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"
16 #include "llvm/ConstantVals.h"
18 // doPassInitialization - For the lower allocations pass, this ensures that a
19 // module contains a declaration for a malloc and a free function.
21 // This function is always successful.
23 bool LowerAllocations::doPassInitialization(Module *M) {
25 const MethodType *MallocType =
26 MethodType::get(PointerType::get(Type::SByteTy),
27 vector<const Type*>(1, Type::UIntTy), false);
29 SymbolTable *SymTab = M->getSymbolTableSure();
31 // Check for a definition of malloc
32 if (Value *V = SymTab->lookup(PointerType::get(MallocType), "malloc")) {
33 MallocMeth = cast<Method>(V); // Yup, got it
34 } else { // Nope, add one
35 M->getMethodList().push_back(MallocMeth = new Method(MallocType, "malloc"));
39 const MethodType *FreeType =
40 MethodType::get(Type::VoidTy,
41 vector<const Type*>(1, PointerType::get(Type::SByteTy)),
44 // Check for a definition of free
45 if (Value *V = SymTab->lookup(PointerType::get(FreeType), "free")) {
46 FreeMeth = cast<Method>(V); // Yup, got it
47 } else { // Nope, add one
48 M->getMethodList().push_back(FreeMeth = new Method(FreeType, "free"));
52 return Changed; // Always successful
55 // doPerMethodWork - This method does the actual work of converting
56 // instructions over, assuming that the pass has already been initialized.
58 bool LowerAllocations::doPerMethodWork(Method *M) {
60 assert(MallocMeth && FreeMeth && M && "Pass not initialized!");
62 // Loop over all of the instructions, looking for malloc or free instructions
63 for (Method::iterator BBI = M->begin(), BBE = M->end(); BBI != BBE; ++BBI) {
64 BasicBlock *BB = *BBI;
65 for (unsigned i = 0; i < BB->size(); ++i) {
66 BasicBlock::InstListType &BBIL = BB->getInstList();
67 if (MallocInst *MI = dyn_cast<MallocInst>(*(BBIL.begin()+i))) {
68 BBIL.remove(BBIL.begin()+i); // remove the malloc instr...
70 const Type *AllocTy =cast<PointerType>(MI->getType())->getElementType();
72 // If the user is allocating an unsized array with a dynamic size arg,
73 // start by getting the size of one element.
75 if (const ArrayType *ATy = dyn_cast<ArrayType>(AllocTy))
76 if (ATy->isUnsized()) AllocTy = ATy->getElementType();
78 // Get the number of bytes to be allocated for one element of the
80 unsigned Size = DataLayout.getTypeSize(AllocTy);
82 // malloc(type) becomes sbyte *malloc(constint)
83 Value *MallocArg = ConstantUInt::get(Type::UIntTy, Size);
84 if (MI->getNumOperands() && Size == 1) {
85 MallocArg = MI->getOperand(0); // Operand * 1 = Operand
86 } else if (MI->getNumOperands()) {
87 // Multiply it by the array size if neccesary...
88 MallocArg = BinaryOperator::create(Instruction::Mul,MI->getOperand(0),
90 BBIL.insert(BBIL.begin()+i++, cast<Instruction>(MallocArg));
93 // Create the call to Malloc...
94 CallInst *MCall = new CallInst(MallocMeth,
95 vector<Value*>(1, MallocArg));
96 BBIL.insert(BBIL.begin()+i, MCall);
98 // Create a cast instruction to convert to the right type...
99 CastInst *MCast = new CastInst(MCall, MI->getType());
100 BBIL.insert(BBIL.begin()+i+1, MCast);
102 // Replace all uses of the old malloc inst with the cast inst
103 MI->replaceAllUsesWith(MCast);
104 delete MI; // Delete the malloc inst
106 } else if (FreeInst *FI = dyn_cast<FreeInst>(*(BBIL.begin()+i))) {
107 BBIL.remove(BB->getInstList().begin()+i);
109 // Cast the argument to free into a ubyte*...
110 CastInst *MCast = new CastInst(FI->getOperand(0),
111 PointerType::get(Type::UByteTy));
112 BBIL.insert(BBIL.begin()+i, MCast);
114 // Insert a call to the free function...
115 CallInst *FCall = new CallInst(FreeMeth,
116 vector<Value*>(1, MCast));
117 BBIL.insert(BBIL.begin()+i+1, FCall);
119 // Delete the old free instruction