include/llvm/Analysis/MemoryBuiltins.h

   1 //==- llvm/Analysis/MemoryBuiltins.h - Calls to memory builtins --*- C++ -*-==//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This family of functions identifies calls to builtin functions that allocate
  10 // or free memory.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_ANALYSIS_MEMORYBUILTINS_H
  15 #define LLVM_ANALYSIS_MEMORYBUILTINS_H
  16
  17 #include "llvm/ADT/APInt.h"
  18 #include "llvm/ADT/DenseMap.h"
  19 #include "llvm/ADT/SmallPtrSet.h"
  20 #include "llvm/Analysis/TargetFolder.h"
  21 #include "llvm/Analysis/TargetLibraryInfo.h"
  22 #include "llvm/IR/CallSite.h"
  23 #include "llvm/IR/IRBuilder.h"
  24 #include "llvm/IR/InstVisitor.h"
  25 #include "llvm/IR/ValueHandle.h"
  26 #include <cstdint>
  27 #include <utility>
  28
  29 namespace llvm {
  30
  31 class AllocaInst;
  32 class Argument;
  33 class CallInst;
  34 class ConstantInt;
  35 class ConstantPointerNull;
  36 class DataLayout;
  37 class ExtractElementInst;
  38 class ExtractValueInst;
  39 class GEPOperator;
  40 class GlobalAlias;
  41 class GlobalVariable;
  42 class Instruction;
  43 class IntegerType;
  44 class IntrinsicInst;
  45 class IntToPtrInst;
  46 class LLVMContext;
  47 class LoadInst;
  48 class PHINode;
  49 class PointerType;
  50 class SelectInst;
  51 class TargetLibraryInfo;
  52 class Type;
  53 class UndefValue;
  54 class Value;
  55
  56 /// Tests if a value is a call or invoke to a library function that
  57 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
  58 /// like).
  59 bool isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
  60                     bool LookThroughBitCast = false);
  61
  62 /// Tests if a value is a call or invoke to a function that returns a
  63 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
  64 bool isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
  65                  bool LookThroughBitCast = false);
  66
  67 /// Tests if a value is a call or invoke to a library function that
  68 /// allocates uninitialized memory (such as malloc).
  69 bool isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
  70                     bool LookThroughBitCast = false);
  71
  72 /// Tests if a value is a call or invoke to a library function that
  73 /// allocates zero-filled memory (such as calloc).
  74 bool isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
  75                     bool LookThroughBitCast = false);
  76
  77 /// Tests if a value is a call or invoke to a library function that
  78 /// allocates memory similar to malloc or calloc.
  79 bool isMallocOrCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
  80                             bool LookThroughBitCast = false);
  81
  82 /// Tests if a value is a call or invoke to a library function that
  83 /// allocates memory (either malloc, calloc, or strdup like).
  84 bool isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
  85                    bool LookThroughBitCast = false);
  86
  87 /// Tests if a value is a call or invoke to a library function that
  88 /// reallocates memory (e.g., realloc).
  89 bool isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
  90                      bool LookThroughBitCast = false);
  91
  92 /// Tests if a function is a call or invoke to a library function that
  93 /// reallocates memory (e.g., realloc).
  94 bool isReallocLikeFn(const Function *F, const TargetLibraryInfo *TLI);
  95
  96 /// Tests if a value is a call or invoke to a library function that
  97 /// allocates memory and throws if an allocation failed (e.g., new).
  98 bool isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
  99                      bool LookThroughBitCast = false);
 100
 101 //===----------------------------------------------------------------------===//
 102 //  malloc Call Utility Functions.
 103 //
 104
 105 /// extractMallocCall - Returns the corresponding CallInst if the instruction
 106 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
 107 /// ignore InvokeInst here.
 108 const CallInst *extractMallocCall(const Value *I, const TargetLibraryInfo *TLI);
 109 inline CallInst *extractMallocCall(Value *I, const TargetLibraryInfo *TLI) {
 110   return const_cast<CallInst*>(extractMallocCall((const Value*)I, TLI));
 111 }
 112
 113 /// getMallocType - Returns the PointerType resulting from the malloc call.
 114 /// The PointerType depends on the number of bitcast uses of the malloc call:
 115 ///   0: PointerType is the malloc calls' return type.
 116 ///   1: PointerType is the bitcast's result type.
 117 ///  >1: Unique PointerType cannot be determined, return NULL.
 118 PointerType *getMallocType(const CallInst *CI, const TargetLibraryInfo *TLI);
 119
 120 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
 121 /// The Type depends on the number of bitcast uses of the malloc call:
 122 ///   0: PointerType is the malloc calls' return type.
 123 ///   1: PointerType is the bitcast's result type.
 124 ///  >1: Unique PointerType cannot be determined, return NULL.
