lib/Analysis/MemoryBuiltins.cpp

   1 //===- MemoryBuiltins.cpp - Identify calls to memory builtins -------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This family of functions identifies calls to builtin functions that allocate
  11 // or free memory.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Analysis/MemoryBuiltins.h"
  16 #include "llvm/ADT/APInt.h"
  17 #include "llvm/ADT/None.h"
  18 #include "llvm/ADT/Optional.h"
  19 #include "llvm/ADT/STLExtras.h"
  20 #include "llvm/ADT/Statistic.h"
  21 #include "llvm/ADT/StringRef.h"
  22 #include "llvm/Analysis/TargetFolder.h"
  23 #include "llvm/Analysis/TargetLibraryInfo.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 "llvm/Transforms/Utils/Local.h"
  44 #include <cassert>
  45 #include <cstdint>
  46 #include <iterator>
  47 #include <utility>
  48
  49 using namespace llvm;
  50
  51 #define DEBUG_TYPE "memory-builtins"
  52
  53 enum AllocType : uint8_t {
  54   OpNewLike          = 1<<0, // allocates; never returns null
  55   MallocLike         = 1<<1 | OpNewLike, // allocates; may return null
  56   CallocLike         = 1<<2, // allocates + bzero
  57   ReallocLike        = 1<<3, // reallocates
  58   StrDupLike         = 1<<4,
  59   MallocOrCallocLike = MallocLike | CallocLike,
  60   AllocLike          = MallocLike | CallocLike | StrDupLike,
  61   AnyAlloc           = AllocLike | ReallocLike
  62 };
  63
  64 struct AllocFnsTy {
  65   AllocType AllocTy;
  66   unsigned NumParams;
  67   // First and Second size parameters (or -1 if unused)
  68   int FstParam, SndParam;
  69 };
  70
  71 // FIXME: certain users need more information. E.g., SimplifyLibCalls needs to
  72 // know which functions are nounwind, noalias, nocapture parameters, etc.
  73 static const std::pair<LibFunc, AllocFnsTy> AllocationFnData[] = {
  74   {LibFunc_malloc,              {MallocLike,  1, 0,  -1}},
  75   {LibFunc_valloc,              {MallocLike,  1, 0,  -1}},
  76   {LibFunc_Znwj,                {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
  77   {LibFunc_ZnwjRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
  78   {LibFunc_Znwm,                {OpNewLike,   1, 0,  -1}}, // new(unsigned long)
  79   {LibFunc_ZnwmRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned long, nothrow)
  80   {LibFunc_Znaj,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
  81   {LibFunc_ZnajRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
  82   {LibFunc_Znam,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned long)
  83   {LibFunc_ZnamRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned long, nothrow)
  84   {LibFunc_msvc_new_int,         {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
  85   {LibFunc_msvc_new_int_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
  86   {LibFunc_msvc_new_longlong,         {OpNewLike,   1, 0,  -1}}, // new(unsigned long long)
  87   {LibFunc_msvc_new_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned long long, nothrow)
  88   {LibFunc_msvc_new_array_int,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
  89   {LibFunc_msvc_new_array_int_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
  90   {LibFunc_msvc_new_array_longlong,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned long long)
  91   {LibFunc_msvc_new_array_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned long long, nothrow)
  92   {LibFunc_calloc,              {CallocLike,  2, 0,   1}},
  93   {LibFunc_realloc,             {ReallocLike, 2, 1,  -1}},
  94   {LibFunc_reallocf,            {ReallocLike, 2, 1,  -1}},
  95   {LibFunc_strdup,              {StrDupLike,  1, -1, -1}},
  96   {LibFunc_strndup,             {StrDupLike,  2, 1,  -1}}
  97   // TODO: Handle "int posix_memalign(void **, size_t, size_t)"
  98 };
  99
 100 static const Function *getCalledFunction(const Value *V, bool LookThroughBitCast,
 101                                          bool &IsNoBuiltin) {
 102   // Don't care about intrinsics in this case.
 103   if (isa<IntrinsicInst>(V))
 104     return nullptr;
 105
 106   if (LookThroughBitCast)
 107     V = V->stripPointerCasts();
 108
 109   ImmutableCallSite CS(V);
 110   if (!CS.getInstruction())
 111     return nullptr;
 112
 113   IsNoBuiltin = CS.isNoBuiltin();
 114
 115   const Function *Callee = CS.getCalledFunction();
 116   if (!Callee || !Callee->isDeclaration())
 117     return nullptr;
 118   return Callee;
 119 }
 120
 121 /// Returns the allocation data for the given value if it's either a call to a
 122 /// known allocation function, or a call to a function with the allocsize
 123 /// attribute.
