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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8242 91177308-0d34-0410-b5e6-96231b3b80d8
127 lines
4.6 KiB
C++
127 lines
4.6 KiB
C++
//===- LowerAllocations.cpp - Reduce malloc & free insts to calls ---------===//
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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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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Module.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/iMemory.h"
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#include "llvm/iOther.h"
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#include "llvm/Constants.h"
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#include "llvm/Pass.h"
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#include "llvm/Target/TargetData.h"
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#include "Support/Statistic.h"
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namespace {
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Statistic<> NumLowered("lowerallocs", "Number of allocations lowered");
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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 LowerAllocations : public BasicBlockPass {
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Function *MallocFunc; // Functions in the module we are processing
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Function *FreeFunc; // Initialized by doInitialization
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public:
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LowerAllocations() : MallocFunc(0), FreeFunc(0) {}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<TargetData>();
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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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/// 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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RegisterOpt<LowerAllocations>
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X("lowerallocs", "Lower allocations from instructions to calls");
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}
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// createLowerAllocationsPass - Interface to this file...
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FunctionPass *createLowerAllocationsPass() {
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return new LowerAllocations();
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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 *SBPTy = PointerType::get(Type::SByteTy);
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MallocFunc = M.getOrInsertFunction("malloc", SBPTy, Type::UIntTy, 0);
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FreeFunc = M.getOrInsertFunction("free" , Type::VoidTy, SBPTy, 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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TargetData &DataLayout = getAnalysis<TargetData>();
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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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// Get the number of bytes to be allocated for one element of the
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// requested type...
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unsigned Size = DataLayout.getTypeSize(AllocTy);
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// malloc(type) becomes sbyte *malloc(constint)
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Value *MallocArg = ConstantUInt::get(Type::UIntTy, Size);
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if (MI->getNumOperands() && Size == 1) {
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MallocArg = MI->getOperand(0); // Operand * 1 = Operand
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} else if (MI->getNumOperands()) {
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// Multiply it by the array size if necessary...
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MallocArg = BinaryOperator::create(Instruction::Mul, MI->getOperand(0),
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MallocArg, "", I);
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}
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// Create the call to Malloc...
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CallInst *MCall = new CallInst(MallocFunc,
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std::vector<Value*>(1, MallocArg), "", I);
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// Create a cast instruction to convert to the right type...
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CastInst *MCast = new CastInst(MCall, MI->getType(), "", I);
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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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// Cast the argument to free into a ubyte*...
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CastInst *MCast = new CastInst(FI->getOperand(0),
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PointerType::get(Type::SByteTy), "", I);
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// Insert a call to the free function...
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CallInst *FCall = new CallInst(FreeFunc, std::vector<Value*>(1, MCast),
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"", I);
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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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