 125 Type *getMallocAllocatedType(const CallInst *CI, const TargetLibraryInfo *TLI);
 126
 127 /// getMallocArraySize - Returns the array size of a malloc call.  If the
 128 /// argument passed to malloc is a multiple of the size of the malloced type,
 129 /// then return that multiple.  For non-array mallocs, the multiple is
 130 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
 131 /// determined.
 132 Value *getMallocArraySize(CallInst *CI, const DataLayout &DL,
 133                           const TargetLibraryInfo *TLI,
 134                           bool LookThroughSExt = false);
 135
 136 //===----------------------------------------------------------------------===//
 137 //  calloc Call Utility Functions.
 138 //
 139
 140 /// extractCallocCall - Returns the corresponding CallInst if the instruction
 141 /// is a calloc call.
 142 const CallInst *extractCallocCall(const Value *I, const TargetLibraryInfo *TLI);
 143 inline CallInst *extractCallocCall(Value *I, const TargetLibraryInfo *TLI) {
 144   return const_cast<CallInst*>(extractCallocCall((const Value*)I, TLI));
 145 }
 146
 147
 148 //===----------------------------------------------------------------------===//
 149 //  free Call Utility Functions.
 150 //
 151
 152 /// isLibFreeFunction - Returns true if the function is a builtin free()
 153 bool isLibFreeFunction(const Function *F, const LibFunc TLIFn);
 154
 155 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
 156 const CallInst *isFreeCall(const Value *I, const TargetLibraryInfo *TLI);
 157
 158 inline CallInst *isFreeCall(Value *I, const TargetLibraryInfo *TLI) {
 159   return const_cast<CallInst*>(isFreeCall((const Value*)I, TLI));
 160 }
 161
 162 //===----------------------------------------------------------------------===//
 163 //  Utility functions to compute size of objects.
 164 //
 165
 166 /// Various options to control the behavior of getObjectSize.
 167 struct ObjectSizeOpts {
 168   /// Controls how we handle conditional statements with unknown conditions.
 169   enum class Mode : uint8_t {
 170     /// Fail to evaluate an unknown condition.
 171     Exact,
 172     /// Evaluate all branches of an unknown condition. If all evaluations
 173     /// succeed, pick the minimum size.
 174     Min,
 175     /// Same as Min, except we pick the maximum size of all of the branches.
 176     Max
 177   };
 178
 179   /// How we want to evaluate this object's size.
 180   Mode EvalMode = Mode::Exact;
 181   /// Whether to round the result up to the alignment of allocas, byval
 182   /// arguments, and global variables.
 183   bool RoundToAlign = false;
 184   /// If this is true, null pointers in address space 0 will be treated as
 185   /// though they can't be evaluated. Otherwise, null is always considered to
 186   /// point to a 0 byte region of memory.
 187   bool NullIsUnknownSize = false;
 188 };
 189
 190 /// Compute the size of the object pointed by Ptr. Returns true and the
 191 /// object size in Size if successful, and false otherwise. In this context, by
 192 /// object we mean the region of memory starting at Ptr to the end of the
 193 /// underlying object pointed to by Ptr.
 194 bool getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
 195                    const TargetLibraryInfo *TLI, ObjectSizeOpts Opts = {});
 196
 197 /// Try to turn a call to \@llvm.objectsize into an integer value of the given
 198 /// Type. Returns null on failure. If MustSucceed is true, this function will
 199 /// not return null, and may return conservative values governed by the second
 200 /// argument of the call to objectsize.
 201 Value *lowerObjectSizeCall(IntrinsicInst *ObjectSize, const DataLayout &DL,
 202                            const TargetLibraryInfo *TLI, bool MustSucceed);
 203
 204
 205
 206 using SizeOffsetType = std::pair<APInt, APInt>;
 207
 208 /// Evaluate the size and offset of an object pointed to by a Value*
 209 /// statically. Fails if size or offset are not known at compile time.
 210 class ObjectSizeOffsetVisitor
 211   : public InstVisitor<ObjectSizeOffsetVisitor, SizeOffsetType> {
 212   const DataLayout &DL;
 213   const TargetLibraryInfo *TLI;
 214   ObjectSizeOpts Options;
 215   unsigned IntTyBits;
 216   APInt Zero;
 217   SmallPtrSet<Instruction *, 8> SeenInsts;
 218
 219   APInt align(APInt Size, uint64_t Align);
 220
 221   SizeOffsetType unknown() {
 222     return std::make_pair(APInt(), APInt());
 223   }
 224
 225 public:
 226   ObjectSizeOffsetVisitor(const DataLayout &DL, const TargetLibraryInfo *TLI,
 227                           LLVMContext &Context, ObjectSizeOpts Options = {});
 228
 229   SizeOffsetType compute(Value *V);
 230
 231   static bool knownSize(const SizeOffsetType &SizeOffset) {
 232     return SizeOffset.first.getBitWidth() > 1;
 233   }
 234
 235   static bool knownOffset(const SizeOffsetType &SizeOffset) {
 236     return SizeOffset.second.getBitWidth() > 1;
 237   }
 238
 239   static bool bothKnown(const SizeOffsetType &SizeOffset) {
 240     return knownSize(SizeOffset) && knownOffset(SizeOffset);
 241   }
 242
 243   // These are "private", except they can't actually be made private. Only
 244   // compute() should be used by external users.
