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 "Support/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 /// runOnBasicBlock - This method does the actual work of converting
42 /// instructions over, assuming that the pass has already been initialized.
44 bool runOnBasicBlock(BasicBlock &BB);
47 RegisterOpt<LowerAllocations>
48 X("lowerallocs", "Lower allocations from instructions to calls");
51 // createLowerAllocationsPass - Interface to this file...
52 FunctionPass *llvm::createLowerAllocationsPass() {
53 return new LowerAllocations();
57 // doInitialization - For the lower allocations pass, this ensures that a
58 // module contains a declaration for a malloc and a free function.
60 // This function is always successful.
62 bool LowerAllocations::doInitialization(Module &M) {
63 const Type *SBPTy = PointerType::get(Type::SByteTy);
64 MallocFunc = M.getNamedFunction("malloc");
65 FreeFunc = M.getNamedFunction("free");
68 MallocFunc = M.getOrInsertFunction("malloc", SBPTy, Type::UIntTy, 0);
70 FreeFunc = M.getOrInsertFunction("free" , Type::VoidTy, SBPTy, 0);
75 static Constant *getSizeof(const Type *Ty) {
76 Constant *Ret = ConstantPointerNull::get(PointerType::get(Ty));
77 std::vector<Constant*> Idx;
78 Idx.push_back(ConstantUInt::get(Type::UIntTy, 1));
79 Ret = ConstantExpr::getGetElementPtr(Ret, Idx);
80 return ConstantExpr::getCast(Ret, Type::UIntTy);
83 // runOnBasicBlock - This method does the actual work of converting
84 // instructions over, assuming that the pass has already been initialized.
86 bool LowerAllocations::runOnBasicBlock(BasicBlock &BB) {
88 assert(MallocFunc && FreeFunc && "Pass not initialized!");
90 BasicBlock::InstListType &BBIL = BB.getInstList();
92 // Loop over all of the instructions, looking for malloc or free instructions
93 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
94 if (MallocInst *MI = dyn_cast<MallocInst>(I)) {
95 const Type *AllocTy = MI->getType()->getElementType();
97 // malloc(type) becomes sbyte *malloc(size)
98 Value *MallocArg = getSizeof(AllocTy);
99 if (MI->isArrayAllocation()) {
100 if (isa<ConstantUInt>(MallocArg) &&
101 cast<ConstantUInt>(MallocArg)->getValue() == 1) {
102 MallocArg = MI->getOperand(0); // Operand * 1 = Operand
103 } else if (Constant *CO = dyn_cast<Constant>(MI->getOperand(0))) {
104 MallocArg = ConstantExpr::getMul(CO, cast<Constant>(MallocArg));
106 // Multiply it by the array size if necessary...
107 MallocArg = BinaryOperator::create(Instruction::Mul,
113 const FunctionType *MallocFTy = MallocFunc->getFunctionType();
114 std::vector<Value*> MallocArgs;
116 if (MallocFTy->getNumParams() > 0 || MallocFTy->isVarArg()) {
117 if (MallocFTy->getNumParams() > 0 &&
118 MallocFTy->getParamType(0) != Type::UIntTy)
119 MallocArg = new CastInst(MallocArg, MallocFTy->getParamType(0), "",I);
120 MallocArgs.push_back(MallocArg);
123 // If malloc is prototyped to take extra arguments, pass nulls.
124 for (unsigned i = 1; i < MallocFTy->getNumParams(); ++i)
125 MallocArgs.push_back(Constant::getNullValue(MallocFTy->getParamType(i)));
127 // Create the call to Malloc...
128 CallInst *MCall = new CallInst(MallocFunc, MallocArgs, "", I);
130 // Create a cast instruction to convert to the right type...
132 if (MCall->getType() != Type::VoidTy)
133 MCast = new CastInst(MCall, MI->getType(), "", I);
135 MCast = Constant::getNullValue(MI->getType());
137 // Replace all uses of the old malloc inst with the cast inst
138 MI->replaceAllUsesWith(MCast);
139 I = --BBIL.erase(I); // remove and delete the malloc instr...
142 } else if (FreeInst *FI = dyn_cast<FreeInst>(I)) {
143 const FunctionType *FreeFTy = FreeFunc->getFunctionType();
144 std::vector<Value*> FreeArgs;
146 if (FreeFTy->getNumParams() > 0 || FreeFTy->isVarArg()) {
147 Value *MCast = FI->getOperand(0);
148 if (FreeFTy->getNumParams() > 0 &&
149 FreeFTy->getParamType(0) != MCast->getType())
150 MCast = new CastInst(MCast, FreeFTy->getParamType(0), "", I);
151 FreeArgs.push_back(MCast);
154 // If malloc is prototyped to take extra arguments, pass nulls.
155 for (unsigned i = 1; i < FreeFTy->getNumParams(); ++i)
156 FreeArgs.push_back(Constant::getNullValue(FreeFTy->getParamType(i)));
158 // Insert a call to the free function...
159 new CallInst(FreeFunc, FreeArgs, "", I);
161 // Delete the old free instruction