text: //===- MemoryBuiltins.cpp - Identify calls to memory builtins -------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This family of functions identifies calls to builtin functions that allocate
  // or free memory.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Analysis/MemoryBuiltins.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/None.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Analysis/TargetFolder.h"
  #include "llvm/Analysis/TargetLibraryInfo.h"
  #include "llvm/Analysis/Utils/Local.h"
  #include "llvm/Analysis/ValueTracking.h"
  #include "llvm/IR/Argument.h"
  #include "llvm/IR/Attributes.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GlobalAlias.h"
  #include "llvm/IR/GlobalVariable.h"
  #include "llvm/IR/Instruction.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/IntrinsicInst.h"
  #include "llvm/IR/Operator.h"
  #include "llvm/IR/Type.h"
  #include "llvm/IR/Value.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/raw_ostream.h"
  #include <cassert>
  #include <cstdint>
  #include <iterator>
  #include <utility>
  
  using namespace llvm;
  
  #define DEBUG_TYPE "memory-builtins"
  
  enum AllocType : uint8_t {
    OpNewLike          = 1<<0, // allocates; never returns null
    MallocLike         = 1<<1 | OpNewLike, // allocates; may return null
    CallocLike         = 1<<2, // allocates + bzero
    ReallocLike        = 1<<3, // reallocates
    StrDupLike         = 1<<4,
    MallocOrCallocLike = MallocLike | CallocLike,
    AllocLike          = MallocLike | CallocLike | StrDupLike,
    AnyAlloc           = AllocLike | ReallocLike
  };
  
  struct AllocFnsTy {
    AllocType AllocTy;
    unsigned NumParams;
    // First and Second size parameters (or -1 if unused)
    int FstParam, SndParam;
  };
  
  // FIXME: certain users need more information. E.g., SimplifyLibCalls needs to
  // know which functions are nounwind, noalias, nocapture parameters, etc.
  static const std::pair<LibFunc, AllocFnsTy> AllocationFnData[] = {
    {LibFunc_malloc,              {MallocLike,  1, 0,  -1}},
    {LibFunc_valloc,              {MallocLike,  1, 0,  -1}},
    {LibFunc_Znwj,                {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
    {LibFunc_ZnwjRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
    {LibFunc_ZnwjSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new(unsigned int, align_val_t)
    {LibFunc_ZnwjSt11align_val_tRKSt9nothrow_t, // new(unsigned int, align_val_t, nothrow)
                                  {MallocLike,  3, 0,  -1}},
    {LibFunc_Znwm,                {OpNewLike,   1, 0,  -1}}, // new(unsigned long)
    {LibFunc_ZnwmRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new(unsigned long, nothrow)
    {LibFunc_ZnwmSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new(unsigned long, align_val_t)
    {LibFunc_ZnwmSt11align_val_tRKSt9nothrow_t, // new(unsigned long, align_val_t, nothrow)
                                  {MallocLike,  3, 0,  -1}},
    {LibFunc_Znaj,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
    {LibFunc_ZnajRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
    {LibFunc_ZnajSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new[](unsigned int, align_val_t)
    {LibFunc_ZnajSt11align_val_tRKSt9nothrow_t, // new[](unsigned int, align_val_t, nothrow)
                                  {MallocLike,  3, 0,  -1}},
    {LibFunc_Znam,                {OpNewLike,   1, 0,  -1}}, // new[](unsigned long)
    {LibFunc_ZnamRKSt9nothrow_t,  {MallocLike,  2, 0,  -1}}, // new[](unsigned long, nothrow)
    {LibFunc_ZnamSt11align_val_t, {OpNewLike,   2, 0,  -1}}, // new[](unsigned long, align_val_t)
    {LibFunc_ZnamSt11align_val_tRKSt9nothrow_t, // new[](unsigned long, align_val_t, nothrow)
                                   {MallocLike,  3, 0,  -1}},
    {LibFunc_msvc_new_int,         {OpNewLike,   1, 0,  -1}}, // new(unsigned int)
    {LibFunc_msvc_new_int_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned int, nothrow)
    {LibFunc_msvc_new_longlong,         {OpNewLike,   1, 0,  -1}}, // new(unsigned long long)
    {LibFunc_msvc_new_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new(unsigned long long, nothrow)
    {LibFunc_msvc_new_array_int,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned int)
    {LibFunc_msvc_new_array_int_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned int, nothrow)
    {LibFunc_msvc_new_array_longlong,         {OpNewLike,   1, 0,  -1}}, // new[](unsigned long long)
    {LibFunc_msvc_new_array_longlong_nothrow, {MallocLike,  2, 0,  -1}}, // new[](unsigned long long, nothrow)
    {LibFunc_calloc,              {CallocLike,  2, 0,   1}},
    {LibFunc_realloc,             {ReallocLike, 2, 1,  -1}},
    {LibFunc_reallocf,            {ReallocLike, 2, 1,  -1}},
    {LibFunc_strdup,              {StrDupLike,  1, -1, -1}},
    {LibFunc_strndup,             {StrDupLike,  2, 1,  -1}}
    // TODO: Handle "int posix_memalign(void **, size_t, size_t)"
  };
  
