Add support for line profiling. Very work-in-progress.

Use debug info in the IR to find the directory/file:line:col. Each time that location changes, bump a counter.

Unlike the existing profiling system, we don't try to look at argv[], and thusly don't require main() to be present in the IR. This matches GCC's technique where you specify the profiling flag when producing each .o file.

The runtime library is minimal, currently just calling printf at program shutdown time. The API is designed to make it possible to emit GCOV data later on.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129340 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 218 insertions, 0 deletions

diff --git a/lib/Transforms/Instrumentation/Instrumentation.cpp b/lib/Transforms/Instrumentation/Instrumentation.cpp
index 96ed4fa5c0..b299bb71a4 100644
--- a/lib/Transforms/Instrumentation/Instrumentation.cpp
+++ b/lib/Transforms/Instrumentation/Instrumentation.cpp
@@ -23,6 +23,7 @@ void llvm::initializeInstrumentation(PassRegistry &Registry) {
   initializeEdgeProfilerPass(Registry);
   initializeOptimalEdgeProfilerPass(Registry);
   initializePathProfilerPass(Registry);
+  initializeLineProfilerPass(Registry);
 }
 
 /// LLVMInitializeInstrumentation - C binding for
diff --git a/lib/Transforms/Instrumentation/LineProfiling.cpp b/lib/Transforms/Instrumentation/LineProfiling.cpp
new file mode 100644
index 0000000000..5628c3a811
--- /dev/null
+++ b/lib/Transforms/Instrumentation/LineProfiling.cpp
@@ -0,0 +1,217 @@
+//===- LineProfiling.cpp - Insert counters for line profiling -------------===//
+//
+//                      The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass creates counters for the number of times that the original source
+// lines of code were executed.
+//
+// The lines are found from existing debug info in the LLVM IR. Iterating
+// through LLVM instructions, every time the debug location changes we insert a
+// new counter and instructions to increment the counter there. A global
+// destructor runs to dump the counters out to a file.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "insert-line-profiling"
+
+#include "ProfilingUtils.h"
+#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/Analysis/DebugInfo.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Instructions.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/DebugLoc.h"
+#include "llvm/Support/InstIterator.h"
+#include "llvm/Support/IRBuilder.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringExtras.h"
+#include <set>
+#include <string>
+using namespace llvm;
+
+STATISTIC(NumUpdatesInserted, "The # of counter increments inserted.");
+
+namespace {
+  class LineProfiler : public ModulePass {
+    bool runOnModule(Module &M);
+  public:
+    static char ID;
+    LineProfiler() : ModulePass(ID) {
+      initializeLineProfilerPass(*PassRegistry::getPassRegistry());
+    }
+    virtual const char *getPassName() const {
+      return "Line Profiler";
+    }
+
+  private:
+    // Get pointers to the functions in the runtime library.
+    Constant *getStartFileFunc();
+    Constant *getCounterFunc();
+    Constant *getEndFileFunc();
+
+    // Insert an increment of the counter before instruction I.
+    void InsertCounterUpdateBefore(Instruction *I);
+
+    // Add the function to write out all our counters to the global destructor
+    // list.
+    void InsertCounterWriteout();
+
+    // Mapping from the source location to the counter tracking that location.
+    DenseMap<DebugLoc, GlobalVariable *> counters;
+
+    Module *Mod;
+    LLVMContext *Ctx;
+  };
+}
+
+char LineProfiler::ID = 0;
+INITIALIZE_PASS(LineProfiler, "insert-line-profiling",
+                "Insert instrumentation for line profiling", false, false)
+
+ModulePass *llvm::createLineProfilerPass() { return new LineProfiler(); }
+
+bool LineProfiler::runOnModule(Module &M) {
+  Mod = &M;
+  Ctx = &M.getContext();
+
+  DebugLoc last_line;  // initializes to unknown
+  bool Changed = false;
+  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+    for (inst_iterator II = inst_begin(F), IE = inst_end(F); II != IE; ++II) {
+      const DebugLoc &loc = II->getDebugLoc();
+      if (loc.isUnknown()) continue;
+      if (loc == last_line) continue;
+      last_line = loc;
+
+      InsertCounterUpdateBefore(&*II);
+      ++NumUpdatesInserted;
+      Changed = true;
+    }
+  }
+
+  if (Changed) {
+    InsertCounterWriteout();
+  }
+
+  return Changed;
+}
+
