1 //===- LowerAllocations.cpp - Reduce malloc & free insts to calls ---------===//
3 // The LowerAllocations transformation is a target dependant tranformation
4 // because it depends on the size of data types and alignment constraints.
6 //===----------------------------------------------------------------------===//
8 #include "llvm/Transforms/ChangeAllocations.h"
9 #include "llvm/Module.h"
10 #include "llvm/Function.h"
11 #include "llvm/BasicBlock.h"
12 #include "llvm/DerivedTypes.h"
13 #include "llvm/iMemory.h"
14 #include "llvm/iOther.h"
15 #include "llvm/Constants.h"
16 #include "llvm/Pass.h"
17 #include "llvm/Target/TargetData.h"
18 #include "Support/StatisticReporter.h"
20 static Statistic<> NumLowered("lowerallocs\t- Number of allocations lowered");
25 // LowerAllocations - Turn malloc and free instructions into %malloc and %free
28 class LowerAllocations : public BasicBlockPass {
29 Function *MallocFunc; // Functions in the module we are processing
30 Function *FreeFunc; // Initialized by doInitialization
32 const TargetData &DataLayout;
34 inline LowerAllocations(const TargetData &TD) : DataLayout(TD) {
35 MallocFunc = FreeFunc = 0;
38 const char *getPassName() const { return "Lower Allocations"; }
40 // doPassInitialization - For the lower allocations pass, this ensures that a
41 // module contains a declaration for a malloc and a free function.
43 bool doInitialization(Module &M);
45 // runOnBasicBlock - This method does the actual work of converting
46 // instructions over, assuming that the pass has already been initialized.
48 bool runOnBasicBlock(BasicBlock &BB);
53 // createLowerAllocationsPass - Interface to this file...
54 Pass *createLowerAllocationsPass(const TargetData &TD) {
55 return new LowerAllocations(TD);
59 // doInitialization - For the lower allocations pass, this ensures that a
60 // module contains a declaration for a malloc and a free function.
62 // This function is always successful.
64 bool LowerAllocations::doInitialization(Module &M) {
65 const FunctionType *MallocType =
66 FunctionType::get(PointerType::get(Type::SByteTy),
67 vector<const Type*>(1, Type::UIntTy), false);
68 const FunctionType *FreeType =
69 FunctionType::get(Type::VoidTy,
70 vector<const Type*>(1, PointerType::get(Type::SByteTy)),
73 MallocFunc = M.getOrInsertFunction("malloc", MallocType);
74 FreeFunc = M.getOrInsertFunction("free" , FreeType);
79 // runOnBasicBlock - This method does the actual work of converting
80 // instructions over, assuming that the pass has already been initialized.
82 bool LowerAllocations::runOnBasicBlock(BasicBlock &BB) {
84 assert(MallocFunc && FreeFunc && "Pass not initialized!");
86 BasicBlock::InstListType &BBIL = BB.getInstList();
88 // Loop over all of the instructions, looking for malloc or free instructions
89 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) {
90 if (MallocInst *MI = dyn_cast<MallocInst>(&*I)) {
91 BBIL.remove(I); // remove the malloc instr...
93 const Type *AllocTy = MI->getType()->getElementType();
95 // Get the number of bytes to be allocated for one element of the
97 unsigned Size = DataLayout.getTypeSize(AllocTy);
99 // malloc(type) becomes sbyte *malloc(constint)
100 Value *MallocArg = ConstantUInt::get(Type::UIntTy, Size);
101 if (MI->getNumOperands() && Size == 1) {
102 MallocArg = MI->getOperand(0); // Operand * 1 = Operand
103 } else if (MI->getNumOperands()) {
104 // Multiply it by the array size if neccesary...
105 MallocArg = BinaryOperator::create(Instruction::Mul,MI->getOperand(0),
107 I = ++BBIL.insert(I, cast<Instruction>(MallocArg));
110 // Create the call to Malloc...
111 CallInst *MCall = new CallInst(MallocFunc,
112 vector<Value*>(1, MallocArg));
113 I = BBIL.insert(I, MCall);
115 // Create a cast instruction to convert to the right type...
116 CastInst *MCast = new CastInst(MCall, MI->getType());
117 I = BBIL.insert(++I, MCast);
119 // Replace all uses of the old malloc inst with the cast inst
120 MI->replaceAllUsesWith(MCast);
121 delete MI; // Delete the malloc inst
124 } else if (FreeInst *FI = dyn_cast<FreeInst>(&*I)) {
127 // Cast the argument to free into a ubyte*...
128 CastInst *MCast = new CastInst(FI->getOperand(0),
129 PointerType::get(Type::UByteTy));
130 I = ++BBIL.insert(I, MCast);
132 // Insert a call to the free function...
133 CallInst *FCall = new CallInst(FreeFunc, vector<Value*>(1, MCast));
134 I = BBIL.insert(I, FCall);
136 // Delete the old free instruction