text: //===------ SimplifyLibCalls.cpp - Library calls simplifier ---------------===//
  //
  // 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 file implements the library calls simplifier. It does not implement
  // any pass, but can't be used by other passes to do simplifications.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
  #include "llvm/ADT/APSInt.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/StringMap.h"
  #include "llvm/ADT/Triple.h"
  #include "llvm/Analysis/BlockFrequencyInfo.h"
  #include "llvm/Analysis/ConstantFolding.h"
  #include "llvm/Analysis/OptimizationRemarkEmitter.h"
  #include "llvm/Analysis/ProfileSummaryInfo.h"
  #include "llvm/Analysis/TargetLibraryInfo.h"
  #include "llvm/Transforms/Utils/Local.h"
  #include "llvm/Analysis/ValueTracking.h"
  #include "llvm/Analysis/CaptureTracking.h"
  #include "llvm/Analysis/Loads.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/IRBuilder.h"
  #include "llvm/IR/IntrinsicInst.h"
  #include "llvm/IR/Intrinsics.h"
  #include "llvm/IR/LLVMContext.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/PatternMatch.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/KnownBits.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Transforms/Utils/BuildLibCalls.h"
  #include "llvm/Transforms/Utils/SizeOpts.h"
  
  using namespace llvm;
  using namespace PatternMatch;
  
  static cl::opt<bool>
      EnableUnsafeFPShrink("enable-double-float-shrink", cl::Hidden,
                           cl::init(false),
                           cl::desc("Enable unsafe double to float "
                                    "shrinking for math lib calls"));
  
  //===----------------------------------------------------------------------===//
  // Helper Functions
  //===----------------------------------------------------------------------===//
  
  static bool ignoreCallingConv(LibFunc Func) {
    return Func == LibFunc_abs || Func == LibFunc_labs ||
           Func == LibFunc_llabs || Func == LibFunc_strlen;
  }
  
  static bool isCallingConvCCompatible(CallInst *CI) {
    switch(CI->getCallingConv()) {
    default:
      return false;
    case llvm::CallingConv::C:
      return true;
    case llvm::CallingConv::ARM_APCS:
    case llvm::CallingConv::ARM_AAPCS:
    case llvm::CallingConv::ARM_AAPCS_VFP: {
  
      // The iOS ABI diverges from the standard in some cases, so for now don't
      // try to simplify those calls.
      if (Triple(CI->getModule()->getTargetTriple()).isiOS())
        return false;
  
      auto *FuncTy = CI->getFunctionType();
  
      if (!FuncTy->getReturnType()->isPointerTy() &&
          !FuncTy->getReturnType()->isIntegerTy() &&
          !FuncTy->getReturnType()->isVoidTy())
        return false;
  
      for (auto Param : FuncTy->params()) {
        if (!Param->isPointerTy() && !Param->isIntegerTy())
          return false;
      }
      return true;
    }
    }
    return false;
  }
  
  /// Return true if it is only used in equality comparisons with With.
  static bool isOnlyUsedInEqualityComparison(Value *V, Value *With) {
    for (User *U : V->users()) {
      if (ICmpInst *IC = dyn_cast<ICmpInst>(U))
        if (IC->isEquality() && IC->getOperand(1) == With)
          continue;
      // Unknown instruction.
      return false;
    }
    return true;
  }
  
  static bool callHasFloatingPointArgument(const CallInst *CI) {
    return any_of(CI->operands(), [](const Use &OI) {
      return OI->getType()->isFloatingPointTy();
    });
  }
  
  static bool callHasFP128Argument(const CallInst *CI) {
    return any_of(CI->operands(), [](const Use &OI) {
      return OI->getType()->isFP128Ty();
    });
  }
  
  static Value *convertStrToNumber(CallInst *CI, StringRef &Str, int64_t Base) {
    if (Base < 2 || Base > 36)
      // handle special zero base
      if (Base != 0)
        return nullptr;
  
    char *End;
    std::string nptr = Str.str();
    errno = 0;
    long long int Result = strtoll(nptr.c_str(), &End, Base);
    if (errno)
      return nullptr;
  
    // if we assume all possible target locales are ASCII supersets,
    // then if strtoll successfully parses a number on the host,
    // it will also successfully parse the same way on the target
    if (*End != '\0')
      return nullptr;
  
    if (!isIntN(CI->getType()->getPrimitiveSizeInBits(), Result))
      return nullptr;
  
    return ConstantInt::get(CI->getType(), Result);
  }
  
  static bool isLocallyOpenedFile(Value *File, CallInst *CI,
                                  const TargetLibraryInfo *TLI) {
    CallInst *FOpen = dyn_cast<CallInst>(File);
    if (!FOpen)
      return false;
  
    Function *InnerCallee = FOpen->getCalledFunction();
    if (!InnerCallee)
      return false;
  
    LibFunc Func;
    if (!TLI->getLibFunc(*InnerCallee, Func) || !TLI->has(Func) ||
        Func != LibFunc_fopen)
      return false;
  
    inferLibFuncAttributes(*CI->getCalledFunction(), *TLI);
    if (PointerMayBeCaptured(File, true, true))
      return false;
  
    return true;
  }
  
  static bool isOnlyUsedInComparisonWithZero(Value *V) {
    for (User *U : V->users()) {
      if (ICmpInst *IC = dyn_cast<ICmpInst>(U))
        if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
          if (C->isNullValue())
            continue;
      // Unknown instruction.
      return false;
    }
    return true;
  }
  
  static bool canTransformToMemCmp(CallInst *CI, Value *Str, uint64_t Len,
                                   const DataLayout &DL) {
    if (!isOnlyUsedInComparisonWithZero(CI))
      return false;
  
    if (!isDereferenceableAndAlignedPointer(Str, Align(1), APInt(64, Len), DL))
      return false;
  
    if (CI->getFunction()->hasFnAttribute(Attribute::SanitizeMemory))
      return false;
  
    return true;
  }
  
  static void annotateDereferenceableBytes(CallInst *CI,
                                           ArrayRef<unsigned> ArgNos,
                                           uint64_t DereferenceableBytes) {
    const Function *F = CI->getCaller();
    if (!F)
      return;
    for (unsigned ArgNo : ArgNos) {
      uint64_t DerefBytes = DereferenceableBytes;
      unsigned AS = CI->getArgOperand(ArgNo)->getType()->getPointerAddressSpace();
      if (!llvm::NullPointerIsDefined(F, AS) ||
          CI->paramHasAttr(ArgNo, Attribute::NonNull))
        DerefBytes = std::max(CI->getDereferenceableOrNullBytes(
                                  ArgNo + AttributeList::FirstArgIndex),
                              DereferenceableBytes);
    
      if (CI->getDereferenceableBytes(ArgNo + AttributeList::FirstArgIndex) <
          DerefBytes) {
        CI->removeParamAttr(ArgNo, Attribute::Dereferenceable);
        if (!llvm::NullPointerIsDefined(F, AS) ||
            CI->paramHasAttr(ArgNo, Attribute::NonNull))
          CI->removeParamAttr(ArgNo, Attribute::DereferenceableOrNull);
        CI->addParamAttr(ArgNo, Attribute::getWithDereferenceableBytes(
                                    CI->getContext(), DerefBytes));
      }
    }
  }
  
  static void annotateNonNullBasedOnAccess(CallInst *CI,
                                           ArrayRef<unsigned> ArgNos) {
    Function *F = CI->getCaller();
    if (!F)
      return;
  
    for (unsigned ArgNo : ArgNos) {
      if (CI->paramHasAttr(ArgNo, Attribute::NonNull))
        continue;
      unsigned AS = CI->getArgOperand(ArgNo)->getType()->getPointerAddressSpace();
      if (llvm::NullPointerIsDefined(F, AS))
        continue;
  
      CI->addParamAttr(ArgNo, Attribute::NonNull);
      annotateDereferenceableBytes(CI, ArgNo, 1);
    }
  }
  
  static void annotateNonNullAndDereferenceable(CallInst *CI, ArrayRef<unsigned> ArgNos,
                                 Value *Size, const DataLayout &DL) {
    if (ConstantInt *LenC = dyn_cast<ConstantInt>(Size)) {
      annotateNonNullBasedOnAccess(CI, ArgNos);
      annotateDereferenceableBytes(CI, ArgNos, LenC->getZExtValue());
    } else if (isKnownNonZero(Size, DL)) {
      annotateNonNullBasedOnAccess(CI, ArgNos);
      const APInt *X, *Y;
      uint64_t DerefMin = 1;
      if (match(Size, m_Select(m_Value(), m_APInt(X), m_APInt(Y)))) {
        DerefMin = std::min(X->getZExtValue(), Y->getZExtValue());
        annotateDereferenceableBytes(CI, ArgNos, DerefMin);
      }
    }
  }
  
  //===----------------------------------------------------------------------===//
  // String and Memory Library Call Optimizations
  //===----------------------------------------------------------------------===//
  
  Value *LibCallSimplifier::optimizeStrCat(CallInst *CI, IRBuilder<> &B) {
    // Extract some information from the instruction
    Value *Dst = CI->getArgOperand(0);
    Value *Src = CI->getArgOperand(1);
    annotateNonNullBasedOnAccess(CI, {0, 1});
  
    // See if we can get the length of the input string.
    uint64_t Len = GetStringLength(Src);
    if (Len)
      annotateDereferenceableBytes(CI, 1, Len);
    else
      return nullptr;
    --Len; // Unbias length.
  
    // Handle the simple, do-nothing case: strcat(x, "") -> x
    if (Len == 0)
      return Dst;
  
    return emitStrLenMemCpy(Src, Dst, Len, B);
  }
  
  Value *LibCallSimplifier::emitStrLenMemCpy(Value *Src, Value *Dst, uint64_t Len,
                                             IRBuilder<> &B) {
    // We need to find the end of the destination string.  That's where the
    // memory is to be moved to. We just generate a call to strlen.
    Value *DstLen = emitStrLen(Dst, B, DL, TLI);
    if (!DstLen)
      return nullptr;
  
    // Now that we have the destination's length, we must index into the
    // destination's pointer to get the actual memcpy destination (end of
    // the string .. we're concatenating).
    Value *CpyDst = B.CreateGEP(B.getInt8Ty(), Dst, DstLen, "endptr");
  
    // We have enough information to now generate the memcpy call to do the
    // concatenation for us.  Make a memcpy to copy the nul byte with align = 1.
    B.CreateMemCpy(
        CpyDst, Align(1), Src, Align(1),
        ConstantInt::get(DL.getIntPtrType(Src->getContext()), Len + 1));
    return Dst;
  }
  
  Value *LibCallSimplifier::optimizeStrNCat(CallInst *CI, IRBuilder<> &B) {
    // Extract some information from the instruction.
    Value *Dst = CI->getArgOperand(0);
    Value *Src = CI->getArgOperand(1);
    Value *Size = CI->getArgOperand(2);
    uint64_t Len;
    annotateNonNullBasedOnAccess(CI, 0);
    if (isKnownNonZero(Size, DL))
      annotateNonNullBasedOnAccess(CI, 1);
  
    // We don't do anything if length is not constant.
    ConstantInt *LengthArg = dyn_cast<ConstantInt>(Size);
    if (LengthArg) {
      Len = LengthArg->getZExtValue();
      // strncat(x, c, 0) -> x
      if (!Len)
        return Dst;
    } else {
      return nullptr;
    }
  
    // See if we can get the length of the input string.
    uint64_t SrcLen = GetStringLength(Src);
    if (SrcLen) {
      annotateDereferenceableBytes(CI, 1, SrcLen);
      --SrcLen; // Unbias length.
    } else {
      return nullptr;
    }
  
    // strncat(x, "", c) -> x
    if (SrcLen == 0)
      return Dst;
  
    // We don't optimize this case.
    if (Len < SrcLen)
      return nullptr;
  
    // strncat(x, s, c) -> strcat(x, s)
    // s is constant so the strcat can be optimized further.
    return emitStrLenMemCpy(Src, Dst, SrcLen, B);
  }
  
  Value *LibCallSimplifier::optimizeStrChr(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    FunctionType *FT = Callee->getFunctionType();
    Value *SrcStr = CI->getArgOperand(0);
    annotateNonNullBasedOnAccess(CI, 0);
  
    // If the second operand is non-constant, see if we can compute the length
    // of the input string and turn this into memchr.
    ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
    if (!CharC) {
      uint64_t Len = GetStringLength(SrcStr);
      if (Len)
        annotateDereferenceableBytes(CI, 0, Len);
      else
        return nullptr;
      if (!FT->getParamType(1)->isIntegerTy(32)) // memchr needs i32.
        return nullptr;
  
      return emitMemChr(SrcStr, CI->getArgOperand(1), // include nul.
                        ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len),
                        B, DL, TLI);
    }
  
    // Otherwise, the character is a constant, see if the first argument is
    // a string literal.  If so, we can constant fold.
    StringRef Str;
    if (!getConstantStringInfo(SrcStr, Str)) {
      if (CharC->isZero()) // strchr(p, 0) -> p + strlen(p)
        if (Value *StrLen = emitStrLen(SrcStr, B, DL, TLI))
          return B.CreateGEP(B.getInt8Ty(), SrcStr, StrLen, "strchr");
      return nullptr;
    }
  
    // Compute the offset, make sure to handle the case when we're searching for
    // zero (a weird way to spell strlen).
    size_t I = (0xFF & CharC->getSExtValue()) == 0
                   ? Str.size()
                   : Str.find(CharC->getSExtValue());
    if (I == StringRef::npos) // Didn't find the char.  strchr returns null.
      return Constant::getNullValue(CI->getType());
  
    // strchr(s+n,c)  -> gep(s+n+i,c)
    return B.CreateGEP(B.getInt8Ty(), SrcStr, B.getInt64(I), "strchr");
  }
  
  Value *LibCallSimplifier::optimizeStrRChr(CallInst *CI, IRBuilder<> &B) {
    Value *SrcStr = CI->getArgOperand(0);
    ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
    annotateNonNullBasedOnAccess(CI, 0);
  
    // Cannot fold anything if we're not looking for a constant.
    if (!CharC)
      return nullptr;
  
    StringRef Str;
    if (!getConstantStringInfo(SrcStr, Str)) {
      // strrchr(s, 0) -> strchr(s, 0)
      if (CharC->isZero())
        return emitStrChr(SrcStr, '\0', B, TLI);
      return nullptr;
    }
  
    // Compute the offset.
    size_t I = (0xFF & CharC->getSExtValue()) == 0
                   ? Str.size()
                   : Str.rfind(CharC->getSExtValue());
    if (I == StringRef::npos) // Didn't find the char. Return null.
      return Constant::getNullValue(CI->getType());
  
    // strrchr(s+n,c) -> gep(s+n+i,c)
    return B.CreateGEP(B.getInt8Ty(), SrcStr, B.getInt64(I), "strrchr");
  }
  
  Value *LibCallSimplifier::optimizeStrCmp(CallInst *CI, IRBuilder<> &B) {
    Value *Str1P = CI->getArgOperand(0), *Str2P = CI->getArgOperand(1);
    if (Str1P == Str2P) // strcmp(x,x)  -> 0
      return ConstantInt::get(CI->getType(), 0);
  
    StringRef Str1, Str2;
    bool HasStr1 = getConstantStringInfo(Str1P, Str1);
    bool HasStr2 = getConstantStringInfo(Str2P, Str2);
  
    // strcmp(x, y)  -> cnst  (if both x and y are constant strings)
    if (HasStr1 && HasStr2)
      return ConstantInt::get(CI->getType(), Str1.compare(Str2));
  
    if (HasStr1 && Str1.empty()) // strcmp("", x) -> -*x
      return B.CreateNeg(B.CreateZExt(
          B.CreateLoad(B.getInt8Ty(), Str2P, "strcmpload"), CI->getType()));
  
    if (HasStr2 && Str2.empty()) // strcmp(x,"") -> *x
      return B.CreateZExt(B.CreateLoad(B.getInt8Ty(), Str1P, "strcmpload"),
                          CI->getType());
  
    // strcmp(P, "x") -> memcmp(P, "x", 2)
    uint64_t Len1 = GetStringLength(Str1P);
    if (Len1)
      annotateDereferenceableBytes(CI, 0, Len1);
    uint64_t Len2 = GetStringLength(Str2P);
    if (Len2)
      annotateDereferenceableBytes(CI, 1, Len2);
  
    if (Len1 && Len2) {
      return emitMemCmp(Str1P, Str2P,
                        ConstantInt::get(DL.getIntPtrType(CI->getContext()),
                                         std::min(Len1, Len2)),
                        B, DL, TLI);
    }
  
    // strcmp to memcmp
    if (!HasStr1 && HasStr2) {
      if (canTransformToMemCmp(CI, Str1P, Len2, DL))
        return emitMemCmp(
            Str1P, Str2P,
            ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len2), B, DL,
            TLI);
    } else if (HasStr1 && !HasStr2) {
      if (canTransformToMemCmp(CI, Str2P, Len1, DL))
        return emitMemCmp(
            Str1P, Str2P,
            ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len1), B, DL,
            TLI);
    }
  
    annotateNonNullBasedOnAccess(CI, {0, 1});
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrNCmp(CallInst *CI, IRBuilder<> &B) {
    Value *Str1P = CI->getArgOperand(0);
    Value *Str2P = CI->getArgOperand(1);
    Value *Size = CI->getArgOperand(2);
    if (Str1P == Str2P) // strncmp(x,x,n)  -> 0
      return ConstantInt::get(CI->getType(), 0);
  
    if (isKnownNonZero(Size, DL))
      annotateNonNullBasedOnAccess(CI, {0, 1});
    // Get the length argument if it is constant.
    uint64_t Length;
    if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(Size))
      Length = LengthArg->getZExtValue();
    else
      return nullptr;
  
    if (Length == 0) // strncmp(x,y,0)   -> 0
      return ConstantInt::get(CI->getType(), 0);
  
    if (Length == 1) // strncmp(x,y,1) -> memcmp(x,y,1)
      return emitMemCmp(Str1P, Str2P, Size, B, DL, TLI);
  
