lib/Analysis/MemoryBuiltins.cpp

   1 //===- MemoryBuiltins.cpp - Identify calls to memory builtins -------------===//
   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 #include "llvm/Analysis/MemoryBuiltins.h"
  15 #include "llvm/ADT/APInt.h"
  16 #include "llvm/ADT/None.h"
  17 #include "llvm/ADT/Optional.h"
  18 #include "llvm/ADT/STLExtras.h"
  19 #include "llvm/ADT/Statistic.h"
  20 #include "llvm/ADT/StringRef.h"
  21 #include "llvm/Analysis/TargetFolder.h"
  22 #include "llvm/Analysis/TargetLibraryInfo.h"
  23 #include "llvm/Analysis/Utils/Local.h"
  24 #include "llvm/Analysis/ValueTracking.h"
  25 #include "llvm/IR/Argument.h"
  26 #include "llvm/IR/Attributes.h"
  27 #include "llvm/IR/Constants.h"
  28 #include "llvm/IR/DataLayout.h"
  29 #include "llvm/IR/DerivedTypes.h"
  30 #include "llvm/IR/Function.h"
  31 #include "llvm/IR/GlobalAlias.h"
  32 #include "llvm/IR/GlobalVariable.h"
  33 #include "llvm/IR/Instruction.h"
  34 #include "llvm/IR/Instructions.h"
  35 #include "llvm/IR/IntrinsicInst.h"
  36 #include "llvm/IR/Operator.h"
  37 #include "llvm/IR/Type.h"
  38 #include "llvm/IR/Value.h"
  39 #include "llvm/Support/Casting.h"
  40 #include "llvm/Support/Debug.h"
  41 #include "llvm/Support/MathExtras.h"
  42 #include "llvm/Support/raw_ostream.h"
  43 #include <cassert>
  44 #include <cstdint>
  45 #include <iterator>
  46 #include <utility>
  47
  48 using namespace llvm;
  49
  50 #define DEBUG_TYPE "memory-builtins"
  51
  52 enum AllocType : uint8_t {
  53   OpNewLike          = 1<<0, // allocates; never returns null
  54   MallocLike         = 1<<1 | OpNewLike, // allocates; may return null
  55   CallocLike         = 1<<2, // allocates + bzero
  56   ReallocLike        = 1<<3, // reallocates
  57   StrDupLike         = 1<<4,
  58   MallocOrCallocLike = MallocLike | CallocLike,
  59   AllocLike          = MallocLike | CallocLike | StrDupLike,
  60   AnyAlloc           = AllocLike | ReallocLike
  61 };
  62
  63 struct AllocFnsTy {
  64   AllocType AllocTy;
  65   unsigned NumParams;
  66   // First and Second size parameters (or -1 if unused)
  67   int FstParam, SndParam;
  68 };
  69
  70 // FIXME: certain users need more information. E.g., SimplifyLibCalls needs to
  71 // know which functions are nounwind, noalias, nocapture parameters, etc.
  72 static const std::pair<LibFunc, AllocFnsTy> AllocationFnData[] = {
  73   {LibFunc_malloc,              {MallocLike,  1, 0,  -1}},
  74   {LibFunc_valloc,              {MallocLike,  1, 0,  -1}},
  75   {LibFunc_Znwj,                {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
  76   {LibFunc_ZnwjRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
  77   {LibFunc_ZnwjSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new(unsigned int, align_val_t)
  78   {LibFunc_ZnwjSt11align_val_tRKSt9nothrow_t, // new(unsigned int, align_val_t, nothrow)
  79                                 {MallocLike,  3, 0,  -1}},
  80   {LibFunc_Znwm,                {OpNewLike,   1, 0,  -1}}, // new(unsigned long)
  81   {LibFunc_ZnwmRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned long, nothrow)
  82   {LibFunc_ZnwmSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new(unsigned long, align_val_t)
  83   {LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t, // new(unsigned long, align_val_t, nothrow)
  84                                 {MallocLike,  3, 0,  -1}},
  85   {LibFunc_Znaj,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
  86   {LibFunc_ZnajRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
  87   {LibFunc_ZnajSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new[](unsigned int, align_val_t)
  88   {LibFunc_ZnajSt11align_val_tRKSt9nothrow_t, // new[](unsigned int, align_val_t, nothrow)
  89                                 {MallocLike,  3, 0,  -1}},
  90   {LibFunc_Znam,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned long)
  91   {LibFunc_ZnamRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned long, nothrow)
  92   {LibFunc_ZnamSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new[](unsigned long, align_val_t)
  93   {LibFunc_ZnamSt11align_val_tRKSt9nothrow_t, // new[](unsigned long, align_val_t, nothrow)
  94                                  {MallocLike,  3, 0,  -1}},
  95   {LibFunc_msvc_new_int,         {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
  96   {LibFunc_msvc_new_int_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
  97   {LibFunc_msvc_new_longlong,         {OpNewLike,   1, 0,  -1}}, // new(unsigned long long)
  98   {LibFunc_msvc_new_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned long long, nothrow)
  99   {LibFunc_msvc_new_array_int,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
 100   {LibFunc_msvc_new_array_int_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
 101   {LibFunc_msvc_new_array_longlong,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned long long)
 102   {LibFunc_msvc_new_array_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned long long, nothrow)
 103   {LibFunc_calloc,              {CallocLike,  2, 0,   1}},
 104   {LibFunc_realloc,             {ReallocLike, 2, 1,  -1}},
 105   {LibFunc_reallocf,            {ReallocLike, 2, 1,  -1}},
 106   {LibFunc_strdup,              {StrDupLike,  1, -1, -1}},
 107   {LibFunc_strndup,             {StrDupLike,  2, 1,  -1}}
 108   // TODO: Handle "int posix_memalign(void **, size_t, size_t)"
 109 };
 110
 111 static const Function *getCalledFunction(const Value *V, bool LookThroughBitCast,
 112                                          bool &IsNoBuiltin) {
 113   // Don't care about intrinsics in this case.
