1 files changed, 107 insertions, 0 deletions
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
new file mode 100644
index 0000000000..253a229a38
--- /dev/null
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -0,0 +1,107 @@
+//===-- Emitter.cpp - Write machine code to executable memory -------------===//
+//
+// This file defines a MachineCodeEmitter object that is used by Jello to write
+// machine code to memory and remember where relocatable values lie.
+//
+//===----------------------------------------------------------------------===//
+
+#include "VM.h"
+#include "llvm/CodeGen/MachineCodeEmitter.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/Function.h"
+#include "Support/Statistic.h"
+
+namespace {
+  Statistic<> NumBytes("jello", "Number of bytes of machine code compiled");
+
+  class Emitter : public MachineCodeEmitter {
+    VM &TheVM;
+
+    unsigned char *CurBlock;
+    unsigned char *CurByte;
+    
+    std::vector<std::pair<BasicBlock*, unsigned *> > BBRefs;
+    std::map<BasicBlock*, unsigned> BBLocations;
+  public:
+    Emitter(VM &vm) : TheVM(vm) {}
+
+    virtual void startFunction(MachineFunction &F);
+    virtual void finishFunction(MachineFunction &F);
+    virtual void startBasicBlock(MachineBasicBlock &BB);
+    virtual void emitByte(unsigned char B);
+    virtual void emitPCRelativeDisp(Value *V);
+    virtual void emitGlobalAddress(GlobalValue *V);
+  };
+}
+
+MachineCodeEmitter *VM::createEmitter(VM &V) {
+  return new Emitter(V);
+}
+
+
+#define _POSIX_MAPPED_FILES
+#include <unistd.h>
+#include <sys/mman.h>
+
+static void *getMemory() {
+  return mmap(0, 4096*2, PROT_READ|PROT_WRITE|PROT_EXEC,
+              MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
+}
+
+
+void Emitter::startFunction(MachineFunction &F) {
+  CurBlock = (unsigned char *)getMemory();
+  CurByte = CurBlock;  // Start writing at the beginning of the fn.
+  TheVM.addGlobalMapping(F.getFunction(), CurBlock);
+}
+
+void Emitter::finishFunction(MachineFunction &F) {
+  for (unsigned i = 0, e = BBRefs.size(); i != e; ++i) {
+    unsigned Location = BBLocations[BBRefs[i].first];
+    unsigned *Ref = BBRefs[i].second;
+    *Ref = Location-(unsigned)Ref-4;
+  }
+  BBRefs.clear();
+  BBLocations.clear();
+
+  NumBytes += CurByte-CurBlock;
+
+  DEBUG(std::cerr << "Finished CodeGen of [" << std::hex << (unsigned)CurBlock
+                  << std::dec << "] Function: " << F.getFunction()->getName()
+                  << ": " << CurByte-CurBlock << " bytes of text\n");
+}
+
+void Emitter::startBasicBlock(MachineBasicBlock &BB) {
+  BBLocations[BB.getBasicBlock()] = (unsigned)CurByte;
+}
+
+
+void Emitter::emitByte(unsigned char B) {
+  *CurByte++ = B;   // Write the byte to memory
+}
+
+
+// emitPCRelativeDisp - For functions, just output a displacement that will
+// cause a reference to the zero page, which will cause a seg-fault, causing
+// things to get resolved on demand.  Keep track of these markers.
+//
+// For basic block references, keep track of where the references are so they
+// may be patched up when the basic block is defined.
+//
+void Emitter::emitPCRelativeDisp(Value *V) {
+  if (Function *F = dyn_cast<Function>(V)) {
+    TheVM.addFunctionRef(CurByte, F);
+    unsigned ZeroAddr = -(unsigned)CurByte-4; // Calculate displacement to null
+    *(unsigned*)CurByte = ZeroAddr;           // 4 byte offset
+    CurByte += 4;
+  } else {
+    BasicBlock *BB = cast<BasicBlock>(V);     // Keep track of reference...
+    BBRefs.push_back(std::make_pair(BB, (unsigned*)CurByte));
+    CurByte += 4;
+  }
+}
+
+void Emitter::emitGlobalAddress(GlobalValue *V) {
+  *(void**)CurByte = TheVM.getPointerToGlobal(V);
+  CurByte += 4;
+}