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 && BB && "Pass not initialized!");
86 // Loop over all of the instructions, looking for malloc or free instructions
87 for (unsigned i = 0; i != BB->size(); ++i) {
88 BasicBlock::InstListType &BBIL = BB->getInstList();
89 if (MallocInst *MI = dyn_cast<MallocInst>(*(BBIL.begin()+i))) {
90 BBIL.remove(BBIL.begin()+i); // remove the malloc instr...
92 const Type *AllocTy = cast<PointerType>(MI->getType())->getElementType();
94 // Get the number of bytes to be allocated for one element of the
96 unsigned Size = DataLayout.getTypeSize(AllocTy);
98 // malloc(type) becomes sbyte *malloc(constint)
99 Value *MallocArg = ConstantUInt::get(Type::UIntTy, Size);
100 if (MI->getNumOperands() && Size == 1) {
101 MallocArg = MI->getOperand(0); // Operand * 1 = Operand
102 } else if (MI->getNumOperands()) {
103 // Multiply it by the array size if neccesary...
104 MallocArg = BinaryOperator::create(Instruction::Mul,MI->getOperand(0),
106 BBIL.insert(BBIL.begin()+i++, cast<Instruction>(MallocArg));
109 // Create the call to Malloc...
110 CallInst *MCall = new CallInst(MallocFunc,
111 vector<Value*>(1, MallocArg));
112 BBIL.insert(BBIL.begin()+i, MCall);
114 // Create a cast instruction to convert to the right type...
115 CastInst *MCast = new CastInst(MCall, MI->getType());
116 BBIL.insert(BBIL.begin()+i+1, MCast);
118 // Replace all uses of the old malloc inst with the cast inst
119 MI->replaceAllUsesWith(MCast);
120 delete MI; // Delete the malloc inst
123 } else if (FreeInst *FI = dyn_cast<FreeInst>(*(BBIL.begin()+i))) {
124 BBIL.remove(BB->getInstList().begin()+i);
126 // Cast the argument to free into a ubyte*...
127 CastInst *MCast = new CastInst(FI->getOperand(0),
128 PointerType::get(Type::UByteTy));
129 BBIL.insert(BBIL.begin()+i, MCast);
131 // Insert a call to the free function...
132 CallInst *FCall = new CallInst(FreeFunc,
133 vector<Value*>(1, MCast));
134 BBIL.insert(BBIL.begin()+i+1, FCall);
136 // Delete the old free instruction