    StringRef Str1, Str2;
    bool HasStr1 = getConstantStringInfo(Str1P, Str1);
    bool HasStr2 = getConstantStringInfo(Str2P, Str2);
  
    // strncmp(x, y)  -> cnst  (if both x and y are constant strings)
    if (HasStr1 && HasStr2) {
      StringRef SubStr1 = Str1.substr(0, Length);
      StringRef SubStr2 = Str2.substr(0, Length);
      return ConstantInt::get(CI->getType(), SubStr1.compare(SubStr2));
    }
  
    if (HasStr1 && Str1.empty()) // strncmp("", x, n) -> -*x
      return B.CreateNeg(B.CreateZExt(
          B.CreateLoad(B.getInt8Ty(), Str2P, "strcmpload"), CI->getType()));
  
    if (HasStr2 && Str2.empty()) // strncmp(x, "", n) -> *x
      return B.CreateZExt(B.CreateLoad(B.getInt8Ty(), Str1P, "strcmpload"),
                          CI->getType());
  
    uint64_t Len1 = GetStringLength(Str1P);
    if (Len1)
      annotateDereferenceableBytes(CI, 0, Len1);
    uint64_t Len2 = GetStringLength(Str2P);
    if (Len2)
      annotateDereferenceableBytes(CI, 1, Len2);
  
    // strncmp to memcmp
    if (!HasStr1 && HasStr2) {
      Len2 = std::min(Len2, Length);
      if (canTransformToMemCmp(CI, Str1P, Len2, DL))
        return emitMemCmp(
            Str1P, Str2P,
            ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len2), B, DL,
            TLI);
    } else if (HasStr1 && !HasStr2) {
      Len1 = std::min(Len1, Length);
      if (canTransformToMemCmp(CI, Str2P, Len1, DL))
        return emitMemCmp(
            Str1P, Str2P,
            ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len1), B, DL,
            TLI);
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrNDup(CallInst *CI, IRBuilder<> &B) {
    Value *Src = CI->getArgOperand(0);
    ConstantInt *Size = dyn_cast<ConstantInt>(CI->getArgOperand(1));
    uint64_t SrcLen = GetStringLength(Src);
    if (SrcLen && Size) {
      annotateDereferenceableBytes(CI, 0, SrcLen);
      if (SrcLen <= Size->getZExtValue() + 1)
        return emitStrDup(Src, B, TLI);
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrCpy(CallInst *CI, IRBuilder<> &B) {
    Value *Dst = CI->getArgOperand(0), *Src = CI->getArgOperand(1);
    if (Dst == Src) // strcpy(x,x)  -> x
      return Src;
    
    annotateNonNullBasedOnAccess(CI, {0, 1});
    // See if we can get the length of the input string.
    uint64_t Len = GetStringLength(Src);
    if (Len)
      annotateDereferenceableBytes(CI, 1, Len);
    else
      return nullptr;
  
    // We have enough information to now generate the memcpy call to do the
    // copy for us.  Make a memcpy to copy the nul byte with align = 1.
    CallInst *NewCI =
        B.CreateMemCpy(Dst, Align(1), Src, Align(1),
                       ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len));
    NewCI->setAttributes(CI->getAttributes());
    return Dst;
  }
  
  Value *LibCallSimplifier::optimizeStpCpy(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Dst = CI->getArgOperand(0), *Src = CI->getArgOperand(1);
    if (Dst == Src) { // stpcpy(x,x)  -> x+strlen(x)
      Value *StrLen = emitStrLen(Src, B, DL, TLI);
      return StrLen ? B.CreateInBoundsGEP(B.getInt8Ty(), Dst, StrLen) : nullptr;
    }
  
    // See if we can get the length of the input string.
    uint64_t Len = GetStringLength(Src);
    if (Len)
      annotateDereferenceableBytes(CI, 1, Len);
    else
      return nullptr;
  
    Type *PT = Callee->getFunctionType()->getParamType(0);
    Value *LenV = ConstantInt::get(DL.getIntPtrType(PT), Len);
    Value *DstEnd = B.CreateGEP(B.getInt8Ty(), Dst,
                                ConstantInt::get(DL.getIntPtrType(PT), Len - 1));
  
    // We have enough information to now generate the memcpy call to do the
    // copy for us.  Make a memcpy to copy the nul byte with align = 1.
    CallInst *NewCI = B.CreateMemCpy(Dst, Align(1), Src, Align(1), LenV);
    NewCI->setAttributes(CI->getAttributes());
    return DstEnd;
  }
  
  Value *LibCallSimplifier::optimizeStrNCpy(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Dst = CI->getArgOperand(0);
    Value *Src = CI->getArgOperand(1);
    Value *Size = CI->getArgOperand(2);
    annotateNonNullBasedOnAccess(CI, 0);
    if (isKnownNonZero(Size, DL))
      annotateNonNullBasedOnAccess(CI, 1);
  
    uint64_t Len;
    if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(Size))
      Len = LengthArg->getZExtValue();
    else
      return nullptr;
  
    // strncpy(x, y, 0) -> x
    if (Len == 0)
      return Dst;
  
    // See if we can get the length of the input string.
    uint64_t SrcLen = GetStringLength(Src);
    if (SrcLen) {
      annotateDereferenceableBytes(CI, 1, SrcLen);
      --SrcLen; // Unbias length.
    } else {
      return nullptr;
    }
  
    if (SrcLen == 0) {
      // strncpy(x, "", y) -> memset(align 1 x, '\0', y)
      CallInst *NewCI = B.CreateMemSet(Dst, B.getInt8('\0'), Size, Align(1));
      AttrBuilder ArgAttrs(CI->getAttributes().getParamAttributes(0));
      NewCI->setAttributes(NewCI->getAttributes().addParamAttributes(
          CI->getContext(), 0, ArgAttrs));
      return Dst;
    }
  
    // Let strncpy handle the zero padding
    if (Len > SrcLen + 1)
      return nullptr;
  
    Type *PT = Callee->getFunctionType()->getParamType(0);
    // strncpy(x, s, c) -> memcpy(align 1 x, align 1 s, c) [s and c are constant]
    CallInst *NewCI = B.CreateMemCpy(Dst, Align(1), Src, Align(1),
                                     ConstantInt::get(DL.getIntPtrType(PT), Len));
    NewCI->setAttributes(CI->getAttributes());
    return Dst;
  }
  
  Value *LibCallSimplifier::optimizeStringLength(CallInst *CI, IRBuilder<> &B,
                                                 unsigned CharSize) {
    Value *Src = CI->getArgOperand(0);
  
    // Constant folding: strlen("xyz") -> 3
    if (uint64_t Len = GetStringLength(Src, CharSize))
      return ConstantInt::get(CI->getType(), Len - 1);
  
    // If s is a constant pointer pointing to a string literal, we can fold
    // strlen(s + x) to strlen(s) - x, when x is known to be in the range
    // [0, strlen(s)] or the string has a single null terminator '\0' at the end.
    // We only try to simplify strlen when the pointer s points to an array
    // of i8. Otherwise, we would need to scale the offset x before doing the
    // subtraction. This will make the optimization more complex, and it's not
    // very useful because calling strlen for a pointer of other types is
    // very uncommon.
    if (GEPOperator *GEP = dyn_cast<GEPOperator>(Src)) {
      if (!isGEPBasedOnPointerToString(GEP, CharSize))
        return nullptr;
  
      ConstantDataArraySlice Slice;
      if (getConstantDataArrayInfo(GEP->getOperand(0), Slice, CharSize)) {
        uint64_t NullTermIdx;
        if (Slice.Array == nullptr) {
          NullTermIdx = 0;
        } else {
          NullTermIdx = ~((uint64_t)0);
          for (uint64_t I = 0, E = Slice.Length; I < E; ++I) {
            if (Slice.Array->getElementAsInteger(I + Slice.Offset) == 0) {
              NullTermIdx = I;
              break;
            }
          }
          // If the string does not have '\0', leave it to strlen to compute
          // its length.
          if (NullTermIdx == ~((uint64_t)0))
            return nullptr;
        }
  
        Value *Offset = GEP->getOperand(2);
        KnownBits Known = computeKnownBits(Offset, DL, 0, nullptr, CI, nullptr);
        Known.Zero.flipAllBits();
        uint64_t ArrSize =
               cast<ArrayType>(GEP->getSourceElementType())->getNumElements();
  
        // KnownZero's bits are flipped, so zeros in KnownZero now represent
        // bits known to be zeros in Offset, and ones in KnowZero represent
        // bits unknown in Offset. Therefore, Offset is known to be in range
        // [0, NullTermIdx] when the flipped KnownZero is non-negative and
        // unsigned-less-than NullTermIdx.
        //
        // If Offset is not provably in the range [0, NullTermIdx], we can still
        // optimize if we can prove that the program has undefined behavior when
        // Offset is outside that range. That is the case when GEP->getOperand(0)
        // is a pointer to an object whose memory extent is NullTermIdx+1.
        if ((Known.Zero.isNonNegative() && Known.Zero.ule(NullTermIdx)) ||
            (GEP->isInBounds() && isa<GlobalVariable>(GEP->getOperand(0)) &&
             NullTermIdx == ArrSize - 1)) {
          Offset = B.CreateSExtOrTrunc(Offset, CI->getType());
          return B.CreateSub(ConstantInt::get(CI->getType(), NullTermIdx),
                             Offset);
        }
      }
  
      return nullptr;
    }
  
    // strlen(x?"foo":"bars") --> x ? 3 : 4
    if (SelectInst *SI = dyn_cast<SelectInst>(Src)) {
      uint64_t LenTrue = GetStringLength(SI->getTrueValue(), CharSize);
      uint64_t LenFalse = GetStringLength(SI->getFalseValue(), CharSize);
      if (LenTrue && LenFalse) {
        ORE.emit([&]() {
          return OptimizationRemark("instcombine", "simplify-libcalls", CI)
                 << "folded strlen(select) to select of constants";
        });
        return B.CreateSelect(SI->getCondition(),
                              ConstantInt::get(CI->getType(), LenTrue - 1),
                              ConstantInt::get(CI->getType(), LenFalse - 1));
      }
    }
  
    // strlen(x) != 0 --> *x != 0
    // strlen(x) == 0 --> *x == 0
    if (isOnlyUsedInZeroEqualityComparison(CI))
      return B.CreateZExt(B.CreateLoad(B.getIntNTy(CharSize), Src, "strlenfirst"),
                          CI->getType());
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrLen(CallInst *CI, IRBuilder<> &B) {
    if (Value *V = optimizeStringLength(CI, B, 8))
      return V;
    annotateNonNullBasedOnAccess(CI, 0);
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeWcslen(CallInst *CI, IRBuilder<> &B) {
    Module &M = *CI->getModule();
    unsigned WCharSize = TLI->getWCharSize(M) * 8;
    // We cannot perform this optimization without wchar_size metadata.
    if (WCharSize == 0)
      return nullptr;
  
    return optimizeStringLength(CI, B, WCharSize);
  }
  
  Value *LibCallSimplifier::optimizeStrPBrk(CallInst *CI, IRBuilder<> &B) {
    StringRef S1, S2;
    bool HasS1 = getConstantStringInfo(CI->getArgOperand(0), S1);
    bool HasS2 = getConstantStringInfo(CI->getArgOperand(1), S2);
  
    // strpbrk(s, "") -> nullptr
    // strpbrk("", s) -> nullptr
    if ((HasS1 && S1.empty()) || (HasS2 && S2.empty()))
      return Constant::getNullValue(CI->getType());
  
    // Constant folding.
    if (HasS1 && HasS2) {
      size_t I = S1.find_first_of(S2);
      if (I == StringRef::npos) // No match.
        return Constant::getNullValue(CI->getType());
  
      return B.CreateGEP(B.getInt8Ty(), CI->getArgOperand(0), B.getInt64(I),
                         "strpbrk");
    }
  
    // strpbrk(s, "a") -> strchr(s, 'a')
    if (HasS2 && S2.size() == 1)
      return emitStrChr(CI->getArgOperand(0), S2[0], B, TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrTo(CallInst *CI, IRBuilder<> &B) {
    Value *EndPtr = CI->getArgOperand(1);
    if (isa<ConstantPointerNull>(EndPtr)) {
      // With a null EndPtr, this function won't capture the main argument.
      // It would be readonly too, except that it still may write to errno.
      CI->addParamAttr(0, Attribute::NoCapture);
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrSpn(CallInst *CI, IRBuilder<> &B) {
    StringRef S1, S2;
    bool HasS1 = getConstantStringInfo(CI->getArgOperand(0), S1);
    bool HasS2 = getConstantStringInfo(CI->getArgOperand(1), S2);
  
    // strspn(s, "") -> 0
    // strspn("", s) -> 0
    if ((HasS1 && S1.empty()) || (HasS2 && S2.empty()))
      return Constant::getNullValue(CI->getType());
  
    // Constant folding.
    if (HasS1 && HasS2) {
      size_t Pos = S1.find_first_not_of(S2);
      if (Pos == StringRef::npos)
        Pos = S1.size();
      return ConstantInt::get(CI->getType(), Pos);
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrCSpn(CallInst *CI, IRBuilder<> &B) {
    StringRef S1, S2;
    bool HasS1 = getConstantStringInfo(CI->getArgOperand(0), S1);
    bool HasS2 = getConstantStringInfo(CI->getArgOperand(1), S2);
  
    // strcspn("", s) -> 0
    if (HasS1 && S1.empty())
      return Constant::getNullValue(CI->getType());
  
    // Constant folding.
    if (HasS1 && HasS2) {
      size_t Pos = S1.find_first_of(S2);
      if (Pos == StringRef::npos)
        Pos = S1.size();
      return ConstantInt::get(CI->getType(), Pos);
    }
  
    // strcspn(s, "") -> strlen(s)
    if (HasS2 && S2.empty())
      return emitStrLen(CI->getArgOperand(0), B, DL, TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrStr(CallInst *CI, IRBuilder<> &B) {
    // fold strstr(x, x) -> x.
    if (CI->getArgOperand(0) == CI->getArgOperand(1))
      return B.CreateBitCast(CI->getArgOperand(0), CI->getType());
  
    // fold strstr(a, b) == a -> strncmp(a, b, strlen(b)) == 0
    if (isOnlyUsedInEqualityComparison(CI, CI->getArgOperand(0))) {
      Value *StrLen = emitStrLen(CI->getArgOperand(1), B, DL, TLI);
      if (!StrLen)
        return nullptr;
      Value *StrNCmp = emitStrNCmp(CI->getArgOperand(0), CI->getArgOperand(1),
                                   StrLen, B, DL, TLI);
      if (!StrNCmp)
        return nullptr;
      for (auto UI = CI->user_begin(), UE = CI->user_end(); UI != UE;) {
        ICmpInst *Old = cast<ICmpInst>(*UI++);
        Value *Cmp =
            B.CreateICmp(Old->getPredicate(), StrNCmp,
                         ConstantInt::getNullValue(StrNCmp->getType()), "cmp");
        replaceAllUsesWith(Old, Cmp);
      }
      return CI;
    }
  
    // See if either input string is a constant string.
    StringRef SearchStr, ToFindStr;
    bool HasStr1 = getConstantStringInfo(CI->getArgOperand(0), SearchStr);
    bool HasStr2 = getConstantStringInfo(CI->getArgOperand(1), ToFindStr);
  
    // fold strstr(x, "") -> x.
    if (HasStr2 && ToFindStr.empty())
      return B.CreateBitCast(CI->getArgOperand(0), CI->getType());
  
    // If both strings are known, constant fold it.
    if (HasStr1 && HasStr2) {
      size_t Offset = SearchStr.find(ToFindStr);
  
      if (Offset == StringRef::npos) // strstr("foo", "bar") -> null
        return Constant::getNullValue(CI->getType());
  
      // strstr("abcd", "bc") -> gep((char*)"abcd", 1)
      Value *Result = castToCStr(CI->getArgOperand(0), B);
      Result =
          B.CreateConstInBoundsGEP1_64(B.getInt8Ty(), Result, Offset, "strstr");
      return B.CreateBitCast(Result, CI->getType());
    }
  
    // fold strstr(x, "y") -> strchr(x, 'y').
    if (HasStr2 && ToFindStr.size() == 1) {
      Value *StrChr = emitStrChr(CI->getArgOperand(0), ToFindStr[0], B, TLI);
      return StrChr ? B.CreateBitCast(StrChr, CI->getType()) : nullptr;
    }
  
    annotateNonNullBasedOnAccess(CI, {0, 1});
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeMemRChr(CallInst *CI, IRBuilder<> &B) {
    if (isKnownNonZero(CI->getOperand(2), DL))
      annotateNonNullBasedOnAccess(CI, 0);
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeMemChr(CallInst *CI, IRBuilder<> &B) {
    Value *SrcStr = CI->getArgOperand(0);
    Value *Size = CI->getArgOperand(2);
    annotateNonNullAndDereferenceable(CI, 0, Size, DL);
    ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
    ConstantInt *LenC = dyn_cast<ConstantInt>(Size);
  
    // memchr(x, y, 0) -> null
    if (LenC) {
      if (LenC->isZero())
        return Constant::getNullValue(CI->getType());
    } else {
      // From now on we need at least constant length and string.
      return nullptr;
    }
  
    StringRef Str;
    if (!getConstantStringInfo(SrcStr, Str, 0, /*TrimAtNul=*/false))
      return nullptr;
  
    // Truncate the string to LenC. If Str is smaller than LenC we will still only
    // scan the string, as reading past the end of it is undefined and we can just
    // return null if we don't find the char.
    Str = Str.substr(0, LenC->getZExtValue());
  
    // If the char is variable but the input str and length are not we can turn
    // this memchr call into a simple bit field test. Of course this only works
    // when the return value is only checked against null.
    //
    // It would be really nice to reuse switch lowering here but we can't change
    // the CFG at this point.
    //
    // memchr("\r\n", C, 2) != nullptr -> (1 << C & ((1 << '\r') | (1 << '\n')))
    // != 0
    //   after bounds check.
    if (!CharC && !Str.empty() && isOnlyUsedInZeroEqualityComparison(CI)) {
      unsigned char Max =
          *std::max_element(reinterpret_cast<const unsigned char *>(Str.begin()),
                            reinterpret_cast<const unsigned char *>(Str.end()));
  