 124 static Optional<AllocFnsTy>
 125 getAllocationDataForFunction(const Function *Callee, AllocType AllocTy,
 126                              const TargetLibraryInfo *TLI) {
 127   // Make sure that the function is available.
 128   StringRef FnName = Callee->getName();
 129   LibFunc TLIFn;
 130   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
 131     return None;
 132
 133   const auto *Iter = find_if(
 134       AllocationFnData, [TLIFn](const std::pair<LibFunc, AllocFnsTy> &P) {
 135         return P.first == TLIFn;
 136       });
 137
 138   if (Iter == std::end(AllocationFnData))
 139     return None;
 140
 141   const AllocFnsTy *FnData = &Iter->second;
 142   if ((FnData->AllocTy & AllocTy) != FnData->AllocTy)
 143     return None;
 144
 145   // Check function prototype.
 146   int FstParam = FnData->FstParam;
 147   int SndParam = FnData->SndParam;
 148   FunctionType *FTy = Callee->getFunctionType();
 149
 150   if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) &&
 151       FTy->getNumParams() == FnData->NumParams &&
 152       (FstParam < 0 ||
 153        (FTy->getParamType(FstParam)->isIntegerTy(32) ||
 154         FTy->getParamType(FstParam)->isIntegerTy(64))) &&
 155       (SndParam < 0 ||
 156        FTy->getParamType(SndParam)->isIntegerTy(32) ||
 157        FTy->getParamType(SndParam)->isIntegerTy(64)))
 158     return *FnData;
 159   return None;
 160 }
 161
 162 static Optional<AllocFnsTy> getAllocationData(const Value *V, AllocType AllocTy,
 163                                               const TargetLibraryInfo *TLI,
 164                                               bool LookThroughBitCast = false) {
 165   bool IsNoBuiltinCall;
 166   if (const Function *Callee =
 167           getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall))
 168     if (!IsNoBuiltinCall)
 169       return getAllocationDataForFunction(Callee, AllocTy, TLI);
 170   return None;
 171 }
 172
 173 static Optional<AllocFnsTy> getAllocationSize(const Value *V,
 174                                               const TargetLibraryInfo *TLI) {
 175   bool IsNoBuiltinCall;
 176   const Function *Callee =
 177       getCalledFunction(V, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
 178   if (!Callee)
 179     return None;
 180
 181   // Prefer to use existing information over allocsize. This will give us an
 182   // accurate AllocTy.
 183   if (!IsNoBuiltinCall)
 184     if (Optional<AllocFnsTy> Data =
 185             getAllocationDataForFunction(Callee, AnyAlloc, TLI))
 186       return Data;
 187
 188   Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize);
 189   if (Attr == Attribute())
 190     return None;
 191
 192   std::pair<unsigned, Optional<unsigned>> Args = Attr.getAllocSizeArgs();
 193
 194   AllocFnsTy Result;
 195   // Because allocsize only tells us how many bytes are allocated, we're not
 196   // really allowed to assume anything, so we use MallocLike.
 197   Result.AllocTy = MallocLike;
 198   Result.NumParams = Callee->getNumOperands();
 199   Result.FstParam = Args.first;
 200   Result.SndParam = Args.second.getValueOr(-1);
 201   return Result;
 202 }
 203
 204 static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
 205   ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V);
 206   return CS && CS.hasRetAttr(Attribute::NoAlias);
 207 }
 208
 209 /// \brief Tests if a value is a call or invoke to a library function that
 210 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
 211 /// like).
 212 bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
 213                           bool LookThroughBitCast) {
 214   return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast).hasValue();
 215 }
 216
 217 /// \brief Tests if a value is a call or invoke to a function that returns a
 218 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
 219 bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
 220                        bool LookThroughBitCast) {
 221   // it's safe to consider realloc as noalias since accessing the original
 222   // pointer is undefined behavior
 223   return isAllocationFn(V, TLI, LookThroughBitCast) ||
 224          hasNoAliasAttr(V, LookThroughBitCast);
 225 }
 226
 227 /// \brief Tests if a value is a call or invoke to a library function that
 228 /// allocates uninitialized memory (such as malloc).
 229 bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 230                           bool LookThroughBitCast) {
 231   return getAllocationData(V, MallocLike, TLI, LookThroughBitCast).hasValue();
 232 }
 233
 234 /// \brief Tests if a value is a call or invoke to a library function that
 235 /// allocates zero-filled memory (such as calloc).
