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      1 //===- llvm/Analysis/MemoryBuiltins.h- Calls to memory builtins -*- C++ -*-===//
      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 #ifndef LLVM_ANALYSIS_MEMORYBUILTINS_H
     16 #define LLVM_ANALYSIS_MEMORYBUILTINS_H
     17 
     18 #include "llvm/ADT/DenseMap.h"
     19 #include "llvm/ADT/SmallPtrSet.h"
     20 #include "llvm/Analysis/TargetFolder.h"
     21 #include "llvm/IR/IRBuilder.h"
     22 #include "llvm/IR/InstVisitor.h"
     23 #include "llvm/IR/Operator.h"
     24 #include "llvm/IR/ValueHandle.h"
     25 #include "llvm/Support/DataTypes.h"
     26 
     27 namespace llvm {
     28 class CallInst;
     29 class PointerType;
     30 class DataLayout;
     31 class TargetLibraryInfo;
     32 class Type;
     33 class Value;
     34 
     35 enum class ObjSizeMode {
     36   Exact = 0,
     37   Min = 1,
     38   Max = 2
     39 };
     40 
     41 /// \brief Tests if a value is a call or invoke to a library function that
     42 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
     43 /// like).
     44 bool isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
     45                     bool LookThroughBitCast = false);
     46 
     47 /// \brief Tests if a value is a call or invoke to a function that returns a
     48 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
     49 bool isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
     50                  bool LookThroughBitCast = false);
     51 
     52 /// \brief Tests if a value is a call or invoke to a library function that
     53 /// allocates uninitialized memory (such as malloc).
     54 bool isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
     55                     bool LookThroughBitCast = false);
     56 
     57 /// \brief Tests if a value is a call or invoke to a library function that
     58 /// allocates zero-filled memory (such as calloc).
     59 bool isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
     60                     bool LookThroughBitCast = false);
     61 
     62 /// \brief Tests if a value is a call or invoke to a library function that
     63 /// allocates memory (either malloc, calloc, or strdup like).
     64 bool isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
     65                    bool LookThroughBitCast = false);
     66 
     67 //===----------------------------------------------------------------------===//
     68 //  malloc Call Utility Functions.
     69 //
     70 
     71 /// extractMallocCall - Returns the corresponding CallInst if the instruction
     72 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
     73 /// ignore InvokeInst here.
     74 const CallInst *extractMallocCall(const Value *I, const TargetLibraryInfo *TLI);
     75 static inline CallInst *extractMallocCall(Value *I,
     76                                           const TargetLibraryInfo *TLI) {
     77   return const_cast<CallInst*>(extractMallocCall((const Value*)I, TLI));
     78 }
     79 
     80 /// getMallocType - Returns the PointerType resulting from the malloc call.
     81 /// The PointerType depends on the number of bitcast uses of the malloc call:
     82 ///   0: PointerType is the malloc calls' return type.
     83 ///   1: PointerType is the bitcast's result type.
     84 ///  >1: Unique PointerType cannot be determined, return NULL.
     85 PointerType *getMallocType(const CallInst *CI, const TargetLibraryInfo *TLI);
     86 
     87 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
     88 /// The Type depends on the number of bitcast uses of the malloc call:
     89 ///   0: PointerType is the malloc calls' return type.
     90 ///   1: PointerType is the bitcast's result type.
     91 ///  >1: Unique PointerType cannot be determined, return NULL.
     92 Type *getMallocAllocatedType(const CallInst *CI, const TargetLibraryInfo *TLI);
     93 
     94 /// getMallocArraySize - Returns the array size of a malloc call.  If the
     95 /// argument passed to malloc is a multiple of the size of the malloced type,
     96 /// then return that multiple.  For non-array mallocs, the multiple is
     97 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
     98 /// determined.
     99 Value *getMallocArraySize(CallInst *CI, const DataLayout &DL,
    100                           const TargetLibraryInfo *TLI,
    101                           bool LookThroughSExt = false);
    102 
    103 //===----------------------------------------------------------------------===//
    104 //  calloc Call Utility Functions.
