+    getNextToken();
+    
+    // Read the precedence if present.
+    if (CurTok == tok_number) {
+      if (NumVal < 1 || NumVal > 100)
+        return ErrorP("Invalid precedecnce: must be 1..100");
+      BinaryPrecedence = (unsigned)NumVal;
+      getNextToken();
+    }
+    break;
+  }
+  
+  if (CurTok != '(')
+    return ErrorP("Expected '(' in prototype");
+  
+  std::vector<std::string> ArgNames;
+  while (getNextToken() == tok_identifier)
+    ArgNames.push_back(IdentifierStr);
+  if (CurTok != ')')
+    return ErrorP("Expected ')' in prototype");
+  
+  // success.
+  getNextToken();  // eat ')'.
+  
+  // Verify right number of names for operator.
+  if (Kind && ArgNames.size() != Kind)
+    return ErrorP("Invalid number of operands for operator");
+  
+  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static FunctionAST *ParseDefinition() {
+  getNextToken();  // eat def.
+  PrototypeAST *Proto = ParsePrototype();
+  if (Proto == 0) return 0;
+
+  if (ExprAST *E = ParseExpression())
+    return new FunctionAST(Proto, E);
+  return 0;
+}
+
+/// toplevelexpr ::= expression
+static FunctionAST *ParseTopLevelExpr() {
+  if (ExprAST *E = ParseExpression()) {
+    // Make an anonymous proto.
+    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
+    return new FunctionAST(Proto, E);
+  }
+  return 0;
+}
+
+/// external ::= 'extern' prototype
+static PrototypeAST *ParseExtern() {
+  getNextToken();  // eat extern.
+  return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Quick and dirty hack
+//===----------------------------------------------------------------------===//
+
+// FIXME: Obviously we can do better than this
+std::string GenerateUniqueName(const char *root)
+{
+  static int i = 0;
+  char s[16];
+  sprintf(s, "%s%d", root, i++);
+  std::string S = s;
+  return S;
+}
+
+std::string MakeLegalFunctionName(std::string Name)
+{
+  std::string NewName;
+  if (!Name.length())
+      return GenerateUniqueName("anon_func_");
+
+  // Start with what we have
+  NewName = Name;
+
+  // Look for a numberic first character
+  if (NewName.find_first_of("0123456789") == 0) {
+    NewName.insert(0, 1, 'n');
+  }
+
+  // Replace illegal characters with their ASCII equivalent
+  std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+  size_t pos;
+  while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
+    char old_c = NewName.at(pos);
+    char new_str[16];
+    sprintf(new_str, "%d", (int)old_c);
+    NewName = NewName.replace(pos, 1, new_str);
+  }
+
+  return NewName;
+}
+
+//===----------------------------------------------------------------------===//
+// MCJIT object cache class
+//===----------------------------------------------------------------------===//
+
+class MCJITObjectCache : public ObjectCache {
+public:
+  MCJITObjectCache() {
+    // Set IR cache directory
+    sys::fs::current_path(CacheDir);
+    sys::path::append(CacheDir, "toy_object_cache");
+  }
+
+  virtual ~MCJITObjectCache() {
+  }
+
+  virtual void notifyObjectCompiled(const Module *M, const MemoryBuffer *Obj) {
+    // Get the ModuleID
+    const std::string ModuleID = M->getModuleIdentifier();
+
+    // If we've flagged this as an IR file, cache it
+    if (0 == ModuleID.compare(0, 3, "IR:")) {
+      std::string IRFileName = ModuleID.substr(3);
+      SmallString<128>IRCacheFile = CacheDir;
+      sys::path::append(IRCacheFile, IRFileName);
+      if (!sys::fs::exists(CacheDir.str()) && sys::fs::create_directory(CacheDir.str())) {
+        fprintf(stderr, "Unable to create cache directory\n");
+        return;
+      }
+      std::string ErrStr;
+      raw_fd_ostream IRObjectFile(IRCacheFile.c_str(), ErrStr, raw_fd_ostream::F_Binary);
+      IRObjectFile << Obj->getBuffer();
+    }
+  }
+
+  // MCJIT will call this function before compiling any module
+  // MCJIT takes ownership of both the MemoryBuffer object and the memory
+  // to which it refers.
+  virtual MemoryBuffer* getObject(const Module* M) {
+    // Get the ModuleID
+    const std::string ModuleID = M->getModuleIdentifier();
+
+    // If we've flagged this as an IR file, cache it
+    if (0 == ModuleID.compare(0, 3, "IR:")) {
+      std::string IRFileName = ModuleID.substr(3);
+      SmallString<128> IRCacheFile = CacheDir;
+      sys::path::append(IRCacheFile, IRFileName);
+      if (!sys::fs::exists(IRCacheFile.str())) {
+        // This file isn't in our cache
+        return NULL;
+      }
+      OwningPtr<MemoryBuffer> IRObjectBuffer;
+      MemoryBuffer::getFile(IRCacheFile.c_str(), IRObjectBuffer, -1, false);
+      // MCJIT will want to write into this buffer, and we don't want that
+      // because the file has probably just been mmapped.  Instead we make
+      // a copy.  The filed-based buffer will be released when it goes
+      // out of scope.
+      return MemoryBuffer::getMemBufferCopy(IRObjectBuffer->getBuffer());
+    }
+
+    return NULL;
+  }
+
+private:
+  SmallString<128> CacheDir;
+};
+
+//===----------------------------------------------------------------------===//
+// MCJIT helper class
+//===----------------------------------------------------------------------===//
+
+class MCJITHelper
+{
+public:
+  MCJITHelper(LLVMContext& C) : Context(C), OpenModule(NULL) {}
+  ~MCJITHelper();
+
+  Function *getFunction(const std::string FnName);
+  Module *getModuleForNewFunction();
+  void *getPointerToFunction(Function* F);
+  void *getPointerToNamedFunction(const std::string &Name);
+  ExecutionEngine *compileModule(Module *M);
+  void closeCurrentModule();
+  void addModule(Module *M);
+  void dump();
+
+private:
+  typedef std::vector<Module*> ModuleVector;
+
+  LLVMContext  &Context;
+  Module       *OpenModule;
+  ModuleVector  Modules;
+  std::map<Module *, ExecutionEngine *> EngineMap;
+  MCJITObjectCache OurObjectCache;
+};
+
+class HelpingMemoryManager : public SectionMemoryManager
+{
+  HelpingMemoryManager(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+  void operator=(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+
+public:
+  HelpingMemoryManager(MCJITHelper *Helper) : MasterHelper(Helper) {}
+  virtual ~HelpingMemoryManager() {}
+
+  /// This method returns the address of the specified function. 
+  /// Our implementation will attempt to find functions in other
+  /// modules associated with the MCJITHelper to cross link functions
+  /// from one generated module to another.
+  ///
+  /// If \p AbortOnFailure is false and no function with the given name is
+  /// found, this function returns a null pointer. Otherwise, it prints a
+  /// message to stderr and aborts.
+  virtual void *getPointerToNamedFunction(const std::string &Name,
+                                          bool AbortOnFailure = true);
+private:
+  MCJITHelper *MasterHelper;
+};
+
+void *HelpingMemoryManager::getPointerToNamedFunction(const std::string &Name,
+                                        bool AbortOnFailure)
+{
+  // Try the standard symbol resolution first, but ask it not to abort.
+  void *pfn = SectionMemoryManager::getPointerToNamedFunction(Name, false);
+  if (pfn)
+    return pfn;
+
+  pfn = MasterHelper->getPointerToNamedFunction(Name);
+  if (!pfn && AbortOnFailure)
+    report_fatal_error("Program used external function '" + Name +
+                        "' which could not be resolved!");
+  return pfn;
+}
+
+MCJITHelper::~MCJITHelper()
+{
+  // Walk the vector of modules.
+  ModuleVector::iterator it, end;
+  for (it = Modules.begin(), end = Modules.end();
+       it != end; ++it) {
+    // See if we have an execution engine for this module.
+    std::map<Module*, ExecutionEngine*>::iterator mapIt = EngineMap.find(*it);
+    // If we have an EE, the EE owns the module so just delete the EE.
+    if (mapIt != EngineMap.end()) {
+      delete mapIt->second;
+    } else {
+      // Otherwise, we still own the module.  Delete it now.
+      delete *it;
+    }
+  }
+}
+
+Function *MCJITHelper::getFunction(const std::string FnName) {
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    Function *F = (*it)->getFunction(FnName);
+    if (F) {
+      if (*it == OpenModule)
+          return F;
+
+      assert(OpenModule != NULL);
+
+      // This function is in a module that has already been JITed.
+      // We need to generate a new prototype for external linkage.
+      Function *PF = OpenModule->getFunction(FnName);
+      if (PF && !PF->empty()) {
+        ErrorF("redefinition of function across modules");
+        return 0;
+      }
+
+      // If we don't have a prototype yet, create one.
+      if (!PF)
+        PF = Function::Create(F->getFunctionType(), 
+                                      Function::ExternalLinkage, 
+                                      FnName, 
+                                      OpenModule);
+      return PF;
+    }
+  }
+  return NULL;
+}
+
+Module *MCJITHelper::getModuleForNewFunction() {
+  // If we have a Module that hasn't been JITed, use that.
+  if (OpenModule)
+    return OpenModule;
+
+  // Otherwise create a new Module.
+  std::string ModName = GenerateUniqueName("mcjit_module_");
+  Module *M = new Module(ModName, Context);
+  Modules.push_back(M);
+  OpenModule = M;
+  return M;
+}
+
+void *MCJITHelper::getPointerToFunction(Function* F) {
+  // Look for this function in an existing module
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  std::string FnName = F->getName();
+  for (it = begin; it != end; ++it) {
+    Function *MF = (*it)->getFunction(FnName);
+    if (MF == F) {
+      std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
+      if (eeIt != EngineMap.end()) {
+        void *P = eeIt->second->getPointerToFunction(F);
+        if (P)
+          return P;
+      } else {
+        ExecutionEngine *EE = compileModule(*it);
+        void *P = EE->getPointerToFunction(F);
+        if (P)
+          return P;
+      }
+    }
+  }
+  return NULL;
+}
+
+void MCJITHelper::closeCurrentModule() {
+  OpenModule = NULL;
+}
+
+ExecutionEngine *MCJITHelper::compileModule(Module *M) {
+  if (M == OpenModule)
+    closeCurrentModule();
+
+  std::string ErrStr;
+  ExecutionEngine *NewEngine = EngineBuilder(M)
+                                            .setErrorStr(&ErrStr)
+                                            .setUseMCJIT(true)
+                                            .setMCJITMemoryManager(new HelpingMemoryManager(this))
+                                            .create();
+  if (!NewEngine) {
+    fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
+    exit(1);
+  }
+
+  if (UseObjectCache)
+    NewEngine->setObjectCache(&OurObjectCache);
+
+  // Get the ModuleID so we can identify IR input files
+  const std::string ModuleID = M->getModuleIdentifier();
+
+  // If we've flagged this as an IR file, it doesn't need function passes run.
+  if (0 != ModuleID.compare(0, 3, "IR:")) {
+    // Create a function pass manager for this engine
+    FunctionPassManager *FPM = new FunctionPassManager(M);
+
+    // Set up the optimizer pipeline.  Start with registering info about how the
+    // target lays out data structures.
+    FPM->add(new DataLayout(*NewEngine->getDataLayout()));
+    // Provide basic AliasAnalysis support for GVN.
+    FPM->add(createBasicAliasAnalysisPass());
+    // Promote allocas to registers.
+    FPM->add(createPromoteMemoryToRegisterPass());
+    // Do simple "peephole" optimizations and bit-twiddling optzns.
+    FPM->add(createInstructionCombiningPass());
+    // Reassociate expressions.
+    FPM->add(createReassociatePass());
+    // Eliminate Common SubExpressions.
+    FPM->add(createGVNPass());
+    // Simplify the control flow graph (deleting unreachable blocks, etc).
+    FPM->add(createCFGSimplificationPass());
+    FPM->doInitialization();
+
+    // For each function in the module
+    Module::iterator it;
+    Module::iterator end = M->end();
+    for (it = M->begin(); it != end; ++it) {
+      // Run the FPM on this function
+      FPM->run(*it);
+    }
+
+    // We don't need this anymore
+    delete FPM;
+  }
+
+  // Store this engine
+  EngineMap[M] = NewEngine;
+  NewEngine->finalizeObject();
+
+  return NewEngine;
+}
+
+void *MCJITHelper::getPointerToNamedFunction(const std::string &Name)
+{
+  // Look for the functions in our modules, compiling only as necessary
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    Function *F = (*it)->getFunction(Name);
+    if (F && !F->empty()) {
+      std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
+      if (eeIt != EngineMap.end()) {
+        void *P = eeIt->second->getPointerToFunction(F);
+        if (P)
+          return P;
+      } else {
+        ExecutionEngine *EE = compileModule(*it);
+        void *P = EE->getPointerToFunction(F);
+        if (P)
+          return P;
+      }
+    }
+  }
+  return NULL;
+}
+
+void MCJITHelper::addModule(Module* M) {
+  Modules.push_back(M);
+}
+
+void MCJITHelper::dump()
+{
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it)
+    (*it)->dump();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+static MCJITHelper *TheHelper;
+static IRBuilder<> Builder(getGlobalContext());
+static std::map<std::string, AllocaInst*> NamedValues;
+
+Value *ErrorV(const char *Str) { Error(Str); return 0; }
+
+/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
+/// the function.  This is used for mutable variables etc.
+static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
+                                          const std::string &VarName) {
+  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
+                 TheFunction->getEntryBlock().begin());
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+                           VarName.c_str());
+}
+
+Value *NumberExprAST::Codegen() {
+  return ConstantFP::get(getGlobalContext(), APFloat(Val));
+}
+
+Value *VariableExprAST::Codegen() {
+  // Look this variable up in the function.
+  Value *V = NamedValues[Name];
+  char ErrStr[256];
+  sprintf(ErrStr, "Unknown variable name %s", Name.c_str());
+  if (V == 0) return ErrorV(ErrStr);
+
+  // Load the value.
+  return Builder.CreateLoad(V, Name.c_str());
+}
+
+Value *UnaryExprAST::Codegen() {
+  Value *OperandV = Operand->Codegen();
+  if (OperandV == 0) return 0;
+  
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
+  if (F == 0)
+    return ErrorV("Unknown unary operator");
+  
+  return Builder.CreateCall(F, OperandV, "unop");
+}
+
+Value *BinaryExprAST::Codegen() {
+  // Special case '=' because we don't want to emit the LHS as an expression.
+  if (Op == '=') {
+    // Assignment requires the LHS to be an identifier.
+    VariableExprAST *LHSE = reinterpret_cast<VariableExprAST*>(LHS);
+    if (!LHSE)
+      return ErrorV("destination of '=' must be a variable");
+    // Codegen the RHS.
+    Value *Val = RHS->Codegen();
+    if (Val == 0) return 0;
+
+    // Look up the name.
+    Value *Variable = NamedValues[LHSE->getName()];
+    if (Variable == 0) return ErrorV("Unknown variable name");
+
+    Builder.CreateStore(Val, Variable);
+    return Val;
+  }
+  
+  Value *L = LHS->Codegen();
+  Value *R = RHS->Codegen();
+  if (L == 0 || R == 0) return 0;
+  
+  switch (Op) {
+  case '+': return Builder.CreateFAdd(L, R, "addtmp");
+  case '-': return Builder.CreateFSub(L, R, "subtmp");
+  case '*': return Builder.CreateFMul(L, R, "multmp");
+  case '/': return Builder.CreateFDiv(L, R, "divtmp");
+  case '<':
+    L = Builder.CreateFCmpULT(L, R, "cmptmp");
+    // Convert bool 0/1 to double 0.0 or 1.0
+    return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+                                "booltmp");
+  default: break;
+  }
+  
+  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+  // a call to it.
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("binary")+Op));
+  assert(F && "binary operator not found!");
+  
+  Value *Ops[] = { L, R };
+  return Builder.CreateCall(F, Ops, "binop");
+}
+
+Value *CallExprAST::Codegen() {
+  // Look up the name in the global module table.
+  Function *CalleeF = TheHelper->getFunction(Callee);
+  if (CalleeF == 0)
+    return ErrorV("Unknown function referenced");
+  
+  // If argument mismatch error.
+  if (CalleeF->arg_size() != Args.size())
+    return ErrorV("Incorrect # arguments passed");
+
+  std::vector<Value*> ArgsV;
+  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+    ArgsV.push_back(Args[i]->Codegen());
+    if (ArgsV.back() == 0) return 0;
+  }
+  
+  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
+}
+
+Value *IfExprAST::Codegen() {
+  Value *CondV = Cond->Codegen();
+  if (CondV == 0) return 0;
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  CondV = Builder.CreateFCmpONE(CondV, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                "ifcond");
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+  
+  // Create blocks for the then and else cases.  Insert the 'then' block at the
+  // end of the function.
+  BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
+  BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
+  BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
+  
+  Builder.CreateCondBr(CondV, ThenBB, ElseBB);
+  
+  // Emit then value.
+  Builder.SetInsertPoint(ThenBB);
+  
+  Value *ThenV = Then->Codegen();
+  if (ThenV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+  ThenBB = Builder.GetInsertBlock();
+  
+  // Emit else block.
+  TheFunction->getBasicBlockList().push_back(ElseBB);
+  Builder.SetInsertPoint(ElseBB);
+  
+  Value *ElseV = Else->Codegen();
+  if (ElseV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+  ElseBB = Builder.GetInsertBlock();
+  
+  // Emit merge block.
+  TheFunction->getBasicBlockList().push_back(MergeBB);
+  Builder.SetInsertPoint(MergeBB);
+  PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
+                                  "iftmp");
+  
+  PN->addIncoming(ThenV, ThenBB);
+  PN->addIncoming(ElseV, ElseBB);
+  return PN;
+}
+
+Value *ForExprAST::Codegen() {
+  // Output this as:
+  //   var = alloca double
+  //   ...
+  //   start = startexpr
+  //   store start -> var
+  //   goto loop
+  // loop: 
+  //   ...
+  //   bodyexpr
+  //   ...
+  // loopend:
+  //   step = stepexpr
+  //   endcond = endexpr
+  //
+  //   curvar = load var
+  //   nextvar = curvar + step
+  //   store nextvar -> var
+  //   br endcond, loop, endloop
+  // outloop:
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Create an alloca for the variable in the entry block.
+  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+  
+  // Emit the start code first, without 'variable' in scope.
+  Value *StartVal = Start->Codegen();
+  if (StartVal == 0) return 0;
+  
+  // Store the value into the alloca.
+  Builder.CreateStore(StartVal, Alloca);
+  
+  // Make the new basic block for the loop header, inserting after current
+  // block.
+  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+  
+  // Insert an explicit fall through from the current block to the LoopBB.
+  Builder.CreateBr(LoopBB);
+
+  // Start insertion in LoopBB.
+  Builder.SetInsertPoint(LoopBB);
+  
+  // Within the loop, the variable is defined equal to the PHI node.  If it
+  // shadows an existing variable, we have to restore it, so save it now.
+  AllocaInst *OldVal = NamedValues[VarName];
+  NamedValues[VarName] = Alloca;
+  
+  // Emit the body of the loop.  This, like any other expr, can change the
+  // current BB.  Note that we ignore the value computed by the body, but don't
+  // allow an error.
+  if (Body->Codegen() == 0)
+    return 0;
+  
+  // Emit the step value.
+  Value *StepVal;
+  if (Step) {
+    StepVal = Step->Codegen();
+    if (StepVal == 0) return 0;
+  } else {
+    // If not specified, use 1.0.
+    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
+  }
+  
+  // Compute the end condition.
+  Value *EndCond = End->Codegen();
+  if (EndCond == 0) return EndCond;
+  
+  // Reload, increment, and restore the alloca.  This handles the case where
+  // the body of the loop mutates the variable.
+  Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
+  Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
+  Builder.CreateStore(NextVar, Alloca);
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  EndCond = Builder.CreateFCmpONE(EndCond, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                  "loopcond");
+  
+  // Create the "after loop" block and insert it.
+  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+  
+  // Insert the conditional branch into the end of LoopEndBB.
+  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
+  
+  // Any new code will be inserted in AfterBB.
+  Builder.SetInsertPoint(AfterBB);
+  
+  // Restore the unshadowed variable.
+  if (OldVal)
+    NamedValues[VarName] = OldVal;
+  else
+    NamedValues.erase(VarName);
+
+  
+  // for expr always returns 0.0.
+  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
+}
+
+Value *VarExprAST::Codegen() {
+  std::vector<AllocaInst *> OldBindings;
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Register all variables and emit their initializer.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
+    const std::string &VarName = VarNames[i].first;
+    ExprAST *Init = VarNames[i].second;
+    
+    // Emit the initializer before adding the variable to scope, this prevents
+    // the initializer from referencing the variable itself, and permits stuff
+    // like this:
+    //  var a = 1 in
+    //    var a = a in ...   # refers to outer 'a'.
+    Value *InitVal;
+    if (Init) {
+      InitVal = Init->Codegen();
+      if (InitVal == 0) return 0;
+    } else { // If not specified, use 0.0.
+      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
+    }
+    
+    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+    Builder.CreateStore(InitVal, Alloca);
+
+    // Remember the old variable binding so that we can restore the binding when
+    // we unrecurse.
+    OldBindings.push_back(NamedValues[VarName]);
+    
+    // Remember this binding.
+    NamedValues[VarName] = Alloca;
+  }
+  
+  // Codegen the body, now that all vars are in scope.
+  Value *BodyVal = Body->Codegen();
+  if (BodyVal == 0) return 0;
+  
+  // Pop all our variables from scope.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
+    NamedValues[VarNames[i].first] = OldBindings[i];
+
+  // Return the body computation.
+  return BodyVal;
+}
+
+Function *PrototypeAST::Codegen() {
+  // Make the function type:  double(double,double) etc.
+  std::vector<Type*> Doubles(Args.size(), 
+                             Type::getDoubleTy(getGlobalContext()));
+  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+                                       Doubles, false);
+
+  std::string FnName = MakeLegalFunctionName(Name);
+
+  Module* M = TheHelper->getModuleForNewFunction();
+
+  Function *F = Function::Create(FT, Function::ExternalLinkage, FnName, M);
+
+  // If F conflicted, there was already something named 'FnName'.  If it has a
+  // body, don't allow redefinition or reextern.
+  if (F->getName() != FnName) {
+    // Delete the one we just made and get the existing one.
+    F->eraseFromParent();
+    F = M->getFunction(Name);
+    
+    // If F already has a body, reject this.
+    if (!F->empty()) {
+      ErrorF("redefinition of function");
+      return 0;
+    }
+    
+    // If F took a different number of args, reject.
+    if (F->arg_size() != Args.size()) {
+      ErrorF("redefinition of function with different # args");
+      return 0;
+    }
+  }
+  
+  // Set names for all arguments.
+  unsigned Idx = 0;
+  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+       ++AI, ++Idx)
+    AI->setName(Args[Idx]);
+    
+  return F;
+}
+
+/// CreateArgumentAllocas - Create an alloca for each argument and register the
+/// argument in the symbol table so that references to it will succeed.
+void PrototypeAST::CreateArgumentAllocas(Function *F) {
+  Function::arg_iterator AI = F->arg_begin();
+  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
+    // Create an alloca for this variable.
+    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
+
+    // Store the initial value into the alloca.
+    Builder.CreateStore(AI, Alloca);
+
+    // Add arguments to variable symbol table.
+    NamedValues[Args[Idx]] = Alloca;
+  }
+}
+
+Function *FunctionAST::Codegen() {
+  NamedValues.clear();
+  
+  Function *TheFunction = Proto->Codegen();
+  if (TheFunction == 0)
+    return 0;
+  
+  // If this is an operator, install it.
+  if (Proto->isBinaryOp())
+    BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
+  
+  // Create a new basic block to start insertion into.
+  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+  Builder.SetInsertPoint(BB);
+  
+  // Add all arguments to the symbol table and create their allocas.
+  Proto->CreateArgumentAllocas(TheFunction);
+
+  if (Value *RetVal = Body->Codegen()) {
+    // Finish off the function.
+    Builder.CreateRet(RetVal);
+
+    // Validate the generated code, checking for consistency.
+    verifyFunction(*TheFunction);
+
+    return TheFunction;
+  }
+
+  // Error reading body, remove function.
+  TheFunction->eraseFromParent();
+
+  if (Proto->isBinaryOp())
+    BinopPrecedence.erase(Proto->getOperatorName());
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static void HandleDefinition() {
+  if (FunctionAST *F = ParseDefinition()) {
+    TheHelper->closeCurrentModule();
+    if (Function *LF = F->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read function definition:");
+      LF->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleExtern() {
+  if (PrototypeAST *P = ParseExtern()) {
+    if (Function *F = P->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read extern: ");
+      F->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleTopLevelExpression() {
+  // Evaluate a top-level expression into an anonymous function.
+  if (FunctionAST *F = ParseTopLevelExpr()) {
+    if (Function *LF = F->Codegen()) {
+      // JIT the function, returning a function pointer.
+      void *FPtr = TheHelper->getPointerToFunction(LF);
+      
+      // Cast it to the right type (takes no arguments, returns a double) so we
+      // can call it as a native function.
+      double (*FP)() = (double (*)())(intptr_t)FPtr;
+#ifdef MINIMAL_STDERR_OUTPUT
+      FP();
+#else
+      fprintf(stderr, "Evaluated to %f\n", FP());
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+  while (1) {
+#ifndef MINIMAL_STDERR_OUTPUT
+    fprintf(stderr, "ready> ");
+#endif
+    switch (CurTok) {
+    case tok_eof:    return;
+    case ';':        getNextToken(); break;  // ignore top-level semicolons.