 236 bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 237                           bool LookThroughBitCast) {
 238   return getAllocationData(V, CallocLike, TLI, LookThroughBitCast).hasValue();
 239 }
 240
 241 /// \brief Tests if a value is a call or invoke to a library function that
 242 /// allocates memory similiar to malloc or calloc.
 243 bool llvm::isMallocOrCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 244                                   bool LookThroughBitCast) {
 245   return getAllocationData(V, MallocOrCallocLike, TLI,
 246                            LookThroughBitCast).hasValue();
 247 }
 248
 249 /// \brief Tests if a value is a call or invoke to a library function that
 250 /// allocates memory (either malloc, calloc, or strdup like).
 251 bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 252                          bool LookThroughBitCast) {
 253   return getAllocationData(V, AllocLike, TLI, LookThroughBitCast).hasValue();
 254 }
 255
 256 /// extractMallocCall - Returns the corresponding CallInst if the instruction
 257 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
 258 /// ignore InvokeInst here.
 259 const CallInst *llvm::extractMallocCall(const Value *I,
 260                                         const TargetLibraryInfo *TLI) {
 261   return isMallocLikeFn(I, TLI) ? dyn_cast<CallInst>(I) : nullptr;
 262 }
 263
 264 static Value *computeArraySize(const CallInst *CI, const DataLayout &DL,
 265                                const TargetLibraryInfo *TLI,
 266                                bool LookThroughSExt = false) {
 267   if (!CI)
 268     return nullptr;
 269
 270   // The size of the malloc's result type must be known to determine array size.
 271   Type *T = getMallocAllocatedType(CI, TLI);
 272   if (!T || !T->isSized())
 273     return nullptr;
 274
 275   unsigned ElementSize = DL.getTypeAllocSize(T);
 276   if (StructType *ST = dyn_cast<StructType>(T))
 277     ElementSize = DL.getStructLayout(ST)->getSizeInBytes();
 278
 279   // If malloc call's arg can be determined to be a multiple of ElementSize,
 280   // return the multiple.  Otherwise, return NULL.
 281   Value *MallocArg = CI->getArgOperand(0);
 282   Value *Multiple = nullptr;
 283   if (ComputeMultiple(MallocArg, ElementSize, Multiple, LookThroughSExt))
 284     return Multiple;
 285
 286   return nullptr;
 287 }
 288
 289 /// getMallocType - Returns the PointerType resulting from the malloc call.
 290 /// The PointerType depends on the number of bitcast uses of the malloc call:
 291 ///   0: PointerType is the calls' return type.
 292 ///   1: PointerType is the bitcast's result type.
 293 ///  >1: Unique PointerType cannot be determined, return NULL.
 294 PointerType *llvm::getMallocType(const CallInst *CI,
 295                                  const TargetLibraryInfo *TLI) {
 296   assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call");
 297
 298   PointerType *MallocType = nullptr;
 299   unsigned NumOfBitCastUses = 0;
 300
 301   // Determine if CallInst has a bitcast use.
 302   for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end();
 303        UI != E;)
 304     if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
 305       MallocType = cast<PointerType>(BCI->getDestTy());
 306       NumOfBitCastUses++;
 307     }
 308
 309   // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
 310   if (NumOfBitCastUses == 1)
 311     return MallocType;
 312
 313   // Malloc call was not bitcast, so type is the malloc function's return type.
 314   if (NumOfBitCastUses == 0)
 315     return cast<PointerType>(CI->getType());
 316
 317   // Type could not be determined.
 318   return nullptr;
 319 }
 320
 321 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
 322 /// The Type depends on the number of bitcast uses of the malloc call:
 323 ///   0: PointerType is the malloc calls' return type.
 324 ///   1: PointerType is the bitcast's result type.
 325 ///  >1: Unique PointerType cannot be determined, return NULL.
 326 Type *llvm::getMallocAllocatedType(const CallInst *CI,
 327                                    const TargetLibraryInfo *TLI) {
 328   PointerType *PT = getMallocType(CI, TLI);
 329   return PT ? PT->getElementType() : nullptr;
 330 }
 331
 332 /// getMallocArraySize - Returns the array size of a malloc call.  If the
 333 /// argument passed to malloc is a multiple of the size of the malloced type,
 334 /// then return that multiple.  For non-array mallocs, the multiple is
 335 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
 336 /// determined.
