1 //===- LowerAllocations.cpp - Reduce malloc & free insts to calls ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // The LowerAllocations transformation is a target-dependent tranformation
11 // because it depends on the size of data types and alignment constraints.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Scalar.h"
16 #include "llvm/Module.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Instructions.h"
19 #include "llvm/Constants.h"
20 #include "llvm/Pass.h"
21 #include "llvm/ADT/Statistic.h"
25 Statistic<> NumLowered("lowerallocs", "Number of allocations lowered");
27 /// LowerAllocations - Turn malloc and free instructions into %malloc and
30 class LowerAllocations : public BasicBlockPass {
31 Function *MallocFunc; // Functions in the module we are processing
32 Function *FreeFunc; // Initialized by doInitialization
34 LowerAllocations() : MallocFunc(0), FreeFunc(0) {}
36 /// doPassInitialization - For the lower allocations pass, this ensures that
37 /// a module contains a declaration for a malloc and a free function.
39 bool doInitialization(Module &M);
41 virtual bool doInitialization(Function&f)
42 { return BasicBlockPass::doInitialization(f); }
44 /// runOnBasicBlock - This method does the actual work of converting
45 /// instructions over, assuming that the pass has already been initialized.
47 bool runOnBasicBlock(BasicBlock &BB);
50 RegisterOpt<LowerAllocations>
51 X("lowerallocs", "Lower allocations from instructions to calls");
54 // createLowerAllocationsPass - Interface to this file...
55 FunctionPass *llvm::createLowerAllocationsPass() {
56 return new LowerAllocations();
60 // doInitialization - For the lower allocations pass, this ensures that a
61 // module contains a declaration for a malloc and a free function.
63 // This function is always successful.
65 bool LowerAllocations::doInitialization(Module &M) {
66 const Type *SBPTy = PointerType::get(Type::SByteTy);
67 MallocFunc = M.getNamedFunction("malloc");
68 FreeFunc = M.getNamedFunction("free");
71 MallocFunc = M.getOrInsertFunction("malloc", SBPTy, Type::UIntTy, 0);
73 FreeFunc = M.getOrInsertFunction("free" , Type::VoidTy, SBPTy, 0);
78 static Constant *getSizeof(const Type *Ty) {
79 Constant *Ret = ConstantPointerNull::get(PointerType::get(Ty));
80 std::vector<Constant*> Idx;
81 Idx.push_back(ConstantUInt::get(Type::UIntTy, 1));
82 Ret = ConstantExpr::getGetElementPtr(Ret, Idx);
83 return ConstantExpr::getCast(Ret, Type::UIntTy);
86 // runOnBasicBlock - This method does the actual work of converting
87 // instructions over, assuming that the pass has already been initialized.
89 bool LowerAllocations::runOnBasicBlock(BasicBlock &BB) {
91 assert(MallocFunc && FreeFunc && "Pass not initialized!");
93 BasicBlock::InstListType &BBIL = BB.getInstList();
95 // Loop over all of the instructions, looking for malloc or free instructions
96 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
97 if (MallocInst *MI = dyn_cast<MallocInst>(I)) {
98 const Type *AllocTy = MI->getType()->getElementType();
100 // malloc(type) becomes sbyte *malloc(size)
101 Value *MallocArg = getSizeof(AllocTy);
102 if (MI->isArrayAllocation()) {
103 if (isa<ConstantUInt>(MallocArg) &&
104 cast<ConstantUInt>(MallocArg)->getValue() == 1) {
105 MallocArg = MI->getOperand(0); // Operand * 1 = Operand
106 } else if (Constant *CO = dyn_cast<Constant>(MI->getOperand(0))) {
107 MallocArg = ConstantExpr::getMul(CO, cast<Constant>(MallocArg));
109 // Multiply it by the array size if necessary...
110 MallocArg = BinaryOperator::create(Instruction::Mul,
116 const FunctionType *MallocFTy = MallocFunc->getFunctionType();
117 std::vector<Value*> MallocArgs;
119 if (MallocFTy->getNumParams() > 0 || MallocFTy->isVarArg()) {
120 if (MallocFTy->getNumParams() > 0 &&
121 MallocFTy->getParamType(0) != Type::UIntTy)
122 MallocArg = new CastInst(MallocArg, MallocFTy->getParamType(0), "",I);
123 MallocArgs.push_back(MallocArg);
126 // If malloc is prototyped to take extra arguments, pass nulls.
127 for (unsigned i = 1; i < MallocFTy->getNumParams(); ++i)
128 MallocArgs.push_back(Constant::getNullValue(MallocFTy->getParamType(i)));
130 // Create the call to Malloc...
131 CallInst *MCall = new CallInst(MallocFunc, MallocArgs, "", I);
133 // Create a cast instruction to convert to the right type...
135 if (MCall->getType() != Type::VoidTy)
136 MCast = new CastInst(MCall, MI->getType(), "", I);
138 MCast = Constant::getNullValue(MI->getType());
140 // Replace all uses of the old malloc inst with the cast inst
141 MI->replaceAllUsesWith(MCast);
142 I = --BBIL.erase(I); // remove and delete the malloc instr...
145 } else if (FreeInst *FI = dyn_cast<FreeInst>(I)) {
146 const FunctionType *FreeFTy = FreeFunc->getFunctionType();
147 std::vector<Value*> FreeArgs;
149 if (FreeFTy->getNumParams() > 0 || FreeFTy->isVarArg()) {
150 Value *MCast = FI->getOperand(0);
151 if (FreeFTy->getNumParams() > 0 &&
152 FreeFTy->getParamType(0) != MCast->getType())
153 MCast = new CastInst(MCast, FreeFTy->getParamType(0), "", I);
154 FreeArgs.push_back(MCast);
157 // If malloc is prototyped to take extra arguments, pass nulls.
158 for (unsigned i = 1; i < FreeFTy->getNumParams(); ++i)
159 FreeArgs.push_back(Constant::getNullValue(FreeFTy->getParamType(i)));
161 // Insert a call to the free function...
162 new CallInst(FreeFunc, FreeArgs, "", I);
164 // Delete the old free instruction