+    case tok_def:    HandleDefinition(); break;
+    case tok_extern: HandleExtern(); break;
+    default:         HandleTopLevelExpression(); break;
+    }
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C" 
+double putchard(double X) {
+  putchar((char)X);
+  return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C" 
+double printd(double X) {
+  printf("%f", X);
+  return 0;
+}
+
+extern "C" 
+double printlf() {
+  printf("\n");
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Command line input file handler
+//===----------------------------------------------------------------------===//
+
+Module* parseInputIR(std::string InputFile) {
+  SMDiagnostic Err;
+  Module *M = ParseIRFile(InputFile, Err, getGlobalContext());
+  if (!M) {
+    Err.print("IR parsing failed: ", errs());
+    return NULL;
+  }
+
+  char ModID[256];
+  sprintf(ModID, "IR:%s", InputFile.c_str());
+  M->setModuleIdentifier(ModID);
+
+  TheHelper->addModule(M);
+  return M;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main(int argc, char **argv) {
+  InitializeNativeTarget();
+  InitializeNativeTargetAsmPrinter();
+  InitializeNativeTargetAsmParser();
+  LLVMContext &Context = getGlobalContext();
+
+  cl::ParseCommandLineOptions(argc, argv,
+                              "Kaleidoscope example program\n");
+
+  // Install standard binary operators.
+  // 1 is lowest precedence.
+  BinopPrecedence['='] = 2;
+  BinopPrecedence['<'] = 10;
+  BinopPrecedence['+'] = 20;
+  BinopPrecedence['-'] = 20;
+  BinopPrecedence['/'] = 40;
+  BinopPrecedence['*'] = 40;  // highest.
+
+  // Prime the first token.
+#ifndef MINIMAL_STDERR_OUTPUT
+  fprintf(stderr, "ready> ");
+#endif
+  getNextToken();
+
+  // Make the helper, which holds all the code.
+  TheHelper = new MCJITHelper(Context);
+
+  if (!InputIR.empty()) {
+    parseInputIR(InputIR);
+  }
+
+  // Run the main "interpreter loop" now.
+  MainLoop();
+
+#ifndef MINIMAL_STDERR_OUTPUT
+  // Print out all of the generated code.
+  TheHelper->dump();
+#endif
+
+  return 0;
+}
diff --git a/examples/Kaleidoscope/MCJIT/complete/Makefile b/examples/Kaleidoscope/MCJIT/complete/Makefile
new file mode 100644
index 0000000000..9e45d17a69
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/complete/Makefile
@@ -0,0 +1,4 @@
+all: toy
+
+toy : toy.cpp
+	clang++ toy.cpp -g -O3 -rdynamic -fno-rtti `llvm-config --cppflags --ldflags --libs core jit mcjit native irreader` -o toy
diff --git a/examples/Kaleidoscope/MCJIT/complete/README.txt b/examples/Kaleidoscope/MCJIT/complete/README.txt
new file mode 100644
index 0000000000..82bc397a4e
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/complete/README.txt
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===/
+//                          Kaleidoscope with MCJIT
+//===----------------------------------------------------------------------===//
+
+The files in this directory are meant to accompany the first in a series of
+three blog posts that describe the process of porting the Kaleidoscope tutorial
+to use the MCJIT execution engine instead of the older JIT engine.
+
+When the blog post is ready this file will be updated with a link to the post.
+
+The source code in this directory combines all previous versions, including the
+old JIT-based implementation, into a single file for easy comparison with
+command line options to select between the various possibilities.
+
+This directory contain a Makefile that allow the code to be built in a
+standalone manner, independent of the larger LLVM build infrastructure. To build
+the program you will need to have 'clang++' and 'llvm-config' in your path. If
+you attempt to build using the LLVM 3.3 release, some minor modifications will
+be required.
+
+This directory also contains a Python script that may be used to generate random
+input for the program and test scripts to capture data for rough performance
+comparisons.  Another Python script will split generated input files into
+definitions and function calls for the purpose of testing the IR input and
+caching facilities.
\ No newline at end of file
diff --git a/examples/Kaleidoscope/MCJIT/complete/genk-timing.py b/examples/Kaleidoscope/MCJIT/complete/genk-timing.py
new file mode 100644
index 0000000000..72591fe8bd
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/complete/genk-timing.py
@@ -0,0 +1,224 @@
+#!/usr/bin/env python
+
+import sys
+import random
+
+class TimingScriptGenerator:
+    """Used to generate a bash script which will invoke the toy and time it"""
+    def __init__(self, scriptname, outputname):
+        self.timeFile = outputname
+        self.shfile = open(scriptname, 'w')
+        self.shfile.write("echo \"\" > %s\n" % self.timeFile)
+
+    def writeTimingCall(self, filename, numFuncs, funcsCalled, totalCalls):
+        """Echo some comments and invoke both versions of toy"""
+        rootname = filename
+        if '.' in filename:
+            rootname = filename[:filename.rfind('.')]
+        self.shfile.write("echo \"%s: Calls %d of %d functions, %d total\" >> %s\n" % (filename, funcsCalled, numFuncs, totalCalls, self.timeFile))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT (original)\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy -suppress-prompts -use-mcjit=true -enable-lazy-compilation=false < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (filename, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT (lazy)\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy -suppress-prompts -use-mcjit=true -enable-lazy-compilation=true < %s > %s-mcjit-lazy.out 2> %s-mcjit-lazy.err\n" % (filename, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With JIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy -suppress-prompts -use-mcjit=false < %s > %s-jit.out 2> %s-jit.err\n" % (filename, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+
+class KScriptGenerator:
+    """Used to generate random Kaleidoscope code"""
+    def __init__(self, filename):
+        self.kfile = open(filename, 'w')
+        self.nextFuncNum = 1
+        self.lastFuncNum = None
+        self.callWeighting = 0.1
+        # A mapping of calls within functions with no duplicates
+        self.calledFunctionTable = {}
+        # A list of function calls which will actually be executed
+        self.calledFunctions = []
+        # A comprehensive mapping of calls within functions
+        # used for computing the total number of calls
+        self.comprehensiveCalledFunctionTable = {}
+        self.totalCallsExecuted = 0
+
+    def updateTotalCallCount(self, callee):
+        # Count this call
+        self.totalCallsExecuted += 1
+        # Then count all the functions it calls
+        if callee in self.comprehensiveCalledFunctionTable:
+            for child in self.comprehensiveCalledFunctionTable[callee]:
+                self.updateTotalCallCount(child)
+
+    def updateFunctionCallMap(self, caller, callee):
+        """Maintains a map of functions that are called from other functions"""
+        if not caller in self.calledFunctionTable:
+            self.calledFunctionTable[caller] = []
+        if not callee in self.calledFunctionTable[caller]:
+            self.calledFunctionTable[caller].append(callee)
+        if not caller in self.comprehensiveCalledFunctionTable:
+            self.comprehensiveCalledFunctionTable[caller] = []
+        self.comprehensiveCalledFunctionTable[caller].append(callee)
+
+    def updateCalledFunctionList(self, callee):
+        """Maintains a list of functions that will actually be called"""
+        # Update the total call count
+        self.updateTotalCallCount(callee)
+        # If this function is already in the list, don't do anything else
+        if callee in self.calledFunctions:
+            return
+        # Add this function to the list of those that will be called.
+        self.calledFunctions.append(callee)
+        # If this function calls other functions, add them too
+        if callee in self.calledFunctionTable:
+            for subCallee in self.calledFunctionTable[callee]:
+                self.updateCalledFunctionList(subCallee)
+
+    def setCallWeighting(self, weight):
+        """ Sets the probably of generating a function call"""
+        self.callWeighting = weight
+
+    def writeln(self, line):
+        self.kfile.write(line + '\n')
+
+    def writeComment(self, comment):
+        self.writeln('# ' + comment)
+
+    def writeEmptyLine(self):
+        self.writeln("")
+
+    def writePredefinedFunctions(self):
+        self.writeComment("Define ':' for sequencing: as a low-precedence operator that ignores operands")
+        self.writeComment("and just returns the RHS.")
+        self.writeln("def binary : 1 (x y) y;")
+        self.writeEmptyLine()
+        self.writeComment("Helper functions defined within toy")
+        self.writeln("extern putchard(x);")
+        self.writeln("extern printd(d);")
+        self.writeln("extern printlf();")
+        self.writeEmptyLine()
+        self.writeComment("Print the result of a function call")
+        self.writeln("def printresult(N Result)")
+        self.writeln("  # 'result('")
+        self.writeln("  putchard(114) : putchard(101) : putchard(115) : putchard(117) : putchard(108) : putchard(116) : putchard(40) :")
+        self.writeln("  printd(N) :");
+        self.writeln("  # ') = '")
+        self.writeln("  putchard(41) : putchard(32) : putchard(61) : putchard(32) :")
+        self.writeln("  printd(Result) :");
+        self.writeln("  printlf();")
+        self.writeEmptyLine()
+
+    def writeRandomOperation(self, LValue, LHS, RHS):
+        shouldCallFunc = (self.lastFuncNum > 2 and random.random() < self.callWeighting)
+        if shouldCallFunc:
+            funcToCall = random.randrange(1, self.lastFuncNum - 1)
+            self.updateFunctionCallMap(self.lastFuncNum, funcToCall)
+            self.writeln("  %s = func%d(%s, %s) :" % (LValue, funcToCall, LHS, RHS))
+        else:
+            possibleOperations = ["+", "-", "*", "/"]
+            operation = random.choice(possibleOperations)
+            if operation == "-":
+                # Don't let our intermediate value become zero
+                # This is complicated by the fact that '<' is our only comparison operator
+                self.writeln("  if %s < %s then" % (LHS, RHS))
+                self.writeln("    %s = %s %s %s" % (LValue, LHS, operation, RHS))
+                self.writeln("  else if %s < %s then" % (RHS, LHS))
+                self.writeln("    %s = %s %s %s" % (LValue, LHS, operation, RHS))
+                self.writeln("  else")
+                self.writeln("    %s = %s %s %f :" % (LValue, LHS, operation, random.uniform(1, 100)))
+            else:
+                self.writeln("  %s = %s %s %s :" % (LValue, LHS, operation, RHS))
+
+    def getNextFuncNum(self):
+        result = self.nextFuncNum
+        self.nextFuncNum += 1
+        self.lastFuncNum = result
+        return result
+
+    def writeFunction(self, elements):
+        funcNum = self.getNextFuncNum()
+        self.writeComment("Auto-generated function number %d" % funcNum)
+        self.writeln("def func%d(X Y)" % funcNum)
+        self.writeln("  var temp1 = X,")
+        self.writeln("      temp2 = Y,")
+        self.writeln("      temp3 in")
+        # Initialize the variable names to be rotated
+        first = "temp3"
+        second = "temp1"
+        third = "temp2"
+        # Write some random operations
+        for i in range(elements):
+            self.writeRandomOperation(first, second, third)
+            # Rotate the variables
+            temp = first
+            first = second
+            second = third
+            third = temp
+        self.writeln("  " + third + ";")
+        self.writeEmptyLine()
+
+    def writeFunctionCall(self):
+        self.writeComment("Call the last function")
+        arg1 = random.uniform(1, 100)
+        arg2 = random.uniform(1, 100)
+        self.writeln("printresult(%d, func%d(%f, %f) )" % (self.lastFuncNum, self.lastFuncNum, arg1, arg2))
+        self.writeEmptyLine()
+        self.updateCalledFunctionList(self.lastFuncNum)
+
+    def writeFinalFunctionCounts(self):
+        self.writeComment("Called %d of %d functions" % (len(self.calledFunctions), self.lastFuncNum))
+
+def generateKScript(filename, numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting, timingScript):
+    """ Generate a random Kaleidoscope script based on the given parameters """
+    print "Generating " + filename
+    print("  %d functions, %d elements per function, %d functions between execution" %
+          (numFuncs, elementsPerFunc, funcsBetweenExec))
+    print("  Call weighting = %f" % callWeighting)
+    script = KScriptGenerator(filename)
+    script.setCallWeighting(callWeighting)
+    script.writeComment("===========================================================================")
+    script.writeComment("Auto-generated script")
+    script.writeComment("  %d functions, %d elements per function, %d functions between execution"
+                         % (numFuncs, elementsPerFunc, funcsBetweenExec))
+    script.writeComment("  call weighting = %f" % callWeighting)
+    script.writeComment("===========================================================================")
+    script.writeEmptyLine()
+    script.writePredefinedFunctions()
+    funcsSinceLastExec = 0
+    for i in range(numFuncs):
+        script.writeFunction(elementsPerFunc)
+        funcsSinceLastExec += 1
+        if funcsSinceLastExec == funcsBetweenExec:
+            script.writeFunctionCall()
+            funcsSinceLastExec = 0
+    # Always end with a function call
+    if funcsSinceLastExec > 0:
+        script.writeFunctionCall()
+    script.writeEmptyLine()
+    script.writeFinalFunctionCounts()
+    funcsCalled = len(script.calledFunctions)
+    print "  Called %d of %d functions, %d total" % (funcsCalled, numFuncs, script.totalCallsExecuted)
+    timingScript.writeTimingCall(filename, numFuncs, funcsCalled, script.totalCallsExecuted)
+
+# Execution begins here
+random.seed()
+
+timingScript = TimingScriptGenerator("time-toy.sh", "timing-data.txt")
+
+dataSets = [(5000, 3,  50, 0.50), (5000, 10, 100, 0.10), (5000, 10, 5, 0.10), (5000, 10, 1, 0.0),
+            (1000, 3,  10, 0.50), (1000, 10, 100, 0.10), (1000, 10, 5, 0.10), (1000, 10, 1, 0.0),
+            ( 200, 3,   2, 0.50), ( 200, 10,  40, 0.10), ( 200, 10, 2, 0.10), ( 200, 10, 1, 0.0)]
+
+# Generate the code
+for (numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting) in dataSets:
+    filename = "test-%d-%d-%d-%d.k" % (numFuncs, elementsPerFunc, funcsBetweenExec, int(callWeighting * 100))
+    generateKScript(filename, numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting, timingScript)
+print "All done!"
diff --git a/examples/Kaleidoscope/MCJIT/complete/split-lib.py b/examples/Kaleidoscope/MCJIT/complete/split-lib.py
new file mode 100644
index 0000000000..f6bec0276d
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/complete/split-lib.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+
+class TimingScriptGenerator:
+    """Used to generate a bash script which will invoke the toy and time it"""
+    def __init__(self, scriptname, outputname):
+        self.shfile = open(scriptname, 'w')
+        self.timeFile = outputname
+        self.shfile.write("echo \"\" > %s\n" % self.timeFile)
+
+    def writeTimingCall(self, irname, callname):
+        """Echo some comments and invoke both versions of toy"""
+        rootname = irname
+        if '.' in irname:
+            rootname = irname[:irname.rfind('.')]
+        self.shfile.write("echo \"%s: Calls %s\" >> %s\n" % (callname, irname, self.timeFile))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy -suppress-prompts -use-mcjit=true -enable-lazy-compilation=true -use-object-cache -input-IR=%s < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (irname, callname, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT again\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy -suppress-prompts -use-mcjit=true -enable-lazy-compilation=true -use-object-cache -input-IR=%s < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (irname, callname, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With JIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy -suppress-prompts -use-mcjit=false -input-IR=%s < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (irname, callname, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+
+class LibScriptGenerator:
+    """Used to generate a bash script which will invoke the toy and time it"""
+    def __init__(self, filename):
+        self.shfile = open(filename, 'w')
+
+    def writeLibGenCall(self, libname, irname):
+        self.shfile.write("./toy -suppress-prompts -use-mcjit=false -dump-modules < %s 2> %s\n" % (libname, irname))
+
+def splitScript(inputname, libGenScript, timingScript):
+  rootname = inputname[:-2]
+  libname = rootname + "-lib.k"
+  irname = rootname + "-lib.ir"
+  callname = rootname + "-call.k"
+  infile = open(inputname, "r")
+  libfile = open(libname, "w")
+  callfile = open(callname, "w")
+  print "Splitting %s into %s and %s" % (inputname, callname, libname)
+  for line in infile:
+    if not line.startswith("#"):
+      if line.startswith("print"):
+        callfile.write(line)
+      else:
+        libfile.write(line)
+  libGenScript.writeLibGenCall(libname, irname)
+  timingScript.writeTimingCall(irname, callname)
+
+# Execution begins here
+libGenScript = LibScriptGenerator("make-libs.sh")
+timingScript = TimingScriptGenerator("time-lib.sh", "lib-timing.txt")
+
+script_list = ["test-5000-3-50-50.k", "test-5000-10-100-10.k", "test-5000-10-5-10.k", "test-5000-10-1-0.k", 
+               "test-1000-3-10-50.k", "test-1000-10-100-10.k", "test-1000-10-5-10.k", "test-1000-10-1-0.k",
+               "test-200-3-2-50.k", "test-200-10-40-10.k", "test-200-10-2-10.k", "test-200-10-1-0.k"]
+
+for script in script_list:
+  splitScript(script, libGenScript, timingScript)
+print "All done!"
diff --git a/examples/Kaleidoscope/MCJIT/complete/toy.cpp b/examples/Kaleidoscope/MCJIT/complete/toy.cpp
new file mode 100644
index 0000000000..da3f3b1769
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/complete/toy.cpp
@@ -0,0 +1,1710 @@
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/JIT.h"
+#include "llvm/ExecutionEngine/MCJIT.h"
+#include "llvm/ExecutionEngine/ObjectCache.h"
+#include "llvm/ExecutionEngine/SectionMemoryManager.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IRReader/IRReader.h"
+#include "llvm/PassManager.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Transforms/Scalar.h"
+#include <cstdio>
+#include <map>
+#include <string>
+#include <vector>
+
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Command-line options
+//===----------------------------------------------------------------------===//
+
+namespace {
+  cl::opt<std::string>
+  InputIR("input-IR",
+              cl::desc("Specify the name of an IR file to load for function definitions"),
+              cl::value_desc("input IR file name"));
+
+  cl::opt<bool>
+  VerboseOutput("verbose", 
+                cl::desc("Enable verbose output (results, IR, etc.) to stderr"),
+                cl::init(false));
+
+  cl::opt<bool>
+  SuppressPrompts("suppress-prompts",
+                  cl::desc("Disable printing the 'ready' prompt"),
+                  cl::init(false));
+
+  cl::opt<bool>
+  DumpModulesOnExit("dump-modules",
+                  cl::desc("Dump IR from modules to stderr on shutdown"),
+                  cl::init(false));
+
+  cl::opt<bool> UseMCJIT(
+    "use-mcjit", cl::desc("Use the MCJIT execution engine"),
+    cl::init(true));
+
+  cl::opt<bool> EnableLazyCompilation(
+    "enable-lazy-compilation", cl::desc("Enable lazy compilation when using the MCJIT engine"),
+    cl::init(true));
+
+  cl::opt<bool> UseObjectCache(
+    "use-object-cache", cl::desc("Enable use of the MCJIT object caching"),
+    cl::init(false));
+} // namespace
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+  tok_eof = -1,
+
+  // commands
+  tok_def = -2, tok_extern = -3,
+
+  // primary
+  tok_identifier = -4, tok_number = -5,
+
+  // control
+  tok_if = -6, tok_then = -7, tok_else = -8,
+  tok_for = -9, tok_in = -10,
+
+  // operators
+  tok_binary = -11, tok_unary = -12,
+
+  // var definition
+  tok_var = -13
+};
+
+static std::string IdentifierStr;  // Filled in if tok_identifier
+static double NumVal;              // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+  static int LastChar = ' ';
+
+  // Skip any whitespace.
+  while (isspace(LastChar))
+    LastChar = getchar();
+
+  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+    IdentifierStr = LastChar;
+    while (isalnum((LastChar = getchar())))
+      IdentifierStr += LastChar;
+
+    if (IdentifierStr == "def") return tok_def;
+    if (IdentifierStr == "extern") return tok_extern;
+    if (IdentifierStr == "if") return tok_if;
+    if (IdentifierStr == "then") return tok_then;
+    if (IdentifierStr == "else") return tok_else;
+    if (IdentifierStr == "for") return tok_for;
+    if (IdentifierStr == "in") return tok_in;
+    if (IdentifierStr == "binary") return tok_binary;
+    if (IdentifierStr == "unary") return tok_unary;
+    if (IdentifierStr == "var") return tok_var;
+    return tok_identifier;
+  }
+
+  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
+    std::string NumStr;
+    do {
+      NumStr += LastChar;
+      LastChar = getchar();
+    } while (isdigit(LastChar) || LastChar == '.');
+
+    NumVal = strtod(NumStr.c_str(), 0);
+    return tok_number;
+  }
+
+  if (LastChar == '#') {
+    // Comment until end of line.
+    do LastChar = getchar();
+    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
+
+    if (LastChar != EOF)
+      return gettok();
+  }
+
+  // Check for end of file.  Don't eat the EOF.
+  if (LastChar == EOF)
+    return tok_eof;
+
+  // Otherwise, just return the character as its ascii value.
+  int ThisChar = LastChar;
+  LastChar = getchar();
+  return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+/// ExprAST - Base class for all expression nodes.
+class ExprAST {
+public:
+  virtual ~ExprAST() {}
+  virtual Value *Codegen() = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+class NumberExprAST : public ExprAST {
+  double Val;
+public:
+  NumberExprAST(double val) : Val(val) {}
+  virtual Value *Codegen();
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+class VariableExprAST : public ExprAST {
+  std::string Name;
+public:
+  VariableExprAST(const std::string &name) : Name(name) {}
+  const std::string &getName() const { return Name; }
+  virtual Value *Codegen();
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+  char Opcode;
+  ExprAST *Operand;
+public:
+  UnaryExprAST(char opcode, ExprAST *operand)
+    : Opcode(opcode), Operand(operand) {}
+  virtual Value *Codegen();
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+class BinaryExprAST : public ExprAST {
+  char Op;
+  ExprAST *LHS, *RHS;
+public:
+  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
+    : Op(op), LHS(lhs), RHS(rhs) {}
+  virtual Value *Codegen();
+};
+
+/// CallExprAST - Expression class for function calls.
+class CallExprAST : public ExprAST {
+  std::string Callee;
+  std::vector<ExprAST*> Args;
+public:
+  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
+    : Callee(callee), Args(args) {}
+  virtual Value *Codegen();
+};
+
+/// IfExprAST - Expression class for if/then/else.
+class IfExprAST : public ExprAST {
+  ExprAST *Cond, *Then, *Else;
+public:
+  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
+  : Cond(cond), Then(then), Else(_else) {}
+  virtual Value *Codegen();
+};
+
+/// ForExprAST - Expression class for for/in.
+class ForExprAST : public ExprAST {
+  std::string VarName;
+  ExprAST *Start, *End, *Step, *Body;
+public:
+  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
+             ExprAST *step, ExprAST *body)
+    : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+  virtual Value *Codegen();
+};
+
+/// VarExprAST - Expression class for var/in
+class VarExprAST : public ExprAST {
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+  ExprAST *Body;
+public:
+  VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
+             ExprAST *body)
+  : VarNames(varnames), Body(body) {}
+
+  virtual Value *Codegen();
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+class PrototypeAST {
+  std::string Name;
+  std::vector<std::string> Args;
+  bool isOperator;
+  unsigned Precedence;  // Precedence if a binary op.
+public:
+  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
+               bool isoperator = false, unsigned prec = 0)
+  : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
+
+  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
+  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
+
+  char getOperatorName() const {
+    assert(isUnaryOp() || isBinaryOp());
+    return Name[Name.size()-1];
+  }
+
+  unsigned getBinaryPrecedence() const { return Precedence; }
+
+  Function *Codegen();
+
+  void CreateArgumentAllocas(Function *F);
+};
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+  PrototypeAST *Proto;
+  ExprAST *Body;
+public:
+  FunctionAST(PrototypeAST *proto, ExprAST *body)
+    : Proto(proto), Body(body) {}
+
+  Function *Codegen();
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
+/// token the parser is looking at.  getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+  return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+  if (!isascii(CurTok))
+    return -1;
+
+  // Make sure it's a declared binop.
+  int TokPrec = BinopPrecedence[CurTok];
+  if (TokPrec <= 0) return -1;
+  return TokPrec;
+}
+
+/// Error* - These are little helper functions for error handling.
+ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
+PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
+FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
+
+static ExprAST *ParseExpression();
+
+/// identifierexpr
+///   ::= identifier
+///   ::= identifier '(' expression* ')'
+static ExprAST *ParseIdentifierExpr() {
+  std::string IdName = IdentifierStr;
+
+  getNextToken();  // eat identifier.
+
+  if (CurTok != '(') // Simple variable ref.
+    return new VariableExprAST(IdName);
+
+  // Call.
+  getNextToken();  // eat (
+  std::vector<ExprAST*> Args;
+  if (CurTok != ')') {
+    while (1) {
+      ExprAST *Arg = ParseExpression();
+      if (!Arg) return 0;
+      Args.push_back(Arg);
+
+      if (CurTok == ')') break;
+
+      if (CurTok != ',')
+        return Error("Expected ')' or ',' in argument list");
+      getNextToken();
+    }
+  }
+
+  // Eat the ')'.
+  getNextToken();
+
+  return new CallExprAST(IdName, Args);
+}
+
+/// numberexpr ::= number
+static ExprAST *ParseNumberExpr() {
+  ExprAST *Result = new NumberExprAST(NumVal);
+  getNextToken(); // consume the number
+  return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static ExprAST *ParseParenExpr() {
+  getNextToken();  // eat (.
+  ExprAST *V = ParseExpression();
+  if (!V) return 0;
+
+  if (CurTok != ')')
+    return Error("expected ')'");
+  getNextToken();  // eat ).
+  return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static ExprAST *ParseIfExpr() {
+  getNextToken();  // eat the if.
+
+  // condition.