 337 Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout &DL,
 338                                 const TargetLibraryInfo *TLI,
 339                                 bool LookThroughSExt) {
 340   assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call");
 341   return computeArraySize(CI, DL, TLI, LookThroughSExt);
 342 }
 343
 344 /// extractCallocCall - Returns the corresponding CallInst if the instruction
 345 /// is a calloc call.
 346 const CallInst *llvm::extractCallocCall(const Value *I,
 347                                         const TargetLibraryInfo *TLI) {
 348   return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : nullptr;
 349 }
 350
 351 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
 352 const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
 353   const CallInst *CI = dyn_cast<CallInst>(I);
 354   if (!CI || isa<IntrinsicInst>(CI))
 355     return nullptr;
 356   Function *Callee = CI->getCalledFunction();
 357   if (Callee == nullptr)
 358     return nullptr;
 359
 360   StringRef FnName = Callee->getName();
 361   LibFunc TLIFn;
 362   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
 363     return nullptr;
 364
 365   unsigned ExpectedNumParams;
 366   if (TLIFn == LibFunc_free ||
 367       TLIFn == LibFunc_ZdlPv || // operator delete(void*)
 368       TLIFn == LibFunc_ZdaPv || // operator delete[](void*)
 369       TLIFn == LibFunc_msvc_delete_ptr32 || // operator delete(void*)
 370       TLIFn == LibFunc_msvc_delete_ptr64 || // operator delete(void*)
 371       TLIFn == LibFunc_msvc_delete_array_ptr32 || // operator delete[](void*)
 372       TLIFn == LibFunc_msvc_delete_array_ptr64)   // operator delete[](void*)
 373     ExpectedNumParams = 1;
 374   else if (TLIFn == LibFunc_ZdlPvj ||              // delete(void*, uint)
 375            TLIFn == LibFunc_ZdlPvm ||              // delete(void*, ulong)
 376            TLIFn == LibFunc_ZdlPvRKSt9nothrow_t || // delete(void*, nothrow)
 377            TLIFn == LibFunc_ZdaPvj ||              // delete[](void*, uint)
 378            TLIFn == LibFunc_ZdaPvm ||              // delete[](void*, ulong)
 379            TLIFn == LibFunc_ZdaPvRKSt9nothrow_t || // delete[](void*, nothrow)
 380            TLIFn == LibFunc_msvc_delete_ptr32_int ||      // delete(void*, uint)
 381            TLIFn == LibFunc_msvc_delete_ptr64_longlong || // delete(void*, ulonglong)
 382            TLIFn == LibFunc_msvc_delete_ptr32_nothrow || // delete(void*, nothrow)
 383            TLIFn == LibFunc_msvc_delete_ptr64_nothrow || // delete(void*, nothrow)
 384            TLIFn == LibFunc_msvc_delete_array_ptr32_int ||      // delete[](void*, uint)
 385            TLIFn == LibFunc_msvc_delete_array_ptr64_longlong || // delete[](void*, ulonglong)
 386            TLIFn == LibFunc_msvc_delete_array_ptr32_nothrow || // delete[](void*, nothrow)
 387            TLIFn == LibFunc_msvc_delete_array_ptr64_nothrow)   // delete[](void*, nothrow)
 388     ExpectedNumParams = 2;
 389   else
 390     return nullptr;
 391
 392   // Check free prototype.
 393   // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
 394   // attribute will exist.
 395   FunctionType *FTy = Callee->getFunctionType();
 396   if (!FTy->getReturnType()->isVoidTy())
 397     return nullptr;
 398   if (FTy->getNumParams() != ExpectedNumParams)
 399     return nullptr;
 400   if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext()))
 401     return nullptr;
 402
 403   return CI;
 404 }
 405
 406 //===----------------------------------------------------------------------===//
 407 //  Utility functions to compute size of objects.
 408 //
 409 static APInt getSizeWithOverflow(const SizeOffsetType &Data) {
 410   if (Data.second.isNegative() || Data.first.ult(Data.second))
 411     return APInt(Data.first.getBitWidth(), 0);
 412   return Data.first - Data.second;
 413 }
 414
 415 /// \brief Compute the size of the object pointed by Ptr. Returns true and the
 416 /// object size in Size if successful, and false otherwise.
 417 /// If RoundToAlign is true, then Size is rounded up to the alignment of
 418 /// allocas, byval arguments, and global variables.
