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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33511 91177308-0d34-0410-b5e6-96231b3b80d8
174 lines
6.4 KiB
C++
174 lines
6.4 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 was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source 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/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 *MallocFunc; // Functions in the module we are processing
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Constant *FreeFunc; // Initialized by doInitialization
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bool LowerMallocArgToInteger;
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public:
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LowerAllocations(bool LowerToInt = false)
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: MallocFunc(0), FreeFunc(0), 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(LowerSelectID);
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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 BasicBlockPass::doInitialization(F);
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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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RegisterPass<LowerAllocations>
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X("lowerallocs", "Lower allocations from instructions to calls");
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}
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// Publically exposed interface to pass...
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const PassInfo *llvm::LowerAllocationsID = X.getPassInfo();
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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::get(Type::Int8Ty);
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// Prototype malloc as "char* malloc(...)", because we don't know in
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// doInitialization whether size_t is int or long.
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FunctionType *FT = FunctionType::get(BPTy, std::vector<const Type*>(), true);
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MallocFunc = M.getOrInsertFunction("malloc", FT);
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FreeFunc = M.getOrInsertFunction("free" , Type::VoidTy, 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(MallocFunc && 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();
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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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const Type *AllocTy = MI->getType()->getElementType();
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// malloc(type) becomes sbyte *malloc(size)
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Value *MallocArg;
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if (LowerMallocArgToInteger)
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MallocArg = ConstantInt::get(Type::Int64Ty, TD.getTypeSize(AllocTy));
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else
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MallocArg = ConstantExpr::getSizeOf(AllocTy);
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MallocArg = ConstantExpr::getTruncOrBitCast(cast<Constant>(MallocArg),
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IntPtrTy);
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if (MI->isArrayAllocation()) {
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if (isa<ConstantInt>(MallocArg) &&
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cast<ConstantInt>(MallocArg)->getZExtValue() == 1) {
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MallocArg = MI->getOperand(0); // Operand * 1 = Operand
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} else if (Constant *CO = dyn_cast<Constant>(MI->getOperand(0))) {
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CO = ConstantExpr::getIntegerCast(CO, IntPtrTy, false /*ZExt*/);
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MallocArg = ConstantExpr::getMul(CO, cast<Constant>(MallocArg));
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} else {
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Value *Scale = MI->getOperand(0);
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if (Scale->getType() != IntPtrTy)
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Scale = CastInst::createIntegerCast(Scale, IntPtrTy, false /*ZExt*/,
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"", I);
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// Multiply it by the array size if necessary...
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MallocArg = BinaryOperator::create(Instruction::Mul, Scale,
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MallocArg, "", I);
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}
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}
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// Create the call to Malloc.
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CallInst *MCall = new CallInst(MallocFunc, MallocArg, "", I);
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MCall->setTailCall();
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// Create a cast instruction to convert to the right type...
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Value *MCast;
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if (MCall->getType() != Type::VoidTy)
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MCast = new BitCastInst(MCall, MI->getType(), "", I);
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else
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MCast = Constant::getNullValue(MI->getType());
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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 = new BitCastInst(FI->getOperand(0),
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PointerType::get(Type::Int8Ty), "", I);
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// Insert a call to the free function...
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(new CallInst(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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