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())
  39     return false;
  40   if (Callee->getName() != "malloc" &&
  41       Callee->getName() != "_Znwj" && // operator new(unsigned int)
  42       Callee->getName() != "_Znwm" && // operator new(unsigned long)
  43       Callee->getName() != "_Znaj" && // operator new[](unsigned int)
  44       Callee->getName() != "_Znam")   // operator new[](unsigned long)
  45     return false;
  46
  47   // Check malloc prototype.
  48   // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
  49   // attribute will exist.
  50   const FunctionType *FTy = Callee->getFunctionType();
  51   if (FTy->getNumParams() != 1)
  52     return false;
  53   return FTy->getParamType(0)->isIntegerTy(32) ||
  54          FTy->getParamType(0)->isIntegerTy(64);
  55 }
  56
  57 /// extractMallocCall - Returns the corresponding CallInst if the instruction
  58 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
  59 /// ignore InvokeInst here.
  60 const CallInst *llvm::extractMallocCall(const Value *I) {
  61   const CallInst *CI = dyn_cast<CallInst>(I);
  62   return (isMallocCall(CI)) ? CI : NULL;
  63 }
  64
  65 CallInst *llvm::extractMallocCall(Value *I) {
  66   CallInst *CI = dyn_cast<CallInst>(I);
  67   return (isMallocCall(CI)) ? CI : NULL;
  68 }
  69
  70 static bool isBitCastOfMallocCall(const BitCastInst *BCI) {
  71   if (!BCI)
  72     return false;
  73
  74   return isMallocCall(dyn_cast<CallInst>(BCI->getOperand(0)));
  75 }
  76
  77 /// extractMallocCallFromBitCast - Returns the corresponding CallInst if the
  78 /// instruction is a bitcast of the result of a malloc call.
  79 CallInst *llvm::extractMallocCallFromBitCast(Value *I) {
  80   BitCastInst *BCI = dyn_cast<BitCastInst>(I);
  81   return (isBitCastOfMallocCall(BCI)) ? cast<CallInst>(BCI->getOperand(0))
  82                                       : NULL;
  83 }
  84
  85 const CallInst *llvm::extractMallocCallFromBitCast(const Value *I) {
  86   const BitCastInst *BCI = dyn_cast<BitCastInst>(I);
  87   return (isBitCastOfMallocCall(BCI)) ? cast<CallInst>(BCI->getOperand(0))
  88                                       : NULL;
  89 }
  90
  91 static Value *computeArraySize(const CallInst *CI, const TargetData *TD,
  92                                bool LookThroughSExt = false) {
  93   if (!CI)
  94     return NULL;
  95
  96   // The size of the malloc's result type must be known to determine array size.
  97   const Type *T = getMallocAllocatedType(CI);
  98   if (!T || !T->isSized() || !TD)
  99     return NULL;
 100
 101   unsigned ElementSize = TD->getTypeAllocSize(T);
 102   if (const StructType *ST = dyn_cast<StructType>(T))
 103     ElementSize = TD->getStructLayout(ST)->getSizeInBytes();
 104
 105   // If malloc call's arg can be determined to be a multiple of ElementSize,
 106   // return the multiple.  Otherwise, return NULL.
 107   Value *MallocArg = CI->getArgOperand(0);
 108   Value *Multiple = NULL;
 109   if (ComputeMultiple(MallocArg, ElementSize, Multiple,
 110                       LookThroughSExt))
 111     return Multiple;
 112
 113   return NULL;
 114 }
 115
 116 /// isArrayMalloc - Returns the corresponding CallInst if the instruction
 117 /// is a call to malloc whose array size can be determined and the array size
 118 /// is not constant 1.  Otherwise, return NULL.
 119 const CallInst *llvm::isArrayMalloc(const Value *I, const TargetData *TD) {
 120   const CallInst *CI = extractMallocCall(I);
 121   Value *ArraySize = computeArraySize(CI, TD);
 122
 123   if (ArraySize &&
 124       ArraySize != ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
 125     return CI;
 126
 127   // CI is a non-array malloc or we can't figure out that it is an array malloc.
 128   return NULL;
 129 }
 130
 131 /// getMallocType - Returns the PointerType resulting from the malloc call.
 132 /// The PointerType depends on the number of bitcast uses of the malloc call:
 133 ///   0: PointerType is the calls' return type.
 134 ///   1: PointerType is the bitcast's result type.
 135 ///  >1: Unique PointerType cannot be determined, return NULL.
 136 const PointerType *llvm::getMallocType(const CallInst *CI) {
 137   assert(isMalloc(CI) && "getMallocType and not malloc call");
 138
 139   const PointerType *MallocType = NULL;
 140   unsigned NumOfBitCastUses = 0;
 141
 142   // Determine if CallInst has a bitcast use.
 143   for (Value::const_use_iterator UI = CI->use_begin(), E = CI->use_end();
 144        UI != E; )
 145     if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
 146       MallocType = cast<PointerType>(BCI->getDestTy());
 147       NumOfBitCastUses++;
 148     }
 149
 150   // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
 151   if (NumOfBitCastUses == 1)
 152     return MallocType;
 153
 154   // Malloc call was not bitcast, so type is the malloc function's return type.
 155   if (NumOfBitCastUses == 0)
 156     return cast<PointerType>(CI->getType());
 157
 158   // Type could not be determined.
 159   return NULL;
 160 }
 161
 162 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
 163 /// The Type depends on the number of bitcast uses of the malloc call:
 164 ///   0: PointerType is the malloc calls' return type.
 165 ///   1: PointerType is the bitcast's result type.
 166 ///  >1: Unique PointerType cannot be determined, return NULL.
 167 const Type *llvm::getMallocAllocatedType(const CallInst *CI) {
 168   const PointerType *PT = getMallocType(CI);
 169   return PT ? PT->getElementType() : NULL;
 170 }
 171
 172 /// getMallocArraySize - Returns the array size of a malloc call.  If the
 173 /// argument passed to malloc is a multiple of the size of the malloced type,
 174 /// then return that multiple.  For non-array mallocs, the multiple is
 175 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
 176 /// determined.
 177 Value *llvm::getMallocArraySize(CallInst *CI, const TargetData *TD,
 178                                 bool LookThroughSExt) {
 179   assert(isMalloc(CI) && "getMallocArraySize and not malloc call");
 180   return computeArraySize(CI, TD, LookThroughSExt);
 181 }
 182
 183 //===----------------------------------------------------------------------===//
 184 //  free Call Utility Functions.
 185 //
 186
 187 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
 188 const CallInst *llvm::isFreeCall(const Value *I) {
 189   const CallInst *CI = dyn_cast<CallInst>(I);
 190   if (!CI)
 191     return 0;
 192   Function *Callee = CI->getCalledFunction();
 193   if (Callee == 0 || !Callee->isDeclaration())
 194     return 0;
 195
 196   if (Callee->getName() != "free" &&
 197       Callee->getName() != "_ZdlPv" && // operator delete(void*)
 198       Callee->getName() != "_ZdaPv")   // operator delete[](void*)
 199     return 0;
 200
 201   // Check free prototype.
 202   // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
 203   // attribute will exist.
 204   const FunctionType *FTy = Callee->getFunctionType();
 205   if (!FTy->getReturnType()->isVoidTy())
 206     return 0;
 207   if (FTy->getNumParams() != 1)
 208     return 0;
 209   if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext()))
 210     return 0;
 211
 212   return CI;
 213 }