 419 bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
 420                          const TargetLibraryInfo *TLI, ObjectSizeOpts Opts) {
 421   ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(), Opts);
 422   SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
 423   if (!Visitor.bothKnown(Data))
 424     return false;
 425
 426   Size = getSizeWithOverflow(Data).getZExtValue();
 427   return true;
 428 }
 429
 430 ConstantInt *llvm::lowerObjectSizeCall(IntrinsicInst *ObjectSize,
 431                                        const DataLayout &DL,
 432                                        const TargetLibraryInfo *TLI,
 433                                        bool MustSucceed) {
 434   assert(ObjectSize->getIntrinsicID() == Intrinsic::objectsize &&
 435          "ObjectSize must be a call to llvm.objectsize!");
 436
 437   bool MaxVal = cast<ConstantInt>(ObjectSize->getArgOperand(1))->isZero();
 438   ObjectSizeOpts EvalOptions;
 439   // Unless we have to fold this to something, try to be as accurate as
 440   // possible.
 441   if (MustSucceed)
 442     EvalOptions.EvalMode =
 443         MaxVal ? ObjectSizeOpts::Mode::Max : ObjectSizeOpts::Mode::Min;
 444   else
 445     EvalOptions.EvalMode = ObjectSizeOpts::Mode::Exact;
 446
 447   EvalOptions.NullIsUnknownSize =
 448       cast<ConstantInt>(ObjectSize->getArgOperand(2))->isOne();
 449
 450   // FIXME: Does it make sense to just return a failure value if the size won't
 451   // fit in the output and `!MustSucceed`?
 452   uint64_t Size;
 453   auto *ResultType = cast<IntegerType>(ObjectSize->getType());
 454   if (getObjectSize(ObjectSize->getArgOperand(0), Size, DL, TLI, EvalOptions) &&
 455       isUIntN(ResultType->getBitWidth(), Size))
 456     return ConstantInt::get(ResultType, Size);
 457
 458   if (!MustSucceed)
 459     return nullptr;
 460
 461   return ConstantInt::get(ResultType, MaxVal ? -1ULL : 0);
 462 }
 463
 464 STATISTIC(ObjectVisitorArgument,
 465           "Number of arguments with unsolved size and offset");
 466 STATISTIC(ObjectVisitorLoad,
 467           "Number of load instructions with unsolved size and offset");
 468
 469 APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) {
 470   if (Options.RoundToAlign && Align)
 471     return APInt(IntTyBits, alignTo(Size.getZExtValue(), Align));
 472   return Size;
 473 }
 474
 475 ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
 476                                                  const TargetLibraryInfo *TLI,
 477                                                  LLVMContext &Context,
 478                                                  ObjectSizeOpts Options)
 479     : DL(DL), TLI(TLI), Options(Options) {
 480   // Pointer size must be rechecked for each object visited since it could have
 481   // a different address space.
 482 }
 483
 484 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
 485   IntTyBits = DL.getPointerTypeSizeInBits(V->getType());
 486   Zero = APInt::getNullValue(IntTyBits);
 487
 488   V = V->stripPointerCasts();
 489   if (Instruction *I = dyn_cast<Instruction>(V)) {
 490     // If we have already seen this instruction, bail out. Cycles can happen in
 491     // unreachable code after constant propagation.
 492     if (!SeenInsts.insert(I).second)
 493       return unknown();
 494
 495     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
 496       return visitGEPOperator(*GEP);
 497     return visit(*I);
 498   }
 499   if (Argument *A = dyn_cast<Argument>(V))
 500     return visitArgument(*A);
 501   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
 502     return visitConstantPointerNull(*P);
 503   if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
 504     return visitGlobalAlias(*GA);
 505   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
 506     return visitGlobalVariable(*GV);
 507   if (UndefValue *UV = dyn_cast<UndefValue>(V))
 508     return visitUndefValue(*UV);
 509   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
 510     if (CE->getOpcode() == Instruction::IntToPtr)
 511       return unknown(); // clueless
 512     if (CE->getOpcode() == Instruction::GetElementPtr)
 513       return visitGEPOperator(cast<GEPOperator>(*CE));
 514   }
 515
 516   DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
 517         << '\n');
 518   return unknown();
 519 }
 520
 521 /// When we're compiling N-bit code, and the user uses parameters that are
 522 /// greater than N bits (e.g. uint64_t on a 32-bit build), we can run into
 523 /// trouble with APInt size issues. This function handles resizing + overflow
 524 /// checks for us. Check and zext or trunc \p I depending on IntTyBits and
 525 /// I's value.