  static const Function *getCalledFunction(const Value *V, bool LookThroughBitCast,
                                           bool &IsNoBuiltin) {
    // Don't care about intrinsics in this case.
    if (isa<IntrinsicInst>(V))
      return nullptr;
  
    if (LookThroughBitCast)
      V = V->stripPointerCasts();
  
    ImmutableCallSite CS(V);
    if (!CS.getInstruction())
      return nullptr;
  
    IsNoBuiltin = CS.isNoBuiltin();
  
    if (const Function *Callee = CS.getCalledFunction())
      return Callee;
    return nullptr;
  }
  
  /// Returns the allocation data for the given value if it's either a call to a
  /// known allocation function, or a call to a function with the allocsize
  /// attribute.
  static Optional<AllocFnsTy>
  getAllocationDataForFunction(const Function *Callee, AllocType AllocTy,
                               const TargetLibraryInfo *TLI) {
    // Make sure that the function is available.
    StringRef FnName = Callee->getName();
    LibFunc TLIFn;
    if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
      return None;
  
    const auto *Iter = find_if(
        AllocationFnData, [TLIFn](const std::pair<LibFunc, AllocFnsTy> &P) {
          return P.first == TLIFn;
        });
  
    if (Iter == std::end(AllocationFnData))
      return None;
  
    const AllocFnsTy *FnData = &Iter->second;
    if ((FnData->AllocTy & AllocTy) != FnData->AllocTy)
      return None;
  
    // Check function prototype.
    int FstParam = FnData->FstParam;
    int SndParam = FnData->SndParam;
    FunctionType *FTy = Callee->getFunctionType();
  
    if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) &&
        FTy->getNumParams() == FnData->NumParams &&
        (FstParam < 0 ||
         (FTy->getParamType(FstParam)->isIntegerTy(32) ||
          FTy->getParamType(FstParam)->isIntegerTy(64))) &&
        (SndParam < 0 ||
         FTy->getParamType(SndParam)->isIntegerTy(32) ||
         FTy->getParamType(SndParam)->isIntegerTy(64)))
      return *FnData;
    return None;
  }
  
  static Optional<AllocFnsTy> getAllocationData(const Value *V, AllocType AllocTy,
                                                const TargetLibraryInfo *TLI,
                                                bool LookThroughBitCast = false) {
    bool IsNoBuiltinCall;
    if (const Function *Callee =
            getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall))
      if (!IsNoBuiltinCall)
        return getAllocationDataForFunction(Callee, AllocTy, TLI);
    return None;
  }
  
  static Optional<AllocFnsTy>
  getAllocationData(const Value *V, AllocType AllocTy,
                    function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
                    bool LookThroughBitCast = false) {
    bool IsNoBuiltinCall;
    if (const Function *Callee =
            getCalledFunction(V, LookThroughBitCast, IsNoBuiltinCall))
      if (!IsNoBuiltinCall)
        return getAllocationDataForFunction(
            Callee, AllocTy, &GetTLI(const_cast<Function &>(*Callee)));
    return None;
  }
  
  static Optional<AllocFnsTy> getAllocationSize(const Value *V,
                                                const TargetLibraryInfo *TLI) {
    bool IsNoBuiltinCall;
    const Function *Callee =
        getCalledFunction(V, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
    if (!Callee)
      return None;
  
    // Prefer to use existing information over allocsize. This will give us an
    // accurate AllocTy.
    if (!IsNoBuiltinCall)
      if (Optional<AllocFnsTy> Data =
              getAllocationDataForFunction(Callee, AnyAlloc, TLI))
        return Data;
  
    Attribute Attr = Callee->getFnAttribute(Attribute::AllocSize);
    if (Attr == Attribute())
      return None;
  
    std::pair<unsigned, Optional<unsigned>> Args = Attr.getAllocSizeArgs();
  
    AllocFnsTy Result;
    // Because allocsize only tells us how many bytes are allocated, we're not
    // really allowed to assume anything, so we use MallocLike.
    Result.AllocTy = MallocLike;
    Result.NumParams = Callee->getNumOperands();
    Result.FstParam = Args.first;
    Result.SndParam = Args.second.getValueOr(-1);
    return Result;
  }
  
  static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
    ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V);
    return CS && CS.hasRetAttr(Attribute::NoAlias);
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
  /// like).
  bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
                            bool LookThroughBitCast) {
    return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast).hasValue();
  }
  bool llvm::isAllocationFn(
      const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
      bool LookThroughBitCast) {
    return getAllocationData(V, AnyAlloc, GetTLI, LookThroughBitCast).hasValue();
  }
  
