1 //===- llvm/Transforms/LowerAllocations.h - Remove Malloc & Free Insts ------=//
3 // This file implements a pass that lowers malloc and free instructions to
4 // calls to %malloc & %free functions. This transformation is a target
5 // dependant tranformation because we depend on the size of data types and
6 // alignment constraints.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/Transforms/LowerAllocations.h"
11 #include "llvm/Target/TargetData.h"
12 #include "llvm/DerivedTypes.h"
13 #include "llvm/iMemory.h"
14 #include "llvm/iOther.h"
15 #include "llvm/SymbolTable.h"
17 // doPassInitialization - For the lower allocations pass, this ensures that a
18 // module contains a declaration for a malloc and a free function.
20 // This function is always successful.
22 bool LowerAllocations::doPassInitialization(Module *M) {
24 const MethodType *MallocType =
25 MethodType::get(PointerType::get(Type::UByteTy),
26 vector<const Type*>(1, Type::UIntTy), false);
28 SymbolTable *SymTab = M->getSymbolTableSure();
30 // Check for a definition of malloc
31 if (Value *V = SymTab->lookup(PointerType::get(MallocType), "malloc")) {
32 MallocMeth = cast<Method>(V); // Yup, got it
33 } else { // Nope, add one
34 M->getMethodList().push_back(MallocMeth = new Method(MallocType, "malloc"));
38 const MethodType *FreeType =
39 MethodType::get(Type::VoidTy,
40 vector<const Type*>(1, PointerType::get(Type::UByteTy)),
43 // Check for a definition of free
44 if (Value *V = SymTab->lookup(PointerType::get(FreeType), "free")) {
45 FreeMeth = cast<Method>(V); // Yup, got it
46 } else { // Nope, add one
47 M->getMethodList().push_back(FreeMeth = new Method(FreeType, "free"));
51 return Changed; // Always successful
54 // doPerMethodWork - This method does the actual work of converting
55 // instructions over, assuming that the pass has already been initialized.
57 bool LowerAllocations::doPerMethodWork(Method *M) {
59 assert(MallocMeth && FreeMeth && M && "Pass not initialized!");
61 // Loop over all of the instructions, looking for malloc or free instructions
62 for (Method::iterator BBI = M->begin(), BBE = M->end(); BBI != BBE; ++BBI) {
63 BasicBlock *BB = *BBI;
64 for (unsigned i = 0; i < BB->size(); ++i) {
65 BasicBlock::InstListType &BBIL = BB->getInstList();
66 if (MallocInst *MI = dyn_cast<MallocInst>(*(BBIL.begin()+i))) {
67 BBIL.remove(BBIL.begin()+i); // remove the malloc instr...
69 const Type *AllocTy = cast<PointerType>(MI->getType())->getValueType();
71 // If the user is allocating an unsized array with a dynamic size arg,
72 // start by getting the size of one element.
74 if (const ArrayType *ATy = dyn_cast<ArrayType>(AllocTy))
75 if (ATy->isUnsized()) AllocTy = ATy->getElementType();
77 // Get the number of bytes to be allocated for one element of the
79 unsigned Size = DataLayout.getTypeSize(AllocTy);
81 // malloc(type) becomes sbyte *malloc(constint)
82 Value *MallocArg = ConstPoolUInt::get(Type::UIntTy, Size);
83 if (MI->getNumOperands() && Size == 1) {
84 MallocArg = MI->getOperand(0); // Operand * 1 = Operand
85 } else if (MI->getNumOperands()) {
86 // Multiply it by the array size if neccesary...
87 MallocArg = BinaryOperator::create(Instruction::Mul,MI->getOperand(0),
89 BBIL.insert(BBIL.begin()+i++, cast<Instruction>(MallocArg));
92 // Create the call to Malloc...
93 CallInst *MCall = new CallInst(MallocMeth,
94 vector<Value*>(1, MallocArg));
95 BBIL.insert(BBIL.begin()+i, MCall);
97 // Create a cast instruction to convert to the right type...
98 CastInst *MCast = new CastInst(MCall, MI->getType());
99 BBIL.insert(BBIL.begin()+i+1, MCast);
101 // Replace all uses of the old malloc inst with the cast inst
102 MI->replaceAllUsesWith(MCast);
103 delete MI; // Delete the malloc inst
105 } else if (FreeInst *FI = dyn_cast<FreeInst>(*(BBIL.begin()+i))) {
106 BBIL.remove(BB->getInstList().begin()+i);
108 // Cast the argument to free into a ubyte*...
109 CastInst *MCast = new CastInst(FI->getOperand(0),
110 PointerType::get(Type::UByteTy));
111 BBIL.insert(BBIL.begin()+i, MCast);
113 // Insert a call to the free function...
114 CallInst *FCall = new CallInst(FreeMeth,
115 vector<Value*>(1, MCast));
116 BBIL.insert(BBIL.begin()+i+1, FCall);
118 // Delete the old free instruction