+  ExprAST *Cond = ParseExpression();
+  if (!Cond) return 0;
+
+  if (CurTok != tok_then)
+    return Error("expected then");
+  getNextToken();  // eat the then
+
+  ExprAST *Then = ParseExpression();
+  if (Then == 0) return 0;
+
+  if (CurTok != tok_else)
+    return Error("expected else");
+
+  getNextToken();
+
+  ExprAST *Else = ParseExpression();
+  if (!Else) return 0;
+
+  return new IfExprAST(Cond, Then, Else);
+}
+
+/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
+static ExprAST *ParseForExpr() {
+  getNextToken();  // eat the for.
+
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after for");
+
+  std::string IdName = IdentifierStr;
+  getNextToken();  // eat identifier.
+
+  if (CurTok != '=')
+    return Error("expected '=' after for");
+  getNextToken();  // eat '='.
+
+
+  ExprAST *Start = ParseExpression();
+  if (Start == 0) return 0;
+  if (CurTok != ',')
+    return Error("expected ',' after for start value");
+  getNextToken();
+
+  ExprAST *End = ParseExpression();
+  if (End == 0) return 0;
+
+  // The step value is optional.
+  ExprAST *Step = 0;
+  if (CurTok == ',') {
+    getNextToken();
+    Step = ParseExpression();
+    if (Step == 0) return 0;
+  }
+
+  if (CurTok != tok_in)
+    return Error("expected 'in' after for");
+  getNextToken();  // eat 'in'.
+
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+
+  return new ForExprAST(IdName, Start, End, Step, Body);
+}
+
+/// varexpr ::= 'var' identifier ('=' expression)?
+//                    (',' identifier ('=' expression)?)* 'in' expression
+static ExprAST *ParseVarExpr() {
+  getNextToken();  // eat the var.
+
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+
+  // At least one variable name is required.
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after var");
+
+  while (1) {
+    std::string Name = IdentifierStr;
+    getNextToken();  // eat identifier.
+
+    // Read the optional initializer.
+    ExprAST *Init = 0;
+    if (CurTok == '=') {
+      getNextToken(); // eat the '='.
+
+      Init = ParseExpression();
+      if (Init == 0) return 0;
+    }
+
+    VarNames.push_back(std::make_pair(Name, Init));
+
+    // End of var list, exit loop.
+    if (CurTok != ',') break;
+    getNextToken(); // eat the ','.
+
+    if (CurTok != tok_identifier)
+      return Error("expected identifier list after var");
+  }
+
+  // At this point, we have to have 'in'.
+  if (CurTok != tok_in)
+    return Error("expected 'in' keyword after 'var'");
+  getNextToken();  // eat 'in'.
+
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+
+  return new VarExprAST(VarNames, Body);
+}
+
+/// primary
+///   ::= identifierexpr
+///   ::= numberexpr
+///   ::= parenexpr
+///   ::= ifexpr
+///   ::= forexpr
+///   ::= varexpr
+static ExprAST *ParsePrimary() {
+  switch (CurTok) {
+  default: return Error("unknown token when expecting an expression");
+  case tok_identifier: return ParseIdentifierExpr();
+  case tok_number:     return ParseNumberExpr();
+  case '(':            return ParseParenExpr();
+  case tok_if:         return ParseIfExpr();
+  case tok_for:        return ParseForExpr();
+  case tok_var:        return ParseVarExpr();
+  }
+}
+
+/// unary
+///   ::= primary
+///   ::= '!' unary
+static ExprAST *ParseUnary() {
+  // If the current token is not an operator, it must be a primary expr.
+  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+    return ParsePrimary();
+
+  // If this is a unary operator, read it.
+  int Opc = CurTok;
+  getNextToken();
+  if (ExprAST *Operand = ParseUnary())
+    return new UnaryExprAST(Opc, Operand);
+  return 0;
+}
+
+/// binoprhs
+///   ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+  // If this is a binop, find its precedence.
+  while (1) {
+    int TokPrec = GetTokPrecedence();
+
+    // If this is a binop that binds at least as tightly as the current binop,
+    // consume it, otherwise we are done.
+    if (TokPrec < ExprPrec)
+      return LHS;
+
+    // Okay, we know this is a binop.
+    int BinOp = CurTok;
+    getNextToken();  // eat binop
+
+    // Parse the unary expression after the binary operator.
+    ExprAST *RHS = ParseUnary();
+    if (!RHS) return 0;
+
+    // If BinOp binds less tightly with RHS than the operator after RHS, let
+    // the pending operator take RHS as its LHS.
+    int NextPrec = GetTokPrecedence();
+    if (TokPrec < NextPrec) {
+      RHS = ParseBinOpRHS(TokPrec+1, RHS);
+      if (RHS == 0) return 0;
+    }
+
+    // Merge LHS/RHS.
+    LHS = new BinaryExprAST(BinOp, LHS, RHS);
+  }
+}
+
+/// expression
+///   ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+  ExprAST *LHS = ParseUnary();
+  if (!LHS) return 0;
+
+  return ParseBinOpRHS(0, LHS);
+}
+
+/// prototype
+///   ::= id '(' id* ')'
+///   ::= binary LETTER number? (id, id)
+///   ::= unary LETTER (id)
+static PrototypeAST *ParsePrototype() {
+  std::string FnName;
+
+  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+  unsigned BinaryPrecedence = 30;
+
+  switch (CurTok) {
+  default:
+    return ErrorP("Expected function name in prototype");
+  case tok_identifier:
+    FnName = IdentifierStr;
+    Kind = 0;
+    getNextToken();
+    break;
+  case tok_unary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected unary operator");
+    FnName = "unary";
+    FnName += (char)CurTok;
+    Kind = 1;
+    getNextToken();
+    break;
+  case tok_binary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected binary operator");
+    FnName = "binary";
+    FnName += (char)CurTok;
+    Kind = 2;
+    getNextToken();
+
+    // Read the precedence if present.
+    if (CurTok == tok_number) {
+      if (NumVal < 1 || NumVal > 100)
+        return ErrorP("Invalid precedecnce: must be 1..100");
+      BinaryPrecedence = (unsigned)NumVal;
+      getNextToken();
+    }
+    break;
+  }
+
+  if (CurTok != '(')
+    return ErrorP("Expected '(' in prototype");
+
+  std::vector<std::string> ArgNames;
+  while (getNextToken() == tok_identifier)
+    ArgNames.push_back(IdentifierStr);
+  if (CurTok != ')')
+    return ErrorP("Expected ')' in prototype");
+
+  // success.
+  getNextToken();  // eat ')'.
+
+  // Verify right number of names for operator.
+  if (Kind && ArgNames.size() != Kind)
+    return ErrorP("Invalid number of operands for operator");
+
+  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static FunctionAST *ParseDefinition() {
+  getNextToken();  // eat def.
+  PrototypeAST *Proto = ParsePrototype();
+  if (Proto == 0) return 0;
+
+  if (ExprAST *E = ParseExpression())
+    return new FunctionAST(Proto, E);
+  return 0;
+}
+
+/// toplevelexpr ::= expression
+static FunctionAST *ParseTopLevelExpr() {
+  if (ExprAST *E = ParseExpression()) {
+    // Make an anonymous proto.
+    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
+    return new FunctionAST(Proto, E);
+  }
+  return 0;
+}
+
+/// external ::= 'extern' prototype
+static PrototypeAST *ParseExtern() {
+  getNextToken();  // eat extern.
+  return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Quick and dirty hack
+//===----------------------------------------------------------------------===//
+
+// FIXME: Obviously we can do better than this
+std::string GenerateUniqueName(const char *root)
+{
+  static int i = 0;
+  char s[16];
+  sprintf(s, "%s%d", root, i++);
+  std::string S = s;
+  return S;
+}
+
+std::string MakeLegalFunctionName(std::string Name)
+{
+  std::string NewName;
+  if (!Name.length())
+      return GenerateUniqueName("anon_func_");
+
+  // Start with what we have
+  NewName = Name;
+
+  // Look for a numberic first character
+  if (NewName.find_first_of("0123456789") == 0) {
+    NewName.insert(0, 1, 'n');
+  }
+
+  // Replace illegal characters with their ASCII equivalent
+  std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+  size_t pos;
+  while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
+    char old_c = NewName.at(pos);
+    char new_str[16];
+    sprintf(new_str, "%d", (int)old_c);
+    NewName = NewName.replace(pos, 1, new_str);
+  }
+
+  return NewName;
+}
+
+//===----------------------------------------------------------------------===//
+// MCJIT object cache class
+//===----------------------------------------------------------------------===//
+
+class MCJITObjectCache : public ObjectCache {
+public:
+  MCJITObjectCache() {
+    // Set IR cache directory
+    sys::fs::current_path(CacheDir);
+    sys::path::append(CacheDir, "toy_object_cache");
+  }
+
+  virtual ~MCJITObjectCache() {
+  }
+
+  virtual void notifyObjectCompiled(const Module *M, const MemoryBuffer *Obj) {
+    // Get the ModuleID
+    const std::string ModuleID = M->getModuleIdentifier();
+
+    // If we've flagged this as an IR file, cache it
+    if (0 == ModuleID.compare(0, 3, "IR:")) {
+      std::string IRFileName = ModuleID.substr(3);
+      SmallString<128>IRCacheFile = CacheDir;
+      sys::path::append(IRCacheFile, IRFileName);
+      if (!sys::fs::exists(CacheDir.str()) && sys::fs::create_directory(CacheDir.str())) {
+        fprintf(stderr, "Unable to create cache directory\n");
+        return;
+      }
+      std::string ErrStr;
+      raw_fd_ostream IRObjectFile(IRCacheFile.c_str(), ErrStr, raw_fd_ostream::F_Binary);
+      IRObjectFile << Obj->getBuffer();
+    }
+  }
+
+  // MCJIT will call this function before compiling any module
+  // MCJIT takes ownership of both the MemoryBuffer object and the memory
+  // to which it refers.
+  virtual MemoryBuffer* getObject(const Module* M) {
+    // Get the ModuleID
+    const std::string ModuleID = M->getModuleIdentifier();
+
+    // If we've flagged this as an IR file, cache it
+    if (0 == ModuleID.compare(0, 3, "IR:")) {
+      std::string IRFileName = ModuleID.substr(3);
+      SmallString<128> IRCacheFile = CacheDir;
+      sys::path::append(IRCacheFile, IRFileName);
+      if (!sys::fs::exists(IRCacheFile.str())) {
+        // This file isn't in our cache
+        return NULL;
+      }
+      OwningPtr<MemoryBuffer> IRObjectBuffer;
+      MemoryBuffer::getFile(IRCacheFile.c_str(), IRObjectBuffer, -1, false);
+      // MCJIT will want to write into this buffer, and we don't want that
+      // because the file has probably just been mmapped.  Instead we make
+      // a copy.  The filed-based buffer will be released when it goes
+      // out of scope.
+      return MemoryBuffer::getMemBufferCopy(IRObjectBuffer->getBuffer());
+    }
+
+    return NULL;
+  }
+
+private:
+  SmallString<128> CacheDir;
+};
+
+//===----------------------------------------------------------------------===//
+// IR input file handler
+//===----------------------------------------------------------------------===//
+
+Module* parseInputIR(std::string InputFile, LLVMContext &Context) {
+  SMDiagnostic Err;
+  Module *M = ParseIRFile(InputFile, Err, Context);
+  if (!M) {
+    Err.print("IR parsing failed: ", errs());
+    return NULL;
+  }
+
+  char ModID[256];
+  sprintf(ModID, "IR:%s", InputFile.c_str());
+  M->setModuleIdentifier(ModID);
+  return M;
+}
+
+//===----------------------------------------------------------------------===//
+// Helper class for execution engine abstraction
+//===----------------------------------------------------------------------===//
+
+class BaseHelper
+{
+public:
+  BaseHelper() {}
+  virtual ~BaseHelper() {}
+
+  virtual Function *getFunction(const std::string FnName) = 0;
+  virtual Module *getModuleForNewFunction() = 0;
+  virtual void *getPointerToFunction(Function* F) = 0;
+  virtual void *getPointerToNamedFunction(const std::string &Name) = 0;
+  virtual void closeCurrentModule() = 0;
+  virtual void runFPM(Function &F) = 0;
+  virtual void dump();
+};
+
+//===----------------------------------------------------------------------===//
+// Helper class for JIT execution engine
+//===----------------------------------------------------------------------===//
+
+class JITHelper : public BaseHelper {
+public:
+  JITHelper(LLVMContext &Context) {
+    // Make the module, which holds all the code.
+    if (!InputIR.empty()) {
+      TheModule = parseInputIR(InputIR, Context);
+    } else {
+      TheModule = new Module("my cool jit", Context);
+    }
+
+    // Create the JIT.  This takes ownership of the module.
+    std::string ErrStr;
+    TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create();
+    if (!TheExecutionEngine) {
+      fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
+      exit(1);
+    }
+
+    TheFPM = new FunctionPassManager(TheModule);
+
+    // Set up the optimizer pipeline.  Start with registering info about how the
+    // target lays out data structures.
+    TheFPM->add(new DataLayout(*TheExecutionEngine->getDataLayout()));
+    // Provide basic AliasAnalysis support for GVN.
+    TheFPM->add(createBasicAliasAnalysisPass());
+    // Promote allocas to registers.
+    TheFPM->add(createPromoteMemoryToRegisterPass());
+    // Do simple "peephole" optimizations and bit-twiddling optzns.
+    TheFPM->add(createInstructionCombiningPass());
+    // Reassociate expressions.
+    TheFPM->add(createReassociatePass());
+    // Eliminate Common SubExpressions.
+    TheFPM->add(createGVNPass());
+    // Simplify the control flow graph (deleting unreachable blocks, etc).
+    TheFPM->add(createCFGSimplificationPass());
+
+    TheFPM->doInitialization();
+  }
+
+  virtual ~JITHelper() {
+    if (TheFPM)
+      delete TheFPM;
+    if (TheExecutionEngine)
+      delete TheExecutionEngine;
+  }
+
+  virtual Function *getFunction(const std::string FnName) {
+    assert(TheModule);
+    return TheModule->getFunction(FnName);
+  }
+
+  virtual Module *getModuleForNewFunction() {
+    assert(TheModule);
+    return TheModule;
+  }
+
+  virtual void *getPointerToFunction(Function* F) {
+    assert(TheExecutionEngine);
+    return TheExecutionEngine->getPointerToFunction(F);
+  }
+
+  virtual void *getPointerToNamedFunction(const std::string &Name) {
+    return TheExecutionEngine->getPointerToNamedFunction(Name);
+  }
+
+  virtual void runFPM(Function &F) {
+    assert(TheFPM);
+    TheFPM->run(F);
+  }
+
+  virtual void closeCurrentModule() {
+    // This should never be called for JIT
+    assert(false);
+  }
+
+  virtual void dump() {
+    assert(TheModule);
+    TheModule->dump();
+  }
+
+private:
+  Module *TheModule;
+  ExecutionEngine *TheExecutionEngine;
+  FunctionPassManager *TheFPM;
+};
+
+//===----------------------------------------------------------------------===//
+// MCJIT helper class
+//===----------------------------------------------------------------------===//
+
+class MCJITHelper : public BaseHelper
+{
+public:
+  MCJITHelper(LLVMContext& C) : Context(C), CurrentModule(NULL) {
+    if (!InputIR.empty()) {
+      Module *M = parseInputIR(InputIR, Context);
+      Modules.push_back(M);
+      if (!EnableLazyCompilation)
+        compileModule(M);
+    }
+  }
+  ~MCJITHelper();
+
+  Function *getFunction(const std::string FnName);
+  Module *getModuleForNewFunction();
+  void *getPointerToFunction(Function* F);
+  void *getPointerToNamedFunction(const std::string &Name);
+  void closeCurrentModule();
+  virtual void runFPM(Function &F) {} // Not needed, see compileModule
+  void dump();
+
+protected:
+  ExecutionEngine *compileModule(Module *M);
+
+private:
+  typedef std::vector<Module*> ModuleVector;
+
+  MCJITObjectCache OurObjectCache;
+
+  LLVMContext  &Context;
+  ModuleVector  Modules;
+
+  std::map<Module *, ExecutionEngine *> EngineMap;
+
+  Module       *CurrentModule;
+};
+
+class HelpingMemoryManager : public SectionMemoryManager
+{
+  HelpingMemoryManager(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+  void operator=(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+
+public:
+  HelpingMemoryManager(MCJITHelper *Helper) : MasterHelper(Helper) {}
+  virtual ~HelpingMemoryManager() {}
+
+  /// This method returns the address of the specified function.
+  /// Our implementation will attempt to find functions in other
+  /// modules associated with the MCJITHelper to cross link functions
+  /// from one generated module to another.
+  ///
+  /// If \p AbortOnFailure is false and no function with the given name is
+  /// found, this function returns a null pointer. Otherwise, it prints a
+  /// message to stderr and aborts.
+  virtual void *getPointerToNamedFunction(const std::string &Name,
+                                          bool AbortOnFailure = true);
+private:
+  MCJITHelper *MasterHelper;
+};
+
+void *HelpingMemoryManager::getPointerToNamedFunction(const std::string &Name,
+                                        bool AbortOnFailure)
+{
+  // Try the standard symbol resolution first, but ask it not to abort.
+  void *pfn = RTDyldMemoryManager::getPointerToNamedFunction(Name, false);
+  if (pfn)
+    return pfn;
+
+  pfn = MasterHelper->getPointerToNamedFunction(Name);
+  if (!pfn && AbortOnFailure)
+    report_fatal_error("Program used external function '" + Name +
+                        "' which could not be resolved!");
+  return pfn;
+}
+
+MCJITHelper::~MCJITHelper()
+{
+  // Walk the vector of modules.
+  ModuleVector::iterator it, end;
+  for (it = Modules.begin(), end = Modules.end();
+       it != end; ++it) {
+    // See if we have an execution engine for this module.
+    std::map<Module*, ExecutionEngine*>::iterator mapIt = EngineMap.find(*it);
+    // If we have an EE, the EE owns the module so just delete the EE.
+    if (mapIt != EngineMap.end()) {
+      delete mapIt->second;
+    } else {
+      // Otherwise, we still own the module.  Delete it now.
+      delete *it;
+    }
+  }
+}
+
+Function *MCJITHelper::getFunction(const std::string FnName) {
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    Function *F = (*it)->getFunction(FnName);
+    if (F) {
+      if (*it == CurrentModule)
+          return F;
+
+      assert(CurrentModule != NULL);
+
+      // This function is in a module that has already been JITed.
+      // We just need a prototype for external linkage.
+      Function *PF = CurrentModule->getFunction(FnName);
+      if (PF && !PF->empty()) {
+        ErrorF("redefinition of function across modules");
+        return 0;
+      }
+
+      // If we don't have a prototype yet, create one.
+      if (!PF)
+        PF = Function::Create(F->getFunctionType(),
+                                      Function::ExternalLinkage,
+                                      FnName,
+                                      CurrentModule);
+      return PF;
+    }
+  }
+  return NULL;
+}
+
+Module *MCJITHelper::getModuleForNewFunction() {
+  // If we have a Module that hasn't been JITed, use that.
+  if (CurrentModule)
+    return CurrentModule;
+
+  // Otherwise create a new Module.
+  std::string ModName = GenerateUniqueName("mcjit_module_");
+  Module *M = new Module(ModName, Context);
+  Modules.push_back(M);
+  CurrentModule = M;
+
+  return M;
+}
+
+ExecutionEngine *MCJITHelper::compileModule(Module *M) {
+  assert(EngineMap.find(M) == EngineMap.end());
+
+  if (M == CurrentModule)
+    closeCurrentModule();
+
+  std::string ErrStr;
+  ExecutionEngine *EE = EngineBuilder(M)
+                            .setErrorStr(&ErrStr)
+                            .setUseMCJIT(true)
+                            .setMCJITMemoryManager(new HelpingMemoryManager(this))
+                            .create();
+  if (!EE) {
+    fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
+    exit(1);
+  }
+
+  if (UseObjectCache)
+    EE->setObjectCache(&OurObjectCache);
+  // Get the ModuleID so we can identify IR input files
+  const std::string ModuleID = M->getModuleIdentifier();
+
+  // If we've flagged this as an IR file, it doesn't need function passes run.
+  if (0 != ModuleID.compare(0, 3, "IR:")) {
+    FunctionPassManager *FPM = 0;
+
+    // Create a FPM for this module
+    FPM = new FunctionPassManager(M);
+
+    // Set up the optimizer pipeline.  Start with registering info about how the
+    // target lays out data structures.
+    FPM->add(new DataLayout(*EE->getDataLayout()));
+    // Provide basic AliasAnalysis support for GVN.
+    FPM->add(createBasicAliasAnalysisPass());
+    // Promote allocas to registers.
+    FPM->add(createPromoteMemoryToRegisterPass());
+    // Do simple "peephole" optimizations and bit-twiddling optzns.
+    FPM->add(createInstructionCombiningPass());
+    // Reassociate expressions.
+    FPM->add(createReassociatePass());
+    // Eliminate Common SubExpressions.
+    FPM->add(createGVNPass());
+    // Simplify the control flow graph (deleting unreachable blocks, etc).
+    FPM->add(createCFGSimplificationPass());
+
+    FPM->doInitialization();
+
+    // For each function in the module
+    Module::iterator it;
+    Module::iterator end = M->end();
+    for (it = M->begin(); it != end; ++it) {
+      // Run the FPM on this function
+      FPM->run(*it);
+    }
+
+    delete FPM;
+  }
+
+  EE->finalizeObject();
+
+  // Store this engine
+  EngineMap[M] = EE;
+
+  return EE;
+}
+
+void *MCJITHelper::getPointerToFunction(Function* F) {
+  // Look for this function in an existing module
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  std::string FnName = F->getName();
+  for (it = begin; it != end; ++it) {
+    Function *MF = (*it)->getFunction(FnName);
+    if (MF == F) {
+      std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
+      if (eeIt != EngineMap.end()) {
+        void *P = eeIt->second->getPointerToFunction(F);
+        if (P)
+          return P;
+      } else {
+        ExecutionEngine *EE = compileModule(*it);
+        void *P = EE->getPointerToFunction(F);
+        if (P)
+          return P;
+      }
+    }
+  }
+  return NULL;
+}
+
+void MCJITHelper::closeCurrentModule() {
+    // If we have an open module (and we should), pack it up
+  if (CurrentModule) {
+    CurrentModule = NULL;
+  }
+}
+
+void *MCJITHelper::getPointerToNamedFunction(const std::string &Name)
+{
+  // Look for the functions in our modules, compiling only as necessary
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    Function *F = (*it)->getFunction(Name);
+    if (F && !F->empty()) {
+      std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
+      if (eeIt != EngineMap.end()) {
+        void *P = eeIt->second->getPointerToFunction(F);
+        if (P)
+          return P;
+      } else {
+        ExecutionEngine *EE = compileModule(*it);
+        void *P = EE->getPointerToFunction(F);
+        if (P)
+          return P;
+      }
+    }
+  }
+  return NULL;
+}
+
+void MCJITHelper::dump()
+{
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it)
+    (*it)->dump();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+static BaseHelper *TheHelper;
+static IRBuilder<> Builder(getGlobalContext());
+static std::map<std::string, AllocaInst*> NamedValues;
+
+Value *ErrorV(const char *Str) { Error(Str); return 0; }
+
+/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
+/// the function.  This is used for mutable variables etc.
+static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
+                                          const std::string &VarName) {
+  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
+                 TheFunction->getEntryBlock().begin());
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+                           VarName.c_str());
+}
+
+Value *NumberExprAST::Codegen() {
+  return ConstantFP::get(getGlobalContext(), APFloat(Val));
+}
+
+Value *VariableExprAST::Codegen() {
+  // Look this variable up in the function.
+  Value *V = NamedValues[Name];
+  if (V == 0) return ErrorV("Unknown variable name");
+
+  // Load the value.
+  return Builder.CreateLoad(V, Name.c_str());
+}
+
+Value *UnaryExprAST::Codegen() {
+  Value *OperandV = Operand->Codegen();
+  if (OperandV == 0) return 0;
+  Function *F;
+  if (UseMCJIT)
+    F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
+  else
+    F = TheHelper->getFunction(std::string("unary")+Opcode);
+  if (F == 0)
+    return ErrorV("Unknown unary operator");
+
+  return Builder.CreateCall(F, OperandV, "unop");
+}
+
+Value *BinaryExprAST::Codegen() {
+  // Special case '=' because we don't want to emit the LHS as an expression.
+  if (Op == '=') {
+    // Assignment requires the LHS to be an identifier.
+    // This assume we're building without RTTI because LLVM builds that way by
+    // default.  If you build LLVM with RTTI this can be changed to a
+    // dynamic_cast for automatic error checking.
+    VariableExprAST *LHSE = reinterpret_cast<VariableExprAST*>(LHS);
+    if (!LHSE)
+      return ErrorV("destination of '=' must be a variable");
+    // Codegen the RHS.
+    Value *Val = RHS->Codegen();
+    if (Val == 0) return 0;
+
+    // Look up the name.
+    Value *Variable = NamedValues[LHSE->getName()];
+    if (Variable == 0) return ErrorV("Unknown variable name");
+
+    Builder.CreateStore(Val, Variable);
+    return Val;
+  }
+
+  Value *L = LHS->Codegen();
+  Value *R = RHS->Codegen();
+  if (L == 0 || R == 0) return 0;
+
+  switch (Op) {
+  case '+': return Builder.CreateFAdd(L, R, "addtmp");
+  case '-': return Builder.CreateFSub(L, R, "subtmp");
+  case '*': return Builder.CreateFMul(L, R, "multmp");
+  case '/': return Builder.CreateFDiv(L, R, "divtmp");
+  case '<':
+    L = Builder.CreateFCmpULT(L, R, "cmptmp");
+    // Convert bool 0/1 to double 0.0 or 1.0
+    return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+                                "booltmp");
+  default: break;
+  }
+
+  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+  // a call to it.
+  Function *F;
+  if (UseMCJIT)
+    F = TheHelper->getFunction(MakeLegalFunctionName(std::string("binary")+Op));
+  else
+    F = TheHelper->getFunction(std::string("binary")+Op);
+  assert(F && "binary operator not found!");
+
+  Value *Ops[] = { L, R };
+  return Builder.CreateCall(F, Ops, "binop");
+}
+
+Value *CallExprAST::Codegen() {
+  // Look up the name in the global module table.