  /// Tests if a value is a call or invoke to a function that returns a
  /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
  bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
                         bool LookThroughBitCast) {
    // it's safe to consider realloc as noalias since accessing the original
    // pointer is undefined behavior
    return isAllocationFn(V, TLI, LookThroughBitCast) ||
           hasNoAliasAttr(V, LookThroughBitCast);
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// allocates uninitialized memory (such as malloc).
  bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                            bool LookThroughBitCast) {
    return getAllocationData(V, MallocLike, TLI, LookThroughBitCast).hasValue();
  }
  bool llvm::isMallocLikeFn(
      const Value *V, function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
      bool LookThroughBitCast) {
    return getAllocationData(V, MallocLike, GetTLI, LookThroughBitCast)
        .hasValue();
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// allocates zero-filled memory (such as calloc).
  bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                            bool LookThroughBitCast) {
    return getAllocationData(V, CallocLike, TLI, LookThroughBitCast).hasValue();
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// allocates memory similar to malloc or calloc.
  bool llvm::isMallocOrCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                                    bool LookThroughBitCast) {
    return getAllocationData(V, MallocOrCallocLike, TLI,
                             LookThroughBitCast).hasValue();
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// allocates memory (either malloc, calloc, or strdup like).
  bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                           bool LookThroughBitCast) {
    return getAllocationData(V, AllocLike, TLI, LookThroughBitCast).hasValue();
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// reallocates memory (e.g., realloc).
  bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                       bool LookThroughBitCast) {
    return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast).hasValue();
  }
  
  /// Tests if a functions is a call or invoke to a library function that
  /// reallocates memory (e.g., realloc).
  bool llvm::isReallocLikeFn(const Function *F, const TargetLibraryInfo *TLI) {
    return getAllocationDataForFunction(F, ReallocLike, TLI).hasValue();
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// allocates memory and throws if an allocation failed (e.g., new).
  bool llvm::isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                       bool LookThroughBitCast) {
    return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast).hasValue();
  }
  
  /// Tests if a value is a call or invoke to a library function that
  /// allocates memory (strdup, strndup).
  bool llvm::isStrdupLikeFn(const Value *V, const TargetLibraryInfo *TLI,
                            bool LookThroughBitCast) {
    return getAllocationData(V, StrDupLike, TLI, LookThroughBitCast).hasValue();
  }
  
  /// extractMallocCall - Returns the corresponding CallInst if the instruction
  /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
  /// ignore InvokeInst here.
  const CallInst *llvm::extractMallocCall(
      const Value *I,
      function_ref<const TargetLibraryInfo &(Function &)> GetTLI) {
    return isMallocLikeFn(I, GetTLI) ? dyn_cast<CallInst>(I) : nullptr;
  }
  
  static Value *computeArraySize(const CallInst *CI, const DataLayout &DL,
                                 const TargetLibraryInfo *TLI,
                                 bool LookThroughSExt = false) {
    if (!CI)
      return nullptr;
  
    // The size of the malloc's result type must be known to determine array size.
    Type *T = getMallocAllocatedType(CI, TLI);
    if (!T || !T->isSized())
      return nullptr;
  
    unsigned ElementSize = DL.getTypeAllocSize(T);
    if (StructType *ST = dyn_cast<StructType>(T))
      ElementSize = DL.getStructLayout(ST)->getSizeInBytes();
  
    // If malloc call's arg can be determined to be a multiple of ElementSize,
    // return the multiple.  Otherwise, return NULL.
    Value *MallocArg = CI->getArgOperand(0);
    Value *Multiple = nullptr;
    if (ComputeMultiple(MallocArg, ElementSize, Multiple, LookThroughSExt))
      return Multiple;
  
    return nullptr;
  }
  
  /// getMallocType - Returns the PointerType resulting from the malloc call.
  /// The PointerType depends on the number of bitcast uses of the malloc call:
  ///   0: PointerType is the calls' return type.
  ///   1: PointerType is the bitcast's result type.
  ///  >1: Unique PointerType cannot be determined, return NULL.
  PointerType *llvm::getMallocType(const CallInst *CI,
                                   const TargetLibraryInfo *TLI) {
    assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call");
  
    PointerType *MallocType = nullptr;
    unsigned NumOfBitCastUses = 0;
  
    // Determine if CallInst has a bitcast use.
    for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end();
         UI != E;)
      if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
        MallocType = cast<PointerType>(BCI->getDestTy());
        NumOfBitCastUses++;
      }
  
    // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
    if (NumOfBitCastUses == 1)
      return MallocType;
  