      // Make sure the bit field we're about to create fits in a register on the
      // target.
      // FIXME: On a 64 bit architecture this prevents us from using the
      // interesting range of alpha ascii chars. We could do better by emitting
      // two bitfields or shifting the range by 64 if no lower chars are used.
      if (!DL.fitsInLegalInteger(Max + 1))
        return nullptr;
  
      // For the bit field use a power-of-2 type with at least 8 bits to avoid
      // creating unnecessary illegal types.
      unsigned char Width = NextPowerOf2(std::max((unsigned char)7, Max));
  
      // Now build the bit field.
      APInt Bitfield(Width, 0);
      for (char C : Str)
        Bitfield.setBit((unsigned char)C);
      Value *BitfieldC = B.getInt(Bitfield);
  
      // Adjust width of "C" to the bitfield width, then mask off the high bits.
      Value *C = B.CreateZExtOrTrunc(CI->getArgOperand(1), BitfieldC->getType());
      C = B.CreateAnd(C, B.getIntN(Width, 0xFF));
  
      // First check that the bit field access is within bounds.
      Value *Bounds = B.CreateICmp(ICmpInst::ICMP_ULT, C, B.getIntN(Width, Width),
                                   "memchr.bounds");
  
      // Create code that checks if the given bit is set in the field.
      Value *Shl = B.CreateShl(B.getIntN(Width, 1ULL), C);
      Value *Bits = B.CreateIsNotNull(B.CreateAnd(Shl, BitfieldC), "memchr.bits");
  
      // Finally merge both checks and cast to pointer type. The inttoptr
      // implicitly zexts the i1 to intptr type.
      return B.CreateIntToPtr(B.CreateAnd(Bounds, Bits, "memchr"), CI->getType());
    }
  
    // Check if all arguments are constants.  If so, we can constant fold.
    if (!CharC)
      return nullptr;
  
    // Compute the offset.
    size_t I = Str.find(CharC->getSExtValue() & 0xFF);
    if (I == StringRef::npos) // Didn't find the char.  memchr returns null.
      return Constant::getNullValue(CI->getType());
  
    // memchr(s+n,c,l) -> gep(s+n+i,c)
    return B.CreateGEP(B.getInt8Ty(), SrcStr, B.getInt64(I), "memchr");
  }
  
  static Value *optimizeMemCmpConstantSize(CallInst *CI, Value *LHS, Value *RHS,
                                           uint64_t Len, IRBuilder<> &B,
                                           const DataLayout &DL) {
    if (Len == 0) // memcmp(s1,s2,0) -> 0
      return Constant::getNullValue(CI->getType());
  
    // memcmp(S1,S2,1) -> *(unsigned char*)LHS - *(unsigned char*)RHS
    if (Len == 1) {
      Value *LHSV =
          B.CreateZExt(B.CreateLoad(B.getInt8Ty(), castToCStr(LHS, B), "lhsc"),
                       CI->getType(), "lhsv");
      Value *RHSV =
          B.CreateZExt(B.CreateLoad(B.getInt8Ty(), castToCStr(RHS, B), "rhsc"),
                       CI->getType(), "rhsv");
      return B.CreateSub(LHSV, RHSV, "chardiff");
    }
  
    // memcmp(S1,S2,N/8)==0 -> (*(intN_t*)S1 != *(intN_t*)S2)==0
    // TODO: The case where both inputs are constants does not need to be limited
    // to legal integers or equality comparison. See block below this.
    if (DL.isLegalInteger(Len * 8) && isOnlyUsedInZeroEqualityComparison(CI)) {
      IntegerType *IntType = IntegerType::get(CI->getContext(), Len * 8);
      unsigned PrefAlignment = DL.getPrefTypeAlignment(IntType);
  
      // First, see if we can fold either argument to a constant.
      Value *LHSV = nullptr;
      if (auto *LHSC = dyn_cast<Constant>(LHS)) {
        LHSC = ConstantExpr::getBitCast(LHSC, IntType->getPointerTo());
        LHSV = ConstantFoldLoadFromConstPtr(LHSC, IntType, DL);
      }
      Value *RHSV = nullptr;
      if (auto *RHSC = dyn_cast<Constant>(RHS)) {
        RHSC = ConstantExpr::getBitCast(RHSC, IntType->getPointerTo());
        RHSV = ConstantFoldLoadFromConstPtr(RHSC, IntType, DL);
      }
  
      // Don't generate unaligned loads. If either source is constant data,
      // alignment doesn't matter for that source because there is no load.
      if ((LHSV || getKnownAlignment(LHS, DL, CI) >= PrefAlignment) &&
          (RHSV || getKnownAlignment(RHS, DL, CI) >= PrefAlignment)) {
        if (!LHSV) {
          Type *LHSPtrTy =
              IntType->getPointerTo(LHS->getType()->getPointerAddressSpace());
          LHSV = B.CreateLoad(IntType, B.CreateBitCast(LHS, LHSPtrTy), "lhsv");
        }
        if (!RHSV) {
          Type *RHSPtrTy =
              IntType->getPointerTo(RHS->getType()->getPointerAddressSpace());
          RHSV = B.CreateLoad(IntType, B.CreateBitCast(RHS, RHSPtrTy), "rhsv");
        }
        return B.CreateZExt(B.CreateICmpNE(LHSV, RHSV), CI->getType(), "memcmp");
      }
    }
  
    // Constant folding: memcmp(x, y, Len) -> constant (all arguments are const).
    // TODO: This is limited to i8 arrays.
    StringRef LHSStr, RHSStr;
    if (getConstantStringInfo(LHS, LHSStr) &&
        getConstantStringInfo(RHS, RHSStr)) {
      // Make sure we're not reading out-of-bounds memory.
      if (Len > LHSStr.size() || Len > RHSStr.size())
        return nullptr;
      // Fold the memcmp and normalize the result.  This way we get consistent
      // results across multiple platforms.
      uint64_t Ret = 0;
      int Cmp = memcmp(LHSStr.data(), RHSStr.data(), Len);
      if (Cmp < 0)
        Ret = -1;
      else if (Cmp > 0)
        Ret = 1;
      return ConstantInt::get(CI->getType(), Ret);
    }
  
    return nullptr;
  }
  
  // Most simplifications for memcmp also apply to bcmp.
  Value *LibCallSimplifier::optimizeMemCmpBCmpCommon(CallInst *CI,
                                                     IRBuilder<> &B) {
    Value *LHS = CI->getArgOperand(0), *RHS = CI->getArgOperand(1);
    Value *Size = CI->getArgOperand(2);
  
    if (LHS == RHS) // memcmp(s,s,x) -> 0
      return Constant::getNullValue(CI->getType());
  
    annotateNonNullAndDereferenceable(CI, {0, 1}, Size, DL);
    // Handle constant lengths.
    ConstantInt *LenC = dyn_cast<ConstantInt>(Size);
    if (!LenC)
      return nullptr;
  
    // memcmp(d,s,0) -> 0
    if (LenC->getZExtValue() == 0)
      return Constant::getNullValue(CI->getType());
  
    if (Value *Res =
            optimizeMemCmpConstantSize(CI, LHS, RHS, LenC->getZExtValue(), B, DL))
      return Res;
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeMemCmp(CallInst *CI, IRBuilder<> &B) {
    if (Value *V = optimizeMemCmpBCmpCommon(CI, B))
      return V;
  
    // memcmp(x, y, Len) == 0 -> bcmp(x, y, Len) == 0
    // bcmp can be more efficient than memcmp because it only has to know that
    // there is a difference, not how different one is to the other.
    if (TLI->has(LibFunc_bcmp) && isOnlyUsedInZeroEqualityComparison(CI)) {
      Value *LHS = CI->getArgOperand(0);
      Value *RHS = CI->getArgOperand(1);
      Value *Size = CI->getArgOperand(2);
      return emitBCmp(LHS, RHS, Size, B, DL, TLI);
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeBCmp(CallInst *CI, IRBuilder<> &B) {
    return optimizeMemCmpBCmpCommon(CI, B);
  }
  
  Value *LibCallSimplifier::optimizeMemCpy(CallInst *CI, IRBuilder<> &B) {
    Value *Size = CI->getArgOperand(2);
    annotateNonNullAndDereferenceable(CI, {0, 1}, Size, DL);
    if (isa<IntrinsicInst>(CI))
      return nullptr;
  
    // memcpy(x, y, n) -> llvm.memcpy(align 1 x, align 1 y, n)
    CallInst *NewCI = B.CreateMemCpy(CI->getArgOperand(0), Align(1),
                                     CI->getArgOperand(1), Align(1), Size);
    NewCI->setAttributes(CI->getAttributes());
    return CI->getArgOperand(0);
  }
  
  Value *LibCallSimplifier::optimizeMemCCpy(CallInst *CI, IRBuilder<> &B) {
    Value *Dst = CI->getArgOperand(0);
    Value *Src = CI->getArgOperand(1);
    ConstantInt *StopChar = dyn_cast<ConstantInt>(CI->getArgOperand(2));
    ConstantInt *N = dyn_cast<ConstantInt>(CI->getArgOperand(3));
    StringRef SrcStr;
    if (CI->use_empty() && Dst == Src)
      return Dst;
    // memccpy(d, s, c, 0) -> nullptr
    if (N) {
      if (N->isNullValue())
        return Constant::getNullValue(CI->getType());
      if (!getConstantStringInfo(Src, SrcStr, /*Offset=*/0,
                                 /*TrimAtNul=*/false) ||
          !StopChar)
        return nullptr;
    } else {
      return nullptr;
    }
  
    // Wrap arg 'c' of type int to char
    size_t Pos = SrcStr.find(StopChar->getSExtValue() & 0xFF);
    if (Pos == StringRef::npos) {
      if (N->getZExtValue() <= SrcStr.size()) {
        B.CreateMemCpy(Dst, Align(1), Src, Align(1), CI->getArgOperand(3));
        return Constant::getNullValue(CI->getType());
      }
      return nullptr;
    }
  
    Value *NewN =
        ConstantInt::get(N->getType(), std::min(uint64_t(Pos + 1), N->getZExtValue()));
    // memccpy -> llvm.memcpy
    B.CreateMemCpy(Dst, Align(1), Src, Align(1), NewN);
    return Pos + 1 <= N->getZExtValue()
               ? B.CreateInBoundsGEP(B.getInt8Ty(), Dst, NewN)
               : Constant::getNullValue(CI->getType());
  }
  
  Value *LibCallSimplifier::optimizeMemPCpy(CallInst *CI, IRBuilder<> &B) {
    Value *Dst = CI->getArgOperand(0);
    Value *N = CI->getArgOperand(2);
    // mempcpy(x, y, n) -> llvm.memcpy(align 1 x, align 1 y, n), x + n
    CallInst *NewCI =
        B.CreateMemCpy(Dst, Align(1), CI->getArgOperand(1), Align(1), N);
    NewCI->setAttributes(CI->getAttributes());
    return B.CreateInBoundsGEP(B.getInt8Ty(), Dst, N);
  }
  
  Value *LibCallSimplifier::optimizeMemMove(CallInst *CI, IRBuilder<> &B) {
    Value *Size = CI->getArgOperand(2);
    annotateNonNullAndDereferenceable(CI, {0, 1}, Size, DL);
    if (isa<IntrinsicInst>(CI))
      return nullptr;
  
    // memmove(x, y, n) -> llvm.memmove(align 1 x, align 1 y, n)
    CallInst *NewCI = B.CreateMemMove(CI->getArgOperand(0), Align(1),
                                      CI->getArgOperand(1), Align(1), Size);
    NewCI->setAttributes(CI->getAttributes());
    return CI->getArgOperand(0);
  }
  
  /// Fold memset[_chk](malloc(n), 0, n) --> calloc(1, n).
  Value *LibCallSimplifier::foldMallocMemset(CallInst *Memset, IRBuilder<> &B) {
    // This has to be a memset of zeros (bzero).
    auto *FillValue = dyn_cast<ConstantInt>(Memset->getArgOperand(1));
    if (!FillValue || FillValue->getZExtValue() != 0)
      return nullptr;
  
    // TODO: We should handle the case where the malloc has more than one use.
    // This is necessary to optimize common patterns such as when the result of
    // the malloc is checked against null or when a memset intrinsic is used in
    // place of a memset library call.
    auto *Malloc = dyn_cast<CallInst>(Memset->getArgOperand(0));
    if (!Malloc || !Malloc->hasOneUse())
      return nullptr;
  
    // Is the inner call really malloc()?
    Function *InnerCallee = Malloc->getCalledFunction();
    if (!InnerCallee)
      return nullptr;
  
    LibFunc Func;
    if (!TLI->getLibFunc(*InnerCallee, Func) || !TLI->has(Func) ||
        Func != LibFunc_malloc)
      return nullptr;
  
    // The memset must cover the same number of bytes that are malloc'd.
    if (Memset->getArgOperand(2) != Malloc->getArgOperand(0))
      return nullptr;
  
    // Replace the malloc with a calloc. We need the data layout to know what the
    // actual size of a 'size_t' parameter is.
    B.SetInsertPoint(Malloc->getParent(), ++Malloc->getIterator());
    const DataLayout &DL = Malloc->getModule()->getDataLayout();
    IntegerType *SizeType = DL.getIntPtrType(B.GetInsertBlock()->getContext());
    if (Value *Calloc = emitCalloc(ConstantInt::get(SizeType, 1),
                                   Malloc->getArgOperand(0),
                                   Malloc->getAttributes(), B, *TLI)) {
      substituteInParent(Malloc, Calloc);
      return Calloc;
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeMemSet(CallInst *CI, IRBuilder<> &B) {
    Value *Size = CI->getArgOperand(2);
    annotateNonNullAndDereferenceable(CI, 0, Size, DL);
    if (isa<IntrinsicInst>(CI))
      return nullptr;
  
    if (auto *Calloc = foldMallocMemset(CI, B))
      return Calloc;
  
    // memset(p, v, n) -> llvm.memset(align 1 p, v, n)
    Value *Val = B.CreateIntCast(CI->getArgOperand(1), B.getInt8Ty(), false);
    CallInst *NewCI = B.CreateMemSet(CI->getArgOperand(0), Val, Size, Align(1));
    NewCI->setAttributes(CI->getAttributes());
    return CI->getArgOperand(0);
  }
  
  Value *LibCallSimplifier::optimizeRealloc(CallInst *CI, IRBuilder<> &B) {
    if (isa<ConstantPointerNull>(CI->getArgOperand(0)))
      return emitMalloc(CI->getArgOperand(1), B, DL, TLI);
  
    return nullptr;
  }
  
  //===----------------------------------------------------------------------===//
  // Math Library Optimizations
  //===----------------------------------------------------------------------===//
  
  // Replace a libcall \p CI with a call to intrinsic \p IID
  static Value *replaceUnaryCall(CallInst *CI, IRBuilder<> &B, Intrinsic::ID IID) {
    // Propagate fast-math flags from the existing call to the new call.
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(CI->getFastMathFlags());
  
    Module *M = CI->getModule();
    Value *V = CI->getArgOperand(0);
    Function *F = Intrinsic::getDeclaration(M, IID, CI->getType());
    CallInst *NewCall = B.CreateCall(F, V);
    NewCall->takeName(CI);
    return NewCall;
  }
  
  /// Return a variant of Val with float type.
  /// Currently this works in two cases: If Val is an FPExtension of a float
  /// value to something bigger, simply return the operand.
  /// If Val is a ConstantFP but can be converted to a float ConstantFP without
  /// loss of precision do so.
  static Value *valueHasFloatPrecision(Value *Val) {
    if (FPExtInst *Cast = dyn_cast<FPExtInst>(Val)) {
      Value *Op = Cast->getOperand(0);
      if (Op->getType()->isFloatTy())
        return Op;
    }
    if (ConstantFP *Const = dyn_cast<ConstantFP>(Val)) {
      APFloat F = Const->getValueAPF();
      bool losesInfo;
      (void)F.convert(APFloat::IEEEsingle(), APFloat::rmNearestTiesToEven,
                      &losesInfo);
      if (!losesInfo)
        return ConstantFP::get(Const->getContext(), F);
    }
    return nullptr;
  }
  
  /// Shrink double -> float functions.
  static Value *optimizeDoubleFP(CallInst *CI, IRBuilder<> &B,
                                 bool isBinary, bool isPrecise = false) {
    Function *CalleeFn = CI->getCalledFunction();
    if (!CI->getType()->isDoubleTy() || !CalleeFn)
      return nullptr;
  
    // If not all the uses of the function are converted to float, then bail out.
    // This matters if the precision of the result is more important than the
    // precision of the arguments.
    if (isPrecise)
      for (User *U : CI->users()) {
        FPTruncInst *Cast = dyn_cast<FPTruncInst>(U);
        if (!Cast || !Cast->getType()->isFloatTy())
          return nullptr;
      }
  
    // If this is something like 'g((double) float)', convert to 'gf(float)'.
    Value *V[2];
    V[0] = valueHasFloatPrecision(CI->getArgOperand(0));
    V[1] = isBinary ? valueHasFloatPrecision(CI->getArgOperand(1)) : nullptr;
    if (!V[0] || (isBinary && !V[1]))
      return nullptr;
  
    // If call isn't an intrinsic, check that it isn't within a function with the
    // same name as the float version of this call, otherwise the result is an
    // infinite loop.  For example, from MinGW-w64:
    //
    // float expf(float val) { return (float) exp((double) val); }
    StringRef CalleeName = CalleeFn->getName();
    bool IsIntrinsic = CalleeFn->isIntrinsic();
    if (!IsIntrinsic) {
      StringRef CallerName = CI->getFunction()->getName();
      if (!CallerName.empty() && CallerName.back() == 'f' &&
          CallerName.size() == (CalleeName.size() + 1) &&
          CallerName.startswith(CalleeName))
        return nullptr;
    }
  