 114   if (isa<IntrinsicInst>(V))
 115     return nullptr;
 116
 117   if (LookThroughBitCast)
 118     V = V->stripPointerCasts();
 119
 120   ImmutableCallSite CS(V);
 121   if (!CS.getInstruction())
 122     return nullptr;
 123
 124   IsNoBuiltin = CS.isNoBuiltin();
 125
 126   if (const Function *Callee = CS.getCalledFunction())
 127     return Callee;
 128   return nullptr;
 129 }
 130
 131 /// Returns the allocation data for the given value if it's either a call to a
 132 /// known allocation function, or a call to a function with the allocsize
 133 /// attribute.
 134 static Optional<AllocFnsTy>
 135 getAllocationDataForFunction(const Function *Callee, AllocType AllocTy,
 136                              const TargetLibraryInfo *TLI) {
 137   // Make sure that the function is available.
 138   StringRef FnName = Callee->getName();
 139   LibFunc TLIFn;
 140   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
 141     return None;
 142
 143   const auto *Iter = find_if(
 144       AllocationFnData, [TLIFn](const std::pair<LibFunc, AllocFnsTy> &P) {
 145         return P.first == TLIFn;
 146       });
 147
 148   if (Iter == std::end(AllocationFnData))
 149     return None;
 150
 151   const AllocFnsTy *FnData = &Iter->second;
 152   if ((FnData->AllocTy & AllocTy) != FnData->AllocTy)
 153     return None;
 154
 155   // Check function prototype.
 156   int FstParam = FnData->FstParam;
 157   int SndParam = FnData->SndParam;
 158   FunctionType *FTy = Callee->getFunctionType();
 159
 160   if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) &&
 161       FTy->getNumParams() == FnData->NumParams &&
 162       (FstParam < 0 ||
 163        (FTy->getParamType(FstParam)->isIntegerTy(32) ||
 164         FTy->getParamType(FstParam)->isIntegerTy(64))) &&
 165       (SndParam < 0 ||
 166        FTy->getParamType(SndParam)->isIntegerTy(32) ||
 167        FTy->getParamType(SndParam)->isIntegerTy(64)))
 168     return *FnData;
 169   return None;
 170 }
 171
 172 static Optional<AllocFnsTy> getAllocationData(const Value *V, AllocType AllocTy,
 173                                               const TargetLibraryInfo *TLI,
 174                                               bool LookThroughBitCast = false) {
 175   bool IsNoBuiltinCall;
 176   if (const Function *Callee =
 177           getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall))
 178     if (!IsNoBuiltinCall)
 179       return getAllocationDataForFunction(Callee, AllocTy, TLI);
 180   return None;
 181 }
 182
 183 static Optional<AllocFnsTy>
 184 getAllocationData(const Value *V, AllocType AllocTy,
 185                   function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
 186                   bool LookThroughBitCast = false) {
 187   bool IsNoBuiltinCall;
 188   if (const Function *Callee =
 189           getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall))
 190     if (!IsNoBuiltinCall)
 191       return getAllocationDataForFunction(
 192           Callee, AllocTy, &GetTLI(const_cast<Function &>(*Callee)));
 193   return None;
 194 }
 195
 196 static Optional<AllocFnsTy> getAllocationSize(const Value *V,
 197                                               const TargetLibraryInfo *TLI) {
 198   bool IsNoBuiltinCall;
 199   const Function *Callee =
 200       getCalledFunction(V, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
 201   if (!Callee)
 202     return None;
 203
 204   // Prefer to use existing information over allocsize. This will give us an
 205   // accurate AllocTy.
 206   if (!IsNoBuiltinCall)
 207     if (Optional<AllocFnsTy> Data =
 208             getAllocationDataForFunction(Callee, AnyAlloc, TLI))
 209       return Data;
 210
 211   Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize);
 212   if (Attr == Attribute())
 213     return None;
 214
 215   std::pair<unsigned, Optional<unsigned>> Args = Attr.getAllocSizeArgs();
 216
 217   AllocFnsTy Result;
 218   // Because allocsize only tells us how many bytes are allocated, we're not
 219   // really allowed to assume anything, so we use MallocLike.
 220   Result.AllocTy = MallocLike;
 221   Result.NumParams = Callee->getNumOperands();
 222   Result.FstParam = Args.first;
 223   Result.SndParam = Args.second.getValueOr(-1);
 224   return Result;
 225 }
 226
 227 static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
 228   ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V);
 229   return CS && CS.hasRetAttr(Attribute::NoAlias);
 230 }
 231
 232 /// Tests if a value is a call or invoke to a library function that
 233 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
 234 /// like).