 526 bool ObjectSizeOffsetVisitor::CheckedZextOrTrunc(APInt &I) {
 527   // More bits than we can handle. Checking the bit width isn't necessary, but
 528   // it's faster than checking active bits, and should give `false` in the
 529   // vast majority of cases.
 530   if (I.getBitWidth() > IntTyBits && I.getActiveBits() > IntTyBits)
 531     return false;
 532   if (I.getBitWidth() != IntTyBits)
 533     I = I.zextOrTrunc(IntTyBits);
 534   return true;
 535 }
 536
 537 SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
 538   if (!I.getAllocatedType()->isSized())
 539     return unknown();
 540
 541   APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType()));
 542   if (!I.isArrayAllocation())
 543     return std::make_pair(align(Size, I.getAlignment()), Zero);
 544
 545   Value *ArraySize = I.getArraySize();
 546   if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
 547     APInt NumElems = C->getValue();
 548     if (!CheckedZextOrTrunc(NumElems))
 549       return unknown();
 550
 551     bool Overflow;
 552     Size = Size.umul_ov(NumElems, Overflow);
 553     return Overflow ? unknown() : std::make_pair(align(Size, I.getAlignment()),
 554                                                  Zero);
 555   }
 556   return unknown();
 557 }
 558
 559 SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
 560   // No interprocedural analysis is done at the moment.
 561   if (!A.hasByValOrInAllocaAttr()) {
 562     ++ObjectVisitorArgument;
 563     return unknown();
 564   }
 565   PointerType *PT = cast<PointerType>(A.getType());
 566   APInt Size(IntTyBits, DL.getTypeAllocSize(PT->getElementType()));
 567   return std::make_pair(align(Size, A.getParamAlignment()), Zero);
 568 }
 569
 570 SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) {
 571   Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI);
 572   if (!FnData)
 573     return unknown();
 574
 575   // Handle strdup-like functions separately.
 576   if (FnData->AllocTy == StrDupLike) {
 577     APInt Size(IntTyBits, GetStringLength(CS.getArgument(0)));
 578     if (!Size)
 579       return unknown();
 580
 581     // Strndup limits strlen.
 582     if (FnData->FstParam > 0) {
 583       ConstantInt *Arg =
 584           dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
 585       if (!Arg)
 586         return unknown();
 587
 588       APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits);
 589       if (Size.ugt(MaxSize))
 590         Size = MaxSize + 1;
 591     }
 592     return std::make_pair(Size, Zero);
 593   }
 594
 595   ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
 596   if (!Arg)
 597     return unknown();
 598
 599   APInt Size = Arg->getValue();
 600   if (!CheckedZextOrTrunc(Size))
 601     return unknown();
 602
 603   // Size is determined by just 1 parameter.
 604   if (FnData->SndParam < 0)
 605     return std::make_pair(Size, Zero);
 606
 607   Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam));
 608   if (!Arg)
 609     return unknown();
 610
 611   APInt NumElems = Arg->getValue();
 612   if (!CheckedZextOrTrunc(NumElems))
 613     return unknown();
 614
 615   bool Overflow;
 616   Size = Size.umul_ov(NumElems, Overflow);
 617   return Overflow ? unknown() : std::make_pair(Size, Zero);
 618
 619   // TODO: handle more standard functions (+ wchar cousins):
 620   // - strdup / strndup
 621   // - strcpy / strncpy
 622   // - strcat / strncat
 623   // - memcpy / memmove
 624   // - strcat / strncat
 625   // - memset
 626 }
 627
 628 SizeOffsetType
 629 ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull& CPN) {
 630   if (Options.NullIsUnknownSize && CPN.getType()->getAddressSpace() == 0)
 631     return unknown();
 632   return std::make_pair(Zero, Zero);
 633 }
 634
 635 SizeOffsetType
 636 ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) {
 637   return unknown();
 638 }
 639
 640 SizeOffsetType
 641 ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
 642   // Easy cases were already folded by previous passes.
 643   return unknown();
 644 }
 645
 646 SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
 647   SizeOffsetType PtrData = compute(GEP.getPointerOperand());
 648   APInt Offset(IntTyBits, 0);
 649   if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset))
 650     return unknown();
 651
 652   return std::make_pair(PtrData.first, PtrData.second + Offset);
 653 }
 654
 655 SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
 656   if (GA.isInterposable())
 657     return unknown();
 658   return compute(GA.getAliasee());
 659 }
 660
 661 SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
 662   if (!GV.hasDefinitiveInitializer())
 663     return unknown();
 664
 665   APInt Size(IntTyBits, DL.getTypeAllocSize(GV.getType()->getElementType()));
 666   return std::make_pair(align(Size, GV.getAlignment()), Zero);
 667 }
 668
 669 SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) {
 670   // clueless
 671   return unknown();
 672 }
 673
 674 SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
 675   ++ObjectVisitorLoad;
 676   return unknown();
 677 }
 678
 679 SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
 680   // too complex to analyze statically.
