lib/Analysis/MemoryBuiltins.cpp

   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"
  21 using 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.
  29 bool llvm::isMalloc(const Value *I) {
  30   return extractMallocCall(I) || extractMallocCallFromBitCast(I);
  31 }
  32
  33 static 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.
  59 const CallInst *llvm::extractMallocCall(const Value *I) {
  60   const CallInst *CI = dyn_cast<CallInst>(I);
  61   return (isMallocCall(CI)) ? CI : NULL;
  62 }
  63
  64 CallInst *llvm::extractMallocCall(Value *I) {
  65   CallInst *CI = dyn_cast<CallInst>(I);
  66   return (isMallocCall(CI)) ? CI : NULL;
  67 }
  68
  69 static 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.
  78 CallInst *llvm::extractMallocCallFromBitCast(Value *I) {
  79   BitCastInst *BCI = dyn_cast<BitCastInst>(I);
  80   return (isBitCastOfMallocCall(BCI)) ? cast<CallInst>(BCI->getOperand(0))
  81                                       : NULL;
  82 }
  83
  84 const 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
  90 static 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 call's arg can be determined to be a multiple of ElementSize,
 105   // return the multiple.  Otherwise, return NULL.
 106   Value *MallocArg = CI->getArgOperand(0);
 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.
 118 const 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->getArgOperand(0)->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.
 135 const 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.
 166 const 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.
 176 Value *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 non-null if the value is a call to the builtin free()
 187 const CallInst *llvm::isFreeCall(const Value *I) {
 188   const CallInst *CI = dyn_cast<CallInst>(I);
 189   if (!CI)
 190     return 0;
 191   Function *Callee = CI->getCalledFunction();
 192   if (Callee == 0 || !Callee->isDeclaration() || Callee->getName() != "free")
 193     return 0;
 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 0;
 201   if (FTy->getNumParams() != 1)
 202     return 0;
 203   if (FTy->param_begin()->get() != Type::getInt8PtrTy(Callee->getContext()))
 204     return 0;
 205
 206   return CI;
 207 }