 235 bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
 236                           bool LookThroughBitCast) {
 237   return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast).hasValue();
 238 }
 239 bool llvm::isAllocationFn(
 240     const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
 241     bool LookThroughBitCast) {
 242   return getAllocationData(V, AnyAlloc, GetTLI, LookThroughBitCast).hasValue();
 243 }
 244
 245 /// Tests if a value is a call or invoke to a function that returns a
 246 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
 247 bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
 248                        bool LookThroughBitCast) {
 249   // it's safe to consider realloc as noalias since accessing the original
 250   // pointer is undefined behavior
 251   return isAllocationFn(V, TLI, LookThroughBitCast) ||
 252          hasNoAliasAttr(V, LookThroughBitCast);
 253 }
 254
 255 /// Tests if a value is a call or invoke to a library function that
 256 /// allocates uninitialized memory (such as malloc).
 257 bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 258                           bool LookThroughBitCast) {
 259   return getAllocationData(V, MallocLike, TLI, LookThroughBitCast).hasValue();
 260 }
 261 bool llvm::isMallocLikeFn(
 262     const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
 263     bool LookThroughBitCast) {
 264   return getAllocationData(V, MallocLike, GetTLI, LookThroughBitCast)
 265       .hasValue();
 266 }
 267
 268 /// Tests if a value is a call or invoke to a library function that
 269 /// allocates zero-filled memory (such as calloc).
 270 bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 271                           bool LookThroughBitCast) {
 272   return getAllocationData(V, CallocLike, TLI, LookThroughBitCast).hasValue();
 273 }
 274
 275 /// Tests if a value is a call or invoke to a library function that
 276 /// allocates memory similar to malloc or calloc.
 277 bool llvm::isMallocOrCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 278                                   bool LookThroughBitCast) {
 279   return getAllocationData(V, MallocOrCallocLike, TLI,
 280                            LookThroughBitCast).hasValue();
 281 }
 282
 283 /// Tests if a value is a call or invoke to a library function that
 284 /// allocates memory (either malloc, calloc, or strdup like).
 285 bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 286                          bool LookThroughBitCast) {
 287   return getAllocationData(V, AllocLike, TLI, LookThroughBitCast).hasValue();
 288 }
 289
 290 /// Tests if a value is a call or invoke to a library function that
 291 /// reallocates memory (e.g., realloc).
 292 bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 293                      bool LookThroughBitCast) {
 294   return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast).hasValue();
 295 }
 296
 297 /// Tests if a functions is a call or invoke to a library function that
 298 /// reallocates memory (e.g., realloc).
 299 bool llvm::isReallocLikeFn(const Function *F, const TargetLibraryInfo *TLI) {
 300   return getAllocationDataForFunction(F, ReallocLike, TLI).hasValue();
 301 }
 302
 303 /// Tests if a value is a call or invoke to a library function that
 304 /// allocates memory and throws if an allocation failed (e.g., new).
 305 bool llvm::isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 306                      bool LookThroughBitCast) {
 307   return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast).hasValue();
 308 }
 309
 310 /// Tests if a value is a call or invoke to a library function that
 311 /// allocates memory (strdup, strndup).
 312 bool llvm::isStrdupLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 313                           bool LookThroughBitCast) {
 314   return getAllocationData(V, StrDupLike, TLI, LookThroughBitCast).hasValue();
 315 }
 316
 317 /// extractMallocCall - Returns the corresponding CallInst if the instruction
 318 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
 319 /// ignore InvokeInst here.
 320 const CallInst *llvm::extractMallocCall(
 321     const Value *I,
 322     function_ref<const TargetLibraryInfo &(Function &)> GetTLI) {
 323   return isMallocLikeFn(I, GetTLI) ? dyn_cast<CallInst>(I) : nullptr;
 324 }
 325
 326 static Value *computeArraySize(const CallInst *CI, const DataLayout &DL,
 327                                const TargetLibraryInfo *TLI,
 328                                bool LookThroughSExt = false) {
 329   if (!CI)
 330     return nullptr;
 331
 332   // The size of the malloc's result type must be known to determine array size.
 333   Type *T = getMallocAllocatedType(CI, TLI);
 334   if (!T || !T->isSized())
 335     return nullptr;
 336
 337   unsigned ElementSize = DL.getTypeAllocSize(T);
 338   if (StructType *ST = dyn_cast<StructType>(T))
 339     ElementSize = DL.getStructLayout(ST)->getSizeInBytes();
 340
 341   // If malloc call's arg can be determined to be a multiple of ElementSize,
 342   // return the multiple.  Otherwise, return NULL.
 343   Value *MallocArg = CI->getArgOperand(0);
 344   Value *Multiple = nullptr;
 345   if (ComputeMultiple(MallocArg, ElementSize, Multiple, LookThroughSExt))
 346     return Multiple;
 347
 348   return nullptr;
 349 }
 350
 351 /// getMallocType - Returns the PointerType resulting from the malloc call.
 352 /// The PointerType depends on the number of bitcast uses of the malloc call:
 353 ///   0: PointerType is the calls' return type.
 354 ///   1: PointerType is the bitcast's result type.
 355 ///  >1: Unique PointerType cannot be determined, return NULL.
 356 PointerType *llvm::getMallocType(const CallInst *CI,
 357                                  const TargetLibraryInfo *TLI) {
 358   assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call");
 359
 360   PointerType *MallocType = nullptr;
 361   unsigned NumOfBitCastUses = 0;
 362
 363   // Determine if CallInst has a bitcast use.