 681   return unknown();
 682 }
 683
 684 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
 685   SizeOffsetType TrueSide  = compute(I.getTrueValue());
 686   SizeOffsetType FalseSide = compute(I.getFalseValue());
 687   if (bothKnown(TrueSide) && bothKnown(FalseSide)) {
 688     if (TrueSide == FalseSide) {
 689         return TrueSide;
 690     }
 691
 692     APInt TrueResult = getSizeWithOverflow(TrueSide);
 693     APInt FalseResult = getSizeWithOverflow(FalseSide);
 694
 695     if (TrueResult == FalseResult) {
 696       return TrueSide;
 697     }
 698     if (Options.EvalMode == ObjectSizeOpts::Mode::Min) {
 699       if (TrueResult.slt(FalseResult))
 700         return TrueSide;
 701       return FalseSide;
 702     }
 703     if (Options.EvalMode == ObjectSizeOpts::Mode::Max) {
 704       if (TrueResult.sgt(FalseResult))
 705         return TrueSide;
 706       return FalseSide;
 707     }
 708   }
 709   return unknown();
 710 }
 711
 712 SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) {
 713   return std::make_pair(Zero, Zero);
 714 }
 715
 716 SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
 717   DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n');
 718   return unknown();
 719 }
 720
 721 ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
 722     const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
 723     bool RoundToAlign)
 724     : DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)),
 725       RoundToAlign(RoundToAlign) {
 726   // IntTy and Zero must be set for each compute() since the address space may
 727   // be different for later objects.
 728 }
 729
 730 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
 731   // XXX - Are vectors of pointers possible here?
 732   IntTy = cast<IntegerType>(DL.getIntPtrType(V->getType()));
 733   Zero = ConstantInt::get(IntTy, 0);
 734
 735   SizeOffsetEvalType Result = compute_(V);
 736
 737   if (!bothKnown(Result)) {
 738     // Erase everything that was computed in this iteration from the cache, so
 739     // that no dangling references are left behind. We could be a bit smarter if
 740     // we kept a dependency graph. It's probably not worth the complexity.
 741     for (const Value *SeenVal : SeenVals) {
 742       CacheMapTy::iterator CacheIt = CacheMap.find(SeenVal);
 743       // non-computable results can be safely cached
 744       if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
 745         CacheMap.erase(CacheIt);
 746     }
 747   }
 748
 749   SeenVals.clear();
 750   return Result;
 751 }
 752
 753 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
 754   ObjectSizeOpts ObjSizeOptions;
 755   ObjSizeOptions.RoundToAlign = RoundToAlign;
 756
 757   ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, ObjSizeOptions);
 758   SizeOffsetType Const = Visitor.compute(V);
 759   if (Visitor.bothKnown(Const))
 760     return std::make_pair(ConstantInt::get(Context, Const.first),
 761                           ConstantInt::get(Context, Const.second));
 762
 763   V = V->stripPointerCasts();
 764
 765   // Check cache.
 766   CacheMapTy::iterator CacheIt = CacheMap.find(V);
 767   if (CacheIt != CacheMap.end())
 768     return CacheIt->second;
 769
 770   // Always generate code immediately before the instruction being
 771   // processed, so that the generated code dominates the same BBs.
 772   BuilderTy::InsertPointGuard Guard(Builder);
 773   if (Instruction *I = dyn_cast<Instruction>(V))
 774     Builder.SetInsertPoint(I);
 775
 776   // Now compute the size and offset.
 777   SizeOffsetEvalType Result;
 778
 779   // Record the pointers that were handled in this run, so that they can be
 780   // cleaned later if something fails. We also use this set to break cycles that
 781   // can occur in dead code.
 782   if (!SeenVals.insert(V).second) {
 783     Result = unknown();
 784   } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
 785     Result = visitGEPOperator(*GEP);
 786   } else if (Instruction *I = dyn_cast<Instruction>(V)) {
 787     Result = visit(*I);
 788   } else if (isa<Argument>(V) ||
 789              (isa<ConstantExpr>(V) &&
 790               cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) ||
 791              isa<GlobalAlias>(V) ||
 792              isa<GlobalVariable>(V)) {
 793     // Ignore values where we cannot do more than ObjectSizeVisitor.