    // Propagate the math semantics from the current function to the new function.
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(CI->getFastMathFlags());
  
    // g((double) float) -> (double) gf(float)
    Value *R;
    if (IsIntrinsic) {
      Module *M = CI->getModule();
      Intrinsic::ID IID = CalleeFn->getIntrinsicID();
      Function *Fn = Intrinsic::getDeclaration(M, IID, B.getFloatTy());
      R = isBinary ? B.CreateCall(Fn, V) : B.CreateCall(Fn, V[0]);
    } else {
      AttributeList CalleeAttrs = CalleeFn->getAttributes();
      R = isBinary ? emitBinaryFloatFnCall(V[0], V[1], CalleeName, B, CalleeAttrs)
                   : emitUnaryFloatFnCall(V[0], CalleeName, B, CalleeAttrs);
    }
    return B.CreateFPExt(R, B.getDoubleTy());
  }
  
  /// Shrink double -> float for unary functions.
  static Value *optimizeUnaryDoubleFP(CallInst *CI, IRBuilder<> &B,
                                      bool isPrecise = false) {
    return optimizeDoubleFP(CI, B, false, isPrecise);
  }
  
  /// Shrink double -> float for binary functions.
  static Value *optimizeBinaryDoubleFP(CallInst *CI, IRBuilder<> &B,
                                       bool isPrecise = false) {
    return optimizeDoubleFP(CI, B, true, isPrecise);
  }
  
  // cabs(z) -> sqrt((creal(z)*creal(z)) + (cimag(z)*cimag(z)))
  Value *LibCallSimplifier::optimizeCAbs(CallInst *CI, IRBuilder<> &B) {
    if (!CI->isFast())
      return nullptr;
  
    // Propagate fast-math flags from the existing call to new instructions.
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(CI->getFastMathFlags());
  
    Value *Real, *Imag;
    if (CI->getNumArgOperands() == 1) {
      Value *Op = CI->getArgOperand(0);
      assert(Op->getType()->isArrayTy() && "Unexpected signature for cabs!");
      Real = B.CreateExtractValue(Op, 0, "real");
      Imag = B.CreateExtractValue(Op, 1, "imag");
    } else {
      assert(CI->getNumArgOperands() == 2 && "Unexpected signature for cabs!");
      Real = CI->getArgOperand(0);
      Imag = CI->getArgOperand(1);
    }
  
    Value *RealReal = B.CreateFMul(Real, Real);
    Value *ImagImag = B.CreateFMul(Imag, Imag);
  
    Function *FSqrt = Intrinsic::getDeclaration(CI->getModule(), Intrinsic::sqrt,
                                                CI->getType());
    return B.CreateCall(FSqrt, B.CreateFAdd(RealReal, ImagImag), "cabs");
  }
  
  static Value *optimizeTrigReflections(CallInst *Call, LibFunc Func,
                                        IRBuilder<> &B) {
    if (!isa<FPMathOperator>(Call))
      return nullptr;
  
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(Call->getFastMathFlags());
  
    // TODO: Can this be shared to also handle LLVM intrinsics?
    Value *X;
    switch (Func) {
    case LibFunc_sin:
    case LibFunc_sinf:
    case LibFunc_sinl:
    case LibFunc_tan:
    case LibFunc_tanf:
    case LibFunc_tanl:
      // sin(-X) --> -sin(X)
      // tan(-X) --> -tan(X)
      if (match(Call->getArgOperand(0), m_OneUse(m_FNeg(m_Value(X)))))
        return B.CreateFNeg(B.CreateCall(Call->getCalledFunction(), X));
      break;
    case LibFunc_cos:
    case LibFunc_cosf:
    case LibFunc_cosl:
      // cos(-X) --> cos(X)
      if (match(Call->getArgOperand(0), m_FNeg(m_Value(X))))
        return B.CreateCall(Call->getCalledFunction(), X, "cos");
      break;
    default:
      break;
    }
    return nullptr;
  }
  
  static Value *getPow(Value *InnerChain[33], unsigned Exp, IRBuilder<> &B) {
    // Multiplications calculated using Addition Chains.
    // Refer: http://wwwhomes.uni-bielefeld.de/achim/addition_chain.html
  
    assert(Exp != 0 && "Incorrect exponent 0 not handled");
  
    if (InnerChain[Exp])
      return InnerChain[Exp];
  
    static const unsigned AddChain[33][2] = {
        {0, 0}, // Unused.
        {0, 0}, // Unused (base case = pow1).
        {1, 1}, // Unused (pre-computed).
        {1, 2},  {2, 2},   {2, 3},  {3, 3},   {2, 5},  {4, 4},
        {1, 8},  {5, 5},   {1, 10}, {6, 6},   {4, 9},  {7, 7},
        {3, 12}, {8, 8},   {8, 9},  {2, 16},  {1, 18}, {10, 10},
        {6, 15}, {11, 11}, {3, 20}, {12, 12}, {8, 17}, {13, 13},
        {3, 24}, {14, 14}, {4, 25}, {15, 15}, {3, 28}, {16, 16},
    };
  
    InnerChain[Exp] = B.CreateFMul(getPow(InnerChain, AddChain[Exp][0], B),
                                   getPow(InnerChain, AddChain[Exp][1], B));
    return InnerChain[Exp];
  }
  
  // Return a properly extended 32-bit integer if the operation is an itofp.
  static Value *getIntToFPVal(Value *I2F, IRBuilder<> &B) {
    if (isa<SIToFPInst>(I2F) || isa<UIToFPInst>(I2F)) {
      Value *Op = cast<Instruction>(I2F)->getOperand(0);
      // Make sure that the exponent fits inside an int32_t,
      // thus avoiding any range issues that FP has not.
      unsigned BitWidth = Op->getType()->getPrimitiveSizeInBits();
      if (BitWidth < 32 ||
          (BitWidth == 32 && isa<SIToFPInst>(I2F)))
        return isa<SIToFPInst>(I2F) ? B.CreateSExt(Op, B.getInt32Ty())
                                    : B.CreateZExt(Op, B.getInt32Ty());
    }
  
    return nullptr;
  }
  
  /// Use exp{,2}(x * y) for pow(exp{,2}(x), y);
  /// ldexp(1.0, x) for pow(2.0, itofp(x)); exp2(n * x) for pow(2.0 ** n, x);
  /// exp10(x) for pow(10.0, x); exp2(log2(n) * x) for pow(n, x).
  Value *LibCallSimplifier::replacePowWithExp(CallInst *Pow, IRBuilder<> &B) {
    Value *Base = Pow->getArgOperand(0), *Expo = Pow->getArgOperand(1);
    AttributeList Attrs = Pow->getCalledFunction()->getAttributes();
    Module *Mod = Pow->getModule();
    Type *Ty = Pow->getType();
    bool Ignored;
  
    // Evaluate special cases related to a nested function as the base.
  
    // pow(exp(x), y) -> exp(x * y)
    // pow(exp2(x), y) -> exp2(x * y)
    // If exp{,2}() is used only once, it is better to fold two transcendental
    // math functions into one.  If used again, exp{,2}() would still have to be
    // called with the original argument, then keep both original transcendental
    // functions.  However, this transformation is only safe with fully relaxed
    // math semantics, since, besides rounding differences, it changes overflow
    // and underflow behavior quite dramatically.  For example:
    //   pow(exp(1000), 0.001) = pow(inf, 0.001) = inf
    // Whereas:
    //   exp(1000 * 0.001) = exp(1)
    // TODO: Loosen the requirement for fully relaxed math semantics.
    // TODO: Handle exp10() when more targets have it available.
    CallInst *BaseFn = dyn_cast<CallInst>(Base);
    if (BaseFn && BaseFn->hasOneUse() && BaseFn->isFast() && Pow->isFast()) {
      LibFunc LibFn;
  
      Function *CalleeFn = BaseFn->getCalledFunction();
      if (CalleeFn &&
          TLI->getLibFunc(CalleeFn->getName(), LibFn) && TLI->has(LibFn)) {
        StringRef ExpName;
        Intrinsic::ID ID;
        Value *ExpFn;
        LibFunc LibFnFloat, LibFnDouble, LibFnLongDouble;
  
        switch (LibFn) {
        default:
          return nullptr;
        case LibFunc_expf:  case LibFunc_exp:  case LibFunc_expl:
          ExpName = TLI->getName(LibFunc_exp);
          ID = Intrinsic::exp;
          LibFnFloat = LibFunc_expf;
          LibFnDouble = LibFunc_exp;
          LibFnLongDouble = LibFunc_expl;
          break;
        case LibFunc_exp2f: case LibFunc_exp2: case LibFunc_exp2l:
          ExpName = TLI->getName(LibFunc_exp2);
          ID = Intrinsic::exp2;
          LibFnFloat = LibFunc_exp2f;
          LibFnDouble = LibFunc_exp2;
          LibFnLongDouble = LibFunc_exp2l;
          break;
        }
  
        // Create new exp{,2}() with the product as its argument.
        Value *FMul = B.CreateFMul(BaseFn->getArgOperand(0), Expo, "mul");
        ExpFn = BaseFn->doesNotAccessMemory()
                ? B.CreateCall(Intrinsic::getDeclaration(Mod, ID, Ty),
                               FMul, ExpName)
                : emitUnaryFloatFnCall(FMul, TLI, LibFnDouble, LibFnFloat,
                                       LibFnLongDouble, B,
                                       BaseFn->getAttributes());
  
        // Since the new exp{,2}() is different from the original one, dead code
        // elimination cannot be trusted to remove it, since it may have side
        // effects (e.g., errno).  When the only consumer for the original
        // exp{,2}() is pow(), then it has to be explicitly erased.
        substituteInParent(BaseFn, ExpFn);
        return ExpFn;
      }
    }
  
    // Evaluate special cases related to a constant base.
  
    const APFloat *BaseF;
    if (!match(Pow->getArgOperand(0), m_APFloat(BaseF)))
      return nullptr;
  
    // pow(2.0, itofp(x)) -> ldexp(1.0, x)
    if (match(Base, m_SpecificFP(2.0)) &&
        (isa<SIToFPInst>(Expo) || isa<UIToFPInst>(Expo)) &&
        hasFloatFn(TLI, Ty, LibFunc_ldexp, LibFunc_ldexpf, LibFunc_ldexpl)) {
      if (Value *ExpoI = getIntToFPVal(Expo, B))
        return emitBinaryFloatFnCall(ConstantFP::get(Ty, 1.0), ExpoI, TLI,
                                     LibFunc_ldexp, LibFunc_ldexpf, LibFunc_ldexpl,
                                     B, Attrs);
    }
  
    // pow(2.0 ** n, x) -> exp2(n * x)
    if (hasFloatFn(TLI, Ty, LibFunc_exp2, LibFunc_exp2f, LibFunc_exp2l)) {
      APFloat BaseR = APFloat(1.0);
      BaseR.convert(BaseF->getSemantics(), APFloat::rmTowardZero, &Ignored);
      BaseR = BaseR / *BaseF;
      bool IsInteger = BaseF->isInteger(), IsReciprocal = BaseR.isInteger();
      const APFloat *NF = IsReciprocal ? &BaseR : BaseF;
      APSInt NI(64, false);
      if ((IsInteger || IsReciprocal) &&
          NF->convertToInteger(NI, APFloat::rmTowardZero, &Ignored) ==
              APFloat::opOK &&
          NI > 1 && NI.isPowerOf2()) {
        double N = NI.logBase2() * (IsReciprocal ? -1.0 : 1.0);
        Value *FMul = B.CreateFMul(Expo, ConstantFP::get(Ty, N), "mul");
        if (Pow->doesNotAccessMemory())
          return B.CreateCall(Intrinsic::getDeclaration(Mod, Intrinsic::exp2, Ty),
                              FMul, "exp2");
        else
          return emitUnaryFloatFnCall(FMul, TLI, LibFunc_exp2, LibFunc_exp2f,
                                      LibFunc_exp2l, B, Attrs);
      }
    }
  
    // pow(10.0, x) -> exp10(x)
    // TODO: There is no exp10() intrinsic yet, but some day there shall be one.
    if (match(Base, m_SpecificFP(10.0)) &&
        hasFloatFn(TLI, Ty, LibFunc_exp10, LibFunc_exp10f, LibFunc_exp10l))
      return emitUnaryFloatFnCall(Expo, TLI, LibFunc_exp10, LibFunc_exp10f,
                                  LibFunc_exp10l, B, Attrs);
  
    // pow(n, x) -> exp2(log2(n) * x)
    if (Pow->hasOneUse() && Pow->hasApproxFunc() && Pow->hasNoNaNs() &&
        Pow->hasNoInfs() && BaseF->isNormal() && !BaseF->isNegative()) {
      Value *Log = nullptr;
      if (Ty->isFloatTy())
        Log = ConstantFP::get(Ty, std::log2(BaseF->convertToFloat()));
      else if (Ty->isDoubleTy())
        Log = ConstantFP::get(Ty, std::log2(BaseF->convertToDouble()));
  
      if (Log) {
        Value *FMul = B.CreateFMul(Log, Expo, "mul");
        if (Pow->doesNotAccessMemory())
          return B.CreateCall(Intrinsic::getDeclaration(Mod, Intrinsic::exp2, Ty),
                              FMul, "exp2");
        else if (hasFloatFn(TLI, Ty, LibFunc_exp2, LibFunc_exp2f, LibFunc_exp2l))
          return emitUnaryFloatFnCall(FMul, TLI, LibFunc_exp2, LibFunc_exp2f,
                                      LibFunc_exp2l, B, Attrs);
      }
    }
  
    return nullptr;
  }
  
  static Value *getSqrtCall(Value *V, AttributeList Attrs, bool NoErrno,
                            Module *M, IRBuilder<> &B,
                            const TargetLibraryInfo *TLI) {
    // If errno is never set, then use the intrinsic for sqrt().
    if (NoErrno) {
      Function *SqrtFn =
          Intrinsic::getDeclaration(M, Intrinsic::sqrt, V->getType());
      return B.CreateCall(SqrtFn, V, "sqrt");
    }
  
    // Otherwise, use the libcall for sqrt().
    if (hasFloatFn(TLI, V->getType(), LibFunc_sqrt, LibFunc_sqrtf, LibFunc_sqrtl))
      // TODO: We also should check that the target can in fact lower the sqrt()
      // libcall. We currently have no way to ask this question, so we ask if
      // the target has a sqrt() libcall, which is not exactly the same.
      return emitUnaryFloatFnCall(V, TLI, LibFunc_sqrt, LibFunc_sqrtf,
                                  LibFunc_sqrtl, B, Attrs);
  
    return nullptr;
  }
  
  /// Use square root in place of pow(x, +/-0.5).
  Value *LibCallSimplifier::replacePowWithSqrt(CallInst *Pow, IRBuilder<> &B) {
    Value *Sqrt, *Base = Pow->getArgOperand(0), *Expo = Pow->getArgOperand(1);
    AttributeList Attrs = Pow->getCalledFunction()->getAttributes();
    Module *Mod = Pow->getModule();
    Type *Ty = Pow->getType();
  
    const APFloat *ExpoF;
    if (!match(Expo, m_APFloat(ExpoF)) ||
        (!ExpoF->isExactlyValue(0.5) && !ExpoF->isExactlyValue(-0.5)))
      return nullptr;
  
    // Converting pow(X, -0.5) to 1/sqrt(X) may introduce an extra rounding step,
    // so that requires fast-math-flags (afn or reassoc).
    if (ExpoF->isNegative() && (!Pow->hasApproxFunc() && !Pow->hasAllowReassoc()))
      return nullptr;
  
    Sqrt = getSqrtCall(Base, Attrs, Pow->doesNotAccessMemory(), Mod, B, TLI);
    if (!Sqrt)
      return nullptr;
  
    // Handle signed zero base by expanding to fabs(sqrt(x)).
    if (!Pow->hasNoSignedZeros()) {
      Function *FAbsFn = Intrinsic::getDeclaration(Mod, Intrinsic::fabs, Ty);
      Sqrt = B.CreateCall(FAbsFn, Sqrt, "abs");
    }
  
    // Handle non finite base by expanding to
    // (x == -infinity ? +infinity : sqrt(x)).
    if (!Pow->hasNoInfs()) {
      Value *PosInf = ConstantFP::getInfinity(Ty),
            *NegInf = ConstantFP::getInfinity(Ty, true);
      Value *FCmp = B.CreateFCmpOEQ(Base, NegInf, "isinf");
      Sqrt = B.CreateSelect(FCmp, PosInf, Sqrt);
    }
  
    // If the exponent is negative, then get the reciprocal.
    if (ExpoF->isNegative())
      Sqrt = B.CreateFDiv(ConstantFP::get(Ty, 1.0), Sqrt, "reciprocal");
  
    return Sqrt;
  }
  
  static Value *createPowWithIntegerExponent(Value *Base, Value *Expo, Module *M,
                                             IRBuilder<> &B) {
    Value *Args[] = {Base, Expo};
    Function *F = Intrinsic::getDeclaration(M, Intrinsic::powi, Base->getType());
    return B.CreateCall(F, Args);
  }
  
  Value *LibCallSimplifier::optimizePow(CallInst *Pow, IRBuilder<> &B) {
    Value *Base = Pow->getArgOperand(0);
    Value *Expo = Pow->getArgOperand(1);
    Function *Callee = Pow->getCalledFunction();
    StringRef Name = Callee->getName();
    Type *Ty = Pow->getType();
    Module *M = Pow->getModule();
    Value *Shrunk = nullptr;
    bool AllowApprox = Pow->hasApproxFunc();
    bool Ignored;
  
    // Bail out if simplifying libcalls to pow() is disabled.
    if (!hasFloatFn(TLI, Ty, LibFunc_pow, LibFunc_powf, LibFunc_powl))
      return nullptr;
  
    // Propagate the math semantics from the call to any created instructions.
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(Pow->getFastMathFlags());
  
    // Shrink pow() to powf() if the arguments are single precision,
    // unless the result is expected to be double precision.
    if (UnsafeFPShrink && Name == TLI->getName(LibFunc_pow) &&
        hasFloatVersion(Name))
      Shrunk = optimizeBinaryDoubleFP(Pow, B, true);
  
    // Evaluate special cases related to the base.
  
