MemoryBuiltins.cpp revision 607a7ab3da72a2eb53553a520507cbb8068dd1d8
1//===------ MemoryBuiltins.cpp - Identify calls to memory builtins --------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This family of functions identifies calls to builtin functions that allocate 11// or free memory. 12// 13//===----------------------------------------------------------------------===// 14 15#include "llvm/Analysis/MemoryBuiltins.h" 16#include "llvm/Constants.h" 17#include "llvm/Instructions.h" 18#include "llvm/Module.h" 19#include "llvm/Analysis/ValueTracking.h" 20#include "llvm/Target/TargetData.h" 21using namespace llvm; 22 23//===----------------------------------------------------------------------===// 24// malloc Call Utility Functions. 25// 26 27/// isMalloc - Returns true if the value is either a malloc call or a 28/// bitcast of the result of a malloc call. 29bool llvm::isMalloc(const Value *I) { 30 return extractMallocCall(I) || extractMallocCallFromBitCast(I); 31} 32 33static bool isMallocCall(const CallInst *CI) { 34 if (!CI) 35 return false; 36 37 Function *Callee = CI->getCalledFunction(); 38 if (Callee == 0 || !Callee->isDeclaration() || Callee->getName() != "malloc") 39 return false; 40 41 // Check malloc prototype. 42 // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin 43 // attribute will exist. 44 const FunctionType *FTy = Callee->getFunctionType(); 45 if (FTy->getNumParams() != 1) 46 return false; 47 if (IntegerType *ITy = dyn_cast<IntegerType>(FTy->param_begin()->get())) { 48 if (ITy->getBitWidth() != 32 && ITy->getBitWidth() != 64) 49 return false; 50 return true; 51 } 52 53 return false; 54} 55 56/// extractMallocCall - Returns the corresponding CallInst if the instruction 57/// is a malloc call. Since CallInst::CreateMalloc() only creates calls, we 58/// ignore InvokeInst here. 59const CallInst *llvm::extractMallocCall(const Value *I) { 60 const CallInst *CI = dyn_cast<CallInst>(I); 61 return (isMallocCall(CI)) ? CI : NULL; 62} 63 64CallInst *llvm::extractMallocCall(Value *I) { 65 CallInst *CI = dyn_cast<CallInst>(I); 66 return (isMallocCall(CI)) ? CI : NULL; 67} 68 69static bool isBitCastOfMallocCall(const BitCastInst *BCI) { 70 if (!BCI) 71 return false; 72 73 return isMallocCall(dyn_cast<CallInst>(BCI->getOperand(0))); 74} 75 76/// extractMallocCallFromBitCast - Returns the corresponding CallInst if the 77/// instruction is a bitcast of the result of a malloc call. 78CallInst *llvm::extractMallocCallFromBitCast(Value *I) { 79 BitCastInst *BCI = dyn_cast<BitCastInst>(I); 80 return (isBitCastOfMallocCall(BCI)) ? cast<CallInst>(BCI->getOperand(0)) 81 : NULL; 82} 83 84const CallInst *llvm::extractMallocCallFromBitCast(const Value *I) { 85 const BitCastInst *BCI = dyn_cast<BitCastInst>(I); 86 return (isBitCastOfMallocCall(BCI)) ? cast<CallInst>(BCI->getOperand(0)) 87 : NULL; 88} 89 90static Value *computeArraySize(const CallInst *CI, const TargetData *TD, 91 bool LookThroughSExt = false) { 92 if (!CI) 93 return NULL; 94 95 // The size of the malloc's result type must be known to determine array size. 96 const Type *T = getMallocAllocatedType(CI); 97 if (!T || !T->isSized() || !TD) 98 return NULL; 99 100 unsigned ElementSize = TD->getTypeAllocSize(T); 101 if (const StructType *ST = dyn_cast<StructType>(T)) 102 ElementSize = TD->getStructLayout(ST)->getSizeInBytes(); 103 104 // If malloc calls' arg can be determined to be a multiple of ElementSize, 105 // return the multiple. Otherwise, return NULL. 106 Value *MallocArg = CI->getOperand(1); 107 Value *Multiple = NULL; 108 if (ComputeMultiple(MallocArg, ElementSize, Multiple, 109 LookThroughSExt)) 110 return Multiple; 111 112 return NULL; 113} 114 115/// isArrayMalloc - Returns the corresponding CallInst if the instruction 116/// is a call to malloc whose array size can be determined and the array size 117/// is not constant 1. Otherwise, return NULL. 118const CallInst *llvm::isArrayMalloc(const Value *I, const TargetData *TD) { 119 const CallInst *CI = extractMallocCall(I); 120 Value *ArraySize = computeArraySize(CI, TD); 121 122 if (ArraySize && 123 ArraySize != ConstantInt::get(CI->getOperand(1)->getType(), 1)) 124 return CI; 125 126 // CI is a non-array malloc or we can't figure out that it is an array malloc. 