 794     Result = unknown();
 795   } else {
 796     DEBUG(dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: "
 797           << *V << '\n');
 798     Result = unknown();
 799   }
 800
 801   // Don't reuse CacheIt since it may be invalid at this point.
 802   CacheMap[V] = Result;
 803   return Result;
 804 }
 805
 806 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
 807   if (!I.getAllocatedType()->isSized())
 808     return unknown();
 809
 810   // must be a VLA
 811   assert(I.isArrayAllocation());
 812   Value *ArraySize = I.getArraySize();
 813   Value *Size = ConstantInt::get(ArraySize->getType(),
 814                                  DL.getTypeAllocSize(I.getAllocatedType()));
 815   Size = Builder.CreateMul(Size, ArraySize);
 816   return std::make_pair(Size, Zero);
 817 }
 818
 819 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) {
 820   Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI);
 821   if (!FnData)
 822     return unknown();
 823
 824   // Handle strdup-like functions separately.
 825   if (FnData->AllocTy == StrDupLike) {
 826     // TODO
 827     return unknown();
 828   }
 829
 830   Value *FirstArg = CS.getArgument(FnData->FstParam);
 831   FirstArg = Builder.CreateZExt(FirstArg, IntTy);
 832   if (FnData->SndParam < 0)
 833     return std::make_pair(FirstArg, Zero);
 834
 835   Value *SecondArg = CS.getArgument(FnData->SndParam);
 836   SecondArg = Builder.CreateZExt(SecondArg, IntTy);
 837   Value *Size = Builder.CreateMul(FirstArg, SecondArg);
 838   return std::make_pair(Size, Zero);
 839
 840   // TODO: handle more standard functions (+ wchar cousins):
 841   // - strdup / strndup
 842   // - strcpy / strncpy
 843   // - strcat / strncat
 844   // - memcpy / memmove
 845   // - strcat / strncat
 846   // - memset
 847 }
 848
 849 SizeOffsetEvalType
 850 ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) {
 851   return unknown();
 852 }
 853
 854 SizeOffsetEvalType
 855 ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) {
 856   return unknown();
 857 }
 858
 859 SizeOffsetEvalType
 860 ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) {
 861   SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand());
 862   if (!bothKnown(PtrData))
 863     return unknown();
 864
 865   Value *Offset = EmitGEPOffset(&Builder, DL, &GEP, /*NoAssumptions=*/true);
 866   Offset = Builder.CreateAdd(PtrData.second, Offset);
 867   return std::make_pair(PtrData.first, Offset);
 868 }
 869
 870 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) {
 871   // clueless
 872   return unknown();
 873 }
 874
 875 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) {
 876   return unknown();
 877 }
 878
 879 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
 880   // Create 2 PHIs: one for size and another for offset.
 881   PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
 882   PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
 883
 884   // Insert right away in the cache to handle recursive PHIs.
 885   CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);
 886
 887   // Compute offset/size for each PHI incoming pointer.
 888   for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
 889     Builder.SetInsertPoint(&*PHI.getIncomingBlock(i)->getFirstInsertionPt());
 890     SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));
 891
 892     if (!bothKnown(EdgeData)) {
 893       OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
 894       OffsetPHI->eraseFromParent();
 895       SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
 896       SizePHI->eraseFromParent();
 897       return unknown();
 898     }
 899     SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
 900     OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
 901   }
 902
 903   Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp;
 904   if ((Tmp = SizePHI->hasConstantValue())) {
 905     Size = Tmp;
 906     SizePHI->replaceAllUsesWith(Size);
 907     SizePHI->eraseFromParent();
 908   }
 909   if ((Tmp = OffsetPHI->hasConstantValue())) {
 910     Offset = Tmp;
 911     OffsetPHI->replaceAllUsesWith(Offset);
 912     OffsetPHI->eraseFromParent();
 913   }
 914   return std::make_pair(Size, Offset);
 915 }
 916
 917 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
 918   SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
 919   SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());
 920
 921   if (!bothKnown(TrueSide) || !bothKnown(FalseSide))
 922     return unknown();
 923   if (TrueSide == FalseSide)
 924     return TrueSide;
 925
 926   Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first,
 927                                      FalseSide.first);
 928   Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second,
 929                                        FalseSide.second);
 930   return std::make_pair(Size, Offset);
 931 }
 932
 933 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) {
 934   DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n');
 935   return unknown();
 936 }