text: //===------ SimplifyLibCalls.cpp - Library calls simplifier ---------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This is a utility pass used for testing the InstructionSimplify analysis.
  // The analysis is applied to every instruction, and if it simplifies then the
  // instruction is replaced by the simplification.  If you are looking for a pass
  // that performs serious instruction folding, use the instcombine pass instead.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/StringMap.h"
  #include "llvm/ADT/Triple.h"
  #include "llvm/Analysis/TargetLibraryInfo.h"
  #include "llvm/Analysis/ValueTracking.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DiagnosticInfo.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/Transforms/Utils/BuildLibCalls.h"
  #include "llvm/Transforms/Utils/Local.h"
  
  using namespace llvm;
  using namespace PatternMatch;
  
  static cl::opt<bool>
      ColdErrorCalls("error-reporting-is-cold", cl::init(true), cl::Hidden,
                     cl::desc("Treat error-reporting calls as cold"));
  
  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 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 only matters that the value is equal or not-equal to zero.
  static bool isOnlyUsedInZeroEqualityComparison(Value *V) {
    for (User *U : V->users()) {
      if (ICmpInst *IC = dyn_cast<ICmpInst>(U))
        if (IC->isEquality())
          if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
            if (C->isNullValue())
              continue;
      // Unknown instruction.
      return false;
    }
    return true;
  }
  
  /// 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();
    });
  }
  
  /// \brief Check whether the overloaded unary floating point function
  /// corresponding to \a Ty is available.
  static bool hasUnaryFloatFn(const TargetLibraryInfo *TLI, Type *Ty,
                              LibFunc::Func DoubleFn, LibFunc::Func FloatFn,
                              LibFunc::Func LongDoubleFn) {
    switch (Ty->getTypeID()) {
    case Type::FloatTyID:
      return TLI->has(FloatFn);
    case Type::DoubleTyID:
      return TLI->has(DoubleFn);
    default:
      return TLI->has(LongDoubleFn);
    }
  }
  
  //===----------------------------------------------------------------------===//
  // 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);
  
    // See if we can get the length of the input string.
    uint64_t Len = GetStringLength(Src);
    if (Len == 0)
      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, Src,
                   ConstantInt::get(DL.getIntPtrType(Src->getContext()), Len + 1),
                   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);
    uint64_t Len;
  
    // We don't do anything if length is not constant.
    if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getArgOperand(2)))
      Len = LengthArg->getZExtValue();
    else
      return nullptr;
  
    // See if we can get the length of the input string.
    uint64_t SrcLen = GetStringLength(Src);
    if (SrcLen == 0)
      return nullptr;
    --SrcLen; // Unbias length.
  
    // Handle the simple, do-nothing cases:
    // strncat(x, "", c) -> x
    // strncat(x,  c, 0) -> x
    if (SrcLen == 0 || Len == 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);
  
    // 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 == 0 || !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)
        return B.CreateGEP(B.getInt8Ty(), SrcStr, emitStrLen(SrcStr, B, DL, TLI),
                           "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));
  
    // 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(Str2P, "strcmpload"), CI->getType()));
  
    if (HasStr2 && Str2.empty()) // strcmp(x,"") -> *x
      return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
  
    // strcmp(P, "x") -> memcmp(P, "x", 2)
    uint64_t Len1 = GetStringLength(Str1P);
    uint64_t Len2 = GetStringLength(Str2P);
    if (Len1 && Len2) {
      return emitMemCmp(Str1P, Str2P,
                        ConstantInt::get(DL.getIntPtrType(CI->getContext()),
                                         std::min(Len1, Len2)),
                        B, DL, TLI);
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeStrNCmp(CallInst *CI, IRBuilder<> &B) {
    Value *Str1P = CI->getArgOperand(0), *Str2P = CI->getArgOperand(1);
    if (Str1P == Str2P) // strncmp(x,x,n)  -> 0
      return ConstantInt::get(CI->getType(), 0);
  
    // Get the length argument if it is constant.
    uint64_t Length;
    if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getArgOperand(2)))
      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, CI->getArgOperand(2), 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(Str2P, "strcmpload"), CI->getType()));
  
    if (HasStr2 && Str2.empty()) // strncmp(x, "", n) -> *x
      return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
  
    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;
  