    // Malloc call was not bitcast, so type is the malloc function's return type.
    if (NumOfBitCastUses == 0)
      return cast<PointerType>(CI->getType());
  
    // Type could not be determined.
    return nullptr;
  }
  
  /// getMallocAllocatedType - Returns the Type allocated by malloc call.
  /// The Type depends on the number of bitcast uses of the malloc call:
  ///   0: PointerType is the malloc calls' return type.
  ///   1: PointerType is the bitcast's result type.
  ///  >1: Unique PointerType cannot be determined, return NULL.
  Type *llvm::getMallocAllocatedType(const CallInst *CI,
                                     const TargetLibraryInfo *TLI) {
    PointerType *PT = getMallocType(CI, TLI);
    return PT ? PT->getElementType() : nullptr;
  }
  
  /// getMallocArraySize - Returns the array size of a malloc call.  If the
  /// argument passed to malloc is a multiple of the size of the malloced type,
  /// then return that multiple.  For non-array mallocs, the multiple is
  /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
  /// determined.
  Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout &DL,
                                  const TargetLibraryInfo *TLI,
                                  bool LookThroughSExt) {
    assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call");
    return computeArraySize(CI, DL, TLI, LookThroughSExt);
  }
  
  /// extractCallocCall - Returns the corresponding CallInst if the instruction
  /// is a calloc call.
  const CallInst *llvm::extractCallocCall(const Value *I,
                                          const TargetLibraryInfo *TLI) {
    return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : nullptr;
  }
  
  /// isLibFreeFunction - Returns true if the function is a builtin free()
  bool llvm::isLibFreeFunction(const Function *F, const LibFunc TLIFn) {
    unsigned ExpectedNumParams;
    if (TLIFn == LibFunc_free ||
        TLIFn == LibFunc_ZdlPv || // operator delete(void*)
        TLIFn == LibFunc_ZdaPv || // operator delete[](void*)
        TLIFn == LibFunc_msvc_delete_ptr32 || // operator delete(void*)
        TLIFn == LibFunc_msvc_delete_ptr64 || // operator delete(void*)
        TLIFn == LibFunc_msvc_delete_array_ptr32 || // operator delete[](void*)
        TLIFn == LibFunc_msvc_delete_array_ptr64)   // operator delete[](void*)
      ExpectedNumParams = 1;
    else if (TLIFn == LibFunc_ZdlPvj ||              // delete(void*, uint)
             TLIFn == LibFunc_ZdlPvm ||              // delete(void*, ulong)
             TLIFn == LibFunc_ZdlPvRKSt9nothrow_t || // delete(void*, nothrow)
             TLIFn == LibFunc_ZdlPvSt11align_val_t || // delete(void*, align_val_t)
             TLIFn == LibFunc_ZdaPvj ||              // delete[](void*, uint)
             TLIFn == LibFunc_ZdaPvm ||              // delete[](void*, ulong)
             TLIFn == LibFunc_ZdaPvRKSt9nothrow_t || // delete[](void*, nothrow)
             TLIFn == LibFunc_ZdaPvSt11align_val_t || // delete[](void*, align_val_t)
             TLIFn == LibFunc_msvc_delete_ptr32_int ||      // delete(void*, uint)
             TLIFn == LibFunc_msvc_delete_ptr64_longlong || // delete(void*, ulonglong)
             TLIFn == LibFunc_msvc_delete_ptr32_nothrow || // delete(void*, nothrow)
             TLIFn == LibFunc_msvc_delete_ptr64_nothrow || // delete(void*, nothrow)
             TLIFn == LibFunc_msvc_delete_array_ptr32_int ||      // delete[](void*, uint)
             TLIFn == LibFunc_msvc_delete_array_ptr64_longlong || // delete[](void*, ulonglong)
             TLIFn == LibFunc_msvc_delete_array_ptr32_nothrow || // delete[](void*, nothrow)
             TLIFn == LibFunc_msvc_delete_array_ptr64_nothrow)   // delete[](void*, nothrow)
      ExpectedNumParams = 2;
    else if (TLIFn == LibFunc_ZdaPvSt11align_val_tRKSt9nothrow_t || // delete(void*, align_val_t, nothrow)
             TLIFn == LibFunc_ZdlPvSt11align_val_tRKSt9nothrow_t) // delete[](void*, align_val_t, nothrow)
      ExpectedNumParams = 3;
    else
      return false;
  
    // Check free prototype.
    // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
    // attribute will exist.
    FunctionType *FTy = F->getFunctionType();
    if (!FTy->getReturnType()->isVoidTy())
      return false;
    if (FTy->getNumParams() != ExpectedNumParams)
      return false;
    if (FTy->getParamType(0) != Type::getInt8PtrTy(F->getContext()))
      return false;
  
    return true;
  }
  
  /// isFreeCall - Returns non-null if the value is a call to the builtin free()
  const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
    bool IsNoBuiltinCall;
    const Function *Callee =
        getCalledFunction(I, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
    if (Callee == nullptr || IsNoBuiltinCall)
      return nullptr;
  
