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::doPassInitializationVirt(Module *M) {
23 const MethodType *MallocType =
24 MethodType::get(PointerType::get(Type::UByteTy),
25 vector<const Type*>(1, Type::UIntTy), false);
27 SymbolTable *SymTab = M->getSymbolTableSure();
29 // Check for a definition of malloc
30 if (Value *V = SymTab->lookup(PointerType::get(MallocType), "malloc")) {
31 MallocMeth = cast<Method>(V); // Yup, got it
32 } else { // Nope, add one
33 M->getMethodList().push_back(MallocMeth = new Method(MallocType, "malloc"));
36 const MethodType *FreeType =
37 MethodType::get(Type::VoidTy,
38 vector<const Type*>(1, PointerType::get(Type::UByteTy)),
41 // Check for a definition of free
42 if (Value *V = SymTab->lookup(PointerType::get(FreeType), "free")) {
43 FreeMeth = cast<Method>(V); // Yup, got it
44 } else { // Nope, add one
45 M->getMethodList().push_back(FreeMeth = new Method(FreeType, "free"));
48 return false; // Always successful
51 // doPerMethodWork - This method does the actual work of converting
52 // instructions over, assuming that the pass has already been initialized.
54 bool LowerAllocations::doPerMethodWorkVirt(Method *M) {
55 assert(MallocMeth && FreeMeth && M && "Pass not initialized!");
57 // Loop over all of the instructions, looking for malloc or free instructions
58 for (Method::iterator BBI = M->begin(), BBE = M->end(); BBI != BBE; ++BBI) {
59 BasicBlock *BB = *BBI;
60 for (unsigned i = 0; i < BB->size(); ++i) {
61 BasicBlock::InstListType &BBIL = BB->getInstList();
62 if (MallocInst *MI = dyn_cast<MallocInst>(*(BBIL.begin()+i))) {
63 BBIL.remove(BBIL.begin()+i); // remove the malloc instr...
65 const Type *AllocTy = cast<PointerType>(MI->getType())->getValueType();
67 // If the user is allocating an unsized array with a dynamic size arg,
68 // start by getting the size of one element.
70 if (const ArrayType *ATy = dyn_cast<ArrayType>(AllocTy))
71 if (ATy->isUnsized()) AllocTy = ATy->getElementType();
73 // Get the number of bytes to be allocated for one element of the
75 unsigned Size = DataLayout.getTypeSize(AllocTy);
77 // malloc(type) becomes sbyte *malloc(constint)
78 Value *MallocArg = ConstPoolUInt::get(Type::UIntTy, Size);
79 if (MI->getNumOperands() && Size == 1) {
80 MallocArg = MI->getOperand(0); // Operand * 1 = Operand
81 } else if (MI->getNumOperands()) {
82 // Multiply it by the array size if neccesary...
83 MallocArg = BinaryOperator::create(Instruction::Mul,MI->getOperand(0),
85 BBIL.insert(BBIL.begin()+i++, cast<Instruction>(MallocArg));
88 // Create the call to Malloc...
89 CallInst *MCall = new CallInst(MallocMeth,
90 vector<Value*>(1, MallocArg));
91 BBIL.insert(BBIL.begin()+i, MCall);
93 // Create a cast instruction to convert to the right type...
94 CastInst *MCast = new CastInst(MCall, MI->getType());
95 BBIL.insert(BBIL.begin()+i+1, MCast);
97 // Replace all uses of the old malloc inst with the cast inst
98 MI->replaceAllUsesWith(MCast);
99 delete MI; // Delete the malloc inst
100 } else if (FreeInst *FI = dyn_cast<FreeInst>(*(BBIL.begin()+i))) {
101 BBIL.remove(BB->getInstList().begin()+i);
103 // Cast the argument to free into a ubyte*...
104 CastInst *MCast = new CastInst(FI->getOperand(0),
105 PointerType::get(Type::UByteTy));
106 BBIL.insert(BBIL.begin()+i, MCast);
108 // Insert a call to the free function...
109 CallInst *FCall = new CallInst(FreeMeth,
110 vector<Value*>(1, MCast));
111 BBIL.insert(BBIL.begin()+i+1, FCall);
113 // Delete the old free instruction
119 return false; // Always successful