    // See if we can get the length of the input string.
    uint64_t Len = GetStringLength(Src);
    if (Len == 0)
      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.
    B.CreateMemCpy(Dst, Src,
                   ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len), 1);
    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 == 0)
      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.
    B.CreateMemCpy(Dst, Src, LenV, 1);
    return DstEnd;
  }
  
  Value *LibCallSimplifier::optimizeStrNCpy(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Dst = CI->getArgOperand(0);
    Value *Src = CI->getArgOperand(1);
    Value *LenOp = CI->getArgOperand(2);
  
    // See if we can get the length of the input string.
    uint64_t SrcLen = GetStringLength(Src);
    if (SrcLen == 0)
      return nullptr;
    --SrcLen;
  
    if (SrcLen == 0) {
      // strncpy(x, "", y) -> memset(x, '\0', y, 1)
      B.CreateMemSet(Dst, B.getInt8('\0'), LenOp, 1);
      return Dst;
    }
  
    uint64_t Len;
    if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(LenOp))
      Len = LengthArg->getZExtValue();
    else
      return nullptr;
  
    if (Len == 0)
      return Dst; // strncpy(x, y, 0) -> x
  
    // Let strncpy handle the zero padding
    if (Len > SrcLen + 1)
      return nullptr;
  
    Type *PT = Callee->getFunctionType()->getParamType(0);
    // strncpy(x, s, c) -> memcpy(x, s, c, 1) [s and c are constant]
    B.CreateMemCpy(Dst, Src, ConstantInt::get(DL.getIntPtrType(PT), Len), 1);
  
    return Dst;
  }
  
  Value *LibCallSimplifier::optimizeStrLen(CallInst *CI, IRBuilder<> &B) {
    Value *Src = CI->getArgOperand(0);
  
    // Constant folding: strlen("xyz") -> 3
    if (uint64_t Len = GetStringLength(Src))
      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))
        return nullptr;
  
      StringRef Str;
      if (getConstantStringInfo(GEP->getOperand(0), Str, 0, false)) {
        size_t NullTermIdx = Str.find('\0');
        
        // If the string does not have '\0', leave it to strlen to compute
        // its length.
        if (NullTermIdx == StringRef::npos)
          return nullptr;
       
        Value *Offset = GEP->getOperand(2);
        unsigned BitWidth = Offset->getType()->getIntegerBitWidth();
        APInt KnownZero(BitWidth, 0);
        APInt KnownOne(BitWidth, 0);
        computeKnownBits(Offset, KnownZero, KnownOne, DL, 0, nullptr, CI, 
                         nullptr);
        KnownZero.flipAllBits();
        size_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 ((KnownZero.isNonNegative() && KnownZero.ule(NullTermIdx)) || 
            (GEP->isInBounds() && isa<GlobalVariable>(GEP->getOperand(0)) &&
             NullTermIdx == ArrSize - 1))
          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());
      uint64_t LenFalse = GetStringLength(SI->getFalseValue());
      if (LenTrue && LenFalse) {
        Function *Caller = CI->getParent()->getParent();
        emitOptimizationRemark(CI->getContext(), "simplify-libcalls", *Caller,
                               SI->getDebugLoc(),
                               "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(Src, "strlenfirst"), CI->getType());
  
    return nullptr;
  }
  
  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->addAttribute(1, 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(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;
    }
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeMemChr(CallInst *CI, IRBuilder<> &B) {
    Value *SrcStr = CI->getArgOperand(0);
    ConstantInt *CharC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
    ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getArgOperand(2));
  
    // memchr(x, y, 0) -> null
    if (LenC && LenC->isNullValue())
      return Constant::getNullValue(CI->getType());
  
    // From now on we need at least constant length and string.
    StringRef Str;
    if (!LenC || !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 -> (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);
  
      // First check that the bit field access is within bounds.
      Value *C = B.CreateZExtOrTrunc(CI->getArgOperand(1), BitfieldC->getType());
      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");
  }
  
  Value *LibCallSimplifier::optimizeMemCmp(CallInst *CI, IRBuilder<> &B) {
    Value *LHS = CI->getArgOperand(0), *RHS = CI->getArgOperand(1);
  
    if (LHS == RHS) // memcmp(s,s,x) -> 0
      return Constant::getNullValue(CI->getType());
  