127 return NULL; 128} 129 130/// getMallocType - Returns the PointerType resulting from the malloc call. 131/// The PointerType depends on the number of bitcast uses of the malloc call: 132/// 0: PointerType is the calls' return type. 133/// 1: PointerType is the bitcast's result type. 134/// >1: Unique PointerType cannot be determined, return NULL. 135const PointerType *llvm::getMallocType(const CallInst *CI) { 136 assert(isMalloc(CI) && "getMallocType and not malloc call"); 137 138 const PointerType *MallocType = NULL; 139 unsigned NumOfBitCastUses = 0; 140 141 // Determine if CallInst has a bitcast use. 142 for (Value::const_use_iterator UI = CI->use_begin(), E = CI->use_end(); 143 UI != E; ) 144 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) { 145 MallocType = cast<PointerType>(BCI->getDestTy()); 146 NumOfBitCastUses++; 147 } 148 149 // Malloc call has 1 bitcast use, so type is the bitcast's destination type. 150 if (NumOfBitCastUses == 1) 151 return MallocType; 152 153 // Malloc call was not bitcast, so type is the malloc function's return type. 154 if (NumOfBitCastUses == 0) 155 return cast<PointerType>(CI->getType()); 156 157 // Type could not be determined. 158 return NULL; 159} 160 161/// getMallocAllocatedType - Returns the Type allocated by malloc call. 162/// The Type depends on the number of bitcast uses of the malloc call: 163/// 0: PointerType is the malloc calls' return type. 164/// 1: PointerType is the bitcast's result type. 165/// >1: Unique PointerType cannot be determined, return NULL. 166const Type *llvm::getMallocAllocatedType(const CallInst *CI) { 167 const PointerType *PT = getMallocType(CI); 168 return PT ? PT->getElementType() : NULL; 169} 170 171/// getMallocArraySize - Returns the array size of a malloc call. If the 172/// argument passed to malloc is a multiple of the size of the malloced type, 173/// then return that multiple. For non-array mallocs, the multiple is 174/// constant 1. Otherwise, return NULL for mallocs whose array size cannot be 175/// determined. 176Value *llvm::getMallocArraySize(CallInst *CI, const TargetData *TD, 177 bool LookThroughSExt) { 178 assert(isMalloc(CI) && "getMallocArraySize and not malloc call"); 179 return computeArraySize(CI, TD, LookThroughSExt); 180} 181 182//===----------------------------------------------------------------------===// 183// free Call Utility Functions. 184// 185 186/// isFreeCall - Returns true if the value is a call to the builtin free() 187bool llvm::isFreeCall(const Value *I) { 188 const CallInst *CI = dyn_cast<CallInst>(I); 189 if (!CI) 190 return false; 191 Function *Callee = CI->getCalledFunction(); 192 if (Callee == 0 || !Callee->isDeclaration() || Callee->getName() != "free") 193 return false; 194 195 // Check free prototype. 196 // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin 197 // attribute will exist. 198 const FunctionType *FTy = Callee->getFunctionType(); 199 if (!FTy->getReturnType()->isVoidTy()) 200 return false; 201 if (FTy->getNumParams() != 1) 202 return false; 203 if (FTy->param_begin()->get() != Type::getInt8PtrTy(Callee->getContext())) 204 return false; 205 206 return true; 207} 208