 364   for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end();
 365        UI != E;)
 366     if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
 367       MallocType = cast<PointerType>(BCI->getDestTy());
 368       NumOfBitCastUses++;
 369     }
 370
 371   // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
 372   if (NumOfBitCastUses == 1)
 373     return MallocType;
 374
 375   // Malloc call was not bitcast, so type is the malloc function's return type.
 376   if (NumOfBitCastUses == 0)
 377     return cast<PointerType>(CI->getType());
 378
 379   // Type could not be determined.
 380   return nullptr;
 381 }
 382
 383 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
 384 /// The Type depends on the number of bitcast uses of the malloc call:
 385 ///   0: PointerType is the malloc calls' return type.
 386 ///   1: PointerType is the bitcast's result type.
 387 ///  >1: Unique PointerType cannot be determined, return NULL.
 388 Type *llvm::getMallocAllocatedType(const CallInst *CI,
 389                                    const TargetLibraryInfo *TLI) {
 390   PointerType *PT = getMallocType(CI, TLI);
 391   return PT ? PT->getElementType() : nullptr;
 392 }
 393
 394 /// getMallocArraySize - Returns the array size of a malloc call.  If the
 395 /// argument passed to malloc is a multiple of the size of the malloced type,
 396 /// then return that multiple.  For non-array mallocs, the multiple is
 397 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
 398 /// determined.
 399 Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout &DL,
 400                                 const TargetLibraryInfo *TLI,
 401                                 bool LookThroughSExt) {
 402   assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call");
 403   return computeArraySize(CI, DL, TLI, LookThroughSExt);
 404 }
 405
 406 /// extractCallocCall - Returns the corresponding CallInst if the instruction
 407 /// is a calloc call.
 408 const CallInst *llvm::extractCallocCall(const Value *I,
 409                                         const TargetLibraryInfo *TLI) {
 410   return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : nullptr;
 411 }
 412
 413 /// isLibFreeFunction - Returns true if the function is a builtin free()
 414 bool llvm::isLibFreeFunction(const Function *F, const LibFunc TLIFn) {
 415   unsigned ExpectedNumParams;
 416   if (TLIFn == LibFunc_free ||
 417       TLIFn == LibFunc_ZdlPv || // operator delete(void*)
 418       TLIFn == LibFunc_ZdaPv || // operator delete[](void*)
 419       TLIFn == LibFunc_msvc_delete_ptr32 || // operator delete(void*)
 420       TLIFn == LibFunc_msvc_delete_ptr64 || // operator delete(void*)
 421       TLIFn == LibFunc_msvc_delete_array_ptr32 || // operator delete[](void*)
 422       TLIFn == LibFunc_msvc_delete_array_ptr64)   // operator delete[](void*)
 423     ExpectedNumParams = 1;
 424   else if (TLIFn == LibFunc_ZdlPvj ||              // delete(void*, uint)
 425            TLIFn == LibFunc_ZdlPvm ||              // delete(void*, ulong)
 426            TLIFn == LibFunc_ZdlPvRKSt9nothrow_t || // delete(void*, nothrow)
 427            TLIFn == LibFunc_ZdlPvSt11align_val_t || // delete(void*, align_val_t)
 428            TLIFn == LibFunc_ZdaPvj ||              // delete[](void*, uint)
 429            TLIFn == LibFunc_ZdaPvm ||              // delete[](void*, ulong)
 430            TLIFn == LibFunc_ZdaPvRKSt9nothrow_t || // delete[](void*, nothrow)
 431            TLIFn == LibFunc_ZdaPvSt11align_val_t || // delete[](void*, align_val_t)
 432            TLIFn == LibFunc_msvc_delete_ptr32_int ||      // delete(void*, uint)
 433            TLIFn == LibFunc_msvc_delete_ptr64_longlong || // delete(void*, ulonglong)
 434            TLIFn == LibFunc_msvc_delete_ptr32_nothrow || // delete(void*, nothrow)
 435            TLIFn == LibFunc_msvc_delete_ptr64_nothrow || // delete(void*, nothrow)
 436            TLIFn == LibFunc_msvc_delete_array_ptr32_int ||      // delete[](void*, uint)
 437            TLIFn == LibFunc_msvc_delete_array_ptr64_longlong || // delete[](void*, ulonglong)
 438            TLIFn == LibFunc_msvc_delete_array_ptr32_nothrow || // delete[](void*, nothrow)
 439            TLIFn == LibFunc_msvc_delete_array_ptr64_nothrow)   // delete[](void*, nothrow)
 440     ExpectedNumParams = 2;
 441   else if (TLIFn == LibFunc_ZdaPvSt11align_val_tRKSt9nothrow_t || // delete(void*, align_val_t, nothrow)
 442            TLIFn == LibFunc_ZdlPvSt11align_val_tRKSt9nothrow_t) // delete[](void*, align_val_t, nothrow)
 443     ExpectedNumParams = 3;
 444   else
 445     return false;
 446
 447   // Check free prototype.
 448   // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
 449   // attribute will exist.
