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