| //===- LowerAllocations.cpp - Reduce malloc & free insts to calls ---------===// |
| // |
| // The LowerAllocations transformation is a target dependant tranformation |
| // because it depends on the size of data types and alignment constraints. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Module.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/iMemory.h" |
| #include "llvm/iOther.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Target/TargetData.h" |
| #include "Support/StatisticReporter.h" |
| |
| static Statistic<> NumLowered("lowerallocs\t- Number of allocations lowered"); |
| using std::vector; |
| |
| namespace { |
| |
| // LowerAllocations - Turn malloc and free instructions into %malloc and %free |
| // calls. |
| // |
| class LowerAllocations : public BasicBlockPass { |
| Function *MallocFunc; // Functions in the module we are processing |
| Function *FreeFunc; // Initialized by doInitialization |
| |
| const TargetData &DataLayout; |
| public: |
| LowerAllocations(const TargetData &TD) : DataLayout(TD) { |
| MallocFunc = FreeFunc = 0; |
| } |
| |
| // 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); |
| |
| // runOnBasicBlock - This method does the actual work of converting |
| // instructions over, assuming that the pass has already been initialized. |
| // |
| bool runOnBasicBlock(BasicBlock &BB); |
| }; |
| } |
| |
| // createLowerAllocationsPass - Interface to this file... |
| Pass *createLowerAllocationsPass(const TargetData &TD) { |
| return new LowerAllocations(TD); |
| } |
| |
| static RegisterOpt<LowerAllocations> |
| X("lowerallocs", "Lower allocations from instructions to calls (TD)", |
| createLowerAllocationsPass); |
| |
| |
| // 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 FunctionType *MallocType = |
| FunctionType::get(PointerType::get(Type::SByteTy), |
| vector<const Type*>(1, Type::UIntTy), false); |
| const FunctionType *FreeType = |
| FunctionType::get(Type::VoidTy, |
| vector<const Type*>(1, PointerType::get(Type::SByteTy)), |
| false); |
| |
| MallocFunc = M.getOrInsertFunction("malloc", MallocType); |
| FreeFunc = M.getOrInsertFunction("free" , FreeType); |
| |
| 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(); |
| |
| // 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(); |
| |
| // Get the number of bytes to be allocated for one element of the |
| // requested type... |
| unsigned Size = DataLayout.getTypeSize(AllocTy); |
| |
| // malloc(type) becomes sbyte *malloc(constint) |
| Value *MallocArg = ConstantUInt::get(Type::UIntTy, Size); |
| if (MI->getNumOperands() && Size == 1) { |
| MallocArg = MI->getOperand(0); // Operand * 1 = Operand |
| } else if (MI->getNumOperands()) { |
| // Multiply it by the array size if neccesary... |
| MallocArg = BinaryOperator::create(Instruction::Mul, MI->getOperand(0), |
| MallocArg, "", I); |
| } |
| |
| // Create the call to Malloc... |
| CallInst *MCall = new CallInst(MallocFunc, |
| vector<Value*>(1, MallocArg), "", I); |
| |
| // Create a cast instruction to convert to the right type... |
| CastInst *MCast = new CastInst(MCall, MI->getType(), "", I); |
| |
| // 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)) { |
| // Cast the argument to free into a ubyte*... |
| CastInst *MCast = new CastInst(FI->getOperand(0), |
| PointerType::get(Type::UByteTy), "", I); |
| |
| // Insert a call to the free function... |
| CallInst *FCall = new CallInst(FreeFunc, vector<Value*>(1, MCast), "", I); |
| |
| // Delete the old free instruction |
| I = --BBIL.erase(I); |
| Changed = true; |
| ++NumLowered; |
| } |
| } |
| |
| return Changed; |
| } |