 450   FunctionType *FTy = F->getFunctionType();
 451   if (!FTy->getReturnType()->isVoidTy())
 452     return false;
 453   if (FTy->getNumParams() != ExpectedNumParams)
 454     return false;
 455   if (FTy->getParamType(0) != Type::getInt8PtrTy(F->getContext()))
 456     return false;
 457
 458   return true;
 459 }
 460
 461 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
 462 const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
 463   bool IsNoBuiltinCall;
 464   const Function *Callee =
 465       getCalledFunction(I, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
 466   if (Callee == nullptr || IsNoBuiltinCall)
 467     return nullptr;
 468
 469   StringRef FnName = Callee->getName();
 470   LibFunc TLIFn;
 471   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
 472     return nullptr;
 473
 474   return isLibFreeFunction(Callee, TLIFn) ? dyn_cast<CallInst>(I) : nullptr;
 475 }
 476
 477
 478 //===----------------------------------------------------------------------===//
 479 //  Utility functions to compute size of objects.
 480 //
 481 static APInt getSizeWithOverflow(const SizeOffsetType &Data) {
 482   if (Data.second.isNegative() || Data.first.ult(Data.second))
 483     return APInt(Data.first.getBitWidth(), 0);
 484   return Data.first - Data.second;
 485 }
 486
 487 /// Compute the size of the object pointed by Ptr. Returns true and the
 488 /// object size in Size if successful, and false otherwise.
 489 /// If RoundToAlign is true, then Size is rounded up to the alignment of
 490 /// allocas, byval arguments, and global variables.
 491 bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
 492                          const TargetLibraryInfo *TLI, ObjectSizeOpts Opts) {
 493   ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(), Opts);
 494   SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
 495   if (!Visitor.bothKnown(Data))
 496     return false;
 497
 498   Size = getSizeWithOverflow(Data).getZExtValue();
 499   return true;
 500 }
 501
 502 Value *llvm::lowerObjectSizeCall(IntrinsicInst *ObjectSize,
 503                                  const DataLayout &DL,
 504                                  const TargetLibraryInfo *TLI,
 505                                  bool MustSucceed) {
 506   assert(ObjectSize->getIntrinsicID() == Intrinsic::objectsize &&
 507          "ObjectSize must be a call to llvm.objectsize!");
 508
 509   bool MaxVal = cast<ConstantInt>(ObjectSize->getArgOperand(1))->isZero();
 510   ObjectSizeOpts EvalOptions;
 511   // Unless we have to fold this to something, try to be as accurate as
 512   // possible.
 513   if (MustSucceed)
 514     EvalOptions.EvalMode =
 515         MaxVal ? ObjectSizeOpts::Mode::Max : ObjectSizeOpts::Mode::Min;
 516   else
 517     EvalOptions.EvalMode = ObjectSizeOpts::Mode::Exact;
 518
 519   EvalOptions.NullIsUnknownSize =
 520       cast<ConstantInt>(ObjectSize->getArgOperand(2))->isOne();
 521
 522   auto *ResultType = cast<IntegerType>(ObjectSize->getType());
 523   bool StaticOnly = cast<ConstantInt>(ObjectSize->getArgOperand(3))->isZero();
 524   if (StaticOnly) {
 525     // FIXME: Does it make sense to just return a failure value if the size won't
 526     // fit in the output and `!MustSucceed`?
 527     uint64_t Size;
 528     if (getObjectSize(ObjectSize->getArgOperand(0), Size, DL, TLI, EvalOptions) &&
 529         isUIntN(ResultType->getBitWidth(), Size))
 530       return ConstantInt::get(ResultType, Size);
 531   } else {
 532     LLVMContext &Ctx = ObjectSize->getFunction()->getContext();
 533     ObjectSizeOffsetEvaluator Eval(DL, TLI, Ctx, EvalOptions);
 534     SizeOffsetEvalType SizeOffsetPair =
 535         Eval.compute(ObjectSize->getArgOperand(0));
 536
 537     if (SizeOffsetPair != ObjectSizeOffsetEvaluator::unknown()) {
 538       IRBuilder<TargetFolder> Builder(Ctx, TargetFolder(DL));
 539       Builder.SetInsertPoint(ObjectSize);
 540
 541       // If we've outside the end of the object, then we can always access
 542       // exactly 0 bytes.
 543       Value *ResultSize =
 544           Builder.CreateSub(SizeOffsetPair.first, SizeOffsetPair.second);
 545       Value *UseZero =
 546           Builder.CreateICmpULT(SizeOffsetPair.first, SizeOffsetPair.second);
 547       return Builder.CreateSelect(UseZero, ConstantInt::get(ResultType, 0),
 548                                   ResultSize);
 549     }
 550   }
 551
 552   if (!MustSucceed)
 553     return nullptr;
 554
 555   return ConstantInt::get(ResultType, MaxVal ? -1ULL : 0);
 556 }
 557
 558 STATISTIC(ObjectVisitorArgument,
 559           "Number of arguments with unsolved size and offset");
 560 STATISTIC(ObjectVisitorLoad,
 561           "Number of load instructions with unsolved size and offset");
 562
 563 APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) {
 564   if (Options.RoundToAlign && Align)
 565     return APInt(IntTyBits, alignTo(Size.getZExtValue(), llvm::Align(Align)));
 566   return Size;
 567 }
 568
 569 ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
 570                                                  const TargetLibraryInfo *TLI,
 571                                                  LLVMContext &Context,
 572                                                  ObjectSizeOpts Options)
 573     : DL(DL), TLI(TLI), Options(Options) {
 574   // Pointer size must be rechecked for each object visited since it could have
 575   // a different address space.
