| //===- LowerAllocations.cpp - Reduce malloc & free insts to calls ---------===// |
| // |
| // 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. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // The LowerAllocations transformation is a target-dependent tranformation |
| // because it depends on the size of data types and alignment constraints. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #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 { |
| /// LowerAllocations - Turn malloc and free instructions into %malloc and |
| /// %free calls. |
| /// |
| class VISIBILITY_HIDDEN LowerAllocations : public BasicBlockPass { |
| Constant *MallocFunc; // Functions in the module we are processing |
| Constant *FreeFunc; // Initialized by doInitialization |
| bool LowerMallocArgToInteger; |
| public: |
| static const int ID; // Pass ID, replacement for typeid |
| LowerAllocations(bool LowerToInt = false) |
| : BasicBlockPass((intptr_t)&ID), MallocFunc(0), FreeFunc(0), |
| LowerMallocArgToInteger(LowerToInt) {} |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<TargetData>(); |
| AU.setPreservesCFG(); |
| |
| // This is a cluster of orthogonal Transforms: |
| AU.addPreserved<UnifyFunctionExitNodes>(); |
| AU.addPreservedID(PromoteMemoryToRegisterID); |
| AU.addPreservedID(LowerSelectID); |
| AU.addPreservedID(LowerSwitchID); |
| AU.addPreservedID(LowerInvokePassID); |
| } |
| |
| /// doPassInitialization - For the lower allocations pass, this ensures that |
| /// a module contains a declaration for a malloc and a free function. |
| /// |
| bool doInitialization(Module &M); |
| |
| virtual bool doInitialization(Function &F) { |
| return BasicBlockPass::doInitialization(F); |
| } |
| |
| /// runOnBasicBlock - This method does the actual work of converting |
| /// instructions over, assuming that the pass has already been initialized. |
| /// |
| bool runOnBasicBlock(BasicBlock &BB); |
| }; |
| |
| const int LowerAllocations::ID = 0; |
| RegisterPass<LowerAllocations> |
| X("lowerallocs", "Lower allocations from instructions to calls"); |
| } |
| |
| // Publically exposed interface to pass... |
| const PassInfo *llvm::LowerAllocationsID = X.getPassInfo(); |
| // createLowerAllocationsPass - Interface to this file... |
| Pass *llvm::createLowerAllocationsPass(bool LowerMallocArgToInteger) { |
| return new LowerAllocations(LowerMallocArgToInteger); |
| } |
| |
| |
| // doInitialization - For the lower allocations pass, this ensures that a |
| // module contains a declaration for a malloc and a free function. |
| // |
| // This function is always successful. |
| // |
| bool LowerAllocations::doInitialization(Module &M) { |
| const Type *BPTy = PointerType::get(Type::Int8Ty); |
| // Prototype malloc as "char* malloc(...)", because we don't know in |
| // doInitialization whether size_t is int or long. |
| 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; |
| } |
| |
| // runOnBasicBlock - This method does the actual work of converting |
| // instructions over, assuming that the pass has already been initialized. |
| // |
| 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(); |
| |
| // Loop over all of the instructions, looking for malloc or free instructions |
| 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(); |
| |
| // malloc(type) becomes sbyte *malloc(size) |
| Value *MallocArg; |
| if (LowerMallocArgToInteger) |
| MallocArg = ConstantInt::get(Type::Int64Ty, TD.getTypeSize(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); // Operand * 1 = Operand |
| } else if (Constant *CO = dyn_cast<Constant>(MI->getOperand(0))) { |
| CO = ConstantExpr::getIntegerCast(CO, IntPtrTy, false /*ZExt*/); |
| MallocArg = ConstantExpr::getMul(CO, cast<Constant>(MallocArg)); |
| } else { |
| Value *Scale = MI->getOperand(0); |
| if (Scale->getType() != IntPtrTy) |
| Scale = CastInst::createIntegerCast(Scale, IntPtrTy, false /*ZExt*/, |
| "", I); |
| |
| // Multiply it by the array size if necessary... |
| MallocArg = BinaryOperator::create(Instruction::Mul, Scale, |
| MallocArg, "", I); |
| } |
| } |
| |
| // Create the call to Malloc. |
| CallInst *MCall = new CallInst(MallocFunc, MallocArg, "", I); |
| MCall->setTailCall(); |
| |
| // Create a cast instruction to convert to the right type... |
| Value *MCast; |
| if (MCall->getType() != Type::VoidTy) |
| MCast = new BitCastInst(MCall, MI->getType(), "", I); |
| else |
| MCast = Constant::getNullValue(MI->getType()); |
| |
| // Replace all uses of the old malloc inst with the cast inst |
| MI->replaceAllUsesWith(MCast); |
| I = --BBIL.erase(I); // remove and delete the malloc instr... |
| Changed = true; |
| ++NumLowered; |
| } else if (FreeInst *FI = dyn_cast<FreeInst>(I)) { |
| Value *PtrCast = new BitCastInst(FI->getOperand(0), |
| PointerType::get(Type::Int8Ty), "", I); |
| |
| // Insert a call to the free function... |
| (new CallInst(FreeFunc, PtrCast, "", I))->setTailCall(); |
| |
| // Delete the old free instruction |
| I = --BBIL.erase(I); |
| Changed = true; |
| ++NumLowered; |
| } |
| } |
| |
| return Changed; |
| } |
| |