    StringRef FnName = Callee->getName();
    LibFunc TLIFn;
    if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
      return nullptr;
  
    return isLibFreeFunction(Callee, TLIFn) ? dyn_cast<CallInst>(I) : nullptr;
  }
  
  
  //===----------------------------------------------------------------------===//
  //  Utility functions to compute size of objects.
  //
  static APInt getSizeWithOverflow(const SizeOffsetType &Data) {
    if (Data.second.isNegative() || Data.first.ult(Data.second))
      return APInt(Data.first.getBitWidth(), 0);
    return Data.first - Data.second;
  }
  
  /// Compute the size of the object pointed by Ptr. Returns true and the
  /// object size in Size if successful, and false otherwise.
  /// If RoundToAlign is true, then Size is rounded up to the alignment of
  /// allocas, byval arguments, and global variables.
  bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
                           const TargetLibraryInfo *TLI, ObjectSizeOpts Opts) {
    ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(), Opts);
    SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
    if (!Visitor.bothKnown(Data))
      return false;
  
    Size = getSizeWithOverflow(Data).getZExtValue();
    return true;
  }
  
  Value *llvm::lowerObjectSizeCall(IntrinsicInst *ObjectSize,
                                   const DataLayout &DL,
                                   const TargetLibraryInfo *TLI,
                                   bool MustSucceed) {
    assert(ObjectSize->getIntrinsicID() == Intrinsic::objectsize &&
           "ObjectSize must be a call to llvm.objectsize!");
  
    bool MaxVal = cast<ConstantInt>(ObjectSize->getArgOperand(1))->isZero();
    ObjectSizeOpts EvalOptions;
    // Unless we have to fold this to something, try to be as accurate as
    // possible.
    if (MustSucceed)
      EvalOptions.EvalMode =
          MaxVal ? ObjectSizeOpts::Mode::Max : ObjectSizeOpts::Mode::Min;
    else
      EvalOptions.EvalMode = ObjectSizeOpts::Mode::Exact;
  
    EvalOptions.NullIsUnknownSize =
        cast<ConstantInt>(ObjectSize->getArgOperand(2))->isOne();
  
    auto *ResultType = cast<IntegerType>(ObjectSize->getType());
    bool StaticOnly = cast<ConstantInt>(ObjectSize->getArgOperand(3))->isZero();
    if (StaticOnly) {
      // FIXME: Does it make sense to just return a failure value if the size won't
      // fit in the output and `!MustSucceed`?
      uint64_t Size;
      if (getObjectSize(ObjectSize->getArgOperand(0), Size, DL, TLI, EvalOptions) &&
          isUIntN(ResultType->getBitWidth(), Size))
        return ConstantInt::get(ResultType, Size);
    } else {
      LLVMContext &Ctx = ObjectSize->getFunction()->getContext();
      ObjectSizeOffsetEvaluator Eval(DL, TLI, Ctx, EvalOptions);
      SizeOffsetEvalType SizeOffsetPair =
          Eval.compute(ObjectSize->getArgOperand(0));
  
      if (SizeOffsetPair != ObjectSizeOffsetEvaluator::unknown()) {
        IRBuilder<TargetFolder> Builder(Ctx, TargetFolder(DL));
        Builder.SetInsertPoint(ObjectSize);
  
        // If we've outside the end of the object, then we can always access
        // exactly 0 bytes.
        Value *ResultSize =
            Builder.CreateSub(SizeOffsetPair.first, SizeOffsetPair.second);
        Value *UseZero =
            Builder.CreateICmpULT(SizeOffsetPair.first, SizeOffsetPair.second);
        ResultSize = Builder.CreateZExtOrTrunc(ResultSize, ResultType);
        return Builder.CreateSelect(UseZero, ConstantInt::get(ResultType, 0),
                                    ResultSize);
      }
    }
  
    if (!MustSucceed)
      return nullptr;
  
    return ConstantInt::get(ResultType, MaxVal ? -1ULL : 0);
  }
  
  STATISTIC(ObjectVisitorArgument,
            "Number of arguments with unsolved size and offset");
  STATISTIC(ObjectVisitorLoad,
            "Number of load instructions with unsolved size and offset");
  
  APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Alignment) {
    if (Options.RoundToAlign && Alignment)
      return APInt(IntTyBits, alignTo(Size.getZExtValue(), Align(Alignment)));
    return Size;
  }
  
  ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
                                                   const TargetLibraryInfo *TLI,
                                                   LLVMContext &Context,
                                                   ObjectSizeOpts Options)
      : DL(DL), TLI(TLI), Options(Options) {
    // Pointer size must be rechecked for each object visited since it could have
    // a different address space.
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
    IntTyBits = DL.getIndexTypeSizeInBits(V->getType());
    Zero = APInt::getNullValue(IntTyBits);
  
    V = V->stripPointerCasts();
    if (Instruction *I = dyn_cast<Instruction>(V)) {
      // If we have already seen this instruction, bail out. Cycles can happen in
      // unreachable code after constant propagation.
      if (!SeenInsts.insert(I).second)
        return unknown();
  
      if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
        return visitGEPOperator(*GEP);
      return visit(*I);
    }
    if (Argument *A = dyn_cast<Argument>(V))
      return visitArgument(*A);
    if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
      return visitConstantPointerNull(*P);
    if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
      return visitGlobalAlias(*GA);
    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
      return visitGlobalVariable(*GV);
    if (UndefValue *UV = dyn_cast<UndefValue>(V))
      return visitUndefValue(*UV);
    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
      if (CE->getOpcode() == Instruction::IntToPtr)
        return unknown(); // clueless
      if (CE->getOpcode() == Instruction::GetElementPtr)
        return visitGEPOperator(cast<GEPOperator>(*CE));
    }
  
    LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: "
                      << *V << '\n');
    return unknown();
  }
  
  /// When we're compiling N-bit code, and the user uses parameters that are
  /// greater than N bits (e.g. uint64_t on a 32-bit build), we can run into
  /// trouble with APInt size issues. This function handles resizing + overflow
  /// checks for us. Check and zext or trunc \p I depending on IntTyBits and
  /// I's value.
  bool ObjectSizeOffsetVisitor::CheckedZextOrTrunc(APInt &I) {
    // More bits than we can handle. Checking the bit width isn't necessary, but
    // it's faster than checking active bits, and should give `false` in the
    // vast majority of cases.
    if (I.getBitWidth() > IntTyBits && I.getActiveBits() > IntTyBits)
      return false;
    if (I.getBitWidth() != IntTyBits)
      I = I.zextOrTrunc(IntTyBits);
    return true;
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
    if (!I.getAllocatedType()->isSized())
      return unknown();
  
    if (I.getAllocatedType()->isVectorTy() &&
        I.getAllocatedType()->getVectorIsScalable())
      return unknown();
  
    APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType()));
    if (!I.isArrayAllocation())
      return std::make_pair(align(Size, I.getAlignment()), Zero);
  
    Value *ArraySize = I.getArraySize();
    if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
      APInt NumElems = C->getValue();
      if (!CheckedZextOrTrunc(NumElems))
        return unknown();
  
      bool Overflow;
      Size = Size.umul_ov(NumElems, Overflow);
      return Overflow ? unknown() : std::make_pair(align(Size, I.getAlignment()),
                                                   Zero);
    }
    return unknown();
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
    // No interprocedural analysis is done at the moment.
    if (!A.hasByValOrInAllocaAttr()) {
      ++ObjectVisitorArgument;
      return unknown();
    }
    PointerType *PT = cast<PointerType>(A.getType());
    APInt Size(IntTyBits, DL.getTypeAllocSize(PT->getElementType()));
    return std::make_pair(align(Size, A.getParamAlignment()), Zero);
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) {
    Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI);
    if (!FnData)
      return unknown();
  
    // Handle strdup-like functions separately.
    if (FnData->AllocTy == StrDupLike) {
      APInt Size(IntTyBits, GetStringLength(CS.getArgument(0)));
      if (!Size)
        return unknown();
  
      // Strndup limits strlen.
      if (FnData->FstParam > 0) {
        ConstantInt *Arg =
            dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
        if (!Arg)
          return unknown();
  
        APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits);
        if (Size.ugt(MaxSize))
          Size = MaxSize + 1;
      }
      return std::make_pair(Size, Zero);
    }
  
    ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
    if (!Arg)
      return unknown();
  
    APInt Size = Arg->getValue();
    if (!CheckedZextOrTrunc(Size))
      return unknown();
  
    // Size is determined by just 1 parameter.
    if (FnData->SndParam < 0)
      return std::make_pair(Size, Zero);
  
    Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam));
    if (!Arg)
      return unknown();
  
    APInt NumElems = Arg->getValue();
    if (!CheckedZextOrTrunc(NumElems))
      return unknown();
  
    bool Overflow;
    Size = Size.umul_ov(NumElems, Overflow);
    return Overflow ? unknown() : std::make_pair(Size, Zero);
  
    // TODO: handle more standard functions (+ wchar cousins):
    // - strdup / strndup
    // - strcpy / strncpy
    // - strcat / strncat
    // - memcpy / memmove
    // - strcat / strncat
    // - memset
  }
  