    // pow(1.0, x) -> 1.0
    if (match(Base, m_FPOne()))
      return Base;
  
    if (Value *Exp = replacePowWithExp(Pow, B))
      return Exp;
  
    // Evaluate special cases related to the exponent.
  
    // pow(x, -1.0) -> 1.0 / x
    if (match(Expo, m_SpecificFP(-1.0)))
      return B.CreateFDiv(ConstantFP::get(Ty, 1.0), Base, "reciprocal");
  
    // pow(x, +/-0.0) -> 1.0
    if (match(Expo, m_AnyZeroFP()))
      return ConstantFP::get(Ty, 1.0);
  
    // pow(x, 1.0) -> x
    if (match(Expo, m_FPOne()))
      return Base;
  
    // pow(x, 2.0) -> x * x
    if (match(Expo, m_SpecificFP(2.0)))
      return B.CreateFMul(Base, Base, "square");
  
    if (Value *Sqrt = replacePowWithSqrt(Pow, B))
      return Sqrt;
  
    // pow(x, n) -> x * x * x * ...
    const APFloat *ExpoF;
    if (AllowApprox && match(Expo, m_APFloat(ExpoF))) {
      // We limit to a max of 7 multiplications, thus the maximum exponent is 32.
      // If the exponent is an integer+0.5 we generate a call to sqrt and an
      // additional fmul.
      // TODO: This whole transformation should be backend specific (e.g. some
      //       backends might prefer libcalls or the limit for the exponent might
      //       be different) and it should also consider optimizing for size.
      APFloat LimF(ExpoF->getSemantics(), 33),
              ExpoA(abs(*ExpoF));
      if (ExpoA.compare(LimF) == APFloat::cmpLessThan) {
        // This transformation applies to integer or integer+0.5 exponents only.
        // For integer+0.5, we create a sqrt(Base) call.
        Value *Sqrt = nullptr;
        if (!ExpoA.isInteger()) {
          APFloat Expo2 = ExpoA;
          // To check if ExpoA is an integer + 0.5, we add it to itself. If there
          // is no floating point exception and the result is an integer, then
          // ExpoA == integer + 0.5
          if (Expo2.add(ExpoA, APFloat::rmNearestTiesToEven) != APFloat::opOK)
            return nullptr;
  
          if (!Expo2.isInteger())
            return nullptr;
  
          Sqrt = getSqrtCall(Base, Pow->getCalledFunction()->getAttributes(),
                             Pow->doesNotAccessMemory(), M, B, TLI);
        }
  
        // We will memoize intermediate products of the Addition Chain.
        Value *InnerChain[33] = {nullptr};
        InnerChain[1] = Base;
        InnerChain[2] = B.CreateFMul(Base, Base, "square");
  
        // We cannot readily convert a non-double type (like float) to a double.
        // So we first convert it to something which could be converted to double.
        ExpoA.convert(APFloat::IEEEdouble(), APFloat::rmTowardZero, &Ignored);
        Value *FMul = getPow(InnerChain, ExpoA.convertToDouble(), B);
  
        // Expand pow(x, y+0.5) to pow(x, y) * sqrt(x).
        if (Sqrt)
          FMul = B.CreateFMul(FMul, Sqrt);
  
        // If the exponent is negative, then get the reciprocal.
        if (ExpoF->isNegative())
          FMul = B.CreateFDiv(ConstantFP::get(Ty, 1.0), FMul, "reciprocal");
  
        return FMul;
      }
  
      APSInt IntExpo(32, /*isUnsigned=*/false);
      // powf(x, n) -> powi(x, n) if n is a constant signed integer value
      if (ExpoF->isInteger() &&
          ExpoF->convertToInteger(IntExpo, APFloat::rmTowardZero, &Ignored) ==
              APFloat::opOK) {
        return createPowWithIntegerExponent(
            Base, ConstantInt::get(B.getInt32Ty(), IntExpo), M, B);
      }
    }
  
    // powf(x, itofp(y)) -> powi(x, y)
    if (AllowApprox && (isa<SIToFPInst>(Expo) || isa<UIToFPInst>(Expo))) {
      if (Value *ExpoI = getIntToFPVal(Expo, B))
        return createPowWithIntegerExponent(Base, ExpoI, M, B);
    }
  
    return Shrunk;
  }
  
  Value *LibCallSimplifier::optimizeExp2(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    StringRef Name = Callee->getName();
    Value *Ret = nullptr;
    if (UnsafeFPShrink && Name == TLI->getName(LibFunc_exp2) &&
        hasFloatVersion(Name))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    Type *Ty = CI->getType();
    Value *Op = CI->getArgOperand(0);
  
    // Turn exp2(sitofp(x)) -> ldexp(1.0, sext(x))  if sizeof(x) <= 32
    // Turn exp2(uitofp(x)) -> ldexp(1.0, zext(x))  if sizeof(x) < 32
    if ((isa<SIToFPInst>(Op) || isa<UIToFPInst>(Op)) &&
        hasFloatFn(TLI, Ty, LibFunc_ldexp, LibFunc_ldexpf, LibFunc_ldexpl)) {
      if (Value *Exp = getIntToFPVal(Op, B))
        return emitBinaryFloatFnCall(ConstantFP::get(Ty, 1.0), Exp, TLI,
                                     LibFunc_ldexp, LibFunc_ldexpf, LibFunc_ldexpl,
                                     B, CI->getCalledFunction()->getAttributes());
    }
  
    return Ret;
  }
  
  Value *LibCallSimplifier::optimizeFMinFMax(CallInst *CI, IRBuilder<> &B) {
    // If we can shrink the call to a float function rather than a double
    // function, do that first.
    Function *Callee = CI->getCalledFunction();
    StringRef Name = Callee->getName();
    if ((Name == "fmin" || Name == "fmax") && hasFloatVersion(Name))
      if (Value *Ret = optimizeBinaryDoubleFP(CI, B))
        return Ret;
  
    // The LLVM intrinsics minnum/maxnum correspond to fmin/fmax. Canonicalize to
    // the intrinsics for improved optimization (for example, vectorization).
    // No-signed-zeros is implied by the definitions of fmax/fmin themselves.
    // From the C standard draft WG14/N1256:
    // "Ideally, fmax would be sensitive to the sign of zero, for example
    // fmax(-0.0, +0.0) would return +0; however, implementation in software
    // might be impractical."
    IRBuilder<>::FastMathFlagGuard Guard(B);
    FastMathFlags FMF = CI->getFastMathFlags();
    FMF.setNoSignedZeros();
    B.setFastMathFlags(FMF);
  
    Intrinsic::ID IID = Callee->getName().startswith("fmin") ? Intrinsic::minnum
                                                             : Intrinsic::maxnum;
    Function *F = Intrinsic::getDeclaration(CI->getModule(), IID, CI->getType());
    return B.CreateCall(F, { CI->getArgOperand(0), CI->getArgOperand(1) });
  }
  
  Value *LibCallSimplifier::optimizeLog(CallInst *Log, IRBuilder<> &B) {
    Function *LogFn = Log->getCalledFunction();
    AttributeList Attrs = LogFn->getAttributes();
    StringRef LogNm = LogFn->getName();
    Intrinsic::ID LogID = LogFn->getIntrinsicID();
    Module *Mod = Log->getModule();
    Type *Ty = Log->getType();
    Value *Ret = nullptr;
  
    if (UnsafeFPShrink && hasFloatVersion(LogNm))
      Ret = optimizeUnaryDoubleFP(Log, B, true);
  
    // The earlier call must also be 'fast' in order to do these transforms.
    CallInst *Arg = dyn_cast<CallInst>(Log->getArgOperand(0));
    if (!Log->isFast() || !Arg || !Arg->isFast() || !Arg->hasOneUse())
      return Ret;
  
    LibFunc LogLb, ExpLb, Exp2Lb, Exp10Lb, PowLb;
  
    // This is only applicable to log(), log2(), log10().
    if (TLI->getLibFunc(LogNm, LogLb))
      switch (LogLb) {
      case LibFunc_logf:
        LogID = Intrinsic::log;
        ExpLb = LibFunc_expf;
        Exp2Lb = LibFunc_exp2f;
        Exp10Lb = LibFunc_exp10f;
        PowLb = LibFunc_powf;
        break;
      case LibFunc_log:
        LogID = Intrinsic::log;
        ExpLb = LibFunc_exp;
        Exp2Lb = LibFunc_exp2;
        Exp10Lb = LibFunc_exp10;
        PowLb = LibFunc_pow;
        break;
      case LibFunc_logl:
        LogID = Intrinsic::log;
        ExpLb = LibFunc_expl;
        Exp2Lb = LibFunc_exp2l;
        Exp10Lb = LibFunc_exp10l;
        PowLb = LibFunc_powl;
        break;
      case LibFunc_log2f:
        LogID = Intrinsic::log2;
        ExpLb = LibFunc_expf;
        Exp2Lb = LibFunc_exp2f;
        Exp10Lb = LibFunc_exp10f;
        PowLb = LibFunc_powf;
        break;
      case LibFunc_log2:
        LogID = Intrinsic::log2;
        ExpLb = LibFunc_exp;
        Exp2Lb = LibFunc_exp2;
        Exp10Lb = LibFunc_exp10;
        PowLb = LibFunc_pow;
        break;
      case LibFunc_log2l:
        LogID = Intrinsic::log2;
        ExpLb = LibFunc_expl;
        Exp2Lb = LibFunc_exp2l;
        Exp10Lb = LibFunc_exp10l;
        PowLb = LibFunc_powl;
        break;
      case LibFunc_log10f:
        LogID = Intrinsic::log10;
        ExpLb = LibFunc_expf;
        Exp2Lb = LibFunc_exp2f;
        Exp10Lb = LibFunc_exp10f;
        PowLb = LibFunc_powf;
        break;
      case LibFunc_log10:
        LogID = Intrinsic::log10;
        ExpLb = LibFunc_exp;
        Exp2Lb = LibFunc_exp2;
        Exp10Lb = LibFunc_exp10;
        PowLb = LibFunc_pow;
        break;
      case LibFunc_log10l:
        LogID = Intrinsic::log10;
        ExpLb = LibFunc_expl;
        Exp2Lb = LibFunc_exp2l;
        Exp10Lb = LibFunc_exp10l;
        PowLb = LibFunc_powl;
        break;
      default:
        return Ret;
      }
    else if (LogID == Intrinsic::log || LogID == Intrinsic::log2 ||
             LogID == Intrinsic::log10) {
      if (Ty->getScalarType()->isFloatTy()) {
        ExpLb = LibFunc_expf;
        Exp2Lb = LibFunc_exp2f;
        Exp10Lb = LibFunc_exp10f;
        PowLb = LibFunc_powf;
      } else if (Ty->getScalarType()->isDoubleTy()) {
        ExpLb = LibFunc_exp;
        Exp2Lb = LibFunc_exp2;
        Exp10Lb = LibFunc_exp10;
        PowLb = LibFunc_pow;
      } else
        return Ret;
    } else
      return Ret;
  
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(FastMathFlags::getFast());
  
    Intrinsic::ID ArgID = Arg->getIntrinsicID();
    LibFunc ArgLb = NotLibFunc;
    TLI->getLibFunc(Arg, ArgLb);
  
    // log(pow(x,y)) -> y*log(x)
    if (ArgLb == PowLb || ArgID == Intrinsic::pow) {
      Value *LogX =
          Log->doesNotAccessMemory()
              ? B.CreateCall(Intrinsic::getDeclaration(Mod, LogID, Ty),
                             Arg->getOperand(0), "log")
              : emitUnaryFloatFnCall(Arg->getOperand(0), LogNm, B, Attrs);
      Value *MulY = B.CreateFMul(Arg->getArgOperand(1), LogX, "mul");
      // Since pow() may have side effects, e.g. errno,
      // dead code elimination may not be trusted to remove it.
      substituteInParent(Arg, MulY);
      return MulY;
    }
  
    // log(exp{,2,10}(y)) -> y*log({e,2,10})
    // TODO: There is no exp10() intrinsic yet.
    if (ArgLb == ExpLb || ArgLb == Exp2Lb || ArgLb == Exp10Lb ||
             ArgID == Intrinsic::exp || ArgID == Intrinsic::exp2) {
      Constant *Eul;
      if (ArgLb == ExpLb || ArgID == Intrinsic::exp)
        // FIXME: Add more precise value of e for long double.
        Eul = ConstantFP::get(Log->getType(), numbers::e);
      else if (ArgLb == Exp2Lb || ArgID == Intrinsic::exp2)
        Eul = ConstantFP::get(Log->getType(), 2.0);
      else
        Eul = ConstantFP::get(Log->getType(), 10.0);
      Value *LogE = Log->doesNotAccessMemory()
                        ? B.CreateCall(Intrinsic::getDeclaration(Mod, LogID, Ty),
                                       Eul, "log")
                        : emitUnaryFloatFnCall(Eul, LogNm, B, Attrs);
      Value *MulY = B.CreateFMul(Arg->getArgOperand(0), LogE, "mul");
      // Since exp() may have side effects, e.g. errno,
      // dead code elimination may not be trusted to remove it.
      substituteInParent(Arg, MulY);
      return MulY;
    }
  
    return Ret;
  }
  
  Value *LibCallSimplifier::optimizeSqrt(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Ret = nullptr;
    // TODO: Once we have a way (other than checking for the existince of the
    // libcall) to tell whether our target can lower @llvm.sqrt, relax the
    // condition below.
    if (TLI->has(LibFunc_sqrtf) && (Callee->getName() == "sqrt" ||
                                    Callee->getIntrinsicID() == Intrinsic::sqrt))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    if (!CI->isFast())
      return Ret;
  
    Instruction *I = dyn_cast<Instruction>(CI->getArgOperand(0));
    if (!I || I->getOpcode() != Instruction::FMul || !I->isFast())
      return Ret;
  
    // We're looking for a repeated factor in a multiplication tree,
    // so we can do this fold: sqrt(x * x) -> fabs(x);
    // or this fold: sqrt((x * x) * y) -> fabs(x) * sqrt(y).
    Value *Op0 = I->getOperand(0);
    Value *Op1 = I->getOperand(1);
    Value *RepeatOp = nullptr;
    Value *OtherOp = nullptr;
    if (Op0 == Op1) {
      // Simple match: the operands of the multiply are identical.
      RepeatOp = Op0;
    } else {
      // Look for a more complicated pattern: one of the operands is itself
      // a multiply, so search for a common factor in that multiply.
      // Note: We don't bother looking any deeper than this first level or for
      // variations of this pattern because instcombine's visitFMUL and/or the
      // reassociation pass should give us this form.
      Value *OtherMul0, *OtherMul1;
      if (match(Op0, m_FMul(m_Value(OtherMul0), m_Value(OtherMul1)))) {
        // Pattern: sqrt((x * y) * z)
        if (OtherMul0 == OtherMul1 && cast<Instruction>(Op0)->isFast()) {
          // Matched: sqrt((x * x) * z)
          RepeatOp = OtherMul0;
          OtherOp = Op1;
        }
      }
    }
    if (!RepeatOp)
      return Ret;
  
    // Fast math flags for any created instructions should match the sqrt
    // and multiply.
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(I->getFastMathFlags());
  
    // If we found a repeated factor, hoist it out of the square root and
    // replace it with the fabs of that factor.
    Module *M = Callee->getParent();
    Type *ArgType = I->getType();
    Function *Fabs = Intrinsic::getDeclaration(M, Intrinsic::fabs, ArgType);
    Value *FabsCall = B.CreateCall(Fabs, RepeatOp, "fabs");
    if (OtherOp) {
      // If we found a non-repeated factor, we still need to get its square
      // root. We then multiply that by the value that was simplified out
      // of the square root calculation.
      Function *Sqrt = Intrinsic::getDeclaration(M, Intrinsic::sqrt, ArgType);
      Value *SqrtCall = B.CreateCall(Sqrt, OtherOp, "sqrt");
      return B.CreateFMul(FabsCall, SqrtCall);
    }
    return FabsCall;
  }
  
  // TODO: Generalize to handle any trig function and its inverse.
  Value *LibCallSimplifier::optimizeTan(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Ret = nullptr;
    StringRef Name = Callee->getName();
    if (UnsafeFPShrink && Name == "tan" && hasFloatVersion(Name))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    Value *Op1 = CI->getArgOperand(0);
    auto *OpC = dyn_cast<CallInst>(Op1);
    if (!OpC)
      return Ret;
  
    // Both calls must be 'fast' in order to remove them.
    if (!CI->isFast() || !OpC->isFast())
      return Ret;
  
    // tan(atan(x)) -> x
    // tanf(atanf(x)) -> x
    // tanl(atanl(x)) -> x
    LibFunc Func;
    Function *F = OpC->getCalledFunction();
    if (F && TLI->getLibFunc(F->getName(), Func) && TLI->has(Func) &&
        ((Func == LibFunc_atan && Callee->getName() == "tan") ||
         (Func == LibFunc_atanf && Callee->getName() == "tanf") ||
         (Func == LibFunc_atanl && Callee->getName() == "tanl")))
      Ret = OpC->getArgOperand(0);
    return Ret;
  }
  
  static bool isTrigLibCall(CallInst *CI) {
    // We can only hope to do anything useful if we can ignore things like errno
    // and floating-point exceptions.
    // We already checked the prototype.
    return CI->hasFnAttr(Attribute::NoUnwind) &&
           CI->hasFnAttr(Attribute::ReadNone);
  }
  
  static void insertSinCosCall(IRBuilder<> &B, Function *OrigCallee, Value *Arg,
                               bool UseFloat, Value *&Sin, Value *&Cos,
                               Value *&SinCos) {
    Type *ArgTy = Arg->getType();
    Type *ResTy;
    StringRef Name;
  