 245   SizeOffsetType visitAllocaInst(AllocaInst &I);
 246   SizeOffsetType visitArgument(Argument &A);
 247   SizeOffsetType visitCallSite(CallSite CS);
 248   SizeOffsetType visitConstantPointerNull(ConstantPointerNull&);
 249   SizeOffsetType visitExtractElementInst(ExtractElementInst &I);
 250   SizeOffsetType visitExtractValueInst(ExtractValueInst &I);
 251   SizeOffsetType visitGEPOperator(GEPOperator &GEP);
 252   SizeOffsetType visitGlobalAlias(GlobalAlias &GA);
 253   SizeOffsetType visitGlobalVariable(GlobalVariable &GV);
 254   SizeOffsetType visitIntToPtrInst(IntToPtrInst&);
 255   SizeOffsetType visitLoadInst(LoadInst &I);
 256   SizeOffsetType visitPHINode(PHINode&);
 257   SizeOffsetType visitSelectInst(SelectInst &I);
 258   SizeOffsetType visitUndefValue(UndefValue&);
 259   SizeOffsetType visitInstruction(Instruction &I);
 260
 261 private:
 262   bool CheckedZextOrTrunc(APInt &I);
 263 };
 264
 265 using SizeOffsetEvalType = std::pair<Value *, Value *>;
 266
 267 /// Evaluate the size and offset of an object pointed to by a Value*.
 268 /// May create code to compute the result at run-time.
 269 class ObjectSizeOffsetEvaluator
 270   : public InstVisitor<ObjectSizeOffsetEvaluator, SizeOffsetEvalType> {
 271   using BuilderTy = IRBuilder<TargetFolder, IRBuilderCallbackInserter>;
 272   using WeakEvalType = std::pair<WeakTrackingVH, WeakTrackingVH>;
 273   using CacheMapTy = DenseMap<const Value *, WeakEvalType>;
 274   using PtrSetTy = SmallPtrSet<const Value *, 8>;
 275
 276   const DataLayout &DL;
 277   const TargetLibraryInfo *TLI;
 278   LLVMContext &Context;
 279   BuilderTy Builder;
 280   IntegerType *IntTy;
 281   Value *Zero;
 282   CacheMapTy CacheMap;
 283   PtrSetTy SeenVals;
 284   ObjectSizeOpts EvalOpts;
 285   SmallPtrSet<Instruction *, 8> InsertedInstructions;
 286
 287   SizeOffsetEvalType compute_(Value *V);
 288
 289 public:
 290   static SizeOffsetEvalType unknown() {
 291     return std::make_pair(nullptr, nullptr);
 292   }
 293
 294   ObjectSizeOffsetEvaluator(const DataLayout &DL, const TargetLibraryInfo *TLI,
 295                             LLVMContext &Context, ObjectSizeOpts EvalOpts = {});
 296
 297   SizeOffsetEvalType compute(Value *V);
 298
 299   bool knownSize(SizeOffsetEvalType SizeOffset) {
 300     return SizeOffset.first;
 301   }
 302
 303   bool knownOffset(SizeOffsetEvalType SizeOffset) {
 304     return SizeOffset.second;
 305   }
 306
 307   bool anyKnown(SizeOffsetEvalType SizeOffset) {
 308     return knownSize(SizeOffset) || knownOffset(SizeOffset);
 309   }
 310
 311   bool bothKnown(SizeOffsetEvalType SizeOffset) {
 312     return knownSize(SizeOffset) && knownOffset(SizeOffset);
 313   }
 314
 315   // The individual instruction visitors should be treated as private.
 316   SizeOffsetEvalType visitAllocaInst(AllocaInst &I);
 317   SizeOffsetEvalType visitCallSite(CallSite CS);
 318   SizeOffsetEvalType visitExtractElementInst(ExtractElementInst &I);
 319   SizeOffsetEvalType visitExtractValueInst(ExtractValueInst &I);
 320   SizeOffsetEvalType visitGEPOperator(GEPOperator &GEP);
 321   SizeOffsetEvalType visitIntToPtrInst(IntToPtrInst&);
 322   SizeOffsetEvalType visitLoadInst(LoadInst &I);
 323   SizeOffsetEvalType visitPHINode(PHINode &PHI);
 324   SizeOffsetEvalType visitSelectInst(SelectInst &I);
 325   SizeOffsetEvalType visitInstruction(Instruction &I);
 326 };
 327
 328 } // end namespace llvm
 329
 330 #endif // LLVM_ANALYSIS_MEMORYBUILTINS_H