+  Function *CalleeF = TheHelper->getFunction(Callee);
+  if (CalleeF == 0) {
+    char error_str[64];
+    sprintf(error_str, "Unknown function referenced %s", Callee.c_str());
+    return ErrorV(error_str);
+  }
+
+  // If argument mismatch error.
+  if (CalleeF->arg_size() != Args.size())
+    return ErrorV("Incorrect # arguments passed");
+
+  std::vector<Value*> ArgsV;
+  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+    ArgsV.push_back(Args[i]->Codegen());
+    if (ArgsV.back() == 0) return 0;
+  }
+
+  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
+}
+
+Value *IfExprAST::Codegen() {
+  Value *CondV = Cond->Codegen();
+  if (CondV == 0) return 0;
+
+  // Convert condition to a bool by comparing equal to 0.0.
+  CondV = Builder.CreateFCmpONE(CondV,
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                "ifcond");
+
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Create blocks for the then and else cases.  Insert the 'then' block at the
+  // end of the function.
+  BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
+  BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
+  BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
+
+  Builder.CreateCondBr(CondV, ThenBB, ElseBB);
+
+  // Emit then value.
+  Builder.SetInsertPoint(ThenBB);
+
+  Value *ThenV = Then->Codegen();
+  if (ThenV == 0) return 0;
+
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+  ThenBB = Builder.GetInsertBlock();
+
+  // Emit else block.
+  TheFunction->getBasicBlockList().push_back(ElseBB);
+  Builder.SetInsertPoint(ElseBB);
+
+  Value *ElseV = Else->Codegen();
+  if (ElseV == 0) return 0;
+
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+  ElseBB = Builder.GetInsertBlock();
+
+  // Emit merge block.
+  TheFunction->getBasicBlockList().push_back(MergeBB);
+  Builder.SetInsertPoint(MergeBB);
+  PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
+                                  "iftmp");
+
+  PN->addIncoming(ThenV, ThenBB);
+  PN->addIncoming(ElseV, ElseBB);
+  return PN;
+}
+
+Value *ForExprAST::Codegen() {
+  // Output this as:
+  //   var = alloca double
+  //   ...
+  //   start = startexpr
+  //   store start -> var
+  //   goto loop
+  // loop:
+  //   ...
+  //   bodyexpr
+  //   ...
+  // loopend:
+  //   step = stepexpr
+  //   endcond = endexpr
+  //
+  //   curvar = load var
+  //   nextvar = curvar + step
+  //   store nextvar -> var
+  //   br endcond, loop, endloop
+  // outloop:
+
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Create an alloca for the variable in the entry block.
+  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+
+  // Emit the start code first, without 'variable' in scope.
+  Value *StartVal = Start->Codegen();
+  if (StartVal == 0) return 0;
+
+  // Store the value into the alloca.
+  Builder.CreateStore(StartVal, Alloca);
+
+  // Make the new basic block for the loop header, inserting after current
+  // block.
+  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+
+  // Insert an explicit fall through from the current block to the LoopBB.
+  Builder.CreateBr(LoopBB);
+
+  // Start insertion in LoopBB.
+  Builder.SetInsertPoint(LoopBB);
+
+  // Within the loop, the variable is defined equal to the PHI node.  If it
+  // shadows an existing variable, we have to restore it, so save it now.
+  AllocaInst *OldVal = NamedValues[VarName];
+  NamedValues[VarName] = Alloca;
+
+  // Emit the body of the loop.  This, like any other expr, can change the
+  // current BB.  Note that we ignore the value computed by the body, but don't
+  // allow an error.
+  if (Body->Codegen() == 0)
+    return 0;
+
+  // Emit the step value.
+  Value *StepVal;
+  if (Step) {
+    StepVal = Step->Codegen();
+    if (StepVal == 0) return 0;
+  } else {
+    // If not specified, use 1.0.
+    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
+  }
+
+  // Compute the end condition.
+  Value *EndCond = End->Codegen();
+  if (EndCond == 0) return EndCond;
+
+  // Reload, increment, and restore the alloca.  This handles the case where
+  // the body of the loop mutates the variable.
+  Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
+  Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
+  Builder.CreateStore(NextVar, Alloca);
+
+  // Convert condition to a bool by comparing equal to 0.0.
+  EndCond = Builder.CreateFCmpONE(EndCond,
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                  "loopcond");
+
+  // Create the "after loop" block and insert it.
+  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+
+  // Insert the conditional branch into the end of LoopEndBB.
+  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
+
+  // Any new code will be inserted in AfterBB.
+  Builder.SetInsertPoint(AfterBB);
+
+  // Restore the unshadowed variable.
+  if (OldVal)
+    NamedValues[VarName] = OldVal;
+  else
+    NamedValues.erase(VarName);
+
+
+  // for expr always returns 0.0.
+  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
+}
+
+Value *VarExprAST::Codegen() {
+  std::vector<AllocaInst *> OldBindings;
+
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Register all variables and emit their initializer.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
+    const std::string &VarName = VarNames[i].first;
+    ExprAST *Init = VarNames[i].second;
+
+    // Emit the initializer before adding the variable to scope, this prevents
+    // the initializer from referencing the variable itself, and permits stuff
+    // like this:
+    //  var a = 1 in
+    //    var a = a in ...   # refers to outer 'a'.
+    Value *InitVal;
+    if (Init) {
+      InitVal = Init->Codegen();
+      if (InitVal == 0) return 0;
+    } else { // If not specified, use 0.0.
+      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
+    }
+
+    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+    Builder.CreateStore(InitVal, Alloca);
+
+    // Remember the old variable binding so that we can restore the binding when
+    // we unrecurse.
+    OldBindings.push_back(NamedValues[VarName]);
+
+    // Remember this binding.
+    NamedValues[VarName] = Alloca;
+  }
+
+  // Codegen the body, now that all vars are in scope.
+  Value *BodyVal = Body->Codegen();
+  if (BodyVal == 0) return 0;
+
+  // Pop all our variables from scope.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
+    NamedValues[VarNames[i].first] = OldBindings[i];
+
+  // Return the body computation.
+  return BodyVal;
+}
+
+Function *PrototypeAST::Codegen() {
+  // Make the function type:  double(double,double) etc.
+  std::vector<Type*> Doubles(Args.size(),
+                             Type::getDoubleTy(getGlobalContext()));
+  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+                                       Doubles, false);
+
+  std::string FnName;
+  if (UseMCJIT)
+    FnName = MakeLegalFunctionName(Name);
+  else
+    FnName = Name;
+
+  Module* M = TheHelper->getModuleForNewFunction();
+  Function *F = Function::Create(FT, Function::ExternalLinkage, FnName, M);
+
+  // FIXME: Implement duplicate function detection.
+  // The check below will only work if the duplicate is in the open module.
+  // If F conflicted, there was already something named 'Name'.  If it has a
+  // body, don't allow redefinition or reextern.
+  if (F->getName() != FnName) {
+    // Delete the one we just made and get the existing one.
+    F->eraseFromParent();
+    F = M->getFunction(FnName);
+    // If F already has a body, reject this.
+    if (!F->empty()) {
+      ErrorF("redefinition of function");
+      return 0;
+    }
+    // If F took a different number of args, reject.
+    if (F->arg_size() != Args.size()) {
+      ErrorF("redefinition of function with different # args");
+      return 0;
+    }
+  }
+
+  // Set names for all arguments.
+  unsigned Idx = 0;
+  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+       ++AI, ++Idx)
+    AI->setName(Args[Idx]);
+
+  return F;
+}
+
+/// CreateArgumentAllocas - Create an alloca for each argument and register the
+/// argument in the symbol table so that references to it will succeed.
+void PrototypeAST::CreateArgumentAllocas(Function *F) {
+  Function::arg_iterator AI = F->arg_begin();
+  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
+    // Create an alloca for this variable.
+    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
+
+    // Store the initial value into the alloca.
+    Builder.CreateStore(AI, Alloca);
+
+    // Add arguments to variable symbol table.
+    NamedValues[Args[Idx]] = Alloca;
+  }
+}
+
+Function *FunctionAST::Codegen() {
+  NamedValues.clear();
+
+  Function *TheFunction = Proto->Codegen();
+  if (TheFunction == 0)
+    return 0;
+
+  // If this is an operator, install it.
+  if (Proto->isBinaryOp())
+    BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
+
+  // Create a new basic block to start insertion into.
+  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+  Builder.SetInsertPoint(BB);
+
+  // Add all arguments to the symbol table and create their allocas.
+  Proto->CreateArgumentAllocas(TheFunction);
+
+  if (Value *RetVal = Body->Codegen()) {
+    // Finish off the function.
+    Builder.CreateRet(RetVal);
+
+    // Validate the generated code, checking for consistency.
+    verifyFunction(*TheFunction);
+
+    // Optimize the function.
+    if (!UseMCJIT)
+      TheHelper->runFPM(*TheFunction);
+
+    return TheFunction;
+  }
+
+  // Error reading body, remove function.
+  TheFunction->eraseFromParent();
+
+  if (Proto->isBinaryOp())
+    BinopPrecedence.erase(Proto->getOperatorName());
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static void HandleDefinition() {
+  if (FunctionAST *F = ParseDefinition()) {
+    if (UseMCJIT && EnableLazyCompilation)
+      TheHelper->closeCurrentModule();
+    Function *LF = F->Codegen();
+    if (LF && VerboseOutput) {
+      fprintf(stderr, "Read function definition:");
+      LF->dump();
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleExtern() {
+  if (PrototypeAST *P = ParseExtern()) {
+    Function *F = P->Codegen();
+    if (F && VerboseOutput) {
+      fprintf(stderr, "Read extern: ");
+      F->dump();
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleTopLevelExpression() {
+  // Evaluate a top-level expression into an anonymous function.
+  if (FunctionAST *F = ParseTopLevelExpr()) {
+    if (Function *LF = F->Codegen()) {
+      // JIT the function, returning a function pointer.
+      void *FPtr = TheHelper->getPointerToFunction(LF);
+      // Cast it to the right type (takes no arguments, returns a double) so we
+      // can call it as a native function.
+      double (*FP)() = (double (*)())(intptr_t)FPtr;
+      double Result = FP();
+      if (VerboseOutput)
+        fprintf(stderr, "Evaluated to %f\n", Result);
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+  while (1) {
+    if (!SuppressPrompts)
+      fprintf(stderr, "ready> ");
+    switch (CurTok) {
+    case tok_eof:    return;
+    case ';':        getNextToken(); break;  // ignore top-level semicolons.
+    case tok_def:    HandleDefinition(); break;
+    case tok_extern: HandleExtern(); break;
+    default:         HandleTopLevelExpression(); break;
+    }
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C"
+double putchard(double X) {
+  putchar((char)X);
+  return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C"
+double printd(double X) {
+  printf("%f", X);
+  return 0;
+}
+
+extern "C"
+double printlf() {
+  printf("\n");
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main(int argc, char **argv) {
+  InitializeNativeTarget();
+  if (UseMCJIT) {
+    InitializeNativeTargetAsmPrinter();
+    InitializeNativeTargetAsmParser();
+  }
+  LLVMContext &Context = getGlobalContext();
+
+  cl::ParseCommandLineOptions(argc, argv,
+                              "Kaleidoscope example program\n");
+
+  // Install standard binary operators.
+  // 1 is lowest precedence.
+  BinopPrecedence['='] = 2;
+  BinopPrecedence['<'] = 10;
+  BinopPrecedence['+'] = 20;
+  BinopPrecedence['-'] = 20;
+  BinopPrecedence['/'] = 40;
+  BinopPrecedence['*'] = 40;  // highest.
+
+  // Make the Helper, which holds all the code.
+  if (UseMCJIT)
+    TheHelper = new MCJITHelper(Context);
+  else
+    TheHelper = new JITHelper(Context);
+
+  // Prime the first token.
+  if (!SuppressPrompts)
+    fprintf(stderr, "ready> ");
+  getNextToken();
+
+  // Run the main "interpreter loop" now.
+  MainLoop();
+
+  // Print out all of the generated code.
+  if (DumpModulesOnExit)
+    TheHelper->dump();
+
+  return 0;
+}
diff --git a/examples/Kaleidoscope/MCJIT/initial/Makefile b/examples/Kaleidoscope/MCJIT/initial/Makefile
new file mode 100644
index 0000000000..2989832d3c
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/initial/Makefile
@@ -0,0 +1,4 @@
+all: toy-mcjit
+
+toy-mcjit : toy.cpp
+	clang++ toy.cpp -g -O3 -rdynamic -fno-rtti `llvm-config --cppflags --ldflags --libs core mcjit native` -o toy-mcjit
diff --git a/examples/Kaleidoscope/MCJIT/initial/README.txt b/examples/Kaleidoscope/MCJIT/initial/README.txt
new file mode 100644
index 0000000000..b352a78452
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/initial/README.txt
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===/
+//                          Kaleidoscope with MCJIT
+//===----------------------------------------------------------------------===//
+
+The files in this directory are meant to accompany the first in a series of
+three blog posts that describe the process of porting the Kaleidoscope tutorial
+to use the MCJIT execution engine instead of the older JIT engine.
+
+When the blog post is ready this file will be updated with a link to the post.
+
+The source code in this directory demonstrates the initial working version of
+the program before subsequent performance improvements are applied.
+
+This directory contain a Makefile that allow the code to be built in a
+standalone manner, independent of the larger LLVM build infrastructure. To build
+the program you will need to have 'clang++' and 'llvm-config' in your path. If
+you attempt to build using the LLVM 3.3 release, some minor modifications will
+be required, as mentioned in the blog posts.
\ No newline at end of file
diff --git a/examples/Kaleidoscope/MCJIT/initial/toy.cpp b/examples/Kaleidoscope/MCJIT/initial/toy.cpp
new file mode 100644
index 0000000000..c6829076fc
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/initial/toy.cpp
@@ -0,0 +1,1381 @@
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/MCJIT.h"
+#include "llvm/ExecutionEngine/SectionMemoryManager.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/PassManager.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Transforms/Scalar.h"
+#include <cstdio>
+#include <map>
+#include <string>
+#include <vector>
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+  tok_eof = -1,
+
+  // commands
+  tok_def = -2, tok_extern = -3,
+
+  // primary
+  tok_identifier = -4, tok_number = -5,
+  
+  // control
+  tok_if = -6, tok_then = -7, tok_else = -8,
+  tok_for = -9, tok_in = -10,
+  
+  // operators
+  tok_binary = -11, tok_unary = -12,
+  
+  // var definition
+  tok_var = -13
+};
+
+static std::string IdentifierStr;  // Filled in if tok_identifier
+static double NumVal;              // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+  static int LastChar = ' ';
+
+  // Skip any whitespace.
+  while (isspace(LastChar))
+    LastChar = getchar();
+
+  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+    IdentifierStr = LastChar;
+    while (isalnum((LastChar = getchar())))
+      IdentifierStr += LastChar;
+
+    if (IdentifierStr == "def") return tok_def;
+    if (IdentifierStr == "extern") return tok_extern;
+    if (IdentifierStr == "if") return tok_if;
+    if (IdentifierStr == "then") return tok_then;
+    if (IdentifierStr == "else") return tok_else;
+    if (IdentifierStr == "for") return tok_for;
+    if (IdentifierStr == "in") return tok_in;
+    if (IdentifierStr == "binary") return tok_binary;
+    if (IdentifierStr == "unary") return tok_unary;
+    if (IdentifierStr == "var") return tok_var;
+    return tok_identifier;
+  }
+
+  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
+    std::string NumStr;
+    do {
+      NumStr += LastChar;
+      LastChar = getchar();
+    } while (isdigit(LastChar) || LastChar == '.');
+
+    NumVal = strtod(NumStr.c_str(), 0);
+    return tok_number;
+  }
+
+  if (LastChar == '#') {
+    // Comment until end of line.
+    do LastChar = getchar();
+    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
+    
+    if (LastChar != EOF)
+      return gettok();
+  }
+  
+  // Check for end of file.  Don't eat the EOF.
+  if (LastChar == EOF)
+    return tok_eof;
+
+  // Otherwise, just return the character as its ascii value.
+  int ThisChar = LastChar;
+  LastChar = getchar();
+  return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+/// ExprAST - Base class for all expression nodes.
+class ExprAST {
+public:
+  virtual ~ExprAST() {}
+  virtual Value *Codegen() = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+class NumberExprAST : public ExprAST {
+  double Val;
+public:
+  NumberExprAST(double val) : Val(val) {}
+  virtual Value *Codegen();
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+class VariableExprAST : public ExprAST {
+  std::string Name;
+public:
+  VariableExprAST(const std::string &name) : Name(name) {}
+  const std::string &getName() const { return Name; }
+  virtual Value *Codegen();
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+  char Opcode;
+  ExprAST *Operand;
+public:
+  UnaryExprAST(char opcode, ExprAST *operand) 
+    : Opcode(opcode), Operand(operand) {}
+  virtual Value *Codegen();
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+class BinaryExprAST : public ExprAST {
+  char Op;
+  ExprAST *LHS, *RHS;
+public:
+  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) 
+    : Op(op), LHS(lhs), RHS(rhs) {}
+  virtual Value *Codegen();
+};
+
+/// CallExprAST - Expression class for function calls.
+class CallExprAST : public ExprAST {
+  std::string Callee;
+  std::vector<ExprAST*> Args;
+public:
+  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
+    : Callee(callee), Args(args) {}
+  virtual Value *Codegen();
+};
+
+/// IfExprAST - Expression class for if/then/else.
+class IfExprAST : public ExprAST {
+  ExprAST *Cond, *Then, *Else;
+public:
+  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
+  : Cond(cond), Then(then), Else(_else) {}
+  virtual Value *Codegen();
+};
+
+/// ForExprAST - Expression class for for/in.
+class ForExprAST : public ExprAST {
+  std::string VarName;
+  ExprAST *Start, *End, *Step, *Body;
+public:
+  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
+             ExprAST *step, ExprAST *body)
+    : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+  virtual Value *Codegen();
+};
+
+/// VarExprAST - Expression class for var/in
+class VarExprAST : public ExprAST {
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+  ExprAST *Body;
+public:
+  VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
+             ExprAST *body)
+  : VarNames(varnames), Body(body) {}
+  
+  virtual Value *Codegen();
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+class PrototypeAST {
+  std::string Name;
+  std::vector<std::string> Args;
+  bool isOperator;
+  unsigned Precedence;  // Precedence if a binary op.
+public:
+  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
+               bool isoperator = false, unsigned prec = 0)
+  : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
+  
+  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
+  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
+  
+  char getOperatorName() const {
+    assert(isUnaryOp() || isBinaryOp());
+    return Name[Name.size()-1];
+  }
+  
+  unsigned getBinaryPrecedence() const { return Precedence; }
+  
+  Function *Codegen();
+  
+  void CreateArgumentAllocas(Function *F);
+};
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+  PrototypeAST *Proto;
+  ExprAST *Body;
+public:
+  FunctionAST(PrototypeAST *proto, ExprAST *body)
+    : Proto(proto), Body(body) {}
+  
+  Function *Codegen();
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
+/// token the parser is looking at.  getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+  return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+  if (!isascii(CurTok))
+    return -1;
+  
+  // Make sure it's a declared binop.
+  int TokPrec = BinopPrecedence[CurTok];
+  if (TokPrec <= 0) return -1;
+  return TokPrec;
+}
+
+/// Error* - These are little helper functions for error handling.
+ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
+PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
+FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
+
+static ExprAST *ParseExpression();
+
+/// identifierexpr
+///   ::= identifier
+///   ::= identifier '(' expression* ')'
+static ExprAST *ParseIdentifierExpr() {
+  std::string IdName = IdentifierStr;
+  
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '(') // Simple variable ref.
+    return new VariableExprAST(IdName);
+  
+  // Call.
+  getNextToken();  // eat (
+  std::vector<ExprAST*> Args;
+  if (CurTok != ')') {
+    while (1) {
+      ExprAST *Arg = ParseExpression();
+      if (!Arg) return 0;
+      Args.push_back(Arg);
+
+      if (CurTok == ')') break;
+
+      if (CurTok != ',')
+        return Error("Expected ')' or ',' in argument list");
+      getNextToken();
+    }
+  }
+
+  // Eat the ')'.
+  getNextToken();
+  
+  return new CallExprAST(IdName, Args);
+}
+
+/// numberexpr ::= number
+static ExprAST *ParseNumberExpr() {
+  ExprAST *Result = new NumberExprAST(NumVal);
+  getNextToken(); // consume the number
+  return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static ExprAST *ParseParenExpr() {
+  getNextToken();  // eat (.
+  ExprAST *V = ParseExpression();
+  if (!V) return 0;
+  
+  if (CurTok != ')')
+    return Error("expected ')'");
+  getNextToken();  // eat ).
+  return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static ExprAST *ParseIfExpr() {
+  getNextToken();  // eat the if.
+  
+  // condition.
+  ExprAST *Cond = ParseExpression();
+  if (!Cond) return 0;
+  
+  if (CurTok != tok_then)
+    return Error("expected then");
+  getNextToken();  // eat the then
+  
+  ExprAST *Then = ParseExpression();
+  if (Then == 0) return 0;
+  
+  if (CurTok != tok_else)
+    return Error("expected else");
+  
+  getNextToken();
+  
+  ExprAST *Else = ParseExpression();
+  if (!Else) return 0;
+  
+  return new IfExprAST(Cond, Then, Else);
+}
+
+/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
+static ExprAST *ParseForExpr() {
+  getNextToken();  // eat the for.
+
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after for");
+  
+  std::string IdName = IdentifierStr;
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '=')
+    return Error("expected '=' after for");
+  getNextToken();  // eat '='.
+  
+  
+  ExprAST *Start = ParseExpression();
+  if (Start == 0) return 0;
+  if (CurTok != ',')
+    return Error("expected ',' after for start value");
+  getNextToken();
+  
+  ExprAST *End = ParseExpression();
+  if (End == 0) return 0;
+  
+  // The step value is optional.
+  ExprAST *Step = 0;
+  if (CurTok == ',') {
+    getNextToken();
+    Step = ParseExpression();
+    if (Step == 0) return 0;
+  }
+  
+  if (CurTok != tok_in)
+    return Error("expected 'in' after for");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+
+  return new ForExprAST(IdName, Start, End, Step, Body);
+}
+
+/// varexpr ::= 'var' identifier ('=' expression)? 
+//                    (',' identifier ('=' expression)?)* 'in' expression
+static ExprAST *ParseVarExpr() {
+  getNextToken();  // eat the var.
+
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+
+  // At least one variable name is required.
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after var");
+  
+  while (1) {
+    std::string Name = IdentifierStr;
+    getNextToken();  // eat identifier.
+
+    // Read the optional initializer.
+    ExprAST *Init = 0;
+    if (CurTok == '=') {
+      getNextToken(); // eat the '='.
+      
+      Init = ParseExpression();
+      if (Init == 0) return 0;
+    }
+    
+    VarNames.push_back(std::make_pair(Name, Init));
+    
+    // End of var list, exit loop.
+    if (CurTok != ',') break;
+    getNextToken(); // eat the ','.
+    
+    if (CurTok != tok_identifier)
+      return Error("expected identifier list after var");
+  }
+  
+  // At this point, we have to have 'in'.
+  if (CurTok != tok_in)
+    return Error("expected 'in' keyword after 'var'");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+  
+  return new VarExprAST(VarNames, Body);
+}
+
+/// primary
+///   ::= identifierexpr
+///   ::= numberexpr
+///   ::= parenexpr
+///   ::= ifexpr
+///   ::= forexpr
+///   ::= varexpr
+static ExprAST *ParsePrimary() {
+  switch (CurTok) {
+  default: return Error("unknown token when expecting an expression");
+  case tok_identifier: return ParseIdentifierExpr();
+  case tok_number:     return ParseNumberExpr();
+  case '(':            return ParseParenExpr();
+  case tok_if:         return ParseIfExpr();
+  case tok_for:        return ParseForExpr();
+  case tok_var:        return ParseVarExpr();
+  }
+}
+
+/// unary
+///   ::= primary
+///   ::= '!' unary
+static ExprAST *ParseUnary() {
+  // If the current token is not an operator, it must be a primary expr.
+  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+    return ParsePrimary();
+  
+  // If this is a unary operator, read it.
+  int Opc = CurTok;
+  getNextToken();
+  if (ExprAST *Operand = ParseUnary())
+    return new UnaryExprAST(Opc, Operand);
+  return 0;
+}
+
+/// binoprhs
+///   ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+  // If this is a binop, find its precedence.
+  while (1) {
+    int TokPrec = GetTokPrecedence();
+    
+    // If this is a binop that binds at least as tightly as the current binop,
+    // consume it, otherwise we are done.
+    if (TokPrec < ExprPrec)
+      return LHS;
+    
+    // Okay, we know this is a binop.
+    int BinOp = CurTok;
+    getNextToken();  // eat binop
+    
+    // Parse the unary expression after the binary operator.
+    ExprAST *RHS = ParseUnary();
+    if (!RHS) return 0;
+    
+    // If BinOp binds less tightly with RHS than the operator after RHS, let
+    // the pending operator take RHS as its LHS.
+    int NextPrec = GetTokPrecedence();
+    if (TokPrec < NextPrec) {
+      RHS = ParseBinOpRHS(TokPrec+1, RHS);
+      if (RHS == 0) return 0;
+    }
+    
+    // Merge LHS/RHS.