    Triple T(OrigCallee->getParent()->getTargetTriple());
    if (UseFloat) {
      Name = "__sincospif_stret";
  
      assert(T.getArch() != Triple::x86 && "x86 messy and unsupported for now");
      // x86_64 can't use {float, float} since that would be returned in both
      // xmm0 and xmm1, which isn't what a real struct would do.
      ResTy = T.getArch() == Triple::x86_64
                  ? static_cast<Type *>(VectorType::get(ArgTy, 2))
                  : static_cast<Type *>(StructType::get(ArgTy, ArgTy));
    } else {
      Name = "__sincospi_stret";
      ResTy = StructType::get(ArgTy, ArgTy);
    }
  
    Module *M = OrigCallee->getParent();
    FunctionCallee Callee =
        M->getOrInsertFunction(Name, OrigCallee->getAttributes(), ResTy, ArgTy);
  
    if (Instruction *ArgInst = dyn_cast<Instruction>(Arg)) {
      // If the argument is an instruction, it must dominate all uses so put our
      // sincos call there.
      B.SetInsertPoint(ArgInst->getParent(), ++ArgInst->getIterator());
    } else {
      // Otherwise (e.g. for a constant) the beginning of the function is as
      // good a place as any.
      BasicBlock &EntryBB = B.GetInsertBlock()->getParent()->getEntryBlock();
      B.SetInsertPoint(&EntryBB, EntryBB.begin());
    }
  
    SinCos = B.CreateCall(Callee, Arg, "sincospi");
  
    if (SinCos->getType()->isStructTy()) {
      Sin = B.CreateExtractValue(SinCos, 0, "sinpi");
      Cos = B.CreateExtractValue(SinCos, 1, "cospi");
    } else {
      Sin = B.CreateExtractElement(SinCos, ConstantInt::get(B.getInt32Ty(), 0),
                                   "sinpi");
      Cos = B.CreateExtractElement(SinCos, ConstantInt::get(B.getInt32Ty(), 1),
                                   "cospi");
    }
  }
  
  Value *LibCallSimplifier::optimizeSinCosPi(CallInst *CI, IRBuilder<> &B) {
    // Make sure the prototype is as expected, otherwise the rest of the
    // function is probably invalid and likely to abort.
    if (!isTrigLibCall(CI))
      return nullptr;
  
    Value *Arg = CI->getArgOperand(0);
    SmallVector<CallInst *, 1> SinCalls;
    SmallVector<CallInst *, 1> CosCalls;
    SmallVector<CallInst *, 1> SinCosCalls;
  
    bool IsFloat = Arg->getType()->isFloatTy();
  
    // Look for all compatible sinpi, cospi and sincospi calls with the same
    // argument. If there are enough (in some sense) we can make the
    // substitution.
    Function *F = CI->getFunction();
    for (User *U : Arg->users())
      classifyArgUse(U, F, IsFloat, SinCalls, CosCalls, SinCosCalls);
  
    // It's only worthwhile if both sinpi and cospi are actually used.
    if (SinCosCalls.empty() && (SinCalls.empty() || CosCalls.empty()))
      return nullptr;
  
    Value *Sin, *Cos, *SinCos;
    insertSinCosCall(B, CI->getCalledFunction(), Arg, IsFloat, Sin, Cos, SinCos);
  
    auto replaceTrigInsts = [this](SmallVectorImpl<CallInst *> &Calls,
                                   Value *Res) {
      for (CallInst *C : Calls)
        replaceAllUsesWith(C, Res);
    };
  
    replaceTrigInsts(SinCalls, Sin);
    replaceTrigInsts(CosCalls, Cos);
    replaceTrigInsts(SinCosCalls, SinCos);
  
    return nullptr;
  }
  
  void LibCallSimplifier::classifyArgUse(
      Value *Val, Function *F, bool IsFloat,
      SmallVectorImpl<CallInst *> &SinCalls,
      SmallVectorImpl<CallInst *> &CosCalls,
      SmallVectorImpl<CallInst *> &SinCosCalls) {
    CallInst *CI = dyn_cast<CallInst>(Val);
  
    if (!CI)
      return;
  
    // Don't consider calls in other functions.
    if (CI->getFunction() != F)
      return;
  
    Function *Callee = CI->getCalledFunction();
    LibFunc Func;
    if (!Callee || !TLI->getLibFunc(*Callee, Func) || !TLI->has(Func) ||
        !isTrigLibCall(CI))
      return;
  
    if (IsFloat) {
      if (Func == LibFunc_sinpif)
        SinCalls.push_back(CI);
      else if (Func == LibFunc_cospif)
        CosCalls.push_back(CI);
      else if (Func == LibFunc_sincospif_stret)
        SinCosCalls.push_back(CI);
    } else {
      if (Func == LibFunc_sinpi)
        SinCalls.push_back(CI);
      else if (Func == LibFunc_cospi)
        CosCalls.push_back(CI);
      else if (Func == LibFunc_sincospi_stret)
        SinCosCalls.push_back(CI);
    }
  }
  
  //===----------------------------------------------------------------------===//
  // Integer Library Call Optimizations
  //===----------------------------------------------------------------------===//
  
  Value *LibCallSimplifier::optimizeFFS(CallInst *CI, IRBuilder<> &B) {
    // ffs(x) -> x != 0 ? (i32)llvm.cttz(x)+1 : 0
    Value *Op = CI->getArgOperand(0);
    Type *ArgType = Op->getType();
    Function *F = Intrinsic::getDeclaration(CI->getCalledFunction()->getParent(),
                                            Intrinsic::cttz, ArgType);
    Value *V = B.CreateCall(F, {Op, B.getTrue()}, "cttz");
    V = B.CreateAdd(V, ConstantInt::get(V->getType(), 1));
    V = B.CreateIntCast(V, B.getInt32Ty(), false);
  
    Value *Cond = B.CreateICmpNE(Op, Constant::getNullValue(ArgType));
    return B.CreateSelect(Cond, V, B.getInt32(0));
  }
  
  Value *LibCallSimplifier::optimizeFls(CallInst *CI, IRBuilder<> &B) {
    // fls(x) -> (i32)(sizeInBits(x) - llvm.ctlz(x, false))
    Value *Op = CI->getArgOperand(0);
    Type *ArgType = Op->getType();
    Function *F = Intrinsic::getDeclaration(CI->getCalledFunction()->getParent(),
                                            Intrinsic::ctlz, ArgType);
    Value *V = B.CreateCall(F, {Op, B.getFalse()}, "ctlz");
    V = B.CreateSub(ConstantInt::get(V->getType(), ArgType->getIntegerBitWidth()),
                    V);
    return B.CreateIntCast(V, CI->getType(), false);
  }
  
  Value *LibCallSimplifier::optimizeAbs(CallInst *CI, IRBuilder<> &B) {
    // abs(x) -> x <s 0 ? -x : x
    // The negation has 'nsw' because abs of INT_MIN is undefined.
    Value *X = CI->getArgOperand(0);
    Value *IsNeg = B.CreateICmpSLT(X, Constant::getNullValue(X->getType()));
    Value *NegX = B.CreateNSWNeg(X, "neg");
    return B.CreateSelect(IsNeg, NegX, X);
  }
  
  Value *LibCallSimplifier::optimizeIsDigit(CallInst *CI, IRBuilder<> &B) {
    // isdigit(c) -> (c-'0') <u 10
    Value *Op = CI->getArgOperand(0);
    Op = B.CreateSub(Op, B.getInt32('0'), "isdigittmp");
    Op = B.CreateICmpULT(Op, B.getInt32(10), "isdigit");
    return B.CreateZExt(Op, CI->getType());
  }
  
  Value *LibCallSimplifier::optimizeIsAscii(CallInst *CI, IRBuilder<> &B) {
    // isascii(c) -> c <u 128
    Value *Op = CI->getArgOperand(0);
    Op = B.CreateICmpULT(Op, B.getInt32(128), "isascii");
    return B.CreateZExt(Op, CI->getType());
  }
  
  Value *LibCallSimplifier::optimizeToAscii(CallInst *CI, IRBuilder<> &B) {
    // toascii(c) -> c & 0x7f
    return B.CreateAnd(CI->getArgOperand(0),
                       ConstantInt::get(CI->getType(), 0x7F));
  }
  
  Value *LibCallSimplifier::optimizeAtoi(CallInst *CI, IRBuilder<> &B) {
    StringRef Str;
    if (!getConstantStringInfo(CI->getArgOperand(0), Str))
      return nullptr;
  
    return convertStrToNumber(CI, Str, 10);
  }
  
  Value *LibCallSimplifier::optimizeStrtol(CallInst *CI, IRBuilder<> &B) {
    StringRef Str;
    if (!getConstantStringInfo(CI->getArgOperand(0), Str))
      return nullptr;
  
    if (!isa<ConstantPointerNull>(CI->getArgOperand(1)))
      return nullptr;
  
    if (ConstantInt *CInt = dyn_cast<ConstantInt>(CI->getArgOperand(2))) {
      return convertStrToNumber(CI, Str, CInt->getSExtValue());
    }
  
    return nullptr;
  }
  
  //===----------------------------------------------------------------------===//
  // Formatting and IO Library Call Optimizations
  //===----------------------------------------------------------------------===//
  
  static bool isReportingError(Function *Callee, CallInst *CI, int StreamArg);
  
  Value *LibCallSimplifier::optimizeErrorReporting(CallInst *CI, IRBuilder<> &B,
                                                   int StreamArg) {
    Function *Callee = CI->getCalledFunction();
    // Error reporting calls should be cold, mark them as such.
    // This applies even to non-builtin calls: it is only a hint and applies to
    // functions that the frontend might not understand as builtins.
  
    // This heuristic was suggested in:
    // Improving Static Branch Prediction in a Compiler
    // Brian L. Deitrich, Ben-Chung Cheng, Wen-mei W. Hwu
    // Proceedings of PACT'98, Oct. 1998, IEEE
    if (!CI->hasFnAttr(Attribute::Cold) &&
        isReportingError(Callee, CI, StreamArg)) {
      CI->addAttribute(AttributeList::FunctionIndex, Attribute::Cold);
    }
  
    return nullptr;
  }
  
  static bool isReportingError(Function *Callee, CallInst *CI, int StreamArg) {
    if (!Callee || !Callee->isDeclaration())
      return false;
  
    if (StreamArg < 0)
      return true;
  
    // These functions might be considered cold, but only if their stream
    // argument is stderr.
  
    if (StreamArg >= (int)CI->getNumArgOperands())
      return false;
    LoadInst *LI = dyn_cast<LoadInst>(CI->getArgOperand(StreamArg));
    if (!LI)
      return false;
    GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getPointerOperand());
    if (!GV || !GV->isDeclaration())
      return false;
    return GV->getName() == "stderr";
  }
  
  Value *LibCallSimplifier::optimizePrintFString(CallInst *CI, IRBuilder<> &B) {
    // Check for a fixed format string.
    StringRef FormatStr;
    if (!getConstantStringInfo(CI->getArgOperand(0), FormatStr))
      return nullptr;
  
    // Empty format string -> noop.
    if (FormatStr.empty()) // Tolerate printf's declared void.
      return CI->use_empty() ? (Value *)CI : ConstantInt::get(CI->getType(), 0);
  
    // Do not do any of the following transformations if the printf return value
    // is used, in general the printf return value is not compatible with either
    // putchar() or puts().
    if (!CI->use_empty())
      return nullptr;
  
    // printf("x") -> putchar('x'), even for "%" and "%%".
    if (FormatStr.size() == 1 || FormatStr == "%%")
      return emitPutChar(B.getInt32(FormatStr[0]), B, TLI);
  
    // printf("%s", "a") --> putchar('a')
    if (FormatStr == "%s" && CI->getNumArgOperands() > 1) {
      StringRef ChrStr;
      if (!getConstantStringInfo(CI->getOperand(1), ChrStr))
        return nullptr;
      if (ChrStr.size() != 1)
        return nullptr;
      return emitPutChar(B.getInt32(ChrStr[0]), B, TLI);
    }
  
    // printf("foo\n") --> puts("foo")
    if (FormatStr[FormatStr.size() - 1] == '\n' &&
        FormatStr.find('%') == StringRef::npos) { // No format characters.
      // Create a string literal with no \n on it.  We expect the constant merge
      // pass to be run after this pass, to merge duplicate strings.
      FormatStr = FormatStr.drop_back();
      Value *GV = B.CreateGlobalString(FormatStr, "str");
      return emitPutS(GV, B, TLI);
    }
  
    // Optimize specific format strings.
    // printf("%c", chr) --> putchar(chr)
    if (FormatStr == "%c" && CI->getNumArgOperands() > 1 &&
        CI->getArgOperand(1)->getType()->isIntegerTy())
      return emitPutChar(CI->getArgOperand(1), B, TLI);
  
    // printf("%s\n", str) --> puts(str)
    if (FormatStr == "%s\n" && CI->getNumArgOperands() > 1 &&
        CI->getArgOperand(1)->getType()->isPointerTy())
      return emitPutS(CI->getArgOperand(1), B, TLI);
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizePrintF(CallInst *CI, IRBuilder<> &B) {
  
    Function *Callee = CI->getCalledFunction();
    FunctionType *FT = Callee->getFunctionType();
    if (Value *V = optimizePrintFString(CI, B)) {
      return V;
    }
  
    // printf(format, ...) -> iprintf(format, ...) if no floating point
    // arguments.
    if (TLI->has(LibFunc_iprintf) && !callHasFloatingPointArgument(CI)) {
      Module *M = B.GetInsertBlock()->getParent()->getParent();
      FunctionCallee IPrintFFn =
          M->getOrInsertFunction("iprintf", FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(IPrintFFn);
      B.Insert(New);
      return New;
    }
  
    // printf(format, ...) -> __small_printf(format, ...) if no 128-bit floating point
    // arguments.
    if (TLI->has(LibFunc_small_printf) && !callHasFP128Argument(CI)) {
      Module *M = B.GetInsertBlock()->getParent()->getParent();
      auto SmallPrintFFn =
          M->getOrInsertFunction(TLI->getName(LibFunc_small_printf),
                                 FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(SmallPrintFFn);
      B.Insert(New);
      return New;
    }
  
    annotateNonNullBasedOnAccess(CI, 0);
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeSPrintFString(CallInst *CI, IRBuilder<> &B) {
    // Check for a fixed format string.
    StringRef FormatStr;
    if (!getConstantStringInfo(CI->getArgOperand(1), FormatStr))
      return nullptr;
  
    // If we just have a format string (nothing else crazy) transform it.
    if (CI->getNumArgOperands() == 2) {
      // Make sure there's no % in the constant array.  We could try to handle
      // %% -> % in the future if we cared.
      if (FormatStr.find('%') != StringRef::npos)
        return nullptr; // we found a format specifier, bail out.
  
      // sprintf(str, fmt) -> llvm.memcpy(align 1 str, align 1 fmt, strlen(fmt)+1)
      B.CreateMemCpy(
          CI->getArgOperand(0), Align(1), CI->getArgOperand(1), Align(1),
          ConstantInt::get(DL.getIntPtrType(CI->getContext()),
                           FormatStr.size() + 1)); // Copy the null byte.
      return ConstantInt::get(CI->getType(), FormatStr.size());
    }
  
    // The remaining optimizations require the format string to be "%s" or "%c"
    // and have an extra operand.
    if (FormatStr.size() != 2 || FormatStr[0] != '%' ||
        CI->getNumArgOperands() < 3)
      return nullptr;
  
    // Decode the second character of the format string.
    if (FormatStr[1] == 'c') {
      // sprintf(dst, "%c", chr) --> *(i8*)dst = chr; *((i8*)dst+1) = 0
      if (!CI->getArgOperand(2)->getType()->isIntegerTy())
        return nullptr;
      Value *V = B.CreateTrunc(CI->getArgOperand(2), B.getInt8Ty(), "char");
      Value *Ptr = castToCStr(CI->getArgOperand(0), B);
      B.CreateStore(V, Ptr);
      Ptr = B.CreateGEP(B.getInt8Ty(), Ptr, B.getInt32(1), "nul");
      B.CreateStore(B.getInt8(0), Ptr);
  
      return ConstantInt::get(CI->getType(), 1);
    }
  
    if (FormatStr[1] == 's') {
      // sprintf(dest, "%s", str) -> llvm.memcpy(align 1 dest, align 1 str,
      // strlen(str)+1)
      if (!CI->getArgOperand(2)->getType()->isPointerTy())
        return nullptr;
  
      Value *Len = emitStrLen(CI->getArgOperand(2), B, DL, TLI);
      if (!Len)
        return nullptr;
      Value *IncLen =
          B.CreateAdd(Len, ConstantInt::get(Len->getType(), 1), "leninc");
      B.CreateMemCpy(CI->getArgOperand(0), Align(1), CI->getArgOperand(2),
                     Align(1), IncLen);
  
      // The sprintf result is the unincremented number of bytes in the string.
      return B.CreateIntCast(Len, CI->getType(), false);
    }
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeSPrintF(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    FunctionType *FT = Callee->getFunctionType();
    if (Value *V = optimizeSPrintFString(CI, B)) {
      return V;
    }
  
    // sprintf(str, format, ...) -> siprintf(str, format, ...) if no floating
    // point arguments.
    if (TLI->has(LibFunc_siprintf) && !callHasFloatingPointArgument(CI)) {
      Module *M = B.GetInsertBlock()->getParent()->getParent();
      FunctionCallee SIPrintFFn =
          M->getOrInsertFunction("siprintf", FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(SIPrintFFn);
      B.Insert(New);
      return New;
    }
  
    // sprintf(str, format, ...) -> __small_sprintf(str, format, ...) if no 128-bit
    // floating point arguments.
    if (TLI->has(LibFunc_small_sprintf) && !callHasFP128Argument(CI)) {
      Module *M = B.GetInsertBlock()->getParent()->getParent();
      auto SmallSPrintFFn =
          M->getOrInsertFunction(TLI->getName(LibFunc_small_sprintf),
                                 FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(SmallSPrintFFn);
      B.Insert(New);
      return New;
    }
  
    annotateNonNullBasedOnAccess(CI, {0, 1});
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeSnPrintFString(CallInst *CI, IRBuilder<> &B) {
    // Check for size
    ConstantInt *Size = dyn_cast<ConstantInt>(CI->getArgOperand(1));
    if (!Size)
      return nullptr;
  
    uint64_t N = Size->getZExtValue();
    // Check for a fixed format string.
    StringRef FormatStr;
    if (!getConstantStringInfo(CI->getArgOperand(2), FormatStr))
      return nullptr;
  