+void LineProfiler::InsertCounterUpdateBefore(Instruction *I) {
+  const DebugLoc &loc = I->getDebugLoc();
+  GlobalVariable *&counter = counters[loc];
+  const Type *Int64Ty = Type::getInt64Ty(*Ctx);
+  if (!counter) {
+    counter = new GlobalVariable(*Mod, Int64Ty, false,
+                                 GlobalValue::InternalLinkage,
+                                 Constant::getNullValue(Int64Ty),
+                                 "__llvm_prof_linecov_ctr", 0, false, 0);
+    counter->setVisibility(GlobalVariable::HiddenVisibility);
+    counter->setUnnamedAddr(true);
+  }
+
+  if (isa<PHINode>(I)) {
+    // We may not error out or crash in this case, because a module could put
+    // changing line numbers on phi nodes and still pass the verifier.
+    dbgs() << "Refusing to insert code before phi: " << *I << "\n";
+    I = I->getParent()->getFirstNonPHI();
+  }
+
+  IRBuilder<> builder(I);
+  Value *ctr = builder.CreateLoad(counter);
+  ctr = builder.CreateAdd(ctr, ConstantInt::get(Int64Ty, 1));
+  builder.CreateStore(ctr, counter);
+}
+
+static DISubprogram FindSubprogram(DIScope scope) {
+  while (!scope.isSubprogram()) {
+    assert(scope.isLexicalBlock() &&
+           "Debug location not lexical block or subprogram");
+    scope = DILexicalBlock(scope).getContext();
+  }
+  return DISubprogram(scope);
+}
+
+Constant *LineProfiler::getStartFileFunc() {
+  const Type *Args[1] = { Type::getInt8PtrTy(*Ctx) };
+  const FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx),
+                                              Args, false);
+  return Mod->getOrInsertFunction("llvm_prof_linectr_start_file", FTy);
+}
+
+Constant *LineProfiler::getCounterFunc() {
+  const Type *Args[] = {
+    Type::getInt8PtrTy(*Ctx),   // const char *dir
+    Type::getInt8PtrTy(*Ctx),   // const char *file
+    Type::getInt32Ty(*Ctx),     // uint32_t line
+    Type::getInt32Ty(*Ctx),     // uint32_t column
+    Type::getInt64PtrTy(*Ctx),  // int64_t *counter
+  };
+  const FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx),
+                                              Args, false);
+  return Mod->getOrInsertFunction("llvm_prof_linectr_emit_counter", FTy);
+}
+
+Constant *LineProfiler::getEndFileFunc() {
+  const FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Ctx), false);
+  return Mod->getOrInsertFunction("llvm_prof_linectr_end_file", FTy);
+}
+
+void LineProfiler::InsertCounterWriteout() {
+  std::set<std::string> compile_units;
+  for (DenseMap<DebugLoc, GlobalVariable *>::iterator I = counters.begin(),
+           E = counters.end(); I != E; ++I) {
+    const DebugLoc &loc = I->first;
+    DISubprogram subprogram(FindSubprogram(DIScope(loc.getScope(*Ctx))));
+    compile_units.insert(subprogram.getCompileUnit().getFilename().str());
+  }
+
+  const FunctionType *WriteoutFTy =
+      FunctionType::get(Type::getVoidTy(*Ctx), false);
+  Function *WriteoutF = Function::Create(WriteoutFTy,
+                                         GlobalValue::InternalLinkage,
+                                         "__llvm_prof_linecov_dtor",
+                                         Mod);
+  WriteoutF->setUnnamedAddr(true);
+  BasicBlock *BB = BasicBlock::Create(*Ctx, "", WriteoutF);
+  IRBuilder<> builder(BB);
+
+  Constant *StartFile = getStartFileFunc();
+  Constant *EmitCounter = getCounterFunc();
+  Constant *EndFile = getEndFileFunc();
+
+  for (std::set<std::string>::const_iterator CUI = compile_units.begin(),
+           CUE = compile_units.end(); CUI != CUE; ++CUI) {
+    builder.CreateCall(StartFile,
+                       builder.CreateGlobalStringPtr(*CUI));
+    for (DenseMap<DebugLoc, GlobalVariable *>::iterator I = counters.begin(),
+             E = counters.end(); I != E; ++I) {
+      const DebugLoc &loc = I->first;
+      DISubprogram subprogram(FindSubprogram(DIScope(loc.getScope(*Ctx))));
+      DICompileUnit compileunit(subprogram.getCompileUnit());
+
+      if (compileunit.getFilename() != *CUI)
+        continue;
+
+      Value *Args[] = {
+        builder.CreateGlobalStringPtr(subprogram.getDirectory()),
+        builder.CreateGlobalStringPtr(subprogram.getFilename()),
+        ConstantInt::get(Type::getInt32Ty(*Ctx), loc.getLine()),
+        ConstantInt::get(Type::getInt32Ty(*Ctx), loc.getCol()),
+        I->second
+      };
+      builder.CreateCall(EmitCounter, Args);
+    }
+    builder.CreateCall(EndFile);
+  }
+  builder.CreateRetVoid();
+
+  InsertProfilingShutdownCall(WriteoutF, Mod);
+}