 576 }
 577
 578 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
 579   IntTyBits = DL.getPointerTypeSizeInBits(V->getType());
 580   Zero = APInt::getNullValue(IntTyBits);
 581
 582   V = V->stripPointerCasts();
 583   if (Instruction *I = dyn_cast<Instruction>(V)) {
 584     // If we have already seen this instruction, bail out. Cycles can happen in
 585     // unreachable code after constant propagation.
 586     if (!SeenInsts.insert(I).second)
 587       return unknown();
 588
 589     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
 590       return visitGEPOperator(*GEP);
 591     return visit(*I);
 592   }
 593   if (Argument *A = dyn_cast<Argument>(V))
 594     return visitArgument(*A);
 595   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
 596     return visitConstantPointerNull(*P);
 597   if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
 598     return visitGlobalAlias(*GA);
 599   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
 600     return visitGlobalVariable(*GV);
 601   if (UndefValue *UV = dyn_cast<UndefValue>(V))
 602     return visitUndefValue(*UV);
 603   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
 604     if (CE->getOpcode() == Instruction::IntToPtr)
 605       return unknown(); // clueless
 606     if (CE->getOpcode() == Instruction::GetElementPtr)
 607       return visitGEPOperator(cast<GEPOperator>(*CE));
 608   }
 609
 610   LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: "
 611                     << *V << '\n');
 612   return unknown();
 613 }
 614
 615 /// When we're compiling N-bit code, and the user uses parameters that are
 616 /// greater than N bits (e.g. uint64_t on a 32-bit build), we can run into
 617 /// trouble with APInt size issues. This function handles resizing + overflow
 618 /// checks for us. Check and zext or trunc \p I depending on IntTyBits and
 619 /// I's value.
 620 bool ObjectSizeOffsetVisitor::CheckedZextOrTrunc(APInt &I) {
 621   // More bits than we can handle. Checking the bit width isn't necessary, but
 622   // it's faster than checking active bits, and should give `false` in the
 623   // vast majority of cases.
 624   if (I.getBitWidth() > IntTyBits && I.getActiveBits() > IntTyBits)
 625     return false;
 626   if (I.getBitWidth() != IntTyBits)
 627     I = I.zextOrTrunc(IntTyBits);
 628   return true;
 629 }
 630
 631 SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
 632   if (!I.getAllocatedType()->isSized())
 633     return unknown();
 634
 635   APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType()));
 636   if (!I.isArrayAllocation())
 637     return std::make_pair(align(Size, I.getAlignment()), Zero);
 638
 639   Value *ArraySize = I.getArraySize();
 640   if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
 641     APInt NumElems = C->getValue();
 642     if (!CheckedZextOrTrunc(NumElems))
 643       return unknown();
 644
 645     bool Overflow;
 646     Size = Size.umul_ov(NumElems, Overflow);
 647     return Overflow ? unknown() : std::make_pair(align(Size, I.getAlignment()),
 648                                                  Zero);
 649   }
 650   return unknown();
 651 }
 652
 653 SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
 654   // No interprocedural analysis is done at the moment.
 655   if (!A.hasByValOrInAllocaAttr()) {
 656     ++ObjectVisitorArgument;
 657     return unknown();
 658   }
 659   PointerType *PT = cast<PointerType>(A.getType());
 660   APInt Size(IntTyBits, DL.getTypeAllocSize(PT->getElementType()));
 661   return std::make_pair(align(Size, A.getParamAlignment()), Zero);
 662 }
 663
 664 SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) {
 665   Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI);
 666   if (!FnData)
 667     return unknown();
 668
 669   // Handle strdup-like functions separately.
 670   if (FnData->AllocTy == StrDupLike) {
 671     APInt Size(IntTyBits, GetStringLength(CS.getArgument(0)));
 672     if (!Size)
 673       return unknown();
 674
 675     // Strndup limits strlen.
 676     if (FnData->FstParam > 0) {
 677       ConstantInt *Arg =
 678           dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
 679       if (!Arg)
 680         return unknown();
 681
 682       APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits);
 683       if (Size.ugt(MaxSize))
 684         Size = MaxSize + 1;
 685     }
 686     return std::make_pair(Size, Zero);
 687   }
 688
 689   ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
 690   if (!Arg)
 691     return unknown();
 692
 693   APInt Size = Arg->getValue();
 694   if (!CheckedZextOrTrunc(Size))
 695     return unknown();
 696
 697   // Size is determined by just 1 parameter.
 698   if (FnData->SndParam < 0)
 699     return std::make_pair(Size, Zero);
 700
 701   Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam));
 702   if (!Arg)
 703     return unknown();
 704
 705   APInt NumElems = Arg->getValue();
 706   if (!CheckedZextOrTrunc(NumElems))
 707     return unknown();
 708
 709   bool Overflow;
 710   Size = Size.umul_ov(NumElems, Overflow);
 711   return Overflow ? unknown() : std::make_pair(Size, Zero);
 712
 713   // TODO: handle more standard functions (+ wchar cousins):
 714   // - strdup / strndup
 715   // - strcpy / strncpy
 716   // - strcat / strncat
 717   // - memcpy / memmove
 718   // - strcat / strncat
 719   // - memset
 720 }
 721
 722 SizeOffsetType
 723 ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull& CPN) {
 724   // If null is unknown, there's nothing we can do. Additionally, non-zero
 725   // address spaces can make use of null, so we don't presume to know anything
 726   // about that.
 727   //
 728   // TODO: How should this work with address space casts? We currently just drop
 729   // them on the floor, but it's unclear what we should do when a NULL from
 730   // addrspace(1) gets casted to addrspace(0) (or vice-versa).