    105 //
    106 
    107 /// extractCallocCall - Returns the corresponding CallInst if the instruction
    108 /// is a calloc call.
    109 const CallInst *extractCallocCall(const Value *I, const TargetLibraryInfo *TLI);
    110 static inline CallInst *extractCallocCall(Value *I,
    111                                           const TargetLibraryInfo *TLI) {
    112   return const_cast<CallInst*>(extractCallocCall((const Value*)I, TLI));
    113 }
    114 
    115 
    116 //===----------------------------------------------------------------------===//
    117 //  free Call Utility Functions.
    118 //
    119 
    120 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
    121 const CallInst *isFreeCall(const Value *I, const TargetLibraryInfo *TLI);
    122 
    123 static inline CallInst *isFreeCall(Value *I, const TargetLibraryInfo *TLI) {
    124   return const_cast<CallInst*>(isFreeCall((const Value*)I, TLI));
    125 }
    126 
    127 
    128 //===----------------------------------------------------------------------===//
    129 //  Utility functions to compute size of objects.
    130 //
    131 
    132 /// \brief Compute the size of the object pointed by Ptr. Returns true and the
    133 /// object size in Size if successful, and false otherwise. In this context, by
    134 /// object we mean the region of memory starting at Ptr to the end of the
    135 /// underlying object pointed to by Ptr.
    136 /// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
    137 /// byval arguments, and global variables.
    138 /// If Mode is Min or Max the size will be evaluated even if it depends on
    139 /// a condition and corresponding value will be returned (min or max).
    140 bool getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
    141                    const TargetLibraryInfo *TLI, bool RoundToAlign = false,
    142                    ObjSizeMode Mode = ObjSizeMode::Exact);
    143 
    144 typedef std::pair<APInt, APInt> SizeOffsetType;
    145 
    146 /// \brief Evaluate the size and offset of an object pointed to by a Value*
    147 /// statically. Fails if size or offset are not known at compile time.
    148 class ObjectSizeOffsetVisitor
    149   : public InstVisitor<ObjectSizeOffsetVisitor, SizeOffsetType> {
    150 
    151   const DataLayout &DL;
    152   const TargetLibraryInfo *TLI;
    153   bool RoundToAlign;
    154   ObjSizeMode Mode;
    155   unsigned IntTyBits;
    156   APInt Zero;
    157   SmallPtrSet<Instruction *, 8> SeenInsts;
    158 
    159   APInt align(APInt Size, uint64_t Align);
    160 
    161   SizeOffsetType unknown() {
    162     return std::make_pair(APInt(), APInt());
    163   }
    164 
    165 public:
    166   ObjectSizeOffsetVisitor(const DataLayout &DL, const TargetLibraryInfo *TLI,
    167                           LLVMContext &Context, bool RoundToAlign = false,
    168                           ObjSizeMode Mode = ObjSizeMode::Exact);
    169 
    170   SizeOffsetType compute(Value *V);
    171 
    172   static bool knownSize(const SizeOffsetType &SizeOffset) {
    173     return SizeOffset.first.getBitWidth() > 1;
    174   }
    175 
    176   static bool knownOffset(const SizeOffsetType &SizeOffset) {
    177     return SizeOffset.second.getBitWidth() > 1;
    178   }
    179 
    180   static bool bothKnown(const SizeOffsetType &SizeOffset) {
    181     return knownSize(SizeOffset) && knownOffset(SizeOffset);
    182   }
    183 
    184   // These are "private", except they can't actually be made private. Only
    185   // compute() should be used by external users.
