Initial checkin of profiling instrumentation pass. So far, despite the

file name, we only support function profiling.  This will be fixed in the
near future.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9547 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Instrumentation/BlockProfiling.cpp

@@ -0,0 +1,127 @@
+//===- BlockProfiling.cpp - Insert counters for block profiling -----------===//
+// 
+//                      The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This pass instruments the specified program with counters for basic block or
+// function profiling.  This is the most basic form of profiling, which can tell
+// which blocks are hot, but cannot reliably detect hot paths through the CFG.
+// Block profiling counts the number of times each basic block executes, and
+// function profiling counts the number of times each function is called.
+//
+// Note that this implementation is very naive.  Control equivalent regions of
+// the CFG should not require duplicate counters, but we do put duplicate
+// counters in.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+
+namespace {
+  class FunctionProfiler : public Pass {
+    bool run(Module &M);
+
+    void insertInitializationCall(Function *MainFn, const char *FnName,
+                                  GlobalValue *Array);
+  };
+
+  RegisterOpt<FunctionProfiler> X("insert-function-profiling",
+                               "Insert instrumentation for function profiling");
+}
+
+
+bool FunctionProfiler::run(Module &M) {
+  Function *Main = M.getMainFunction();
+  if (Main == 0) {
+    std::cerr << "WARNING: cannot insert function profiling into a module"
+              << " with no main function!\n";
+    return false;  // No main, no instrumentation!
+  }
+
+  unsigned NumFunctions = 0;
+  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 
+    if (!I->isExternal())
+      ++NumFunctions;
+
+  const Type *ATy = ArrayType::get(Type::UIntTy, NumFunctions);
+  GlobalVariable *Counters =
+    new GlobalVariable(ATy, false, GlobalValue::InternalLinkage,
+                       Constant::getNullValue(ATy), "FuncProfCounters", &M);
+
+  ConstantPointerRef *CounterCPR = ConstantPointerRef::get(Counters);
+  std::vector<Constant*> GEPIndices;
+  GEPIndices.resize(2);
+  GEPIndices[0] = Constant::getNullValue(Type::LongTy);
+
+  // Instrument all of the functions...
+  unsigned i = 0;
+  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 
+    if (!I->isExternal()) {
+      // Insert counter at the start of the function, but after any allocas.
+      BasicBlock *Entry = I->begin();
+      BasicBlock::iterator InsertPos = Entry->begin();
+      while (isa<AllocaInst>(InsertPos)) ++InsertPos;
+
+      GEPIndices[1] = ConstantSInt::get(Type::LongTy, i++);
+      Constant *ElementPtr =
+        ConstantExpr::getGetElementPtr(CounterCPR, GEPIndices);
+
+      Value *OldVal = new LoadInst(ElementPtr, "OldFuncCounter", InsertPos);
+      Value *NewVal = BinaryOperator::create(Instruction::Add, OldVal,
+                                             ConstantInt::get(Type::UIntTy, 1),
+                                             "NewFuncCounter", InsertPos);
+      new StoreInst(NewVal, ElementPtr, InsertPos);
+    }
+
+  // Add the initialization call to main.
+  insertInitializationCall(Main, "llvm_start_func_profiling", Counters);
+  return true;
+}
+
+void FunctionProfiler::insertInitializationCall(Function *MainFn,
+                                                const char *FnName,
+                                                GlobalValue *Array) {
+  const Type *ArgVTy = PointerType::get(PointerType::get(Type::SByteTy));
+  const Type *UIntPtr = PointerType::get(Type::UIntTy);
+  Module &M = *MainFn->getParent();
+  Function *InitFn = M.getOrInsertFunction(FnName, Type::VoidTy, Type::IntTy,
+                                           ArgVTy, UIntPtr, Type::UIntTy, 0);
+
+  // This could force argc and argv into programs that wouldn't otherwise have
+  // them, but instead we just pass null values in.
+  std::vector<Value*> Args(4);
+  Args[0] = Constant::getNullValue(Type::IntTy);
+  Args[1] = Constant::getNullValue(ArgVTy);
+
+  /* FIXME: We should pass in the command line arguments here! */
+  switch (MainFn->asize()) {
+  default:
+  case 2:
+  case 1:
+  case 0:
+    break;
+  }
+
+  ConstantPointerRef *ArrayCPR = ConstantPointerRef::get(Array);
+  std::vector<Constant*> GEPIndices(2, Constant::getNullValue(Type::LongTy));
+  Args[2] = ConstantExpr::getGetElementPtr(ArrayCPR, GEPIndices);
+  
+  unsigned NumElements =
+    cast<ArrayType>(Array->getType()->getElementType())->getNumElements();
+  Args[3] = ConstantUInt::get(Type::UIntTy, NumElements);
+  
+  // Skip over any allocas in the entry block.
+  BasicBlock *Entry = MainFn->begin();
+  BasicBlock::iterator InsertPos = Entry->begin();
+  while (isa<AllocaInst>(InsertPos)) ++InsertPos;
+
+  new CallInst(InitFn, Args, "", InsertPos);
+}