 731   if (Options.NullIsUnknownSize || CPN.getType()->getAddressSpace())
 732     return unknown();
 733   return std::make_pair(Zero, Zero);
 734 }
 735
 736 SizeOffsetType
 737 ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) {
 738   return unknown();
 739 }
 740
 741 SizeOffsetType
 742 ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
 743   // Easy cases were already folded by previous passes.
 744   return unknown();
 745 }
 746
 747 SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
 748   SizeOffsetType PtrData = compute(GEP.getPointerOperand());
 749   APInt Offset(IntTyBits, 0);
 750   if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset))
 751     return unknown();
 752
 753   return std::make_pair(PtrData.first, PtrData.second + Offset);
 754 }
 755
 756 SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
 757   if (GA.isInterposable())
 758     return unknown();
 759   return compute(GA.getAliasee());
 760 }
 761
 762 SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
 763   if (!GV.hasDefinitiveInitializer())
 764     return unknown();
 765
 766   APInt Size(IntTyBits, DL.getTypeAllocSize(GV.getValueType()));
 767   return std::make_pair(align(Size, GV.getAlignment()), Zero);
 768 }
 769
 770 SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) {
 771   // clueless
 772   return unknown();
 773 }
 774
 775 SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
 776   ++ObjectVisitorLoad;
 777   return unknown();
 778 }
 779
 780 SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
 781   // too complex to analyze statically.
 782   return unknown();
 783 }
 784
 785 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
 786   SizeOffsetType TrueSide  = compute(I.getTrueValue());
 787   SizeOffsetType FalseSide = compute(I.getFalseValue());
 788   if (bothKnown(TrueSide) && bothKnown(FalseSide)) {
 789     if (TrueSide == FalseSide) {
 790         return TrueSide;
 791     }
 792
 793     APInt TrueResult = getSizeWithOverflow(TrueSide);
 794     APInt FalseResult = getSizeWithOverflow(FalseSide);
 795
 796     if (TrueResult == FalseResult) {
 797       return TrueSide;
 798     }
 799     if (Options.EvalMode == ObjectSizeOpts::Mode::Min) {
 800       if (TrueResult.slt(FalseResult))
 801         return TrueSide;
 802       return FalseSide;
 803     }
 804     if (Options.EvalMode == ObjectSizeOpts::Mode::Max) {
 805       if (TrueResult.sgt(FalseResult))
 806         return TrueSide;
 807       return FalseSide;
 808     }
 809   }
 810   return unknown();
 811 }
 812
 813 SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) {
 814   return std::make_pair(Zero, Zero);
 815 }
 816
 817 SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
 818   LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I
 819                     << '\n');
 820   return unknown();
 821 }
 822
 823 ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
 824     const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
 825     ObjectSizeOpts EvalOpts)
 826     : DL(DL), TLI(TLI), Context(Context),
 827       Builder(Context, TargetFolder(DL),
 828               IRBuilderCallbackInserter(
 829                   [&](Instruction *I) { InsertedInstructions.insert(I); })),
 830       EvalOpts(EvalOpts) {
 831   // IntTy and Zero must be set for each compute() since the address space may
 832   // be different for later objects.
 833 }
 834
 835 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
 836   // XXX - Are vectors of pointers possible here?
 837   IntTy = cast<IntegerType>(DL.getIntPtrType(V->getType()));
 838   Zero = ConstantInt::get(IntTy, 0);
 839
 840   SizeOffsetEvalType Result = compute_(V);
 841
 842   if (!bothKnown(Result)) {
 843     // Erase everything that was computed in this iteration from the cache, so
 844     // that no dangling references are left behind. We could be a bit smarter if
 845     // we kept a dependency graph. It's probably not worth the complexity.
 846     for (const Value *SeenVal : SeenVals) {
 847       CacheMapTy::iterator CacheIt = CacheMap.find(SeenVal);
 848       // non-computable results can be safely cached
 849       if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
 850         CacheMap.erase(CacheIt);
 851     }
 852
 853     // Erase any instructions we inserted as part of the traversal.
 854     for (Instruction *I : InsertedInstructions) {
 855       I->replaceAllUsesWith(UndefValue::get(I->getType()));
 856       I->eraseFromParent();
 857     }
 858   }
 859
 860   SeenVals.clear();
 861   InsertedInstructions.clear();
 862   return Result;
 863 }
 864
 865 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
 866   ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, EvalOpts);
 867   SizeOffsetType Const = Visitor.compute(V);
 868   if (Visitor.bothKnown(Const))
 869     return std::make_pair(ConstantInt::get(Context, Const.first),
 870                           ConstantInt::get(Context, Const.second));
 871
 872   V = V->stripPointerCasts();
 873
 874   // Check cache.
 875   CacheMapTy::iterator CacheIt = CacheMap.find(V);
 876   if (CacheIt != CacheMap.end())
 877     return CacheIt->second;
 878
 879   // Always generate code immediately before the instruction being
 880   // processed, so that the generated code dominates the same BBs.
 881   BuilderTy::InsertPointGuard Guard(Builder);
 882   if (Instruction *I = dyn_cast<Instruction>(V))
 883     Builder.SetInsertPoint(I);
 884
 885   // Now compute the size and offset.