    186   SizeOffsetType visitAllocaInst(AllocaInst &I);
    187   SizeOffsetType visitArgument(Argument &A);
    188   SizeOffsetType visitCallSite(CallSite CS);
    189   SizeOffsetType visitConstantPointerNull(ConstantPointerNull&);
    190   SizeOffsetType visitExtractElementInst(ExtractElementInst &I);
    191   SizeOffsetType visitExtractValueInst(ExtractValueInst &I);
    192   SizeOffsetType visitGEPOperator(GEPOperator &GEP);
    193   SizeOffsetType visitGlobalAlias(GlobalAlias &GA);
    194   SizeOffsetType visitGlobalVariable(GlobalVariable &GV);
    195   SizeOffsetType visitIntToPtrInst(IntToPtrInst&);
    196   SizeOffsetType visitLoadInst(LoadInst &I);
    197   SizeOffsetType visitPHINode(PHINode&);
    198   SizeOffsetType visitSelectInst(SelectInst &I);
    199   SizeOffsetType visitUndefValue(UndefValue&);
    200   SizeOffsetType visitInstruction(Instruction &I);
    201 };
    202 
    203 typedef std::pair<Value*, Value*> SizeOffsetEvalType;
    204 
    205 
    206 /// \brief Evaluate the size and offset of an object pointed to by a Value*.
    207 /// May create code to compute the result at run-time.
    208 class ObjectSizeOffsetEvaluator
    209   : public InstVisitor<ObjectSizeOffsetEvaluator, SizeOffsetEvalType> {
    210 
    211   typedef IRBuilder<TargetFolder> BuilderTy;
    212   typedef std::pair<WeakVH, WeakVH> WeakEvalType;
    213   typedef DenseMap<const Value*, WeakEvalType> CacheMapTy;
    214   typedef SmallPtrSet<const Value*, 8> PtrSetTy;
    215 
    216   const DataLayout &DL;
    217   const TargetLibraryInfo *TLI;
    218   LLVMContext &Context;
    219   BuilderTy Builder;
    220   IntegerType *IntTy;
    221   Value *Zero;
    222   CacheMapTy CacheMap;
    223   PtrSetTy SeenVals;
    224   bool RoundToAlign;
    225 
    226   SizeOffsetEvalType unknown() {
    227     return std::make_pair(nullptr, nullptr);
    228   }
    229   SizeOffsetEvalType compute_(Value *V);
    230 
    231 public:
    232   ObjectSizeOffsetEvaluator(const DataLayout &DL, const TargetLibraryInfo *TLI,
    233                             LLVMContext &Context, bool RoundToAlign = false);
    234   SizeOffsetEvalType compute(Value *V);
    235 
    236   bool knownSize(SizeOffsetEvalType SizeOffset) {
    237     return SizeOffset.first;
    238   }
    239 
    240   bool knownOffset(SizeOffsetEvalType SizeOffset) {
    241     return SizeOffset.second;
    242   }
    243 
    244   bool anyKnown(SizeOffsetEvalType SizeOffset) {
    245     return knownSize(SizeOffset) || knownOffset(SizeOffset);
    246   }
    247 
    248   bool bothKnown(SizeOffsetEvalType SizeOffset) {
    249     return knownSize(SizeOffset) && knownOffset(SizeOffset);
    250   }
    251 
    252   // The individual instruction visitors should be treated as private.
    253   SizeOffsetEvalType visitAllocaInst(AllocaInst &I);
    254   SizeOffsetEvalType visitCallSite(CallSite CS);
    255   SizeOffsetEvalType visitExtractElementInst(ExtractElementInst &I);
    256   SizeOffsetEvalType visitExtractValueInst(ExtractValueInst &I);
    257   SizeOffsetEvalType visitGEPOperator(GEPOperator &GEP);
    258   SizeOffsetEvalType visitIntToPtrInst(IntToPtrInst&);
    259   SizeOffsetEvalType visitLoadInst(LoadInst &I);
    260   SizeOffsetEvalType visitPHINode(PHINode &PHI);
    261   SizeOffsetEvalType visitSelectInst(SelectInst &I);
    262   SizeOffsetEvalType visitInstruction(Instruction &I);
    263 };
    264 
    265 } // End llvm namespace
    266 
    267 #endif
    268