    // If we just have a format string (nothing else crazy) transform it.
    if (CI->getNumArgOperands() == 3) {
      // Make sure there's no % in the constant array.  We could try to handle
      // %% -> % in the future if we cared.
      if (FormatStr.find('%') != StringRef::npos)
        return nullptr; // we found a format specifier, bail out.
  
      if (N == 0)
        return ConstantInt::get(CI->getType(), FormatStr.size());
      else if (N < FormatStr.size() + 1)
        return nullptr;
  
      // snprintf(dst, size, fmt) -> llvm.memcpy(align 1 dst, align 1 fmt,
      // strlen(fmt)+1)
      B.CreateMemCpy(
          CI->getArgOperand(0), Align(1), CI->getArgOperand(2), Align(1),
          ConstantInt::get(DL.getIntPtrType(CI->getContext()),
                           FormatStr.size() + 1)); // Copy the null byte.
      return ConstantInt::get(CI->getType(), FormatStr.size());
    }
  
    // The remaining optimizations require the format string to be "%s" or "%c"
    // and have an extra operand.
    if (FormatStr.size() == 2 && FormatStr[0] == '%' &&
        CI->getNumArgOperands() == 4) {
  
      // Decode the second character of the format string.
      if (FormatStr[1] == 'c') {
        if (N == 0)
          return ConstantInt::get(CI->getType(), 1);
        else if (N == 1)
          return nullptr;
  
        // snprintf(dst, size, "%c", chr) --> *(i8*)dst = chr; *((i8*)dst+1) = 0
        if (!CI->getArgOperand(3)->getType()->isIntegerTy())
          return nullptr;
        Value *V = B.CreateTrunc(CI->getArgOperand(3), B.getInt8Ty(), "char");
        Value *Ptr = castToCStr(CI->getArgOperand(0), B);
        B.CreateStore(V, Ptr);
        Ptr = B.CreateGEP(B.getInt8Ty(), Ptr, B.getInt32(1), "nul");
        B.CreateStore(B.getInt8(0), Ptr);
  
        return ConstantInt::get(CI->getType(), 1);
      }
  
      if (FormatStr[1] == 's') {
        // snprintf(dest, size, "%s", str) to llvm.memcpy(dest, str, len+1, 1)
        StringRef Str;
        if (!getConstantStringInfo(CI->getArgOperand(3), Str))
          return nullptr;
  
        if (N == 0)
          return ConstantInt::get(CI->getType(), Str.size());
        else if (N < Str.size() + 1)
          return nullptr;
  
        B.CreateMemCpy(CI->getArgOperand(0), Align(1), CI->getArgOperand(3),
                       Align(1), ConstantInt::get(CI->getType(), Str.size() + 1));
  
        // The snprintf result is the unincremented number of bytes in the string.
        return ConstantInt::get(CI->getType(), Str.size());
      }
    }
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeSnPrintF(CallInst *CI, IRBuilder<> &B) {
    if (Value *V = optimizeSnPrintFString(CI, B)) {
      return V;
    }
  
    if (isKnownNonZero(CI->getOperand(1), DL))
      annotateNonNullBasedOnAccess(CI, 0);
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFPrintFString(CallInst *CI, IRBuilder<> &B) {
    optimizeErrorReporting(CI, B, 0);
  
    // All the optimizations depend on the format string.
    StringRef FormatStr;
    if (!getConstantStringInfo(CI->getArgOperand(1), FormatStr))
      return nullptr;
  
    // Do not do any of the following transformations if the fprintf return
    // value is used, in general the fprintf return value is not compatible
    // with fwrite(), fputc() or fputs().
    if (!CI->use_empty())
      return nullptr;
  
    // fprintf(F, "foo") --> fwrite("foo", 3, 1, F)
    if (CI->getNumArgOperands() == 2) {
      // Could handle %% -> % if we cared.
      if (FormatStr.find('%') != StringRef::npos)
        return nullptr; // We found a format specifier.
  
      return emitFWrite(
          CI->getArgOperand(1),
          ConstantInt::get(DL.getIntPtrType(CI->getContext()), FormatStr.size()),
          CI->getArgOperand(0), B, DL, TLI);
    }
  
    // The remaining optimizations require the format string to be "%s" or "%c"
    // and have an extra operand.
    if (FormatStr.size() != 2 || FormatStr[0] != '%' ||
        CI->getNumArgOperands() < 3)
      return nullptr;
  
    // Decode the second character of the format string.
    if (FormatStr[1] == 'c') {
      // fprintf(F, "%c", chr) --> fputc(chr, F)
      if (!CI->getArgOperand(2)->getType()->isIntegerTy())
        return nullptr;
      return emitFPutC(CI->getArgOperand(2), CI->getArgOperand(0), B, TLI);
    }
  
    if (FormatStr[1] == 's') {
      // fprintf(F, "%s", str) --> fputs(str, F)
      if (!CI->getArgOperand(2)->getType()->isPointerTy())
        return nullptr;
      return emitFPutS(CI->getArgOperand(2), CI->getArgOperand(0), B, TLI);
    }
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFPrintF(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    FunctionType *FT = Callee->getFunctionType();
    if (Value *V = optimizeFPrintFString(CI, B)) {
      return V;
    }
  
    // fprintf(stream, format, ...) -> fiprintf(stream, format, ...) if no
    // floating point arguments.
    if (TLI->has(LibFunc_fiprintf) && !callHasFloatingPointArgument(CI)) {
      Module *M = B.GetInsertBlock()->getParent()->getParent();
      FunctionCallee FIPrintFFn =
          M->getOrInsertFunction("fiprintf", FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(FIPrintFFn);
      B.Insert(New);
      return New;
    }
  
    // fprintf(stream, format, ...) -> __small_fprintf(stream, format, ...) if no
    // 128-bit floating point arguments.
    if (TLI->has(LibFunc_small_fprintf) && !callHasFP128Argument(CI)) {
      Module *M = B.GetInsertBlock()->getParent()->getParent();
      auto SmallFPrintFFn =
          M->getOrInsertFunction(TLI->getName(LibFunc_small_fprintf),
                                 FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(SmallFPrintFFn);
      B.Insert(New);
      return New;
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFWrite(CallInst *CI, IRBuilder<> &B) {
    optimizeErrorReporting(CI, B, 3);
  
    // Get the element size and count.
    ConstantInt *SizeC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
    ConstantInt *CountC = dyn_cast<ConstantInt>(CI->getArgOperand(2));
    if (SizeC && CountC) {
      uint64_t Bytes = SizeC->getZExtValue() * CountC->getZExtValue();
  
      // If this is writing zero records, remove the call (it's a noop).
      if (Bytes == 0)
        return ConstantInt::get(CI->getType(), 0);
  
      // If this is writing one byte, turn it into fputc.
      // This optimisation is only valid, if the return value is unused.
      if (Bytes == 1 && CI->use_empty()) { // fwrite(S,1,1,F) -> fputc(S[0],F)
        Value *Char = B.CreateLoad(B.getInt8Ty(),
                                   castToCStr(CI->getArgOperand(0), B), "char");
        Value *NewCI = emitFPutC(Char, CI->getArgOperand(3), B, TLI);
        return NewCI ? ConstantInt::get(CI->getType(), 1) : nullptr;
      }
    }
  
    if (isLocallyOpenedFile(CI->getArgOperand(3), CI, TLI))
      return emitFWriteUnlocked(CI->getArgOperand(0), CI->getArgOperand(1),
                                CI->getArgOperand(2), CI->getArgOperand(3), B, DL,
                                TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFPuts(CallInst *CI, IRBuilder<> &B) {
    optimizeErrorReporting(CI, B, 1);
  
    // Don't rewrite fputs to fwrite when optimising for size because fwrite
    // requires more arguments and thus extra MOVs are required.
    bool OptForSize = CI->getFunction()->hasOptSize() ||
                      llvm::shouldOptimizeForSize(CI->getParent(), PSI, BFI,
                                                  PGSOQueryType::IRPass);
    if (OptForSize)
      return nullptr;
  
    // Check if has any use
    if (!CI->use_empty()) {
      if (isLocallyOpenedFile(CI->getArgOperand(1), CI, TLI))
        return emitFPutSUnlocked(CI->getArgOperand(0), CI->getArgOperand(1), B,
                                 TLI);
      else
        // We can't optimize if return value is used.
        return nullptr;
    }
  
    // fputs(s,F) --> fwrite(s,strlen(s),1,F)
    uint64_t Len = GetStringLength(CI->getArgOperand(0));
    if (!Len)
      return nullptr;
  
    // Known to have no uses (see above).
    return emitFWrite(
        CI->getArgOperand(0),
        ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len - 1),
        CI->getArgOperand(1), B, DL, TLI);
  }
  
  Value *LibCallSimplifier::optimizeFPutc(CallInst *CI, IRBuilder<> &B) {
    optimizeErrorReporting(CI, B, 1);
  
    if (isLocallyOpenedFile(CI->getArgOperand(1), CI, TLI))
      return emitFPutCUnlocked(CI->getArgOperand(0), CI->getArgOperand(1), B,
                               TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFGetc(CallInst *CI, IRBuilder<> &B) {
    if (isLocallyOpenedFile(CI->getArgOperand(0), CI, TLI))
      return emitFGetCUnlocked(CI->getArgOperand(0), B, TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFGets(CallInst *CI, IRBuilder<> &B) {
    if (isLocallyOpenedFile(CI->getArgOperand(2), CI, TLI))
      return emitFGetSUnlocked(CI->getArgOperand(0), CI->getArgOperand(1),
                               CI->getArgOperand(2), B, TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFRead(CallInst *CI, IRBuilder<> &B) {
    if (isLocallyOpenedFile(CI->getArgOperand(3), CI, TLI))
      return emitFReadUnlocked(CI->getArgOperand(0), CI->getArgOperand(1),
                               CI->getArgOperand(2), CI->getArgOperand(3), B, DL,
                               TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizePuts(CallInst *CI, IRBuilder<> &B) {
    annotateNonNullBasedOnAccess(CI, 0);
    if (!CI->use_empty())
      return nullptr;
  
    // Check for a constant string.
    // puts("") -> putchar('\n')
    StringRef Str;
    if (getConstantStringInfo(CI->getArgOperand(0), Str) && Str.empty())
      return emitPutChar(B.getInt32('\n'), B, TLI);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeBCopy(CallInst *CI, IRBuilder<> &B) {
    // bcopy(src, dst, n) -> llvm.memmove(dst, src, n)
    return B.CreateMemMove(CI->getArgOperand(1), Align(1), CI->getArgOperand(0),
                           Align(1), CI->getArgOperand(2));
  }
  
  bool LibCallSimplifier::hasFloatVersion(StringRef FuncName) {
    LibFunc Func;
    SmallString<20> FloatFuncName = FuncName;
    FloatFuncName += 'f';
    if (TLI->getLibFunc(FloatFuncName, Func))
      return TLI->has(Func);
    return false;
  }
  
  Value *LibCallSimplifier::optimizeStringMemoryLibCall(CallInst *CI,
                                                        IRBuilder<> &Builder) {
    LibFunc Func;
    Function *Callee = CI->getCalledFunction();
    // Check for string/memory library functions.
    if (TLI->getLibFunc(*Callee, Func) && TLI->has(Func)) {
      // Make sure we never change the calling convention.
      assert((ignoreCallingConv(Func) ||
              isCallingConvCCompatible(CI)) &&
        "Optimizing string/memory libcall would change the calling convention");
      switch (Func) {
      case LibFunc_strcat:
        return optimizeStrCat(CI, Builder);
      case LibFunc_strncat:
        return optimizeStrNCat(CI, Builder);
      case LibFunc_strchr:
        return optimizeStrChr(CI, Builder);
      case LibFunc_strrchr:
        return optimizeStrRChr(CI, Builder);
      case LibFunc_strcmp:
        return optimizeStrCmp(CI, Builder);
      case LibFunc_strncmp:
        return optimizeStrNCmp(CI, Builder);
      case LibFunc_strcpy:
        return optimizeStrCpy(CI, Builder);
      case LibFunc_stpcpy:
        return optimizeStpCpy(CI, Builder);
      case LibFunc_strncpy:
        return optimizeStrNCpy(CI, Builder);
      case LibFunc_strlen:
        return optimizeStrLen(CI, Builder);
      case LibFunc_strpbrk:
        return optimizeStrPBrk(CI, Builder);
      case LibFunc_strndup:
        return optimizeStrNDup(CI, Builder);
      case LibFunc_strtol:
      case LibFunc_strtod:
      case LibFunc_strtof:
      case LibFunc_strtoul:
      case LibFunc_strtoll:
      case LibFunc_strtold:
      case LibFunc_strtoull:
        return optimizeStrTo(CI, Builder);
      case LibFunc_strspn:
        return optimizeStrSpn(CI, Builder);
      case LibFunc_strcspn:
        return optimizeStrCSpn(CI, Builder);
      case LibFunc_strstr:
        return optimizeStrStr(CI, Builder);
      case LibFunc_memchr:
        return optimizeMemChr(CI, Builder);
      case LibFunc_memrchr:
        return optimizeMemRChr(CI, Builder);
      case LibFunc_bcmp:
        return optimizeBCmp(CI, Builder);
      case LibFunc_memcmp:
        return optimizeMemCmp(CI, Builder);
      case LibFunc_memcpy:
        return optimizeMemCpy(CI, Builder);
      case LibFunc_memccpy:
        return optimizeMemCCpy(CI, Builder);
      case LibFunc_mempcpy:
        return optimizeMemPCpy(CI, Builder);
      case LibFunc_memmove:
        return optimizeMemMove(CI, Builder);
      case LibFunc_memset:
        return optimizeMemSet(CI, Builder);
      case LibFunc_realloc:
        return optimizeRealloc(CI, Builder);
      case LibFunc_wcslen:
        return optimizeWcslen(CI, Builder);
      case LibFunc_bcopy:
        return optimizeBCopy(CI, Builder);
      default:
        break;
      }
    }
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFloatingPointLibCall(CallInst *CI,
                                                         LibFunc Func,
                                                         IRBuilder<> &Builder) {
    // Don't optimize calls that require strict floating point semantics.
    if (CI->isStrictFP())
      return nullptr;
  
    if (Value *V = optimizeTrigReflections(CI, Func, Builder))
      return V;
  
    switch (Func) {
    case LibFunc_sinpif:
    case LibFunc_sinpi:
    case LibFunc_cospif:
    case LibFunc_cospi:
      return optimizeSinCosPi(CI, Builder);
    case LibFunc_powf:
    case LibFunc_pow:
    case LibFunc_powl:
      return optimizePow(CI, Builder);
    case LibFunc_exp2l:
    case LibFunc_exp2:
    case LibFunc_exp2f:
      return optimizeExp2(CI, Builder);
    case LibFunc_fabsf:
    case LibFunc_fabs:
    case LibFunc_fabsl:
      return replaceUnaryCall(CI, Builder, Intrinsic::fabs);
    case LibFunc_sqrtf:
    case LibFunc_sqrt:
    case LibFunc_sqrtl:
      return optimizeSqrt(CI, Builder);
    case LibFunc_logf:
    case LibFunc_log:
    case LibFunc_logl:
    case LibFunc_log10f:
    case LibFunc_log10:
    case LibFunc_log10l:
    case LibFunc_log1pf:
    case LibFunc_log1p:
    case LibFunc_log1pl:
    case LibFunc_log2f:
    case LibFunc_log2:
    case LibFunc_log2l:
    case LibFunc_logbf:
    case LibFunc_logb:
    case LibFunc_logbl:
      return optimizeLog(CI, Builder);
    case LibFunc_tan:
    case LibFunc_tanf:
    case LibFunc_tanl:
      return optimizeTan(CI, Builder);
    case LibFunc_ceil:
      return replaceUnaryCall(CI, Builder, Intrinsic::ceil);
    case LibFunc_floor:
      return replaceUnaryCall(CI, Builder, Intrinsic::floor);
    case LibFunc_round:
      return replaceUnaryCall(CI, Builder, Intrinsic::round);
    case LibFunc_nearbyint:
      return replaceUnaryCall(CI, Builder, Intrinsic::nearbyint);
    case LibFunc_rint:
      return replaceUnaryCall(CI, Builder, Intrinsic::rint);
    case LibFunc_trunc:
      return replaceUnaryCall(CI, Builder, Intrinsic::trunc);
    case LibFunc_acos:
    case LibFunc_acosh:
    case LibFunc_asin:
    case LibFunc_asinh:
    case LibFunc_atan:
    case LibFunc_atanh:
    case LibFunc_cbrt:
    case LibFunc_cosh:
    case LibFunc_exp:
    case LibFunc_exp10:
    case LibFunc_expm1:
    case LibFunc_cos:
    case LibFunc_sin:
    case LibFunc_sinh:
    case LibFunc_tanh:
      if (UnsafeFPShrink && hasFloatVersion(CI->getCalledFunction()->getName()))
        return optimizeUnaryDoubleFP(CI, Builder, true);
      return nullptr;
    case LibFunc_copysign:
      if (hasFloatVersion(CI->getCalledFunction()->getName()))
        return optimizeBinaryDoubleFP(CI, Builder);
      return nullptr;
    case LibFunc_fminf:
    case LibFunc_fmin:
    case LibFunc_fminl:
    case LibFunc_fmaxf:
    case LibFunc_fmax:
    case LibFunc_fmaxl:
      return optimizeFMinFMax(CI, Builder);
    case LibFunc_cabs:
    case LibFunc_cabsf:
    case LibFunc_cabsl:
      return optimizeCAbs(CI, Builder);
    default:
      return nullptr;
    }
  }
  
  Value *LibCallSimplifier::optimizeCall(CallInst *CI) {
    // TODO: Split out the code below that operates on FP calls so that
    //       we can all non-FP calls with the StrictFP attribute to be
    //       optimized.
    if (CI->isNoBuiltin())
      return nullptr;
  
