forked from OSchip/llvm-project
141 lines
5.0 KiB
C++
141 lines
5.0 KiB
C++
//===- LowerAllocations.cpp - Reduce malloc & free insts to calls ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// The LowerAllocations transformation is a target-dependent tranformation
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// because it depends on the size of data types and alignment constraints.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "lowerallocs"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
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#include "llvm/Module.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Constants.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Support/Compiler.h"
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using namespace llvm;
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STATISTIC(NumLowered, "Number of allocations lowered");
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namespace {
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/// LowerAllocations - Turn malloc and free instructions into @malloc and
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/// @free calls.
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///
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class VISIBILITY_HIDDEN LowerAllocations : public BasicBlockPass {
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Constant *FreeFunc; // Functions in the module we are processing
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// Initialized by doInitialization
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bool LowerMallocArgToInteger;
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public:
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static char ID; // Pass ID, replacement for typeid
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explicit LowerAllocations(bool LowerToInt = false)
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: BasicBlockPass(&ID), FreeFunc(0),
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LowerMallocArgToInteger(LowerToInt) {}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<TargetData>();
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AU.setPreservesCFG();
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// This is a cluster of orthogonal Transforms:
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AU.addPreserved<UnifyFunctionExitNodes>();
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AU.addPreservedID(PromoteMemoryToRegisterID);
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AU.addPreservedID(LowerSwitchID);
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AU.addPreservedID(LowerInvokePassID);
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}
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/// doPassInitialization - For the lower allocations pass, this ensures that
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/// a module contains a declaration for a malloc and a free function.
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///
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bool doInitialization(Module &M);
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virtual bool doInitialization(Function &F) {
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return doInitialization(*F.getParent());
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}
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/// runOnBasicBlock - This method does the actual work of converting
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/// instructions over, assuming that the pass has already been initialized.
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///
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bool runOnBasicBlock(BasicBlock &BB);
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};
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}
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char LowerAllocations::ID = 0;
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static RegisterPass<LowerAllocations>
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X("lowerallocs", "Lower allocations from instructions to calls");
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// Publically exposed interface to pass...
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const PassInfo *const llvm::LowerAllocationsID = &X;
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// createLowerAllocationsPass - Interface to this file...
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Pass *llvm::createLowerAllocationsPass(bool LowerMallocArgToInteger) {
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return new LowerAllocations(LowerMallocArgToInteger);
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}
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// doInitialization - For the lower allocations pass, this ensures that a
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// module contains a declaration for a malloc and a free function.
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//
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// This function is always successful.
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//
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bool LowerAllocations::doInitialization(Module &M) {
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const Type *BPTy = PointerType::getUnqual(Type::getInt8Ty(M.getContext()));
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FreeFunc = M.getOrInsertFunction("free" , Type::getVoidTy(M.getContext()),
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BPTy, (Type *)0);
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return true;
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}
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// runOnBasicBlock - This method does the actual work of converting
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// instructions over, assuming that the pass has already been initialized.
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//
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bool LowerAllocations::runOnBasicBlock(BasicBlock &BB) {
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bool Changed = false;
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assert(FreeFunc && "Pass not initialized!");
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BasicBlock::InstListType &BBIL = BB.getInstList();
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const TargetData &TD = getAnalysis<TargetData>();
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const Type *IntPtrTy = TD.getIntPtrType(BB.getContext());
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// Loop over all of the instructions, looking for malloc or free instructions
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for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
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if (MallocInst *MI = dyn_cast<MallocInst>(I)) {
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Value *ArraySize = MI->getOperand(0);
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if (ArraySize->getType() != IntPtrTy)
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ArraySize = CastInst::CreateIntegerCast(ArraySize, IntPtrTy,
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false /*ZExt*/, "", I);
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Value *MCast = CallInst::CreateMalloc(I, IntPtrTy,
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MI->getAllocatedType(), ArraySize);
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// Replace all uses of the old malloc inst with the cast inst
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MI->replaceAllUsesWith(MCast);
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I = --BBIL.erase(I); // remove and delete the malloc instr...
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Changed = true;
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++NumLowered;
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} else if (FreeInst *FI = dyn_cast<FreeInst>(I)) {
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Value *PtrCast =
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new BitCastInst(FI->getOperand(0),
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PointerType::getUnqual(Type::getInt8Ty(BB.getContext())), "", I);
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// Insert a call to the free function...
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CallInst::Create(FreeFunc, PtrCast, "", I)->setTailCall();
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// Delete the old free instruction
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I = --BBIL.erase(I);
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Changed = true;
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++NumLowered;
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}
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}
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return Changed;
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}
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