+    LHS = new BinaryExprAST(BinOp, LHS, RHS);
+  }
+}
+
+/// expression
+///   ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+  ExprAST *LHS = ParseUnary();
+  if (!LHS) return 0;
+  
+  return ParseBinOpRHS(0, LHS);
+}
+
+/// prototype
+///   ::= id '(' id* ')'
+///   ::= binary LETTER number? (id, id)
+///   ::= unary LETTER (id)
+static PrototypeAST *ParsePrototype() {
+  std::string FnName;
+  
+  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+  unsigned BinaryPrecedence = 30;
+  
+  switch (CurTok) {
+  default:
+    return ErrorP("Expected function name in prototype");
+  case tok_identifier:
+    FnName = IdentifierStr;
+    Kind = 0;
+    getNextToken();
+    break;
+  case tok_unary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected unary operator");
+    FnName = "unary";
+    FnName += (char)CurTok;
+    Kind = 1;
+    getNextToken();
+    break;
+  case tok_binary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected binary operator");
+    FnName = "binary";
+    FnName += (char)CurTok;
+    Kind = 2;
+    getNextToken();
+    
+    // Read the precedence if present.
+    if (CurTok == tok_number) {
+      if (NumVal < 1 || NumVal > 100)
+        return ErrorP("Invalid precedecnce: must be 1..100");
+      BinaryPrecedence = (unsigned)NumVal;
+      getNextToken();
+    }
+    break;
+  }
+  
+  if (CurTok != '(')
+    return ErrorP("Expected '(' in prototype");
+  
+  std::vector<std::string> ArgNames;
+  while (getNextToken() == tok_identifier)
+    ArgNames.push_back(IdentifierStr);
+  if (CurTok != ')')
+    return ErrorP("Expected ')' in prototype");
+  
+  // success.
+  getNextToken();  // eat ')'.
+  
+  // Verify right number of names for operator.
+  if (Kind && ArgNames.size() != Kind)
+    return ErrorP("Invalid number of operands for operator");
+  
+  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static FunctionAST *ParseDefinition() {
+  getNextToken();  // eat def.
+  PrototypeAST *Proto = ParsePrototype();
+  if (Proto == 0) return 0;
+
+  if (ExprAST *E = ParseExpression())
+    return new FunctionAST(Proto, E);
+  return 0;
+}
+
+/// toplevelexpr ::= expression
+static FunctionAST *ParseTopLevelExpr() {
+  if (ExprAST *E = ParseExpression()) {
+    // Make an anonymous proto.
+    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
+    return new FunctionAST(Proto, E);
+  }
+  return 0;
+}
+
+/// external ::= 'extern' prototype
+static PrototypeAST *ParseExtern() {
+  getNextToken();  // eat extern.
+  return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Quick and dirty hack
+//===----------------------------------------------------------------------===//
+
+// FIXME: Obviously we can do better than this
+std::string GenerateUniqueName(const char *root)
+{
+  static int i = 0;
+  char s[16];
+  sprintf(s, "%s%d", root, i++);
+  std::string S = s;
+  return S;
+}
+
+std::string MakeLegalFunctionName(std::string Name)
+{
+  std::string NewName;
+  if (!Name.length())
+      return GenerateUniqueName("anon_func_");
+
+  // Start with what we have
+  NewName = Name;
+
+  // Look for a numberic first character
+  if (NewName.find_first_of("0123456789") == 0) {
+    NewName.insert(0, 1, 'n');
+  }
+
+  // Replace illegal characters with their ASCII equivalent
+  std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+  size_t pos;
+  while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
+    char old_c = NewName.at(pos);
+    char new_str[16];
+    sprintf(new_str, "%d", (int)old_c);
+    NewName = NewName.replace(pos, 1, new_str);
+  }
+
+  return NewName;
+}
+
+//===----------------------------------------------------------------------===//
+// MCJIT helper class
+//===----------------------------------------------------------------------===//
+
+class MCJITHelper
+{
+public:
+  MCJITHelper(LLVMContext& C) : Context(C), OpenModule(NULL) {}
+  ~MCJITHelper();
+
+  Function *getFunction(const std::string FnName);
+  Module *getModuleForNewFunction();
+  void *getPointerToFunction(Function* F);
+  void *getPointerToNamedFunction(const std::string &Name);
+  void dump();
+
+private:
+  typedef std::vector<Module*> ModuleVector;
+  typedef std::vector<ExecutionEngine*> EngineVector;
+
+  LLVMContext  &Context;
+  Module       *OpenModule;
+  ModuleVector  Modules;
+  EngineVector  Engines;
+};
+
+class HelpingMemoryManager : public SectionMemoryManager
+{
+  HelpingMemoryManager(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+  void operator=(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+
+public:
+  HelpingMemoryManager(MCJITHelper *Helper) : MasterHelper(Helper) {}
+  virtual ~HelpingMemoryManager() {}
+
+  /// This method returns the address of the specified function. 
+  /// Our implementation will attempt to find functions in other
+  /// modules associated with the MCJITHelper to cross link functions
+  /// from one generated module to another.
+  ///
+  /// If \p AbortOnFailure is false and no function with the given name is
+  /// found, this function returns a null pointer. Otherwise, it prints a
+  /// message to stderr and aborts.
+  virtual void *getPointerToNamedFunction(const std::string &Name,
+                                          bool AbortOnFailure = true);
+private:
+  MCJITHelper *MasterHelper;
+};
+
+void *HelpingMemoryManager::getPointerToNamedFunction(const std::string &Name,
+                                        bool AbortOnFailure)
+{
+  // Try the standard symbol resolution first, but ask it not to abort.
+  void *pfn = SectionMemoryManager::getPointerToNamedFunction(Name, false);
+  if (pfn)
+    return pfn;
+
+  pfn = MasterHelper->getPointerToNamedFunction(Name);
+  if (!pfn && AbortOnFailure)
+    report_fatal_error("Program used external function '" + Name +
+                        "' which could not be resolved!");
+  return pfn;
+}
+
+MCJITHelper::~MCJITHelper()
+{
+  if (OpenModule)
+    delete OpenModule;
+  EngineVector::iterator begin = Engines.begin();
+  EngineVector::iterator end = Engines.end();
+  EngineVector::iterator it;
+  for (it = begin; it != end; ++it)
+    delete *it;
+}
+
+Function *MCJITHelper::getFunction(const std::string FnName) {
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    Function *F = (*it)->getFunction(FnName);
+    if (F) {
+      if (*it == OpenModule)
+          return F;
+
+      assert(OpenModule != NULL);
+
+      // This function is in a module that has already been JITed.
+      // We need to generate a new prototype for external linkage.
+      Function *PF = OpenModule->getFunction(FnName);
+      if (PF && !PF->empty()) {
+        ErrorF("redefinition of function across modules");
+        return 0;
+      }
+
+      // If we don't have a prototype yet, create one.
+      if (!PF)
+        PF = Function::Create(F->getFunctionType(), 
+                                      Function::ExternalLinkage, 
+                                      FnName, 
+                                      OpenModule);
+      return PF;
+    }
+  }
+  return NULL;
+}
+
+Module *MCJITHelper::getModuleForNewFunction() {
+  // If we have a Module that hasn't been JITed, use that.
+  if (OpenModule)
+    return OpenModule;
+
+  // Otherwise create a new Module.
+  std::string ModName = GenerateUniqueName("mcjit_module_");
+  Module *M = new Module(ModName, Context);
+  Modules.push_back(M);
+  OpenModule = M;
+  return M;
+}
+
+void *MCJITHelper::getPointerToFunction(Function* F) {
+  // See if an existing instance of MCJIT has this function.
+  EngineVector::iterator begin = Engines.begin();
+  EngineVector::iterator end = Engines.end();
+  EngineVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    void *P = (*it)->getPointerToFunction(F);
+    if (P)
+      return P;
+  }
+
+  // If we didn't find the function, see if we can generate it.
+  if (OpenModule) {
+    std::string ErrStr;
+    ExecutionEngine *NewEngine = EngineBuilder(OpenModule)
+                                              .setErrorStr(&ErrStr)
+                                              .setUseMCJIT(true)
+                                              .setMCJITMemoryManager(new HelpingMemoryManager(this))
+                                              .create();
+    if (!NewEngine) {
+      fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
+      exit(1);
+    }
+
+    // Create a function pass manager for this engine
+    FunctionPassManager *FPM = new FunctionPassManager(OpenModule);
+
+    // Set up the optimizer pipeline.  Start with registering info about how the
+    // target lays out data structures.
+    FPM->add(new DataLayout(*NewEngine->getDataLayout()));
+    // Provide basic AliasAnalysis support for GVN.
+    FPM->add(createBasicAliasAnalysisPass());
+    // Promote allocas to registers.
+    FPM->add(createPromoteMemoryToRegisterPass());
+    // Do simple "peephole" optimizations and bit-twiddling optzns.
+    FPM->add(createInstructionCombiningPass());
+    // Reassociate expressions.
+    FPM->add(createReassociatePass());
+    // Eliminate Common SubExpressions.
+    FPM->add(createGVNPass());
+    // Simplify the control flow graph (deleting unreachable blocks, etc).
+    FPM->add(createCFGSimplificationPass());
+    FPM->doInitialization();
+
+    // For each function in the module
+    Module::iterator it;
+    Module::iterator end = OpenModule->end();
+    for (it = OpenModule->begin(); it != end; ++it) {
+      // Run the FPM on this function
+      FPM->run(*it);
+    }
+
+    // We don't need this anymore
+    delete FPM;
+
+    OpenModule = NULL;
+    Engines.push_back(NewEngine);
+    NewEngine->finalizeObject();
+    return NewEngine->getPointerToFunction(F);
+  }
+  return NULL;
+}
+
+void *MCJITHelper::getPointerToNamedFunction(const std::string &Name)
+{
+  // Look for the function in each of our execution engines.
+  EngineVector::iterator begin = Engines.begin();
+  EngineVector::iterator end = Engines.end();
+  EngineVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    if (Function *F = (*it)->FindFunctionNamed(Name.c_str()))
+        return (*it)->getPointerToFunction(F);
+  }
+
+  return NULL;
+}
+
+void MCJITHelper::dump()
+{
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it)
+    (*it)->dump();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+static MCJITHelper *TheHelper;
+static IRBuilder<> Builder(getGlobalContext());
+static std::map<std::string, AllocaInst*> NamedValues;
+
+Value *ErrorV(const char *Str) { Error(Str); return 0; }
+
+/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
+/// the function.  This is used for mutable variables etc.
+static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
+                                          const std::string &VarName) {
+  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
+                 TheFunction->getEntryBlock().begin());
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+                           VarName.c_str());
+}
+
+Value *NumberExprAST::Codegen() {
+  return ConstantFP::get(getGlobalContext(), APFloat(Val));
+}
+
+Value *VariableExprAST::Codegen() {
+  // Look this variable up in the function.
+  Value *V = NamedValues[Name];
+  char ErrStr[256];
+  sprintf(ErrStr, "Unknown variable name %s", Name.c_str());
+  if (V == 0) return ErrorV(ErrStr);
+
+  // Load the value.
+  return Builder.CreateLoad(V, Name.c_str());
+}
+
+Value *UnaryExprAST::Codegen() {
+  Value *OperandV = Operand->Codegen();
+  if (OperandV == 0) return 0;
+  
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
+  if (F == 0)
+    return ErrorV("Unknown unary operator");
+  
+  return Builder.CreateCall(F, OperandV, "unop");
+}
+
+Value *BinaryExprAST::Codegen() {
+  // Special case '=' because we don't want to emit the LHS as an expression.
+  if (Op == '=') {
+    // Assignment requires the LHS to be an identifier.
+    VariableExprAST *LHSE = reinterpret_cast<VariableExprAST*>(LHS);
+    if (!LHSE)
+      return ErrorV("destination of '=' must be a variable");
+    // Codegen the RHS.
+    Value *Val = RHS->Codegen();
+    if (Val == 0) return 0;
+
+    // Look up the name.
+    Value *Variable = NamedValues[LHSE->getName()];
+    if (Variable == 0) return ErrorV("Unknown variable name");
+
+    Builder.CreateStore(Val, Variable);
+    return Val;
+  }
+  
+  Value *L = LHS->Codegen();
+  Value *R = RHS->Codegen();
+  if (L == 0 || R == 0) return 0;
+  
+  switch (Op) {
+  case '+': return Builder.CreateFAdd(L, R, "addtmp");
+  case '-': return Builder.CreateFSub(L, R, "subtmp");
+  case '*': return Builder.CreateFMul(L, R, "multmp");
+  case '/': return Builder.CreateFDiv(L, R, "divtmp");
+  case '<':
+    L = Builder.CreateFCmpULT(L, R, "cmptmp");
+    // Convert bool 0/1 to double 0.0 or 1.0
+    return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+                                "booltmp");
+  default: break;
+  }
+  
+  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+  // a call to it.
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("binary")+Op));
+  assert(F && "binary operator not found!");
+  
+  Value *Ops[] = { L, R };
+  return Builder.CreateCall(F, Ops, "binop");
+}
+
+Value *CallExprAST::Codegen() {
+  // Look up the name in the global module table.
+  Function *CalleeF = TheHelper->getFunction(Callee);
+  if (CalleeF == 0)
+    return ErrorV("Unknown function referenced");
+  
+  // If argument mismatch error.
+  if (CalleeF->arg_size() != Args.size())
+    return ErrorV("Incorrect # arguments passed");
+
+  std::vector<Value*> ArgsV;
+  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+    ArgsV.push_back(Args[i]->Codegen());
+    if (ArgsV.back() == 0) return 0;
+  }
+  
+  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
+}
+
+Value *IfExprAST::Codegen() {
+  Value *CondV = Cond->Codegen();
+  if (CondV == 0) return 0;
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  CondV = Builder.CreateFCmpONE(CondV, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                "ifcond");
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+  
+  // Create blocks for the then and else cases.  Insert the 'then' block at the
+  // end of the function.
+  BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
+  BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
+  BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
+  
+  Builder.CreateCondBr(CondV, ThenBB, ElseBB);
+  
+  // Emit then value.
+  Builder.SetInsertPoint(ThenBB);
+  
+  Value *ThenV = Then->Codegen();
+  if (ThenV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+  ThenBB = Builder.GetInsertBlock();
+  
+  // Emit else block.
+  TheFunction->getBasicBlockList().push_back(ElseBB);
+  Builder.SetInsertPoint(ElseBB);
+  
+  Value *ElseV = Else->Codegen();
+  if (ElseV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+  ElseBB = Builder.GetInsertBlock();
+  
+  // Emit merge block.
+  TheFunction->getBasicBlockList().push_back(MergeBB);
+  Builder.SetInsertPoint(MergeBB);
+  PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
+                                  "iftmp");
+  
+  PN->addIncoming(ThenV, ThenBB);
+  PN->addIncoming(ElseV, ElseBB);
+  return PN;
+}
+
+Value *ForExprAST::Codegen() {
+  // Output this as:
+  //   var = alloca double
+  //   ...
+  //   start = startexpr
+  //   store start -> var
+  //   goto loop
+  // loop: 
+  //   ...
+  //   bodyexpr
+  //   ...
+  // loopend:
+  //   step = stepexpr
+  //   endcond = endexpr
+  //
+  //   curvar = load var
+  //   nextvar = curvar + step
+  //   store nextvar -> var
+  //   br endcond, loop, endloop
+  // outloop:
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Create an alloca for the variable in the entry block.
+  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+  
+  // Emit the start code first, without 'variable' in scope.
+  Value *StartVal = Start->Codegen();
+  if (StartVal == 0) return 0;
+  
+  // Store the value into the alloca.
+  Builder.CreateStore(StartVal, Alloca);
+  
+  // Make the new basic block for the loop header, inserting after current
+  // block.
+  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+  
+  // Insert an explicit fall through from the current block to the LoopBB.
+  Builder.CreateBr(LoopBB);
+
+  // Start insertion in LoopBB.
+  Builder.SetInsertPoint(LoopBB);
+  
+  // Within the loop, the variable is defined equal to the PHI node.  If it
+  // shadows an existing variable, we have to restore it, so save it now.
+  AllocaInst *OldVal = NamedValues[VarName];
+  NamedValues[VarName] = Alloca;
+  
+  // Emit the body of the loop.  This, like any other expr, can change the
+  // current BB.  Note that we ignore the value computed by the body, but don't
+  // allow an error.
+  if (Body->Codegen() == 0)
+    return 0;
+  
+  // Emit the step value.
+  Value *StepVal;
+  if (Step) {
+    StepVal = Step->Codegen();
+    if (StepVal == 0) return 0;
+  } else {
+    // If not specified, use 1.0.
+    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
+  }
+  
+  // Compute the end condition.
+  Value *EndCond = End->Codegen();
+  if (EndCond == 0) return EndCond;
+  
+  // Reload, increment, and restore the alloca.  This handles the case where
+  // the body of the loop mutates the variable.
+  Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
+  Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
+  Builder.CreateStore(NextVar, Alloca);
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  EndCond = Builder.CreateFCmpONE(EndCond, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                  "loopcond");
+  
+  // Create the "after loop" block and insert it.
+  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+  
+  // Insert the conditional branch into the end of LoopEndBB.
+  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
+  
+  // Any new code will be inserted in AfterBB.
+  Builder.SetInsertPoint(AfterBB);
+  
+  // Restore the unshadowed variable.
+  if (OldVal)
+    NamedValues[VarName] = OldVal;
+  else
+    NamedValues.erase(VarName);
+
+  
+  // for expr always returns 0.0.
+  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
+}
+
+Value *VarExprAST::Codegen() {
+  std::vector<AllocaInst *> OldBindings;
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Register all variables and emit their initializer.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
+    const std::string &VarName = VarNames[i].first;
+    ExprAST *Init = VarNames[i].second;
+    
+    // Emit the initializer before adding the variable to scope, this prevents
+    // the initializer from referencing the variable itself, and permits stuff
+    // like this:
+    //  var a = 1 in
+    //    var a = a in ...   # refers to outer 'a'.
+    Value *InitVal;
+    if (Init) {
+      InitVal = Init->Codegen();
+      if (InitVal == 0) return 0;
+    } else { // If not specified, use 0.0.
+      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
+    }
+    
+    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+    Builder.CreateStore(InitVal, Alloca);
+
+    // Remember the old variable binding so that we can restore the binding when
+    // we unrecurse.
+    OldBindings.push_back(NamedValues[VarName]);
+    
+    // Remember this binding.
+    NamedValues[VarName] = Alloca;
+  }
+  
+  // Codegen the body, now that all vars are in scope.
+  Value *BodyVal = Body->Codegen();
+  if (BodyVal == 0) return 0;
+  
+  // Pop all our variables from scope.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
+    NamedValues[VarNames[i].first] = OldBindings[i];
+
+  // Return the body computation.
+  return BodyVal;
+}
+
+Function *PrototypeAST::Codegen() {
+  // Make the function type:  double(double,double) etc.
+  std::vector<Type*> Doubles(Args.size(), 
+                             Type::getDoubleTy(getGlobalContext()));
+  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+                                       Doubles, false);
+
+  std::string FnName = MakeLegalFunctionName(Name);
+
+  Module* M = TheHelper->getModuleForNewFunction();
+
+  Function *F = Function::Create(FT, Function::ExternalLinkage, FnName, M);
+
+  // If F conflicted, there was already something named 'FnName'.  If it has a
+  // body, don't allow redefinition or reextern.
+  if (F->getName() != FnName) {
+    // Delete the one we just made and get the existing one.
+    F->eraseFromParent();
+    F = M->getFunction(Name);
+    
+    // If F already has a body, reject this.
+    if (!F->empty()) {
+      ErrorF("redefinition of function");
+      return 0;
+    }
+    
+    // If F took a different number of args, reject.
+    if (F->arg_size() != Args.size()) {
+      ErrorF("redefinition of function with different # args");
+      return 0;
+    }
+  }
+  
+  // Set names for all arguments.
+  unsigned Idx = 0;
+  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+       ++AI, ++Idx)
+    AI->setName(Args[Idx]);
+    
+  return F;
+}
+
+/// CreateArgumentAllocas - Create an alloca for each argument and register the
+/// argument in the symbol table so that references to it will succeed.
+void PrototypeAST::CreateArgumentAllocas(Function *F) {
+  Function::arg_iterator AI = F->arg_begin();
+  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
+    // Create an alloca for this variable.
+    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
+
+    // Store the initial value into the alloca.
+    Builder.CreateStore(AI, Alloca);
+
+    // Add arguments to variable symbol table.
+    NamedValues[Args[Idx]] = Alloca;
+  }
+}
+
+Function *FunctionAST::Codegen() {
+  NamedValues.clear();
+  
+  Function *TheFunction = Proto->Codegen();
+  if (TheFunction == 0)
+    return 0;
+  
+  // If this is an operator, install it.
+  if (Proto->isBinaryOp())
+    BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
+  
+  // Create a new basic block to start insertion into.
+  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+  Builder.SetInsertPoint(BB);
+  
+  // Add all arguments to the symbol table and create their allocas.
+  Proto->CreateArgumentAllocas(TheFunction);
+
+  if (Value *RetVal = Body->Codegen()) {
+    // Finish off the function.
+    Builder.CreateRet(RetVal);
+
+    // Validate the generated code, checking for consistency.
+    verifyFunction(*TheFunction);
+
+    return TheFunction;
+  }
+  
+  // Error reading body, remove function.
+  TheFunction->eraseFromParent();
+
+  if (Proto->isBinaryOp())
+    BinopPrecedence.erase(Proto->getOperatorName());
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static void HandleDefinition() {
+  if (FunctionAST *F = ParseDefinition()) {
+    if (Function *LF = F->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read function definition:");
+      LF->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleExtern() {
+  if (PrototypeAST *P = ParseExtern()) {
+    if (Function *F = P->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read extern: ");
+      F->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleTopLevelExpression() {
+  // Evaluate a top-level expression into an anonymous function.
+  if (FunctionAST *F = ParseTopLevelExpr()) {
+    if (Function *LF = F->Codegen()) {
+      // JIT the function, returning a function pointer.
+      void *FPtr = TheHelper->getPointerToFunction(LF);
+      
+      // Cast it to the right type (takes no arguments, returns a double) so we
+      // can call it as a native function.
+      double (*FP)() = (double (*)())(intptr_t)FPtr;
+#ifdef MINIMAL_STDERR_OUTPUT
+      FP();
+#else
+      fprintf(stderr, "Evaluated to %f\n", FP());
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+  while (1) {
+#ifndef MINIMAL_STDERR_OUTPUT
+    fprintf(stderr, "ready> ");
+#endif
+    switch (CurTok) {
+    case tok_eof:    return;
+    case ';':        getNextToken(); break;  // ignore top-level semicolons.
+    case tok_def:    HandleDefinition(); break;
+    case tok_extern: HandleExtern(); break;
+    default:         HandleTopLevelExpression(); break;
+    }
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C" 
+double putchard(double X) {
+  putchar((char)X);
+  return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C" 
+double printd(double X) {
+  printf("%f", X);
+  return 0;
+}
+
+extern "C" 
+double printlf() {
+  printf("\n");
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main() {
+  InitializeNativeTarget();
+  InitializeNativeTargetAsmPrinter();
+  InitializeNativeTargetAsmParser();
+  LLVMContext &Context = getGlobalContext();
+
+  // Install standard binary operators.
+  // 1 is lowest precedence.
+  BinopPrecedence['='] = 2;
+  BinopPrecedence['<'] = 10;
+  BinopPrecedence['+'] = 20;
+  BinopPrecedence['-'] = 20;
+  BinopPrecedence['/'] = 40;
+  BinopPrecedence['*'] = 40;  // highest.
+
+  // Prime the first token.
+#ifndef MINIMAL_STDERR_OUTPUT
+  fprintf(stderr, "ready> ");
+#endif
+  getNextToken();
+
+  // Make the helper, which holds all the code.
+  TheHelper = new MCJITHelper(Context);
+
+  // Run the main "interpreter loop" now.
+  MainLoop();
+
+#ifndef MINIMAL_STDERR_OUTPUT
+  // Print out all of the generated code.
+  TheHelper->dump();
+#endif
+
+  return 0;
+}
diff --git a/examples/Kaleidoscope/MCJIT/lazy/Makefile b/examples/Kaleidoscope/MCJIT/lazy/Makefile
new file mode 100644
index 0000000000..21cbc18d6e
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/lazy/Makefile
@@ -0,0 +1,7 @@
+all: toy-mcjit toy-jit
+
+toy-mcjit : toy.cpp
+	clang++ toy.cpp -g -O3 -rdynamic -fno-rtti `llvm-config --cppflags --ldflags --libs core mcjit native` -o toy-mcjit
+
+toy-jit : toy-jit.cpp
+	clang++ toy-jit.cpp -g -O3 -rdynamic `llvm-config --cppflags --ldflags --libs core jit native` -o toy-jit
diff --git a/examples/Kaleidoscope/MCJIT/lazy/README.txt b/examples/Kaleidoscope/MCJIT/lazy/README.txt
new file mode 100644
index 0000000000..c5c271e02f
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/lazy/README.txt
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===/
+//                          Kaleidoscope with MCJIT
+//===----------------------------------------------------------------------===//
+
+The files in this directory are meant to accompany the first in a series of
+three blog posts that describe the process of porting the Kaleidoscope tutorial
+to use the MCJIT execution engine instead of the older JIT engine.
+
+When the blog post is ready this file will be updated with a link to the post.
+
+The source code in this directory demonstrates the second version of the
+program, now modified to implement a sort of 'lazy' compilation.
+
+The toy-jit.cpp file contains a version of the original JIT-based source code
+that has been modified to disable most stderr output for timing purposes.
+
+This directory contain a Makefile that allow the code to be built in a
+standalone manner, independent of the larger LLVM build infrastructure. To build
+the program you will need to have 'clang++' and 'llvm-config' in your path. If
+you attempt to build using the LLVM 3.3 release, some minor modifications will
+be required.
+
+This directory also contains a Python script that may be used to generate random
+input for the program and test scripts to capture data for rough performance
+comparisons.
