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//===- 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);
// Skip over any allocas in the entry block.
BasicBlock *Entry = MainFn->begin();
BasicBlock::iterator InsertPos = Entry->begin();
while (isa<AllocaInst>(InsertPos)) ++InsertPos;
Function::aiterator AI;
switch (MainFn->asize()) {
default:
case 2:
AI = MainFn->abegin(); ++AI;
if (AI->getType() != ArgVTy) {
Args[1] = new CastInst(AI, ArgVTy, "argv.cast", InsertPos);
} else {
Args[1] = AI;
}
case 1:
AI = MainFn->abegin();
if (AI->getType() != Type::IntTy) {
Args[0] = new CastInst(AI, Type::IntTy, "argc.cast", InsertPos);
} else {
Args[0] = AI;
}
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);
new CallInst(InitFn, Args, "", InsertPos);
}
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