  SizeOffsetType
  ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull& CPN) {
    // If null is unknown, there's nothing we can do. Additionally, non-zero
    // address spaces can make use of null, so we don't presume to know anything
    // about that.
    //
    // TODO: How should this work with address space casts? We currently just drop
    // them on the floor, but it's unclear what we should do when a NULL from
    // addrspace(1) gets casted to addrspace(0) (or vice-versa).
    if (Options.NullIsUnknownSize || CPN.getType()->getAddressSpace())
      return unknown();
    return std::make_pair(Zero, Zero);
  }
  
  SizeOffsetType
  ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) {
    return unknown();
  }
  
  SizeOffsetType
  ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
    // Easy cases were already folded by previous passes.
    return unknown();
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
    SizeOffsetType PtrData = compute(GEP.getPointerOperand());
    APInt Offset(DL.getIndexTypeSizeInBits(GEP.getPointerOperand()->getType()), 0);
    if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset))
      return unknown();
  
    return std::make_pair(PtrData.first, PtrData.second + Offset);
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
    if (GA.isInterposable())
      return unknown();
    return compute(GA.getAliasee());
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
    if (!GV.hasDefinitiveInitializer())
      return unknown();
  
    APInt Size(IntTyBits, DL.getTypeAllocSize(GV.getValueType()));
    return std::make_pair(align(Size, GV.getAlignment()), Zero);
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) {
    // clueless
    return unknown();
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
    ++ObjectVisitorLoad;
    return unknown();
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
    // too complex to analyze statically.
    return unknown();
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
    SizeOffsetType TrueSide  = compute(I.getTrueValue());
    SizeOffsetType FalseSide = compute(I.getFalseValue());
    if (bothKnown(TrueSide) && bothKnown(FalseSide)) {
      if (TrueSide == FalseSide) {
          return TrueSide;
      }
  
      APInt TrueResult = getSizeWithOverflow(TrueSide);
      APInt FalseResult = getSizeWithOverflow(FalseSide);
  
      if (TrueResult == FalseResult) {
        return TrueSide;
      }
      if (Options.EvalMode == ObjectSizeOpts::Mode::Min) {
        if (TrueResult.slt(FalseResult))
          return TrueSide;
        return FalseSide;
      }
      if (Options.EvalMode == ObjectSizeOpts::Mode::Max) {
        if (TrueResult.sgt(FalseResult))
          return TrueSide;
        return FalseSide;
      }
    }
    return unknown();
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) {
    return std::make_pair(Zero, Zero);
  }
  
  SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
    LLVM_DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I
                      << '\n');
    return unknown();
  }
  
  ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
      const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
      ObjectSizeOpts EvalOpts)
      : DL(DL), TLI(TLI), Context(Context),
        Builder(Context, TargetFolder(DL),
                IRBuilderCallbackInserter(
                    [&](Instruction *I) { InsertedInstructions.insert(I); })),
        EvalOpts(EvalOpts) {
    // IntTy and Zero must be set for each compute() since the address space may
    // be different for later objects.
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
    // XXX - Are vectors of pointers possible here?
    IntTy = cast<IntegerType>(DL.getIndexType(V->getType()));
    Zero = ConstantInt::get(IntTy, 0);
  
    SizeOffsetEvalType Result = compute_(V);
  
    if (!bothKnown(Result)) {
      // Erase everything that was computed in this iteration from the cache, so
      // that no dangling references are left behind. We could be a bit smarter if
      // we kept a dependency graph. It's probably not worth the complexity.
      for (const Value *SeenVal : SeenVals) {
        CacheMapTy::iterator CacheIt = CacheMap.find(SeenVal);
        // non-computable results can be safely cached
        if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
          CacheMap.erase(CacheIt);
      }
  
      // Erase any instructions we inserted as part of the traversal.
      for (Instruction *I : InsertedInstructions) {
        I->replaceAllUsesWith(UndefValue::get(I->getType()));
        I->eraseFromParent();
      }
    }
  
    SeenVals.clear();
    InsertedInstructions.clear();
    return Result;
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
    ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, EvalOpts);
    SizeOffsetType Const = Visitor.compute(V);
    if (Visitor.bothKnown(Const))
      return std::make_pair(ConstantInt::get(Context, Const.first),
                            ConstantInt::get(Context, Const.second));
  
    V = V->stripPointerCasts();
  
    // Check cache.
    CacheMapTy::iterator CacheIt = CacheMap.find(V);
    if (CacheIt != CacheMap.end())
      return CacheIt->second;
  
    // Always generate code immediately before the instruction being
    // processed, so that the generated code dominates the same BBs.
    BuilderTy::InsertPointGuard Guard(Builder);
    if (Instruction *I = dyn_cast<Instruction>(V))
      Builder.SetInsertPoint(I);
  