\ No newline at end of file
diff --git a/examples/Kaleidoscope/MCJIT/lazy/genk-timing.py b/examples/Kaleidoscope/MCJIT/lazy/genk-timing.py
new file mode 100644
index 0000000000..96dd6db5da
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/lazy/genk-timing.py
@@ -0,0 +1,219 @@
+#!/usr/bin/env python
+
+import sys
+import random
+
+class TimingScriptGenerator:
+    """Used to generate a bash script which will invoke the toy and time it"""
+    def __init__(self, scriptname, outputname):
+        self.timeFile = outputname
+        self.shfile = open(scriptname, 'w')
+        self.shfile.write("echo \"\" > %s\n" % self.timeFile)
+
+    def writeTimingCall(self, filename, numFuncs, funcsCalled, totalCalls):
+        """Echo some comments and invoke both versions of toy"""
+        rootname = filename
+        if '.' in filename:
+            rootname = filename[:filename.rfind('.')]
+        self.shfile.write("echo \"%s: Calls %d of %d functions, %d total\" >> %s\n" % (filename, funcsCalled, numFuncs, totalCalls, self.timeFile))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With MCJIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy-mcjit < %s > %s-mcjit.out 2> %s-mcjit.err\n" % (filename, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"With JIT\" >> %s\n" % self.timeFile)
+        self.shfile.write("/usr/bin/time -f \"Command %C\\n\\tuser time: %U s\\n\\tsytem time: %S s\\n\\tmax set: %M kb\"")
+        self.shfile.write(" -o %s -a " % self.timeFile)
+        self.shfile.write("./toy-jit < %s > %s-jit.out 2> %s-jit.err\n" % (filename, rootname, rootname))
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+        self.shfile.write("echo \"\" >> %s\n" % self.timeFile)
+
+class KScriptGenerator:
+    """Used to generate random Kaleidoscope code"""
+    def __init__(self, filename):
+        self.kfile = open(filename, 'w')
+        self.nextFuncNum = 1
+        self.lastFuncNum = None
+        self.callWeighting = 0.1
+        # A mapping of calls within functions with no duplicates
+        self.calledFunctionTable = {}
+        # A list of function calls which will actually be executed
+        self.calledFunctions = []
+        # A comprehensive mapping of calls within functions
+        # used for computing the total number of calls
+        self.comprehensiveCalledFunctionTable = {}
+        self.totalCallsExecuted = 0
+
+    def updateTotalCallCount(self, callee):
+        # Count this call
+        self.totalCallsExecuted += 1
+        # Then count all the functions it calls
+        if callee in self.comprehensiveCalledFunctionTable:
+            for child in self.comprehensiveCalledFunctionTable[callee]:
+                self.updateTotalCallCount(child)
+
+    def updateFunctionCallMap(self, caller, callee):
+        """Maintains a map of functions that are called from other functions"""
+        if not caller in self.calledFunctionTable:
+            self.calledFunctionTable[caller] = []
+        if not callee in self.calledFunctionTable[caller]:
+            self.calledFunctionTable[caller].append(callee)
+        if not caller in self.comprehensiveCalledFunctionTable:
+            self.comprehensiveCalledFunctionTable[caller] = []
+        self.comprehensiveCalledFunctionTable[caller].append(callee)
+
+    def updateCalledFunctionList(self, callee):
+        """Maintains a list of functions that will actually be called"""
+        # Update the total call count
+        self.updateTotalCallCount(callee)
+        # If this function is already in the list, don't do anything else
+        if callee in self.calledFunctions:
+            return
+        # Add this function to the list of those that will be called.
+        self.calledFunctions.append(callee)
+        # If this function calls other functions, add them too
+        if callee in self.calledFunctionTable:
+            for subCallee in self.calledFunctionTable[callee]:
+                self.updateCalledFunctionList(subCallee)
+
+    def setCallWeighting(self, weight):
+        """ Sets the probably of generating a function call"""
+        self.callWeighting = weight
+
+    def writeln(self, line):
+        self.kfile.write(line + '\n')
+
+    def writeComment(self, comment):
+        self.writeln('# ' + comment)
+
+    def writeEmptyLine(self):
+        self.writeln("")
+
+    def writePredefinedFunctions(self):
+        self.writeComment("Define ':' for sequencing: as a low-precedence operator that ignores operands")
+        self.writeComment("and just returns the RHS.")
+        self.writeln("def binary : 1 (x y) y;")
+        self.writeEmptyLine()
+        self.writeComment("Helper functions defined within toy")
+        self.writeln("extern putchard(x);")
+        self.writeln("extern printd(d);")
+        self.writeln("extern printlf();")
+        self.writeEmptyLine()
+        self.writeComment("Print the result of a function call")
+        self.writeln("def printresult(N Result)")
+        self.writeln("  # 'result('")
+        self.writeln("  putchard(114) : putchard(101) : putchard(115) : putchard(117) : putchard(108) : putchard(116) : putchard(40) :")
+        self.writeln("  printd(N) :");
+        self.writeln("  # ') = '")
+        self.writeln("  putchard(41) : putchard(32) : putchard(61) : putchard(32) :")
+        self.writeln("  printd(Result) :");
+        self.writeln("  printlf();")
+        self.writeEmptyLine()
+
+    def writeRandomOperation(self, LValue, LHS, RHS):
+        shouldCallFunc = (self.lastFuncNum > 2 and random.random() < self.callWeighting)
+        if shouldCallFunc:
+            funcToCall = random.randrange(1, self.lastFuncNum - 1)
+            self.updateFunctionCallMap(self.lastFuncNum, funcToCall)
+            self.writeln("  %s = func%d(%s, %s) :" % (LValue, funcToCall, LHS, RHS))
+        else:
+            possibleOperations = ["+", "-", "*", "/"]
+            operation = random.choice(possibleOperations)
+            if operation == "-":
+                # Don't let our intermediate value become zero
+                # This is complicated by the fact that '<' is our only comparison operator
+                self.writeln("  if %s < %s then" % (LHS, RHS))
+                self.writeln("    %s = %s %s %s" % (LValue, LHS, operation, RHS))
+                self.writeln("  else if %s < %s then" % (RHS, LHS))
+                self.writeln("    %s = %s %s %s" % (LValue, LHS, operation, RHS))
+                self.writeln("  else")
+                self.writeln("    %s = %s %s %f :" % (LValue, LHS, operation, random.uniform(1, 100)))
+            else:
+                self.writeln("  %s = %s %s %s :" % (LValue, LHS, operation, RHS))
+
+    def getNextFuncNum(self):
+        result = self.nextFuncNum
+        self.nextFuncNum += 1
+        self.lastFuncNum = result
+        return result
+
+    def writeFunction(self, elements):
+        funcNum = self.getNextFuncNum()
+        self.writeComment("Auto-generated function number %d" % funcNum)
+        self.writeln("def func%d(X Y)" % funcNum)
+        self.writeln("  var temp1 = X,")
+        self.writeln("      temp2 = Y,")
+        self.writeln("      temp3 in")
+        # Initialize the variable names to be rotated
+        first = "temp3"
+        second = "temp1"
+        third = "temp2"
+        # Write some random operations
+        for i in range(elements):
+            self.writeRandomOperation(first, second, third)
+            # Rotate the variables
+            temp = first
+            first = second
+            second = third
+            third = temp
+        self.writeln("  " + third + ";")
+        self.writeEmptyLine()
+
+    def writeFunctionCall(self):
+        self.writeComment("Call the last function")
+        arg1 = random.uniform(1, 100)
+        arg2 = random.uniform(1, 100)
+        self.writeln("printresult(%d, func%d(%f, %f) )" % (self.lastFuncNum, self.lastFuncNum, arg1, arg2))
+        self.writeEmptyLine()
+        self.updateCalledFunctionList(self.lastFuncNum)
+
+    def writeFinalFunctionCounts(self):
+        self.writeComment("Called %d of %d functions" % (len(self.calledFunctions), self.lastFuncNum))
+
+def generateKScript(filename, numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting, timingScript):
+    """ Generate a random Kaleidoscope script based on the given parameters """
+    print "Generating " + filename
+    print("  %d functions, %d elements per function, %d functions between execution" %
+          (numFuncs, elementsPerFunc, funcsBetweenExec))
+    print("  Call weighting = %f" % callWeighting)
+    script = KScriptGenerator(filename)
+    script.setCallWeighting(callWeighting)
+    script.writeComment("===========================================================================")
+    script.writeComment("Auto-generated script")
+    script.writeComment("  %d functions, %d elements per function, %d functions between execution"
+                         % (numFuncs, elementsPerFunc, funcsBetweenExec))
+    script.writeComment("  call weighting = %f" % callWeighting)
+    script.writeComment("===========================================================================")
+    script.writeEmptyLine()
+    script.writePredefinedFunctions()
+    funcsSinceLastExec = 0
+    for i in range(numFuncs):
+        script.writeFunction(elementsPerFunc)
+        funcsSinceLastExec += 1
+        if funcsSinceLastExec == funcsBetweenExec:
+            script.writeFunctionCall()
+            funcsSinceLastExec = 0
+    # Always end with a function call
+    if funcsSinceLastExec > 0:
+        script.writeFunctionCall()
+    script.writeEmptyLine()
+    script.writeFinalFunctionCounts()
+    funcsCalled = len(script.calledFunctions)
+    print "  Called %d of %d functions, %d total" % (funcsCalled, numFuncs, script.totalCallsExecuted)
+    timingScript.writeTimingCall(filename, numFuncs, funcsCalled, script.totalCallsExecuted)
+
+# Execution begins here
+random.seed()
+
+timingScript = TimingScriptGenerator("time-toy.sh", "timing-data.txt")
+
+dataSets = [(5000, 3,  50, 0.50), (5000, 10, 100, 0.10), (5000, 10, 5, 0.10), (5000, 10, 1, 0.0),
+            (1000, 3,  10, 0.50), (1000, 10, 100, 0.10), (1000, 10, 5, 0.10), (1000, 10, 1, 0.0),
+            ( 200, 3,   2, 0.50), ( 200, 10,  40, 0.10), ( 200, 10, 2, 0.10), ( 200, 10, 1, 0.0)]
+
+# Generate the code
+for (numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting) in dataSets:
+    filename = "test-%d-%d-%d-%d.k" % (numFuncs, elementsPerFunc, funcsBetweenExec, int(callWeighting * 100))
+    generateKScript(filename, numFuncs, elementsPerFunc, funcsBetweenExec, callWeighting, timingScript)
+print "All done!"
diff --git a/examples/Kaleidoscope/MCJIT/lazy/toy-jit.cpp b/examples/Kaleidoscope/MCJIT/lazy/toy-jit.cpp
new file mode 100644
index 0000000000..8650019fe3
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/lazy/toy-jit.cpp
@@ -0,0 +1,1167 @@
+#define MINIMAL_STDERR_OUTPUT
+
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/JIT.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/PassManager.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Transforms/Scalar.h"
+#include <cstdio>
+#include <map>
+#include <string>
+#include <vector>
+
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+  tok_eof = -1,
+
+  // commands
+  tok_def = -2, tok_extern = -3,
+
+  // primary
+  tok_identifier = -4, tok_number = -5,
+  
+  // control
+  tok_if = -6, tok_then = -7, tok_else = -8,
+  tok_for = -9, tok_in = -10,
+  
+  // operators
+  tok_binary = -11, tok_unary = -12,
+  
+  // var definition
+  tok_var = -13
+};
+
+static std::string IdentifierStr;  // Filled in if tok_identifier
+static double NumVal;              // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+  static int LastChar = ' ';
+
+  // Skip any whitespace.
+  while (isspace(LastChar))
+    LastChar = getchar();
+
+  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+    IdentifierStr = LastChar;
+    while (isalnum((LastChar = getchar())))
+      IdentifierStr += LastChar;
+
+    if (IdentifierStr == "def") return tok_def;
+    if (IdentifierStr == "extern") return tok_extern;
+    if (IdentifierStr == "if") return tok_if;
+    if (IdentifierStr == "then") return tok_then;
+    if (IdentifierStr == "else") return tok_else;
+    if (IdentifierStr == "for") return tok_for;
+    if (IdentifierStr == "in") return tok_in;
+    if (IdentifierStr == "binary") return tok_binary;
+    if (IdentifierStr == "unary") return tok_unary;
+    if (IdentifierStr == "var") return tok_var;
+    return tok_identifier;
+  }
+
+  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
+    std::string NumStr;
+    do {
+      NumStr += LastChar;
+      LastChar = getchar();
+    } while (isdigit(LastChar) || LastChar == '.');
+
+    NumVal = strtod(NumStr.c_str(), 0);
+    return tok_number;
+  }
+
+  if (LastChar == '#') {
+    // Comment until end of line.
+    do LastChar = getchar();
+    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
+    
+    if (LastChar != EOF)
+      return gettok();
+  }
+  
+  // Check for end of file.  Don't eat the EOF.
+  if (LastChar == EOF)
+    return tok_eof;
+
+  // Otherwise, just return the character as its ascii value.
+  int ThisChar = LastChar;
+  LastChar = getchar();
+  return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+/// ExprAST - Base class for all expression nodes.
+class ExprAST {
+public:
+  virtual ~ExprAST() {}
+  virtual Value *Codegen() = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+class NumberExprAST : public ExprAST {
+  double Val;
+public:
+  NumberExprAST(double val) : Val(val) {}
+  virtual Value *Codegen();
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+class VariableExprAST : public ExprAST {
+  std::string Name;
+public:
+  VariableExprAST(const std::string &name) : Name(name) {}
+  const std::string &getName() const { return Name; }
+  virtual Value *Codegen();
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+  char Opcode;
+  ExprAST *Operand;
+public:
+  UnaryExprAST(char opcode, ExprAST *operand) 
+    : Opcode(opcode), Operand(operand) {}
+  virtual Value *Codegen();
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+class BinaryExprAST : public ExprAST {
+  char Op;
+  ExprAST *LHS, *RHS;
+public:
+  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) 
+    : Op(op), LHS(lhs), RHS(rhs) {}
+  virtual Value *Codegen();
+};
+
+/// CallExprAST - Expression class for function calls.
+class CallExprAST : public ExprAST {
+  std::string Callee;
+  std::vector<ExprAST*> Args;
+public:
+  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
+    : Callee(callee), Args(args) {}
+  virtual Value *Codegen();
+};
+
+/// IfExprAST - Expression class for if/then/else.
+class IfExprAST : public ExprAST {
+  ExprAST *Cond, *Then, *Else;
+public:
+  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
+  : Cond(cond), Then(then), Else(_else) {}
+  virtual Value *Codegen();
+};
+
+/// ForExprAST - Expression class for for/in.
+class ForExprAST : public ExprAST {
+  std::string VarName;
+  ExprAST *Start, *End, *Step, *Body;
+public:
+  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
+             ExprAST *step, ExprAST *body)
+    : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+  virtual Value *Codegen();
+};
+
+/// VarExprAST - Expression class for var/in
+class VarExprAST : public ExprAST {
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+  ExprAST *Body;
+public:
+  VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
+             ExprAST *body)
+  : VarNames(varnames), Body(body) {}
+  
+  virtual Value *Codegen();
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+class PrototypeAST {
+  std::string Name;
+  std::vector<std::string> Args;
+  bool isOperator;
+  unsigned Precedence;  // Precedence if a binary op.
+public:
+  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
+               bool isoperator = false, unsigned prec = 0)
+  : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
+  
+  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
+  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
+  
+  char getOperatorName() const {
+    assert(isUnaryOp() || isBinaryOp());
+    return Name[Name.size()-1];
+  }
+  
+  unsigned getBinaryPrecedence() const { return Precedence; }
+  
+  Function *Codegen();
+  
+  void CreateArgumentAllocas(Function *F);
+};
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+  PrototypeAST *Proto;
+  ExprAST *Body;
+public:
+  FunctionAST(PrototypeAST *proto, ExprAST *body)
+    : Proto(proto), Body(body) {}
+  
+  Function *Codegen();
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
+/// token the parser is looking at.  getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+  return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+  if (!isascii(CurTok))
+    return -1;
+  
+  // Make sure it's a declared binop.
+  int TokPrec = BinopPrecedence[CurTok];
+  if (TokPrec <= 0) return -1;
+  return TokPrec;
+}
+
+/// Error* - These are little helper functions for error handling.
+ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
+PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
+FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
+
+static ExprAST *ParseExpression();
+
+/// identifierexpr
+///   ::= identifier
+///   ::= identifier '(' expression* ')'
+static ExprAST *ParseIdentifierExpr() {
+  std::string IdName = IdentifierStr;
+  
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '(') // Simple variable ref.
+    return new VariableExprAST(IdName);
+  
+  // Call.
+  getNextToken();  // eat (
+  std::vector<ExprAST*> Args;
+  if (CurTok != ')') {
+    while (1) {
+      ExprAST *Arg = ParseExpression();
+      if (!Arg) return 0;
+      Args.push_back(Arg);
+
+      if (CurTok == ')') break;
+
+      if (CurTok != ',')
+        return Error("Expected ')' or ',' in argument list");
+      getNextToken();
+    }
+  }
+
+  // Eat the ')'.
+  getNextToken();
+  
+  return new CallExprAST(IdName, Args);
+}
+
+/// numberexpr ::= number
+static ExprAST *ParseNumberExpr() {
+  ExprAST *Result = new NumberExprAST(NumVal);
+  getNextToken(); // consume the number
+  return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static ExprAST *ParseParenExpr() {
+  getNextToken();  // eat (.
+  ExprAST *V = ParseExpression();
+  if (!V) return 0;
+  
+  if (CurTok != ')')
+    return Error("expected ')'");
+  getNextToken();  // eat ).
+  return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static ExprAST *ParseIfExpr() {
+  getNextToken();  // eat the if.
+  
+  // condition.
+  ExprAST *Cond = ParseExpression();
+  if (!Cond) return 0;
+  
+  if (CurTok != tok_then)
+    return Error("expected then");
+  getNextToken();  // eat the then
+  
+  ExprAST *Then = ParseExpression();
+  if (Then == 0) return 0;
+  
+  if (CurTok != tok_else)
+    return Error("expected else");
+  
+  getNextToken();
+  
+  ExprAST *Else = ParseExpression();
+  if (!Else) return 0;
+  
+  return new IfExprAST(Cond, Then, Else);
+}
+
+/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
+static ExprAST *ParseForExpr() {
+  getNextToken();  // eat the for.
+
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after for");
+  
+  std::string IdName = IdentifierStr;
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '=')
+    return Error("expected '=' after for");
+  getNextToken();  // eat '='.
+  
+  
+  ExprAST *Start = ParseExpression();
+  if (Start == 0) return 0;
+  if (CurTok != ',')
+    return Error("expected ',' after for start value");
+  getNextToken();
+  
+  ExprAST *End = ParseExpression();
+  if (End == 0) return 0;
+  
+  // The step value is optional.
+  ExprAST *Step = 0;
+  if (CurTok == ',') {
+    getNextToken();
+    Step = ParseExpression();
+    if (Step == 0) return 0;
+  }
+  
+  if (CurTok != tok_in)
+    return Error("expected 'in' after for");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+
+  return new ForExprAST(IdName, Start, End, Step, Body);
+}
+
+/// varexpr ::= 'var' identifier ('=' expression)? 
+//                    (',' identifier ('=' expression)?)* 'in' expression
+static ExprAST *ParseVarExpr() {
+  getNextToken();  // eat the var.
+
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+
+  // At least one variable name is required.
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after var");
+  
+  while (1) {
+    std::string Name = IdentifierStr;
+    getNextToken();  // eat identifier.
+
+    // Read the optional initializer.
+    ExprAST *Init = 0;
+    if (CurTok == '=') {
+      getNextToken(); // eat the '='.
+      
+      Init = ParseExpression();
+      if (Init == 0) return 0;
+    }
+    
+    VarNames.push_back(std::make_pair(Name, Init));
+    
+    // End of var list, exit loop.
+    if (CurTok != ',') break;
+    getNextToken(); // eat the ','.
+    
+    if (CurTok != tok_identifier)
+      return Error("expected identifier list after var");
+  }
+  
+  // At this point, we have to have 'in'.
+  if (CurTok != tok_in)
+    return Error("expected 'in' keyword after 'var'");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+  
+  return new VarExprAST(VarNames, Body);
+}
+
+/// primary
+///   ::= identifierexpr
+///   ::= numberexpr
+///   ::= parenexpr
+///   ::= ifexpr
+///   ::= forexpr
+///   ::= varexpr
+static ExprAST *ParsePrimary() {
+  switch (CurTok) {
+  default: return Error("unknown token when expecting an expression");
+  case tok_identifier: return ParseIdentifierExpr();
+  case tok_number:     return ParseNumberExpr();
+  case '(':            return ParseParenExpr();
+  case tok_if:         return ParseIfExpr();
+  case tok_for:        return ParseForExpr();
+  case tok_var:        return ParseVarExpr();
+  }
+}
+
+/// unary
+///   ::= primary
+///   ::= '!' unary
+static ExprAST *ParseUnary() {
+  // If the current token is not an operator, it must be a primary expr.
+  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+    return ParsePrimary();
+  
+  // If this is a unary operator, read it.
+  int Opc = CurTok;
+  getNextToken();
+  if (ExprAST *Operand = ParseUnary())
+    return new UnaryExprAST(Opc, Operand);
+  return 0;
+}
+
+/// binoprhs
+///   ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+  // If this is a binop, find its precedence.
+  while (1) {
+    int TokPrec = GetTokPrecedence();
+    
+    // If this is a binop that binds at least as tightly as the current binop,
+    // consume it, otherwise we are done.
+    if (TokPrec < ExprPrec)
+      return LHS;
+    
+    // Okay, we know this is a binop.
+    int BinOp = CurTok;
+    getNextToken();  // eat binop
+    
+    // Parse the unary expression after the binary operator.
+    ExprAST *RHS = ParseUnary();
+    if (!RHS) return 0;
+    
+    // If BinOp binds less tightly with RHS than the operator after RHS, let
+    // the pending operator take RHS as its LHS.
+    int NextPrec = GetTokPrecedence();
+    if (TokPrec < NextPrec) {
+      RHS = ParseBinOpRHS(TokPrec+1, RHS);
+      if (RHS == 0) return 0;
+    }
+    
+    // Merge LHS/RHS.
+    LHS = new BinaryExprAST(BinOp, LHS, RHS);
+  }
+}
+
+/// expression
+///   ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+  ExprAST *LHS = ParseUnary();
+  if (!LHS) return 0;
+  
+  return ParseBinOpRHS(0, LHS);
+}
+
+/// prototype
+///   ::= id '(' id* ')'
+///   ::= binary LETTER number? (id, id)
+///   ::= unary LETTER (id)
+static PrototypeAST *ParsePrototype() {
+  std::string FnName;
+  
+  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+  unsigned BinaryPrecedence = 30;
+  
+  switch (CurTok) {
+  default:
+    return ErrorP("Expected function name in prototype");
+  case tok_identifier:
+    FnName = IdentifierStr;
+    Kind = 0;
+    getNextToken();
+    break;
+  case tok_unary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected unary operator");
+    FnName = "unary";
+    FnName += (char)CurTok;
+    Kind = 1;
+    getNextToken();
+    break;
+  case tok_binary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected binary operator");
+    FnName = "binary";
+    FnName += (char)CurTok;
+    Kind = 2;
+    getNextToken();
+    
+    // Read the precedence if present.
+    if (CurTok == tok_number) {
+      if (NumVal < 1 || NumVal > 100)
+        return ErrorP("Invalid precedecnce: must be 1..100");
+      BinaryPrecedence = (unsigned)NumVal;
+      getNextToken();
+    }
+    break;
+  }
+  
+  if (CurTok != '(')
+    return ErrorP("Expected '(' in prototype");
+  
+  std::vector<std::string> ArgNames;
+  while (getNextToken() == tok_identifier)
+    ArgNames.push_back(IdentifierStr);
+  if (CurTok != ')')
+    return ErrorP("Expected ')' in prototype");
+  
+  // success.
+  getNextToken();  // eat ')'.
+  
+  // Verify right number of names for operator.
+  if (Kind && ArgNames.size() != Kind)
+    return ErrorP("Invalid number of operands for operator");
+  
+  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static FunctionAST *ParseDefinition() {
+  getNextToken();  // eat def.
+  PrototypeAST *Proto = ParsePrototype();
+  if (Proto == 0) return 0;
+
+  if (ExprAST *E = ParseExpression())
+    return new FunctionAST(Proto, E);
+  return 0;
+}
+
+/// toplevelexpr ::= expression
+static FunctionAST *ParseTopLevelExpr() {
+  if (ExprAST *E = ParseExpression()) {
+    // Make an anonymous proto.
+    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
+    return new FunctionAST(Proto, E);
+  }
+  return 0;
+}
+
+/// external ::= 'extern' prototype
+static PrototypeAST *ParseExtern() {
+  getNextToken();  // eat extern.
+  return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+static Module *TheModule;
+static FunctionPassManager *TheFPM;
+static IRBuilder<> Builder(getGlobalContext());
+static std::map<std::string, AllocaInst*> NamedValues;
+
+Value *ErrorV(const char *Str) { Error(Str); return 0; }
+
+/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
+/// the function.  This is used for mutable variables etc.
+static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
+                                          const std::string &VarName) {
+  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
+                 TheFunction->getEntryBlock().begin());
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+                           VarName.c_str());
+}
+
+Value *NumberExprAST::Codegen() {
+  return ConstantFP::get(getGlobalContext(), APFloat(Val));
+}
+
+Value *VariableExprAST::Codegen() {
+  // Look this variable up in the function.
+  Value *V = NamedValues[Name];
+  if (V == 0) return ErrorV("Unknown variable name");
+
+  // Load the value.
+  return Builder.CreateLoad(V, Name.c_str());
+}
+
+Value *UnaryExprAST::Codegen() {
+  Value *OperandV = Operand->Codegen();
+  if (OperandV == 0) return 0;
+#ifdef USE_MCJIT
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
+#else
+  Function *F = TheModule->getFunction(std::string("unary")+Opcode);
+#endif
+  if (F == 0)
+    return ErrorV("Unknown unary operator");
+  
+  return Builder.CreateCall(F, OperandV, "unop");
+}
+
+Value *BinaryExprAST::Codegen() {
+  // Special case '=' because we don't want to emit the LHS as an expression.
