LowerAllocations.cpp [plain text]
#define DEBUG_TYPE "lowerallocs"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
#include "llvm/Module.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Constants.h"
#include "llvm/Pass.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/Compiler.h"
using namespace llvm;
STATISTIC(NumLowered, "Number of allocations lowered");
namespace {
class VISIBILITY_HIDDEN LowerAllocations : public BasicBlockPass {
Constant *MallocFunc; Constant *FreeFunc; bool LowerMallocArgToInteger;
public:
static char ID; explicit LowerAllocations(bool LowerToInt = false)
: BasicBlockPass(&ID), MallocFunc(0), FreeFunc(0),
LowerMallocArgToInteger(LowerToInt) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetData>();
AU.setPreservesCFG();
AU.addPreserved<UnifyFunctionExitNodes>();
AU.addPreservedID(PromoteMemoryToRegisterID);
AU.addPreservedID(LowerSwitchID);
AU.addPreservedID(LowerInvokePassID);
}
bool doInitialization(Module &M);
virtual bool doInitialization(Function &F) {
return doInitialization(*F.getParent());
}
bool runOnBasicBlock(BasicBlock &BB);
};
}
char LowerAllocations::ID = 0;
static RegisterPass<LowerAllocations>
X("lowerallocs", "Lower allocations from instructions to calls");
const PassInfo *const llvm::LowerAllocationsID = &X;
Pass *llvm::createLowerAllocationsPass(bool LowerMallocArgToInteger) {
return new LowerAllocations(LowerMallocArgToInteger);
}
bool LowerAllocations::doInitialization(Module &M) {
const Type *BPTy = PointerType::getUnqual(Type::Int8Ty);
FunctionType *FT = FunctionType::get(BPTy, std::vector<const Type*>(), true);
MallocFunc = M.getOrInsertFunction("malloc", FT);
FreeFunc = M.getOrInsertFunction("free" , Type::VoidTy, BPTy, (Type *)0);
return true;
}
bool LowerAllocations::runOnBasicBlock(BasicBlock &BB) {
bool Changed = false;
assert(MallocFunc && FreeFunc && "Pass not initialized!");
BasicBlock::InstListType &BBIL = BB.getInstList();
const TargetData &TD = getAnalysis<TargetData>();
const Type *IntPtrTy = TD.getIntPtrType();
for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
if (MallocInst *MI = dyn_cast<MallocInst>(I)) {
const Type *AllocTy = MI->getType()->getElementType();
Value *MallocArg;
if (LowerMallocArgToInteger)
MallocArg = ConstantInt::get(Type::Int64Ty,
TD.getTypePaddedSize(AllocTy));
else
MallocArg = ConstantExpr::getSizeOf(AllocTy);
MallocArg = ConstantExpr::getTruncOrBitCast(cast<Constant>(MallocArg),
IntPtrTy);
if (MI->isArrayAllocation()) {
if (isa<ConstantInt>(MallocArg) &&
cast<ConstantInt>(MallocArg)->isOne()) {
MallocArg = MI->getOperand(0); } else if (Constant *CO = dyn_cast<Constant>(MI->getOperand(0))) {
CO = ConstantExpr::getIntegerCast(CO, IntPtrTy, false );
MallocArg = ConstantExpr::getMul(CO, cast<Constant>(MallocArg));
} else {
Value *Scale = MI->getOperand(0);
if (Scale->getType() != IntPtrTy)
Scale = CastInst::CreateIntegerCast(Scale, IntPtrTy, false ,
"", I);
MallocArg = BinaryOperator::Create(Instruction::Mul, Scale,
MallocArg, "", I);
}
}
CallInst *MCall = CallInst::Create(MallocFunc, MallocArg, "", I);
MCall->setTailCall();
Value *MCast;
if (MCall->getType() != Type::VoidTy)
MCast = new BitCastInst(MCall, MI->getType(), "", I);
else
MCast = Constant::getNullValue(MI->getType());
MI->replaceAllUsesWith(MCast);
I = --BBIL.erase(I); Changed = true;
++NumLowered;
} else if (FreeInst *FI = dyn_cast<FreeInst>(I)) {
Value *PtrCast =
new BitCastInst(FI->getOperand(0),
PointerType::getUnqual(Type::Int8Ty), "", I);
CallInst::Create(FreeFunc, PtrCast, "", I)->setTailCall();
I = --BBIL.erase(I);
Changed = true;
++NumLowered;
}
}
return Changed;
}