    // Now compute the size and offset.
    SizeOffsetEvalType Result;
  
    // Record the pointers that were handled in this run, so that they can be
    // cleaned later if something fails. We also use this set to break cycles that
    // can occur in dead code.
    if (!SeenVals.insert(V).second) {
      Result = unknown();
    } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
      Result = visitGEPOperator(*GEP);
    } else if (Instruction *I = dyn_cast<Instruction>(V)) {
      Result = visit(*I);
    } else if (isa<Argument>(V) ||
               (isa<ConstantExpr>(V) &&
                cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) ||
               isa<GlobalAlias>(V) ||
               isa<GlobalVariable>(V)) {
      // Ignore values where we cannot do more than ObjectSizeVisitor.
      Result = unknown();
    } else {
      LLVM_DEBUG(
          dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: " << *V
                 << '\n');
      Result = unknown();
    }
  
    // Don't reuse CacheIt since it may be invalid at this point.
    CacheMap[V] = Result;
    return Result;
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
    if (!I.getAllocatedType()->isSized())
      return unknown();
  
    // must be a VLA
    assert(I.isArrayAllocation());
    Value *ArraySize = I.getArraySize();
    Value *Size = ConstantInt::get(ArraySize->getType(),
                                   DL.getTypeAllocSize(I.getAllocatedType()));
    Size = Builder.CreateMul(Size, ArraySize);
    return std::make_pair(Size, Zero);
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) {
    Optional<AllocFnsTy> FnData = getAllocationSize(CS.getInstruction(), TLI);
    if (!FnData)
      return unknown();
  
    // Handle strdup-like functions separately.
    if (FnData->AllocTy == StrDupLike) {
      // TODO
      return unknown();
    }
  
    Value *FirstArg = CS.getArgument(FnData->FstParam);
    FirstArg = Builder.CreateZExtOrTrunc(FirstArg, IntTy);
    if (FnData->SndParam < 0)
      return std::make_pair(FirstArg, Zero);
  
    Value *SecondArg = CS.getArgument(FnData->SndParam);
    SecondArg = Builder.CreateZExtOrTrunc(SecondArg, IntTy);
    Value *Size = Builder.CreateMul(FirstArg, SecondArg);
    return std::make_pair(Size, Zero);
  
    // TODO: handle more standard functions (+ wchar cousins):
    // - strdup / strndup
    // - strcpy / strncpy
    // - strcat / strncat
    // - memcpy / memmove
    // - strcat / strncat
    // - memset
  }
  
  SizeOffsetEvalType
  ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) {
    return unknown();
  }
  
  SizeOffsetEvalType
  ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) {
    return unknown();
  }
  
  SizeOffsetEvalType
  ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) {
    SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand());
    if (!bothKnown(PtrData))
      return unknown();
  
    Value *Offset = EmitGEPOffset(&Builder, DL, &GEP, /*NoAssumptions=*/true);
    Offset = Builder.CreateAdd(PtrData.second, Offset);
    return std::make_pair(PtrData.first, Offset);
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) {
    // clueless
    return unknown();
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) {
    return unknown();
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
    // Create 2 PHIs: one for size and another for offset.
    PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
    PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
  
    // Insert right away in the cache to handle recursive PHIs.
    CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);
  
    // Compute offset/size for each PHI incoming pointer.
    for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
      Builder.SetInsertPoint(&*PHI.getIncomingBlock(i)->getFirstInsertionPt());
      SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));
  
      if (!bothKnown(EdgeData)) {
        OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
        OffsetPHI->eraseFromParent();
        InsertedInstructions.erase(OffsetPHI);
        SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
        SizePHI->eraseFromParent();
        InsertedInstructions.erase(SizePHI);
        return unknown();
      }
      SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
      OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
    }
  
    Value *Size = SizePHI, *Offset = OffsetPHI;
    if (Value *Tmp = SizePHI->hasConstantValue()) {
      Size = Tmp;
      SizePHI->replaceAllUsesWith(Size);
      SizePHI->eraseFromParent();
      InsertedInstructions.erase(SizePHI);
    }
    if (Value *Tmp = OffsetPHI->hasConstantValue()) {
      Offset = Tmp;
      OffsetPHI->replaceAllUsesWith(Offset);
      OffsetPHI->eraseFromParent();
      InsertedInstructions.erase(OffsetPHI);
    }
    return std::make_pair(Size, Offset);
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
    SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
    SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());
  
    if (!bothKnown(TrueSide) || !bothKnown(FalseSide))
      return unknown();
    if (TrueSide == FalseSide)
      return TrueSide;
  
    Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first,
                                       FalseSide.first);
    Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second,
                                         FalseSide.second);
    return std::make_pair(Size, Offset);
  }
  
  SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) {
    LLVM_DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I
                      << '\n');
    return unknown();
  }
  