+  if (Op == '=') {
+    // Assignment requires the LHS to be an identifier.
+    VariableExprAST *LHSE = dynamic_cast<VariableExprAST*>(LHS);
+    if (!LHSE)
+      return ErrorV("destination of '=' must be a variable");
+    // Codegen the RHS.
+    Value *Val = RHS->Codegen();
+    if (Val == 0) return 0;
+
+    // Look up the name.
+    Value *Variable = NamedValues[LHSE->getName()];
+    if (Variable == 0) return ErrorV("Unknown variable name");
+
+    Builder.CreateStore(Val, Variable);
+    return Val;
+  }
+  
+  Value *L = LHS->Codegen();
+  Value *R = RHS->Codegen();
+  if (L == 0 || R == 0) return 0;
+  
+  switch (Op) {
+  case '+': return Builder.CreateFAdd(L, R, "addtmp");
+  case '-': return Builder.CreateFSub(L, R, "subtmp");
+  case '*': return Builder.CreateFMul(L, R, "multmp");
+  case '/': return Builder.CreateFDiv(L, R, "divtmp");
+  case '<':
+    L = Builder.CreateFCmpULT(L, R, "cmptmp");
+    // Convert bool 0/1 to double 0.0 or 1.0
+    return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+                                "booltmp");
+  default: break;
+  }
+  
+  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+  // a call to it.
+  Function *F = TheModule->getFunction(std::string("binary")+Op);
+  assert(F && "binary operator not found!");
+  
+  Value *Ops[] = { L, R };
+  return Builder.CreateCall(F, Ops, "binop");
+}
+
+Value *CallExprAST::Codegen() {
+  // Look up the name in the global module table.
+  Function *CalleeF = TheModule->getFunction(Callee);
+  if (CalleeF == 0) {
+    char error_str[64];
+    sprintf(error_str, "Unknown function referenced %s", Callee.c_str()); 
+    return ErrorV(error_str);
+  }
+  
+  // If argument mismatch error.
+  if (CalleeF->arg_size() != Args.size())
+    return ErrorV("Incorrect # arguments passed");
+
+  std::vector<Value*> ArgsV;
+  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+    ArgsV.push_back(Args[i]->Codegen());
+    if (ArgsV.back() == 0) return 0;
+  }
+  
+  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
+}
+
+Value *IfExprAST::Codegen() {
+  Value *CondV = Cond->Codegen();
+  if (CondV == 0) return 0;
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  CondV = Builder.CreateFCmpONE(CondV, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                "ifcond");
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+  
+  // Create blocks for the then and else cases.  Insert the 'then' block at the
+  // end of the function.
+  BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
+  BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
+  BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
+  
+  Builder.CreateCondBr(CondV, ThenBB, ElseBB);
+  
+  // Emit then value.
+  Builder.SetInsertPoint(ThenBB);
+  
+  Value *ThenV = Then->Codegen();
+  if (ThenV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+  ThenBB = Builder.GetInsertBlock();
+  
+  // Emit else block.
+  TheFunction->getBasicBlockList().push_back(ElseBB);
+  Builder.SetInsertPoint(ElseBB);
+  
+  Value *ElseV = Else->Codegen();
+  if (ElseV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+  ElseBB = Builder.GetInsertBlock();
+  
+  // Emit merge block.
+  TheFunction->getBasicBlockList().push_back(MergeBB);
+  Builder.SetInsertPoint(MergeBB);
+  PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
+                                  "iftmp");
+  
+  PN->addIncoming(ThenV, ThenBB);
+  PN->addIncoming(ElseV, ElseBB);
+  return PN;
+}
+
+Value *ForExprAST::Codegen() {
+  // Output this as:
+  //   var = alloca double
+  //   ...
+  //   start = startexpr
+  //   store start -> var
+  //   goto loop
+  // loop: 
+  //   ...
+  //   bodyexpr
+  //   ...
+  // loopend:
+  //   step = stepexpr
+  //   endcond = endexpr
+  //
+  //   curvar = load var
+  //   nextvar = curvar + step
+  //   store nextvar -> var
+  //   br endcond, loop, endloop
+  // outloop:
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Create an alloca for the variable in the entry block.
+  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+  
+  // Emit the start code first, without 'variable' in scope.
+  Value *StartVal = Start->Codegen();
+  if (StartVal == 0) return 0;
+  
+  // Store the value into the alloca.
+  Builder.CreateStore(StartVal, Alloca);
+  
+  // Make the new basic block for the loop header, inserting after current
+  // block.
+  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+  
+  // Insert an explicit fall through from the current block to the LoopBB.
+  Builder.CreateBr(LoopBB);
+
+  // Start insertion in LoopBB.
+  Builder.SetInsertPoint(LoopBB);
+  
+  // Within the loop, the variable is defined equal to the PHI node.  If it
+  // shadows an existing variable, we have to restore it, so save it now.
+  AllocaInst *OldVal = NamedValues[VarName];
+  NamedValues[VarName] = Alloca;
+  
+  // Emit the body of the loop.  This, like any other expr, can change the
+  // current BB.  Note that we ignore the value computed by the body, but don't
+  // allow an error.
+  if (Body->Codegen() == 0)
+    return 0;
+  
+  // Emit the step value.
+  Value *StepVal;
+  if (Step) {
+    StepVal = Step->Codegen();
+    if (StepVal == 0) return 0;
+  } else {
+    // If not specified, use 1.0.
+    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
+  }
+  
+  // Compute the end condition.
+  Value *EndCond = End->Codegen();
+  if (EndCond == 0) return EndCond;
+  
+  // Reload, increment, and restore the alloca.  This handles the case where
+  // the body of the loop mutates the variable.
+  Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
+  Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
+  Builder.CreateStore(NextVar, Alloca);
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  EndCond = Builder.CreateFCmpONE(EndCond, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                  "loopcond");
+  
+  // Create the "after loop" block and insert it.
+  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+  
+  // Insert the conditional branch into the end of LoopEndBB.
+  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
+  
+  // Any new code will be inserted in AfterBB.
+  Builder.SetInsertPoint(AfterBB);
+  
+  // Restore the unshadowed variable.
+  if (OldVal)
+    NamedValues[VarName] = OldVal;
+  else
+    NamedValues.erase(VarName);
+
+  
+  // for expr always returns 0.0.
+  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
+}
+
+Value *VarExprAST::Codegen() {
+  std::vector<AllocaInst *> OldBindings;
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Register all variables and emit their initializer.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
+    const std::string &VarName = VarNames[i].first;
+    ExprAST *Init = VarNames[i].second;
+    
+    // Emit the initializer before adding the variable to scope, this prevents
+    // the initializer from referencing the variable itself, and permits stuff
+    // like this:
+    //  var a = 1 in
+    //    var a = a in ...   # refers to outer 'a'.
+    Value *InitVal;
+    if (Init) {
+      InitVal = Init->Codegen();
+      if (InitVal == 0) return 0;
+    } else { // If not specified, use 0.0.
+      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
+    }
+    
+    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+    Builder.CreateStore(InitVal, Alloca);
+
+    // Remember the old variable binding so that we can restore the binding when
+    // we unrecurse.
+    OldBindings.push_back(NamedValues[VarName]);
+    
+    // Remember this binding.
+    NamedValues[VarName] = Alloca;
+  }
+  
+  // Codegen the body, now that all vars are in scope.
+  Value *BodyVal = Body->Codegen();
+  if (BodyVal == 0) return 0;
+  
+  // Pop all our variables from scope.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
+    NamedValues[VarNames[i].first] = OldBindings[i];
+
+  // Return the body computation.
+  return BodyVal;
+}
+
+Function *PrototypeAST::Codegen() {
+  // Make the function type:  double(double,double) etc.
+  std::vector<Type*> Doubles(Args.size(), 
+                             Type::getDoubleTy(getGlobalContext()));
+  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+                                       Doubles, false);
+
+  Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
+  // If F conflicted, there was already something named 'Name'.  If it has a
+  // body, don't allow redefinition or reextern.
+  if (F->getName() != Name) {
+    // Delete the one we just made and get the existing one.
+    F->eraseFromParent();
+    F = TheModule->getFunction(Name);
+    // If F already has a body, reject this.
+    if (!F->empty()) {
+      ErrorF("redefinition of function");
+      return 0;
+    }
+    // If F took a different number of args, reject.
+    if (F->arg_size() != Args.size()) {
+      ErrorF("redefinition of function with different # args");
+      return 0;
+    }
+  }
+
+  // Set names for all arguments.
+  unsigned Idx = 0;
+  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+       ++AI, ++Idx)
+    AI->setName(Args[Idx]);
+    
+  return F;
+}
+
+/// CreateArgumentAllocas - Create an alloca for each argument and register the
+/// argument in the symbol table so that references to it will succeed.
+void PrototypeAST::CreateArgumentAllocas(Function *F) {
+  Function::arg_iterator AI = F->arg_begin();
+  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
+    // Create an alloca for this variable.
+    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
+
+    // Store the initial value into the alloca.
+    Builder.CreateStore(AI, Alloca);
+
+    // Add arguments to variable symbol table.
+    NamedValues[Args[Idx]] = Alloca;
+  }
+}
+
+Function *FunctionAST::Codegen() {
+  NamedValues.clear();
+  
+  Function *TheFunction = Proto->Codegen();
+  if (TheFunction == 0)
+    return 0;
+
+  // If this is an operator, install it.
+  if (Proto->isBinaryOp())
+    BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
+
+  // Create a new basic block to start insertion into.
+  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+  Builder.SetInsertPoint(BB);
+  
+  // Add all arguments to the symbol table and create their allocas.
+  Proto->CreateArgumentAllocas(TheFunction);
+
+  if (Value *RetVal = Body->Codegen()) {
+    // Finish off the function.
+    Builder.CreateRet(RetVal);
+
+    // Validate the generated code, checking for consistency.
+    verifyFunction(*TheFunction);
+
+    // Optimize the function.
+    TheFPM->run(*TheFunction);
+
+    return TheFunction;
+  }
+  
+  // Error reading body, remove function.
+  TheFunction->eraseFromParent();
+
+  if (Proto->isBinaryOp())
+    BinopPrecedence.erase(Proto->getOperatorName());
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static ExecutionEngine *TheExecutionEngine;
+
+static void HandleDefinition() {
+  if (FunctionAST *F = ParseDefinition()) {
+    if (Function *LF = F->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read function definition:");
+      LF->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleExtern() {
+  if (PrototypeAST *P = ParseExtern()) {
+    if (Function *F = P->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read extern: ");
+      F->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleTopLevelExpression() {
+  // Evaluate a top-level expression into an anonymous function.
+  if (FunctionAST *F = ParseTopLevelExpr()) {
+    if (Function *LF = F->Codegen()) {
+      // JIT the function, returning a function pointer.
+      void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
+      // Cast it to the right type (takes no arguments, returns a double) so we
+      // can call it as a native function.
+      double (*FP)() = (double (*)())(intptr_t)FPtr;
+#ifdef MINIMAL_STDERR_OUTPUT
+      FP();
+#else
+      fprintf(stderr, "Evaluated to %f\n", FP());
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+  while (1) {
+#ifndef MINIMAL_STDERR_OUTPUT
+    fprintf(stderr, "ready> ");
+#endif
+    switch (CurTok) {
+    case tok_eof:    return;
+    case ';':        getNextToken(); break;  // ignore top-level semicolons.
+    case tok_def:    HandleDefinition(); break;
+    case tok_extern: HandleExtern(); break;
+    default:         HandleTopLevelExpression(); break;
+    }
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C" 
+double putchard(double X) {
+  putchar((char)X);
+  return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C" 
+double printd(double X) {
+  printf("%f", X);
+  return 0;
+}
+
+extern "C" 
+double printlf() {
+  printf("\n");
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main(int argc, char **argv) {
+  InitializeNativeTarget();
+  LLVMContext &Context = getGlobalContext();
+
+  // Install standard binary operators.
+  // 1 is lowest precedence.
+  BinopPrecedence['='] = 2;
+  BinopPrecedence['<'] = 10;
+  BinopPrecedence['+'] = 20;
+  BinopPrecedence['-'] = 20;
+  BinopPrecedence['/'] = 40;
+  BinopPrecedence['*'] = 40;  // highest.
+
+  // Make the module, which holds all the code.
+  TheModule = new Module("my cool jit", Context);
+
+  // Create the JIT.  This takes ownership of the module.
+  std::string ErrStr;
+  TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create();
+  if (!TheExecutionEngine) {
+    fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
+    exit(1);
+  }
+
+  FunctionPassManager OurFPM(TheModule);
+
+  // Set up the optimizer pipeline.  Start with registering info about how the
+  // target lays out data structures.
+  OurFPM.add(new DataLayout(*TheExecutionEngine->getDataLayout()));
+  // Provide basic AliasAnalysis support for GVN.
+  OurFPM.add(createBasicAliasAnalysisPass());
+  // Promote allocas to registers.
+  OurFPM.add(createPromoteMemoryToRegisterPass());
+  // Do simple "peephole" optimizations and bit-twiddling optzns.
+  OurFPM.add(createInstructionCombiningPass());
+  // Reassociate expressions.
+  OurFPM.add(createReassociatePass());
+  // Eliminate Common SubExpressions.
+  OurFPM.add(createGVNPass());
+  // Simplify the control flow graph (deleting unreachable blocks, etc).
+  OurFPM.add(createCFGSimplificationPass());
+
+  OurFPM.doInitialization();
+
+  // Set the global so the code gen can use this.
+  TheFPM = &OurFPM;
+
+  // Prime the first token.
+#ifndef MINIMAL_STDERR_OUTPUT
+  fprintf(stderr, "ready> ");
+#endif
+  getNextToken();
+
+  // Run the main "interpreter loop" now.
+  MainLoop();
+
+  // Print out all of the generated code.
+  TheFPM = 0;
+#ifndef MINIMAL_STDERR_OUTPUT
+  TheModule->dump();
+#endif
+  return 0;
+}
diff --git a/examples/Kaleidoscope/MCJIT/lazy/toy.cpp b/examples/Kaleidoscope/MCJIT/lazy/toy.cpp
new file mode 100644
index 0000000000..0a8d80e25a
--- /dev/null
+++ b/examples/Kaleidoscope/MCJIT/lazy/toy.cpp
@@ -0,0 +1,1422 @@
+#define MINIMAL_STDERR_OUTPUT
+
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/MCJIT.h"
+#include "llvm/ExecutionEngine/SectionMemoryManager.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/PassManager.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Transforms/Scalar.h"
+#include <cstdio>
+#include <map>
+#include <string>
+#include <vector>
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+  tok_eof = -1,
+
+  // commands
+  tok_def = -2, tok_extern = -3,
+
+  // primary
+  tok_identifier = -4, tok_number = -5,
+  
+  // control
+  tok_if = -6, tok_then = -7, tok_else = -8,
+  tok_for = -9, tok_in = -10,
+  
+  // operators
+  tok_binary = -11, tok_unary = -12,
+  
+  // var definition
+  tok_var = -13
+};
+
+static std::string IdentifierStr;  // Filled in if tok_identifier
+static double NumVal;              // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+  static int LastChar = ' ';
+
+  // Skip any whitespace.
+  while (isspace(LastChar))
+    LastChar = getchar();
+
+  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+    IdentifierStr = LastChar;
+    while (isalnum((LastChar = getchar())))
+      IdentifierStr += LastChar;
+
+    if (IdentifierStr == "def") return tok_def;
+    if (IdentifierStr == "extern") return tok_extern;
+    if (IdentifierStr == "if") return tok_if;
+    if (IdentifierStr == "then") return tok_then;
+    if (IdentifierStr == "else") return tok_else;
+    if (IdentifierStr == "for") return tok_for;
+    if (IdentifierStr == "in") return tok_in;
+    if (IdentifierStr == "binary") return tok_binary;
+    if (IdentifierStr == "unary") return tok_unary;
+    if (IdentifierStr == "var") return tok_var;
+    return tok_identifier;
+  }
+
+  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
+    std::string NumStr;
+    do {
+      NumStr += LastChar;
+      LastChar = getchar();
+    } while (isdigit(LastChar) || LastChar == '.');
+
+    NumVal = strtod(NumStr.c_str(), 0);
+    return tok_number;
+  }
+
+  if (LastChar == '#') {
+    // Comment until end of line.
+    do LastChar = getchar();
+    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
+    
+    if (LastChar != EOF)
+      return gettok();
+  }
+  
+  // Check for end of file.  Don't eat the EOF.
+  if (LastChar == EOF)
+    return tok_eof;
+
+  // Otherwise, just return the character as its ascii value.
+  int ThisChar = LastChar;
+  LastChar = getchar();
+  return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+/// ExprAST - Base class for all expression nodes.
+class ExprAST {
+public:
+  virtual ~ExprAST() {}
+  virtual Value *Codegen() = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+class NumberExprAST : public ExprAST {
+  double Val;
+public:
+  NumberExprAST(double val) : Val(val) {}
+  virtual Value *Codegen();
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+class VariableExprAST : public ExprAST {
+  std::string Name;
+public:
+  VariableExprAST(const std::string &name) : Name(name) {}
+  const std::string &getName() const { return Name; }
+  virtual Value *Codegen();
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+  char Opcode;
+  ExprAST *Operand;
+public:
+  UnaryExprAST(char opcode, ExprAST *operand) 
+    : Opcode(opcode), Operand(operand) {}
+  virtual Value *Codegen();
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+class BinaryExprAST : public ExprAST {
+  char Op;
+  ExprAST *LHS, *RHS;
+public:
+  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) 
+    : Op(op), LHS(lhs), RHS(rhs) {}
+  virtual Value *Codegen();
+};
+
+/// CallExprAST - Expression class for function calls.
+class CallExprAST : public ExprAST {
+  std::string Callee;
+  std::vector<ExprAST*> Args;
+public:
+  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
+    : Callee(callee), Args(args) {}
+  virtual Value *Codegen();
+};
+
+/// IfExprAST - Expression class for if/then/else.
+class IfExprAST : public ExprAST {
+  ExprAST *Cond, *Then, *Else;
+public:
+  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
+  : Cond(cond), Then(then), Else(_else) {}
+  virtual Value *Codegen();
+};
+
+/// ForExprAST - Expression class for for/in.
+class ForExprAST : public ExprAST {
+  std::string VarName;
+  ExprAST *Start, *End, *Step, *Body;
+public:
+  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
+             ExprAST *step, ExprAST *body)
+    : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+  virtual Value *Codegen();
+};
+
+/// VarExprAST - Expression class for var/in
+class VarExprAST : public ExprAST {
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+  ExprAST *Body;
+public:
+  VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
+             ExprAST *body)
+  : VarNames(varnames), Body(body) {}
+  
+  virtual Value *Codegen();
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+class PrototypeAST {
+  std::string Name;
+  std::vector<std::string> Args;
+  bool isOperator;
+  unsigned Precedence;  // Precedence if a binary op.
+public:
+  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
+               bool isoperator = false, unsigned prec = 0)
+  : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
+  
+  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
+  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
+  
+  char getOperatorName() const {
+    assert(isUnaryOp() || isBinaryOp());
+    return Name[Name.size()-1];
+  }
+  
+  unsigned getBinaryPrecedence() const { return Precedence; }
+  
+  Function *Codegen();
+  
+  void CreateArgumentAllocas(Function *F);
+};
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+  PrototypeAST *Proto;
+  ExprAST *Body;
+public:
+  FunctionAST(PrototypeAST *proto, ExprAST *body)
+    : Proto(proto), Body(body) {}
+  
+  Function *Codegen();
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
+/// token the parser is looking at.  getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+  return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+  if (!isascii(CurTok))
+    return -1;
+  
+  // Make sure it's a declared binop.
+  int TokPrec = BinopPrecedence[CurTok];
+  if (TokPrec <= 0) return -1;
+  return TokPrec;
+}
+
+/// Error* - These are little helper functions for error handling.
+ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
+PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
+FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
+
+static ExprAST *ParseExpression();
+
+/// identifierexpr
+///   ::= identifier
+///   ::= identifier '(' expression* ')'
+static ExprAST *ParseIdentifierExpr() {
+  std::string IdName = IdentifierStr;
+  
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '(') // Simple variable ref.
+    return new VariableExprAST(IdName);
+  
+  // Call.
+  getNextToken();  // eat (
+  std::vector<ExprAST*> Args;
+  if (CurTok != ')') {
+    while (1) {
+      ExprAST *Arg = ParseExpression();
+      if (!Arg) return 0;
+      Args.push_back(Arg);
+
+      if (CurTok == ')') break;
+
+      if (CurTok != ',')
+        return Error("Expected ')' or ',' in argument list");
+      getNextToken();
+    }
+  }
+
+  // Eat the ')'.
+  getNextToken();
+  
+  return new CallExprAST(IdName, Args);
+}
+
+/// numberexpr ::= number
+static ExprAST *ParseNumberExpr() {
+  ExprAST *Result = new NumberExprAST(NumVal);
+  getNextToken(); // consume the number
+  return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static ExprAST *ParseParenExpr() {
+  getNextToken();  // eat (.
+  ExprAST *V = ParseExpression();
+  if (!V) return 0;
+  
+  if (CurTok != ')')
+    return Error("expected ')'");
+  getNextToken();  // eat ).
+  return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static ExprAST *ParseIfExpr() {
+  getNextToken();  // eat the if.
+  
+  // condition.
+  ExprAST *Cond = ParseExpression();
+  if (!Cond) return 0;
+  
+  if (CurTok != tok_then)
+    return Error("expected then");
+  getNextToken();  // eat the then
+  
+  ExprAST *Then = ParseExpression();
+  if (Then == 0) return 0;
+  
+  if (CurTok != tok_else)
+    return Error("expected else");
+  
+  getNextToken();
+  
+  ExprAST *Else = ParseExpression();
+  if (!Else) return 0;
+  
+  return new IfExprAST(Cond, Then, Else);
+}
+
+/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
+static ExprAST *ParseForExpr() {
+  getNextToken();  // eat the for.
+
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after for");
+  
+  std::string IdName = IdentifierStr;
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '=')
+    return Error("expected '=' after for");
+  getNextToken();  // eat '='.
+  
+  
+  ExprAST *Start = ParseExpression();
+  if (Start == 0) return 0;
+  if (CurTok != ',')
+    return Error("expected ',' after for start value");
+  getNextToken();
+  
+  ExprAST *End = ParseExpression();
+  if (End == 0) return 0;
+  
+  // The step value is optional.
+  ExprAST *Step = 0;
+  if (CurTok == ',') {
+    getNextToken();
+    Step = ParseExpression();
+    if (Step == 0) return 0;
+  }
+  
+  if (CurTok != tok_in)
+    return Error("expected 'in' after for");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+
+  return new ForExprAST(IdName, Start, End, Step, Body);
+}
+
+/// varexpr ::= 'var' identifier ('=' expression)? 
+//                    (',' identifier ('=' expression)?)* 'in' expression
+static ExprAST *ParseVarExpr() {
+  getNextToken();  // eat the var.
+
+  std::vector<std::pair<std::string, ExprAST*> > VarNames;
+
+  // At least one variable name is required.
+  if (CurTok != tok_identifier)
+    return Error("expected identifier after var");
+  
+  while (1) {
+    std::string Name = IdentifierStr;
+    getNextToken();  // eat identifier.
+
+    // Read the optional initializer.
+    ExprAST *Init = 0;
+    if (CurTok == '=') {
+      getNextToken(); // eat the '='.
+      
+      Init = ParseExpression();
+      if (Init == 0) return 0;
+    }
+    
+    VarNames.push_back(std::make_pair(Name, Init));
+    
+    // End of var list, exit loop.
+    if (CurTok != ',') break;
+    getNextToken(); // eat the ','.
+    
+    if (CurTok != tok_identifier)
+      return Error("expected identifier list after var");
+  }
+  
+  // At this point, we have to have 'in'.
+  if (CurTok != tok_in)
+    return Error("expected 'in' keyword after 'var'");
+  getNextToken();  // eat 'in'.
+  
+  ExprAST *Body = ParseExpression();
+  if (Body == 0) return 0;
+  
+  return new VarExprAST(VarNames, Body);
+}
+
+/// primary
+///   ::= identifierexpr
+///   ::= numberexpr
+///   ::= parenexpr
+///   ::= ifexpr
+///   ::= forexpr
+///   ::= varexpr
+static ExprAST *ParsePrimary() {
+  switch (CurTok) {
+  default: return Error("unknown token when expecting an expression");
+  case tok_identifier: return ParseIdentifierExpr();
+  case tok_number:     return ParseNumberExpr();
+  case '(':            return ParseParenExpr();
+  case tok_if:         return ParseIfExpr();
+  case tok_for:        return ParseForExpr();
+  case tok_var:        return ParseVarExpr();
+  }
+}
+
+/// unary
+///   ::= primary
+///   ::= '!' unary
+static ExprAST *ParseUnary() {
+  // If the current token is not an operator, it must be a primary expr.
+  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+    return ParsePrimary();
+  
+  // If this is a unary operator, read it.
+  int Opc = CurTok;
+  getNextToken();
+  if (ExprAST *Operand = ParseUnary())
+    return new UnaryExprAST(Opc, Operand);
+  return 0;
+}
+
+/// binoprhs
+///   ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+  // If this is a binop, find its precedence.
+  while (1) {
+    int TokPrec = GetTokPrecedence();
+    
+    // If this is a binop that binds at least as tightly as the current binop,
+    // consume it, otherwise we are done.
+    if (TokPrec < ExprPrec)
+      return LHS;
+    
+    // Okay, we know this is a binop.
+    int BinOp = CurTok;
+    getNextToken();  // eat binop
+    
+    // Parse the unary expression after the binary operator.