 886   SizeOffsetEvalType Result;
 887
 888   // Record the pointers that were handled in this run, so that they can be
 889   // cleaned later if something fails. We also use this set to break cycles that
 890   // can occur in dead code.
 891   if (!SeenVals.insert(V).second) {
 892     Result = unknown();
 893   } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
 894     Result = visitGEPOperator(*GEP);
 895   } else if (Instruction *I = dyn_cast<Instruction>(V)) {
 896     Result = visit(*I);
 897   } else if (isa<Argument>(V) ||
 898              (isa<ConstantExpr>(V) &&
 899               cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) ||
 900              isa<GlobalAlias>(V) ||
 901              isa<GlobalVariable>(V)) {
 902     // Ignore values where we cannot do more than ObjectSizeVisitor.
 903     Result = unknown();
 904   } else {
 905     LLVM_DEBUG(
 906         dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: " << *V
 907                << '\n');
 908     Result = unknown();
 909   }
 910
 911   // Don't reuse CacheIt since it may be invalid at this point.
 912   CacheMap[V] = Result;
 913   return Result;
 914 }
 915
 916 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
 917   if (!I.getAllocatedType()->isSized())
 918     return unknown();
 919
 920   // must be a VLA
 921   assert(I.isArrayAllocation());
 922   Value *ArraySize = I.getArraySize();
 923   Value *Size = ConstantInt::get(ArraySize->getType(),
 924                                  DL.getTypeAllocSize(I.getAllocatedType()));
 925   Size = Builder.CreateMul(Size, ArraySize);
 926   return std::make_pair(Size, Zero);
 927 }
 928
 929 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) {
 930   Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI);
 931   if (!FnData)
 932     return unknown();
 933
 934   // Handle strdup-like functions separately.
 935   if (FnData->AllocTy == StrDupLike) {
 936     // TODO
 937     return unknown();
 938   }
 939
 940   Value *FirstArg = CS.getArgument(FnData->FstParam);
 941   FirstArg = Builder.CreateZExt(FirstArg, IntTy);
 942   if (FnData->SndParam < 0)
 943     return std::make_pair(FirstArg, Zero);
 944
 945   Value *SecondArg = CS.getArgument(FnData->SndParam);
 946   SecondArg = Builder.CreateZExt(SecondArg, IntTy);
 947   Value *Size = Builder.CreateMul(FirstArg, SecondArg);
 948   return std::make_pair(Size, Zero);
 949
 950   // TODO: handle more standard functions (+ wchar cousins):
 951   // - strdup / strndup
 952   // - strcpy / strncpy
 953   // - strcat / strncat
 954   // - memcpy / memmove
 955   // - strcat / strncat
 956   // - memset
 957 }
 958
 959 SizeOffsetEvalType
 960 ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) {
 961   return unknown();
 962 }
 963
 964 SizeOffsetEvalType
 965 ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) {
 966   return unknown();
 967 }
 968
 969 SizeOffsetEvalType
 970 ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) {
 971   SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand());
 972   if (!bothKnown(PtrData))
 973     return unknown();
 974
 975   Value *Offset = EmitGEPOffset(&Builder, DL, &GEP, /*NoAssumptions=*/true);
 976   Offset = Builder.CreateAdd(PtrData.second, Offset);
 977   return std::make_pair(PtrData.first, Offset);
 978 }
 979
 980 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) {
 981   // clueless
 982   return unknown();
 983 }
 984
 985 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) {
 986   return unknown();
 987 }
 988
 989 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
 990   // Create 2 PHIs: one for size and another for offset.
 991   PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
 992   PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
 993
 994   // Insert right away in the cache to handle recursive PHIs.
 995   CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);
 996
 997   // Compute offset/size for each PHI incoming pointer.
 998   for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
 999     Builder.SetInsertPoint(&*PHI.getIncomingBlock(i)->getFirstInsertionPt());
1000     SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));
1001
1002     if (!bothKnown(EdgeData)) {
1003       OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
1004       OffsetPHI->eraseFromParent();
1005       InsertedInstructions.erase(OffsetPHI);
1006       SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
1007       SizePHI->eraseFromParent();
1008       InsertedInstructions.erase(SizePHI);
1009       return unknown();
1010     }
1011     SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
1012     OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
1013   }
1014
1015   Value *Size = SizePHI, *Offset = OffsetPHI;
1016   if (Value *Tmp = SizePHI->hasConstantValue()) {
1017     Size = Tmp;
1018     SizePHI->replaceAllUsesWith(Size);
1019     SizePHI->eraseFromParent();
1020     InsertedInstructions.erase(SizePHI);
1021   }
1022   if (Value *Tmp = OffsetPHI->hasConstantValue()) {
1023     Offset = Tmp;
1024     OffsetPHI->replaceAllUsesWith(Offset);
1025     OffsetPHI->eraseFromParent();
1026     InsertedInstructions.erase(OffsetPHI);
1027   }
1028   return std::make_pair(Size, Offset);
1029 }
1030
1031 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
1032   SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
1033   SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());
1034
1035   if (!bothKnown(TrueSide) || !bothKnown(FalseSide))
1036     return unknown();
1037   if (TrueSide == FalseSide)
1038     return TrueSide;
1039
1040   Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first,
1041                                      FalseSide.first);
1042   Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second,
1043                                        FalseSide.second);
1044   return std::make_pair(Size, Offset);
1045 }
1046
1047 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) {
1048   LLVM_DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I
1049                     << '\n');
1050   return unknown();
1051 }