    LibFunc Func;
    Function *Callee = CI->getCalledFunction();
  
    SmallVector<OperandBundleDef, 2> OpBundles;
    CI->getOperandBundlesAsDefs(OpBundles);
    IRBuilder<> Builder(CI, /*FPMathTag=*/nullptr, OpBundles);
    bool isCallingConvC = isCallingConvCCompatible(CI);
  
    // Command-line parameter overrides instruction attribute.
    // This can't be moved to optimizeFloatingPointLibCall() because it may be
    // used by the intrinsic optimizations.
    if (EnableUnsafeFPShrink.getNumOccurrences() > 0)
      UnsafeFPShrink = EnableUnsafeFPShrink;
    else if (isa<FPMathOperator>(CI) && CI->isFast())
      UnsafeFPShrink = true;
  
    // First, check for intrinsics.
    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
      if (!isCallingConvC)
        return nullptr;
      // The FP intrinsics have corresponding constrained versions so we don't
      // need to check for the StrictFP attribute here.
      switch (II->getIntrinsicID()) {
      case Intrinsic::pow:
        return optimizePow(CI, Builder);
      case Intrinsic::exp2:
        return optimizeExp2(CI, Builder);
      case Intrinsic::log:
      case Intrinsic::log2:
      case Intrinsic::log10:
        return optimizeLog(CI, Builder);
      case Intrinsic::sqrt:
        return optimizeSqrt(CI, Builder);
      // TODO: Use foldMallocMemset() with memset intrinsic.
      case Intrinsic::memset:
        return optimizeMemSet(CI, Builder);
      case Intrinsic::memcpy:
        return optimizeMemCpy(CI, Builder);
      case Intrinsic::memmove:
        return optimizeMemMove(CI, Builder);
      default:
        return nullptr;
      }
    }
  
    // Also try to simplify calls to fortified library functions.
    if (Value *SimplifiedFortifiedCI = FortifiedSimplifier.optimizeCall(CI)) {
      // Try to further simplify the result.
      CallInst *SimplifiedCI = dyn_cast<CallInst>(SimplifiedFortifiedCI);
      if (SimplifiedCI && SimplifiedCI->getCalledFunction()) {
        // Use an IR Builder from SimplifiedCI if available instead of CI
        // to guarantee we reach all uses we might replace later on.
        IRBuilder<> TmpBuilder(SimplifiedCI);
        if (Value *V = optimizeStringMemoryLibCall(SimplifiedCI, TmpBuilder)) {
          // If we were able to further simplify, remove the now redundant call.
          substituteInParent(SimplifiedCI, V);
          return V;
        }
      }
      return SimplifiedFortifiedCI;
    }
  
    // Then check for known library functions.
    if (TLI->getLibFunc(*Callee, Func) && TLI->has(Func)) {
      // We never change the calling convention.
      if (!ignoreCallingConv(Func) && !isCallingConvC)
        return nullptr;
      if (Value *V = optimizeStringMemoryLibCall(CI, Builder))
        return V;
      if (Value *V = optimizeFloatingPointLibCall(CI, Func, Builder))
        return V;
      switch (Func) {
      case LibFunc_ffs:
      case LibFunc_ffsl:
      case LibFunc_ffsll:
        return optimizeFFS(CI, Builder);
      case LibFunc_fls:
      case LibFunc_flsl:
      case LibFunc_flsll:
        return optimizeFls(CI, Builder);
      case LibFunc_abs:
      case LibFunc_labs:
      case LibFunc_llabs:
        return optimizeAbs(CI, Builder);
      case LibFunc_isdigit:
        return optimizeIsDigit(CI, Builder);
      case LibFunc_isascii:
        return optimizeIsAscii(CI, Builder);
      case LibFunc_toascii:
        return optimizeToAscii(CI, Builder);
      case LibFunc_atoi:
      case LibFunc_atol:
      case LibFunc_atoll:
        return optimizeAtoi(CI, Builder);
      case LibFunc_strtol:
      case LibFunc_strtoll:
        return optimizeStrtol(CI, Builder);
      case LibFunc_printf:
        return optimizePrintF(CI, Builder);
      case LibFunc_sprintf:
        return optimizeSPrintF(CI, Builder);
      case LibFunc_snprintf:
        return optimizeSnPrintF(CI, Builder);
      case LibFunc_fprintf:
        return optimizeFPrintF(CI, Builder);
      case LibFunc_fwrite:
        return optimizeFWrite(CI, Builder);
      case LibFunc_fread:
        return optimizeFRead(CI, Builder);
      case LibFunc_fputs:
        return optimizeFPuts(CI, Builder);
      case LibFunc_fgets:
        return optimizeFGets(CI, Builder);
      case LibFunc_fputc:
        return optimizeFPutc(CI, Builder);
      case LibFunc_fgetc:
        return optimizeFGetc(CI, Builder);
      case LibFunc_puts:
        return optimizePuts(CI, Builder);
      case LibFunc_perror:
        return optimizeErrorReporting(CI, Builder);
      case LibFunc_vfprintf:
      case LibFunc_fiprintf:
        return optimizeErrorReporting(CI, Builder, 0);
      default:
        return nullptr;
      }
    }
    return nullptr;
  }
  
  LibCallSimplifier::LibCallSimplifier(
      const DataLayout &DL, const TargetLibraryInfo *TLI,
      OptimizationRemarkEmitter &ORE,
      BlockFrequencyInfo *BFI, ProfileSummaryInfo *PSI,
      function_ref<void(Instruction *, Value *)> Replacer,
      function_ref<void(Instruction *)> Eraser)
      : FortifiedSimplifier(TLI), DL(DL), TLI(TLI), ORE(ORE), BFI(BFI), PSI(PSI),
        UnsafeFPShrink(false), Replacer(Replacer), Eraser(Eraser) {}
  
  void LibCallSimplifier::replaceAllUsesWith(Instruction *I, Value *With) {
    // Indirect through the replacer used in this instance.
    Replacer(I, With);
  }
  
  void LibCallSimplifier::eraseFromParent(Instruction *I) {
    Eraser(I);
  }
  
  // TODO:
  //   Additional cases that we need to add to this file:
  //
  // cbrt:
  //   * cbrt(expN(X))  -> expN(x/3)
  //   * cbrt(sqrt(x))  -> pow(x,1/6)
  //   * cbrt(cbrt(x))  -> pow(x,1/9)
  //
  // exp, expf, expl:
  //   * exp(log(x))  -> x
  //
  // log, logf, logl:
  //   * log(exp(x))   -> x
  //   * log(exp(y))   -> y*log(e)
  //   * log(exp10(y)) -> y*log(10)
  //   * log(sqrt(x))  -> 0.5*log(x)
  //
  // pow, powf, powl:
  //   * pow(sqrt(x),y) -> pow(x,y*0.5)
  //   * pow(pow(x,y),z)-> pow(x,y*z)
  //
  // signbit:
  //   * signbit(cnst) -> cnst'
  //   * signbit(nncst) -> 0 (if pstv is a non-negative constant)
  //
  // sqrt, sqrtf, sqrtl:
  //   * sqrt(expN(x))  -> expN(x*0.5)
  //   * sqrt(Nroot(x)) -> pow(x,1/(2*N))
  //   * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
  //
  
  //===----------------------------------------------------------------------===//
  // Fortified Library Call Optimizations
  //===----------------------------------------------------------------------===//
  
  bool
  FortifiedLibCallSimplifier::isFortifiedCallFoldable(CallInst *CI,
                                                      unsigned ObjSizeOp,
                                                      Optional<unsigned> SizeOp,
                                                      Optional<unsigned> StrOp,
                                                      Optional<unsigned> FlagOp) {
    // If this function takes a flag argument, the implementation may use it to
    // perform extra checks. Don't fold into the non-checking variant.
    if (FlagOp) {
      ConstantInt *Flag = dyn_cast<ConstantInt>(CI->getArgOperand(*FlagOp));
      if (!Flag || !Flag->isZero())
        return false;
    }
  
    if (SizeOp && CI->getArgOperand(ObjSizeOp) == CI->getArgOperand(*SizeOp))
      return true;
  
    if (ConstantInt *ObjSizeCI =
            dyn_cast<ConstantInt>(CI->getArgOperand(ObjSizeOp))) {
      if (ObjSizeCI->isMinusOne())
        return true;
      // If the object size wasn't -1 (unknown), bail out if we were asked to.
      if (OnlyLowerUnknownSize)
        return false;
      if (StrOp) {
        uint64_t Len = GetStringLength(CI->getArgOperand(*StrOp));
        // If the length is 0 we don't know how long it is and so we can't
        // remove the check.
        if (Len)
          annotateDereferenceableBytes(CI, *StrOp, Len);
        else
          return false;
        return ObjSizeCI->getZExtValue() >= Len;
      }
  
      if (SizeOp) {
        if (ConstantInt *SizeCI =
                dyn_cast<ConstantInt>(CI->getArgOperand(*SizeOp)))
          return ObjSizeCI->getZExtValue() >= SizeCI->getZExtValue();
      }
    }
    return false;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeMemCpyChk(CallInst *CI,
                                                       IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3, 2)) {
      CallInst *NewCI =
          B.CreateMemCpy(CI->getArgOperand(0), Align(1), CI->getArgOperand(1),
                         Align(1), CI->getArgOperand(2));
      NewCI->setAttributes(CI->getAttributes());
      return CI->getArgOperand(0);
    }
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeMemMoveChk(CallInst *CI,
                                                        IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3, 2)) {
      CallInst *NewCI =
          B.CreateMemMove(CI->getArgOperand(0), Align(1), CI->getArgOperand(1),
                          Align(1), CI->getArgOperand(2));
      NewCI->setAttributes(CI->getAttributes());
      return CI->getArgOperand(0);
    }
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeMemSetChk(CallInst *CI,
                                                       IRBuilder<> &B) {
    // TODO: Try foldMallocMemset() here.
  
    if (isFortifiedCallFoldable(CI, 3, 2)) {
      Value *Val = B.CreateIntCast(CI->getArgOperand(1), B.getInt8Ty(), false);
      CallInst *NewCI = B.CreateMemSet(CI->getArgOperand(0), Val,
                                       CI->getArgOperand(2), Align(1));
      NewCI->setAttributes(CI->getAttributes());
      return CI->getArgOperand(0);
    }
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeStrpCpyChk(CallInst *CI,
                                                        IRBuilder<> &B,
                                                        LibFunc Func) {
    const DataLayout &DL = CI->getModule()->getDataLayout();
    Value *Dst = CI->getArgOperand(0), *Src = CI->getArgOperand(1),
          *ObjSize = CI->getArgOperand(2);
  
    // __stpcpy_chk(x,x,...)  -> x+strlen(x)
    if (Func == LibFunc_stpcpy_chk && !OnlyLowerUnknownSize && Dst == Src) {
      Value *StrLen = emitStrLen(Src, B, DL, TLI);
      return StrLen ? B.CreateInBoundsGEP(B.getInt8Ty(), Dst, StrLen) : nullptr;
    }
  
    // If a) we don't have any length information, or b) we know this will
    // fit then just lower to a plain st[rp]cpy. Otherwise we'll keep our
    // st[rp]cpy_chk call which may fail at runtime if the size is too long.
    // TODO: It might be nice to get a maximum length out of the possible
    // string lengths for varying.
    if (isFortifiedCallFoldable(CI, 2, None, 1)) {
      if (Func == LibFunc_strcpy_chk)
        return emitStrCpy(Dst, Src, B, TLI);
      else
        return emitStpCpy(Dst, Src, B, TLI);
    }
  
    if (OnlyLowerUnknownSize)
      return nullptr;
  
    // Maybe we can stil fold __st[rp]cpy_chk to __memcpy_chk.
    uint64_t Len = GetStringLength(Src);
    if (Len)
      annotateDereferenceableBytes(CI, 1, Len);
    else
      return nullptr;
  
    Type *SizeTTy = DL.getIntPtrType(CI->getContext());
    Value *LenV = ConstantInt::get(SizeTTy, Len);
    Value *Ret = emitMemCpyChk(Dst, Src, LenV, ObjSize, B, DL, TLI);
    // If the function was an __stpcpy_chk, and we were able to fold it into
    // a __memcpy_chk, we still need to return the correct end pointer.
    if (Ret && Func == LibFunc_stpcpy_chk)
      return B.CreateGEP(B.getInt8Ty(), Dst, ConstantInt::get(SizeTTy, Len - 1));
    return Ret;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeStrpNCpyChk(CallInst *CI,
                                                         IRBuilder<> &B,
                                                         LibFunc Func) {
    if (isFortifiedCallFoldable(CI, 3, 2)) {
      if (Func == LibFunc_strncpy_chk)
        return emitStrNCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                                 CI->getArgOperand(2), B, TLI);
      else
        return emitStpNCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                           CI->getArgOperand(2), B, TLI);
    }
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeMemCCpyChk(CallInst *CI,
                                                        IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 4, 3))
      return emitMemCCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                         CI->getArgOperand(2), CI->getArgOperand(3), B, TLI);
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeSNPrintfChk(CallInst *CI,
                                                         IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3, 1, None, 2)) {
      SmallVector<Value *, 8> VariadicArgs(CI->arg_begin() + 5, CI->arg_end());
      return emitSNPrintf(CI->getArgOperand(0), CI->getArgOperand(1),
                          CI->getArgOperand(4), VariadicArgs, B, TLI);
    }
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeSPrintfChk(CallInst *CI,
                                                        IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 2, None, None, 1)) {
      SmallVector<Value *, 8> VariadicArgs(CI->arg_begin() + 4, CI->arg_end());
      return emitSPrintf(CI->getArgOperand(0), CI->getArgOperand(3), VariadicArgs,
                         B, TLI);
    }
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeStrCatChk(CallInst *CI,
                                                       IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 2))
      return emitStrCat(CI->getArgOperand(0), CI->getArgOperand(1), B, TLI);
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeStrLCat(CallInst *CI,
                                                     IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3))
      return emitStrLCat(CI->getArgOperand(0), CI->getArgOperand(1),
                         CI->getArgOperand(2), B, TLI);
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeStrNCatChk(CallInst *CI,
                                                        IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3))
      return emitStrNCat(CI->getArgOperand(0), CI->getArgOperand(1),
                         CI->getArgOperand(2), B, TLI);
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeStrLCpyChk(CallInst *CI,
                                                        IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3))
      return emitStrLCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                         CI->getArgOperand(2), B, TLI);
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeVSNPrintfChk(CallInst *CI,
                                                          IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3, 1, None, 2))
      return emitVSNPrintf(CI->getArgOperand(0), CI->getArgOperand(1),
                           CI->getArgOperand(4), CI->getArgOperand(5), B, TLI);
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeVSPrintfChk(CallInst *CI,
                                                         IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 2, None, None, 1))
      return emitVSPrintf(CI->getArgOperand(0), CI->getArgOperand(3),
                          CI->getArgOperand(4), B, TLI);
  
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeCall(CallInst *CI) {
    // FIXME: We shouldn't be changing "nobuiltin" or TLI unavailable calls here.
    // Some clang users checked for _chk libcall availability using:
    //   __has_builtin(__builtin___memcpy_chk)
    // When compiling with -fno-builtin, this is always true.
    // When passing -ffreestanding/-mkernel, which both imply -fno-builtin, we
    // end up with fortified libcalls, which isn't acceptable in a freestanding
    // environment which only provides their non-fortified counterparts.
    //
    // Until we change clang and/or teach external users to check for availability
    // differently, disregard the "nobuiltin" attribute and TLI::has.
    //
    // PR23093.
  
    LibFunc Func;
    Function *Callee = CI->getCalledFunction();
  
    SmallVector<OperandBundleDef, 2> OpBundles;
    CI->getOperandBundlesAsDefs(OpBundles);
    IRBuilder<> Builder(CI, /*FPMathTag=*/nullptr, OpBundles);
    bool isCallingConvC = isCallingConvCCompatible(CI);
  
    // First, check that this is a known library functions and that the prototype
    // is correct.
    if (!TLI->getLibFunc(*Callee, Func))
      return nullptr;
  
    // We never change the calling convention.
    if (!ignoreCallingConv(Func) && !isCallingConvC)
      return nullptr;
  
    switch (Func) {
    case LibFunc_memcpy_chk:
      return optimizeMemCpyChk(CI, Builder);
    case LibFunc_memmove_chk:
      return optimizeMemMoveChk(CI, Builder);
    case LibFunc_memset_chk:
      return optimizeMemSetChk(CI, Builder);
    case LibFunc_stpcpy_chk:
    case LibFunc_strcpy_chk:
      return optimizeStrpCpyChk(CI, Builder, Func);
    case LibFunc_stpncpy_chk:
    case LibFunc_strncpy_chk:
      return optimizeStrpNCpyChk(CI, Builder, Func);
    case LibFunc_memccpy_chk:
      return optimizeMemCCpyChk(CI, Builder);
    case LibFunc_snprintf_chk:
      return optimizeSNPrintfChk(CI, Builder);
    case LibFunc_sprintf_chk:
      return optimizeSPrintfChk(CI, Builder);
    case LibFunc_strcat_chk:
      return optimizeStrCatChk(CI, Builder);
    case LibFunc_strlcat_chk:
      return optimizeStrLCat(CI, Builder);
    case LibFunc_strncat_chk:
      return optimizeStrNCatChk(CI, Builder);
    case LibFunc_strlcpy_chk:
      return optimizeStrLCpyChk(CI, Builder);
    case LibFunc_vsnprintf_chk:
      return optimizeVSNPrintfChk(CI, Builder);
    case LibFunc_vsprintf_chk:
      return optimizeVSPrintfChk(CI, Builder);
    default:
      break;
    }
    return nullptr;
  }
  
  FortifiedLibCallSimplifier::FortifiedLibCallSimplifier(
      const TargetLibraryInfo *TLI, bool OnlyLowerUnknownSize)
      : TLI(TLI), OnlyLowerUnknownSize(OnlyLowerUnknownSize) {}
  