+    ExprAST *RHS = ParseUnary();
+    if (!RHS) return 0;
+    
+    // If BinOp binds less tightly with RHS than the operator after RHS, let
+    // the pending operator take RHS as its LHS.
+    int NextPrec = GetTokPrecedence();
+    if (TokPrec < NextPrec) {
+      RHS = ParseBinOpRHS(TokPrec+1, RHS);
+      if (RHS == 0) return 0;
+    }
+    
+    // Merge LHS/RHS.
+    LHS = new BinaryExprAST(BinOp, LHS, RHS);
+  }
+}
+
+/// expression
+///   ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+  ExprAST *LHS = ParseUnary();
+  if (!LHS) return 0;
+  
+  return ParseBinOpRHS(0, LHS);
+}
+
+/// prototype
+///   ::= id '(' id* ')'
+///   ::= binary LETTER number? (id, id)
+///   ::= unary LETTER (id)
+static PrototypeAST *ParsePrototype() {
+  std::string FnName;
+  
+  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+  unsigned BinaryPrecedence = 30;
+  
+  switch (CurTok) {
+  default:
+    return ErrorP("Expected function name in prototype");
+  case tok_identifier:
+    FnName = IdentifierStr;
+    Kind = 0;
+    getNextToken();
+    break;
+  case tok_unary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected unary operator");
+    FnName = "unary";
+    FnName += (char)CurTok;
+    Kind = 1;
+    getNextToken();
+    break;
+  case tok_binary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorP("Expected binary operator");
+    FnName = "binary";
+    FnName += (char)CurTok;
+    Kind = 2;
+    getNextToken();
+    
+    // Read the precedence if present.
+    if (CurTok == tok_number) {
+      if (NumVal < 1 || NumVal > 100)
+        return ErrorP("Invalid precedecnce: must be 1..100");
+      BinaryPrecedence = (unsigned)NumVal;
+      getNextToken();
+    }
+    break;
+  }
+  
+  if (CurTok != '(')
+    return ErrorP("Expected '(' in prototype");
+  
+  std::vector<std::string> ArgNames;
+  while (getNextToken() == tok_identifier)
+    ArgNames.push_back(IdentifierStr);
+  if (CurTok != ')')
+    return ErrorP("Expected ')' in prototype");
+  
+  // success.
+  getNextToken();  // eat ')'.
+  
+  // Verify right number of names for operator.
+  if (Kind && ArgNames.size() != Kind)
+    return ErrorP("Invalid number of operands for operator");
+  
+  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static FunctionAST *ParseDefinition() {
+  getNextToken();  // eat def.
+  PrototypeAST *Proto = ParsePrototype();
+  if (Proto == 0) return 0;
+
+  if (ExprAST *E = ParseExpression())
+    return new FunctionAST(Proto, E);
+  return 0;
+}
+
+/// toplevelexpr ::= expression
+static FunctionAST *ParseTopLevelExpr() {
+  if (ExprAST *E = ParseExpression()) {
+    // Make an anonymous proto.
+    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
+    return new FunctionAST(Proto, E);
+  }
+  return 0;
+}
+
+/// external ::= 'extern' prototype
+static PrototypeAST *ParseExtern() {
+  getNextToken();  // eat extern.
+  return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Quick and dirty hack
+//===----------------------------------------------------------------------===//
+
+// FIXME: Obviously we can do better than this
+std::string GenerateUniqueName(const char *root)
+{
+  static int i = 0;
+  char s[16];
+  sprintf(s, "%s%d", root, i++);
+  std::string S = s;
+  return S;
+}
+
+std::string MakeLegalFunctionName(std::string Name)
+{
+  std::string NewName;
+  if (!Name.length())
+      return GenerateUniqueName("anon_func_");
+
+  // Start with what we have
+  NewName = Name;
+
+  // Look for a numberic first character
+  if (NewName.find_first_of("0123456789") == 0) {
+    NewName.insert(0, 1, 'n');
+  }
+
+  // Replace illegal characters with their ASCII equivalent
+  std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+  size_t pos;
+  while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
+    char old_c = NewName.at(pos);
+    char new_str[16];
+    sprintf(new_str, "%d", (int)old_c);
+    NewName = NewName.replace(pos, 1, new_str);
+  }
+
+  return NewName;
+}
+
+//===----------------------------------------------------------------------===//
+// MCJIT helper class
+//===----------------------------------------------------------------------===//
+
+class MCJITHelper
+{
+public:
+  MCJITHelper(LLVMContext& C) : Context(C), OpenModule(NULL) {}
+  ~MCJITHelper();
+
+  Function *getFunction(const std::string FnName);
+  Module *getModuleForNewFunction();
+  void *getPointerToFunction(Function* F);
+  void *getPointerToNamedFunction(const std::string &Name);
+  ExecutionEngine *compileModule(Module *M);
+  void closeCurrentModule();
+  void dump();
+
+private:
+  typedef std::vector<Module*> ModuleVector;
+
+  LLVMContext  &Context;
+  Module       *OpenModule;
+  ModuleVector  Modules;
+  std::map<Module *, ExecutionEngine *> EngineMap;
+};
+
+class HelpingMemoryManager : public SectionMemoryManager
+{
+  HelpingMemoryManager(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+  void operator=(const HelpingMemoryManager&) LLVM_DELETED_FUNCTION;
+
+public:
+  HelpingMemoryManager(MCJITHelper *Helper) : MasterHelper(Helper) {}
+  virtual ~HelpingMemoryManager() {}
+
+  /// This method returns the address of the specified function. 
+  /// Our implementation will attempt to find functions in other
+  /// modules associated with the MCJITHelper to cross link functions
+  /// from one generated module to another.
+  ///
+  /// If \p AbortOnFailure is false and no function with the given name is
+  /// found, this function returns a null pointer. Otherwise, it prints a
+  /// message to stderr and aborts.
+  virtual void *getPointerToNamedFunction(const std::string &Name,
+                                          bool AbortOnFailure = true);
+private:
+  MCJITHelper *MasterHelper;
+};
+
+void *HelpingMemoryManager::getPointerToNamedFunction(const std::string &Name,
+                                        bool AbortOnFailure)
+{
+  // Try the standard symbol resolution first, but ask it not to abort.
+  void *pfn = SectionMemoryManager::getPointerToNamedFunction(Name, false);
+  if (pfn)
+    return pfn;
+
+  pfn = MasterHelper->getPointerToNamedFunction(Name);
+  if (!pfn && AbortOnFailure)
+    report_fatal_error("Program used external function '" + Name +
+                        "' which could not be resolved!");
+  return pfn;
+}
+
+MCJITHelper::~MCJITHelper()
+{
+  // Walk the vector of modules.
+  ModuleVector::iterator it, end;
+  for (it = Modules.begin(), end = Modules.end();
+       it != end; ++it) {
+    // See if we have an execution engine for this module.
+    std::map<Module*, ExecutionEngine*>::iterator mapIt = EngineMap.find(*it);
+    // If we have an EE, the EE owns the module so just delete the EE.
+    if (mapIt != EngineMap.end()) {
+      delete mapIt->second;
+    } else {
+      // Otherwise, we still own the module.  Delete it now.
+      delete *it;
+    }
+  }
+}
+
+Function *MCJITHelper::getFunction(const std::string FnName) {
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    Function *F = (*it)->getFunction(FnName);
+    if (F) {
+      if (*it == OpenModule)
+          return F;
+
+      assert(OpenModule != NULL);
+
+      // This function is in a module that has already been JITed.
+      // We need to generate a new prototype for external linkage.
+      Function *PF = OpenModule->getFunction(FnName);
+      if (PF && !PF->empty()) {
+        ErrorF("redefinition of function across modules");
+        return 0;
+      }
+
+      // If we don't have a prototype yet, create one.
+      if (!PF)
+        PF = Function::Create(F->getFunctionType(), 
+                                      Function::ExternalLinkage, 
+                                      FnName, 
+                                      OpenModule);
+      return PF;
+    }
+  }
+  return NULL;
+}
+
+Module *MCJITHelper::getModuleForNewFunction() {
+  // If we have a Module that hasn't been JITed, use that.
+  if (OpenModule)
+    return OpenModule;
+
+  // Otherwise create a new Module.
+  std::string ModName = GenerateUniqueName("mcjit_module_");
+  Module *M = new Module(ModName, Context);
+  Modules.push_back(M);
+  OpenModule = M;
+  return M;
+}
+
+void *MCJITHelper::getPointerToFunction(Function* F) {
+  // Look for this function in an existing module
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  std::string FnName = F->getName();
+  for (it = begin; it != end; ++it) {
+    Function *MF = (*it)->getFunction(FnName);
+    if (MF == F) {
+      std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
+      if (eeIt != EngineMap.end()) {
+        void *P = eeIt->second->getPointerToFunction(F);
+        if (P)
+          return P;
+      } else {
+        ExecutionEngine *EE = compileModule(*it);
+        void *P = EE->getPointerToFunction(F);
+        if (P)
+          return P;
+      }
+    }
+  }
+  return NULL;
+}
+
+void MCJITHelper::closeCurrentModule() {
+  OpenModule = NULL;
+}
+
+ExecutionEngine *MCJITHelper::compileModule(Module *M) {
+  if (M == OpenModule)
+    closeCurrentModule();
+
+  std::string ErrStr;
+  ExecutionEngine *NewEngine = EngineBuilder(M)
+                                            .setErrorStr(&ErrStr)
+                                            .setUseMCJIT(true)
+                                            .setMCJITMemoryManager(new HelpingMemoryManager(this))
+                                            .create();
+  if (!NewEngine) {
+    fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
+    exit(1);
+  }
+
+  // Create a function pass manager for this engine
+  FunctionPassManager *FPM = new FunctionPassManager(M);
+
+  // Set up the optimizer pipeline.  Start with registering info about how the
+  // target lays out data structures.
+  FPM->add(new DataLayout(*NewEngine->getDataLayout()));
+  // Provide basic AliasAnalysis support for GVN.
+  FPM->add(createBasicAliasAnalysisPass());
+  // Promote allocas to registers.
+  FPM->add(createPromoteMemoryToRegisterPass());
+  // Do simple "peephole" optimizations and bit-twiddling optzns.
+  FPM->add(createInstructionCombiningPass());
+  // Reassociate expressions.
+  FPM->add(createReassociatePass());
+  // Eliminate Common SubExpressions.
+  FPM->add(createGVNPass());
+  // Simplify the control flow graph (deleting unreachable blocks, etc).
+  FPM->add(createCFGSimplificationPass());
+  FPM->doInitialization();
+
+  // For each function in the module
+  Module::iterator it;
+  Module::iterator end = M->end();
+  for (it = M->begin(); it != end; ++it) {
+    // Run the FPM on this function
+    FPM->run(*it);
+  }
+
+  // We don't need this anymore
+  delete FPM;
+
+  // Store this engine
+  EngineMap[M] = NewEngine;
+  NewEngine->finalizeObject();
+
+  return NewEngine;
+}
+
+void *MCJITHelper::getPointerToNamedFunction(const std::string &Name)
+{
+  // Look for the functions in our modules, compiling only as necessary
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it) {
+    Function *F = (*it)->getFunction(Name);
+    if (F && !F->empty()) {
+      std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
+      if (eeIt != EngineMap.end()) {
+        void *P = eeIt->second->getPointerToFunction(F);
+        if (P)
+          return P;
+      } else {
+        ExecutionEngine *EE = compileModule(*it);
+        void *P = EE->getPointerToFunction(F);
+        if (P)
+          return P;
+      }
+    }
+  }
+  return NULL;
+}
+
+void MCJITHelper::dump()
+{
+  ModuleVector::iterator begin = Modules.begin();
+  ModuleVector::iterator end = Modules.end();
+  ModuleVector::iterator it;
+  for (it = begin; it != end; ++it)
+    (*it)->dump();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+static MCJITHelper *TheHelper;
+static IRBuilder<> Builder(getGlobalContext());
+static std::map<std::string, AllocaInst*> NamedValues;
+
+Value *ErrorV(const char *Str) { Error(Str); return 0; }
+
+/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
+/// the function.  This is used for mutable variables etc.
+static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
+                                          const std::string &VarName) {
+  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
+                 TheFunction->getEntryBlock().begin());
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+                           VarName.c_str());
+}
+
+Value *NumberExprAST::Codegen() {
+  return ConstantFP::get(getGlobalContext(), APFloat(Val));
+}
+
+Value *VariableExprAST::Codegen() {
+  // Look this variable up in the function.
+  Value *V = NamedValues[Name];
+  char ErrStr[256];
+  sprintf(ErrStr, "Unknown variable name %s", Name.c_str());
+  if (V == 0) return ErrorV(ErrStr);
+
+  // Load the value.
+  return Builder.CreateLoad(V, Name.c_str());
+}
+
+Value *UnaryExprAST::Codegen() {
+  Value *OperandV = Operand->Codegen();
+  if (OperandV == 0) return 0;
+  
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
+  if (F == 0)
+    return ErrorV("Unknown unary operator");
+  
+  return Builder.CreateCall(F, OperandV, "unop");
+}
+
+Value *BinaryExprAST::Codegen() {
+  // Special case '=' because we don't want to emit the LHS as an expression.
+  if (Op == '=') {
+    // Assignment requires the LHS to be an identifier.
+    VariableExprAST *LHSE = reinterpret_cast<VariableExprAST*>(LHS);
+    if (!LHSE)
+      return ErrorV("destination of '=' must be a variable");
+    // Codegen the RHS.
+    Value *Val = RHS->Codegen();
+    if (Val == 0) return 0;
+
+    // Look up the name.
+    Value *Variable = NamedValues[LHSE->getName()];
+    if (Variable == 0) return ErrorV("Unknown variable name");
+
+    Builder.CreateStore(Val, Variable);
+    return Val;
+  }
+  
+  Value *L = LHS->Codegen();
+  Value *R = RHS->Codegen();
+  if (L == 0 || R == 0) return 0;
+  
+  switch (Op) {
+  case '+': return Builder.CreateFAdd(L, R, "addtmp");
+  case '-': return Builder.CreateFSub(L, R, "subtmp");
+  case '*': return Builder.CreateFMul(L, R, "multmp");
+  case '/': return Builder.CreateFDiv(L, R, "divtmp");
+  case '<':
+    L = Builder.CreateFCmpULT(L, R, "cmptmp");
+    // Convert bool 0/1 to double 0.0 or 1.0
+    return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+                                "booltmp");
+  default: break;
+  }
+  
+  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+  // a call to it.
+  Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("binary")+Op));
+  assert(F && "binary operator not found!");
+  
+  Value *Ops[] = { L, R };
+  return Builder.CreateCall(F, Ops, "binop");
+}
+
+Value *CallExprAST::Codegen() {
+  // Look up the name in the global module table.
+  Function *CalleeF = TheHelper->getFunction(Callee);
+  if (CalleeF == 0)
+    return ErrorV("Unknown function referenced");
+  
+  // If argument mismatch error.
+  if (CalleeF->arg_size() != Args.size())
+    return ErrorV("Incorrect # arguments passed");
+
+  std::vector<Value*> ArgsV;
+  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+    ArgsV.push_back(Args[i]->Codegen());
+    if (ArgsV.back() == 0) return 0;
+  }
+  
+  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
+}
+
+Value *IfExprAST::Codegen() {
+  Value *CondV = Cond->Codegen();
+  if (CondV == 0) return 0;
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  CondV = Builder.CreateFCmpONE(CondV, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                "ifcond");
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+  
+  // Create blocks for the then and else cases.  Insert the 'then' block at the
+  // end of the function.
+  BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
+  BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
+  BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
+  
+  Builder.CreateCondBr(CondV, ThenBB, ElseBB);
+  
+  // Emit then value.
+  Builder.SetInsertPoint(ThenBB);
+  
+  Value *ThenV = Then->Codegen();
+  if (ThenV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+  ThenBB = Builder.GetInsertBlock();
+  
+  // Emit else block.
+  TheFunction->getBasicBlockList().push_back(ElseBB);
+  Builder.SetInsertPoint(ElseBB);
+  
+  Value *ElseV = Else->Codegen();
+  if (ElseV == 0) return 0;
+  
+  Builder.CreateBr(MergeBB);
+  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+  ElseBB = Builder.GetInsertBlock();
+  
+  // Emit merge block.
+  TheFunction->getBasicBlockList().push_back(MergeBB);
+  Builder.SetInsertPoint(MergeBB);
+  PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
+                                  "iftmp");
+  
+  PN->addIncoming(ThenV, ThenBB);
+  PN->addIncoming(ElseV, ElseBB);
+  return PN;
+}
+
+Value *ForExprAST::Codegen() {
+  // Output this as:
+  //   var = alloca double
+  //   ...
+  //   start = startexpr
+  //   store start -> var
+  //   goto loop
+  // loop: 
+  //   ...
+  //   bodyexpr
+  //   ...
+  // loopend:
+  //   step = stepexpr
+  //   endcond = endexpr
+  //
+  //   curvar = load var
+  //   nextvar = curvar + step
+  //   store nextvar -> var
+  //   br endcond, loop, endloop
+  // outloop:
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Create an alloca for the variable in the entry block.
+  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+  
+  // Emit the start code first, without 'variable' in scope.
+  Value *StartVal = Start->Codegen();
+  if (StartVal == 0) return 0;
+  
+  // Store the value into the alloca.
+  Builder.CreateStore(StartVal, Alloca);
+  
+  // Make the new basic block for the loop header, inserting after current
+  // block.
+  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+  
+  // Insert an explicit fall through from the current block to the LoopBB.
+  Builder.CreateBr(LoopBB);
+
+  // Start insertion in LoopBB.
+  Builder.SetInsertPoint(LoopBB);
+  
+  // Within the loop, the variable is defined equal to the PHI node.  If it
+  // shadows an existing variable, we have to restore it, so save it now.
+  AllocaInst *OldVal = NamedValues[VarName];
+  NamedValues[VarName] = Alloca;
+  
+  // Emit the body of the loop.  This, like any other expr, can change the
+  // current BB.  Note that we ignore the value computed by the body, but don't
+  // allow an error.
+  if (Body->Codegen() == 0)
+    return 0;
+  
+  // Emit the step value.
+  Value *StepVal;
+  if (Step) {
+    StepVal = Step->Codegen();
+    if (StepVal == 0) return 0;
+  } else {
+    // If not specified, use 1.0.
+    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
+  }
+  
+  // Compute the end condition.
+  Value *EndCond = End->Codegen();
+  if (EndCond == 0) return EndCond;
+  
+  // Reload, increment, and restore the alloca.  This handles the case where
+  // the body of the loop mutates the variable.
+  Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
+  Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
+  Builder.CreateStore(NextVar, Alloca);
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  EndCond = Builder.CreateFCmpONE(EndCond, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                  "loopcond");
+  
+  // Create the "after loop" block and insert it.
+  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+  
+  // Insert the conditional branch into the end of LoopEndBB.
+  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
+  
+  // Any new code will be inserted in AfterBB.
+  Builder.SetInsertPoint(AfterBB);
+  
+  // Restore the unshadowed variable.
+  if (OldVal)
+    NamedValues[VarName] = OldVal;
+  else
+    NamedValues.erase(VarName);
+
+  
+  // for expr always returns 0.0.
+  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
+}
+
+Value *VarExprAST::Codegen() {
+  std::vector<AllocaInst *> OldBindings;
+  
+  Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+  // Register all variables and emit their initializer.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
+    const std::string &VarName = VarNames[i].first;
+    ExprAST *Init = VarNames[i].second;
+    
+    // Emit the initializer before adding the variable to scope, this prevents
+    // the initializer from referencing the variable itself, and permits stuff
+    // like this:
+    //  var a = 1 in
+    //    var a = a in ...   # refers to outer 'a'.
+    Value *InitVal;
+    if (Init) {
+      InitVal = Init->Codegen();
+      if (InitVal == 0) return 0;
+    } else { // If not specified, use 0.0.
+      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
+    }
+    
+    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+    Builder.CreateStore(InitVal, Alloca);
+
+    // Remember the old variable binding so that we can restore the binding when
+    // we unrecurse.
+    OldBindings.push_back(NamedValues[VarName]);
+    
+    // Remember this binding.
+    NamedValues[VarName] = Alloca;
+  }
+  
+  // Codegen the body, now that all vars are in scope.
+  Value *BodyVal = Body->Codegen();
+  if (BodyVal == 0) return 0;
+  
+  // Pop all our variables from scope.
+  for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
+    NamedValues[VarNames[i].first] = OldBindings[i];
+
+  // Return the body computation.
+  return BodyVal;
+}
+
+Function *PrototypeAST::Codegen() {
+  // Make the function type:  double(double,double) etc.
+  std::vector<Type*> Doubles(Args.size(), 
+                             Type::getDoubleTy(getGlobalContext()));
+  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+                                       Doubles, false);
+
+  std::string FnName = MakeLegalFunctionName(Name);
+
+  Module* M = TheHelper->getModuleForNewFunction();
+
+  Function *F = Function::Create(FT, Function::ExternalLinkage, FnName, M);
+
+  // If F conflicted, there was already something named 'FnName'.  If it has a
+  // body, don't allow redefinition or reextern.
+  if (F->getName() != FnName) {
+    // Delete the one we just made and get the existing one.
+    F->eraseFromParent();
+    F = M->getFunction(Name);
+    
+    // If F already has a body, reject this.
+    if (!F->empty()) {
+      ErrorF("redefinition of function");
+      return 0;
+    }
+    
+    // If F took a different number of args, reject.
+    if (F->arg_size() != Args.size()) {
+      ErrorF("redefinition of function with different # args");
+      return 0;
+    }
+  }
+  
+  // Set names for all arguments.
+  unsigned Idx = 0;
+  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+       ++AI, ++Idx)
+    AI->setName(Args[Idx]);
+    
+  return F;
+}
+
+/// CreateArgumentAllocas - Create an alloca for each argument and register the
+/// argument in the symbol table so that references to it will succeed.
+void PrototypeAST::CreateArgumentAllocas(Function *F) {
+  Function::arg_iterator AI = F->arg_begin();
+  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
+    // Create an alloca for this variable.
+    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
+
+    // Store the initial value into the alloca.
+    Builder.CreateStore(AI, Alloca);
+
+    // Add arguments to variable symbol table.
+    NamedValues[Args[Idx]] = Alloca;
+  }
+}
+
+Function *FunctionAST::Codegen() {
+  NamedValues.clear();
+  
+  Function *TheFunction = Proto->Codegen();
+  if (TheFunction == 0)
+    return 0;
+  
+  // If this is an operator, install it.
+  if (Proto->isBinaryOp())
+    BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
+  
+  // Create a new basic block to start insertion into.
+  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+  Builder.SetInsertPoint(BB);
+  
+  // Add all arguments to the symbol table and create their allocas.
+  Proto->CreateArgumentAllocas(TheFunction);
+
+  if (Value *RetVal = Body->Codegen()) {
+    // Finish off the function.
+    Builder.CreateRet(RetVal);
+
+    // Validate the generated code, checking for consistency.
+    verifyFunction(*TheFunction);
+
+    return TheFunction;
+  }
+
+  // Error reading body, remove function.
+  TheFunction->eraseFromParent();
+
+  if (Proto->isBinaryOp())
+    BinopPrecedence.erase(Proto->getOperatorName());
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static void HandleDefinition() {
+  if (FunctionAST *F = ParseDefinition()) {
+    TheHelper->closeCurrentModule();
+    if (Function *LF = F->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read function definition:");
+      LF->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleExtern() {
+  if (PrototypeAST *P = ParseExtern()) {
+    if (Function *F = P->Codegen()) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      fprintf(stderr, "Read extern: ");
+      F->dump();
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleTopLevelExpression() {
+  // Evaluate a top-level expression into an anonymous function.
+  if (FunctionAST *F = ParseTopLevelExpr()) {
+    if (Function *LF = F->Codegen()) {
+      // JIT the function, returning a function pointer.
+      void *FPtr = TheHelper->getPointerToFunction(LF);
+      
+      // Cast it to the right type (takes no arguments, returns a double) so we
+      // can call it as a native function.
+      double (*FP)() = (double (*)())(intptr_t)FPtr;
+#ifdef MINIMAL_STDERR_OUTPUT
+      FP();
+#else
+      fprintf(stderr, "Evaluated to %f\n", FP());
+#endif
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+  while (1) {
+#ifndef MINIMAL_STDERR_OUTPUT
+    fprintf(stderr, "ready> ");
+#endif
+    switch (CurTok) {
+    case tok_eof:    return;
+    case ';':        getNextToken(); break;  // ignore top-level semicolons.
+    case tok_def:    HandleDefinition(); break;
+    case tok_extern: HandleExtern(); break;
+    default:         HandleTopLevelExpression(); break;
+    }
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C" 
+double putchard(double X) {
+  putchar((char)X);
+  return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C" 
+double printd(double X) {
+  printf("%f", X);
+  return 0;
+}
+
+extern "C" 
+double printlf() {
+  printf("\n");
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main() {
+  InitializeNativeTarget();
+  InitializeNativeTargetAsmPrinter();
+  InitializeNativeTargetAsmParser();
+  LLVMContext &Context = getGlobalContext();
+
+  // Install standard binary operators.
+  // 1 is lowest precedence.
+  BinopPrecedence['='] = 2;
+  BinopPrecedence['<'] = 10;
+  BinopPrecedence['+'] = 20;
+  BinopPrecedence['-'] = 20;
+  BinopPrecedence['/'] = 40;
+  BinopPrecedence['*'] = 40;  // highest.
+
+  // Prime the first token.
+#ifndef MINIMAL_STDERR_OUTPUT
+  fprintf(stderr, "ready> ");
+#endif
+  getNextToken();
+
+  // Make the helper, which holds all the code.
+  TheHelper = new MCJITHelper(Context);
+
+  // Run the main "interpreter loop" now.
+  MainLoop();
+
+#ifndef MINIMAL_STDERR_OUTPUT
+  // Print out all of the generated code.
+  TheHelper->dump();
+#endif
+
+  return 0;
+}