    // Make sure we have a constant length.
    ConstantInt *LenC = dyn_cast<ConstantInt>(CI->getArgOperand(2));
    if (!LenC)
      return nullptr;
    uint64_t Len = LenC->getZExtValue();
  
    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(castToCStr(LHS, B), "lhsc"),
                                 CI->getType(), "lhsv");
      Value *RHSV = B.CreateZExt(B.CreateLoad(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
    if (DL.isLegalInteger(Len * 8) && isOnlyUsedInZeroEqualityComparison(CI)) {
  
      IntegerType *IntType = IntegerType::get(CI->getContext(), Len * 8);
      unsigned PrefAlignment = DL.getPrefTypeAlignment(IntType);
  
      if (getKnownAlignment(LHS, DL, CI) >= PrefAlignment &&
          getKnownAlignment(RHS, DL, CI) >= PrefAlignment) {
  
        Type *LHSPtrTy =
            IntType->getPointerTo(LHS->getType()->getPointerAddressSpace());
        Type *RHSPtrTy =
            IntType->getPointerTo(RHS->getType()->getPointerAddressSpace());
  
        Value *LHSV =
            B.CreateLoad(B.CreateBitCast(LHS, LHSPtrTy, "lhsc"), "lhsv");
        Value *RHSV =
            B.CreateLoad(B.CreateBitCast(RHS, RHSPtrTy, "rhsc"), "rhsv");
  
        return B.CreateZExt(B.CreateICmpNE(LHSV, RHSV), CI->getType(), "memcmp");
      }
    }
  
    // Constant folding: memcmp(x, y, l) -> cnst (all arguments are constant)
    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;
  }
  
  Value *LibCallSimplifier::optimizeMemCpy(CallInst *CI, IRBuilder<> &B) {
    // memcpy(x, y, n) -> llvm.memcpy(x, y, n, 1)
    B.CreateMemCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                   CI->getArgOperand(2), 1);
    return CI->getArgOperand(0);
  }
  
  Value *LibCallSimplifier::optimizeMemMove(CallInst *CI, IRBuilder<> &B) {
    // memmove(x, y, n) -> llvm.memmove(x, y, n, 1)
    B.CreateMemMove(CI->getArgOperand(0), CI->getArgOperand(1),
                    CI->getArgOperand(2), 1);
    return CI->getArgOperand(0);
  }
  
  // TODO: Does this belong in BuildLibCalls or should all of those similar
  // functions be moved here?
  static Value *emitCalloc(Value *Num, Value *Size, const AttributeSet &Attrs,
                           IRBuilder<> &B, const TargetLibraryInfo &TLI) {
    LibFunc::Func Func;
    if (!TLI.getLibFunc("calloc", Func) || !TLI.has(Func))
      return nullptr;
  
    Module *M = B.GetInsertBlock()->getModule();
    const DataLayout &DL = M->getDataLayout();
    IntegerType *PtrType = DL.getIntPtrType((B.GetInsertBlock()->getContext()));
    Value *Calloc = M->getOrInsertFunction("calloc", Attrs, B.getInt8PtrTy(),
                                           PtrType, PtrType, nullptr);
    CallInst *CI = B.CreateCall(Calloc, { Num, Size }, "calloc");
  
    if (const auto *F = dyn_cast<Function>(Calloc->stripPointerCasts()))
      CI->setCallingConv(F->getCallingConv());
  
    return CI;
  }
  
  /// Fold memset[_chk](malloc(n), 0, n) --> calloc(1, n).
  static Value *foldMallocMemset(CallInst *Memset, IRBuilder<> &B,
                                 const TargetLibraryInfo &TLI) {
    // 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();
    LibFunc::Func 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());
    Value *Calloc = emitCalloc(ConstantInt::get(SizeType, 1),
                               Malloc->getArgOperand(0), Malloc->getAttributes(),
                               B, TLI);
    if (!Calloc)
      return nullptr;
  
    Malloc->replaceAllUsesWith(Calloc);
    Malloc->eraseFromParent();
  
    return Calloc;
  }
  
  Value *LibCallSimplifier::optimizeMemSet(CallInst *CI, IRBuilder<> &B) {
    if (auto *Calloc = foldMallocMemset(CI, B, *TLI))
      return Calloc;
  
    // memset(p, v, n) -> llvm.memset(p, v, n, 1)
    Value *Val = B.CreateIntCast(CI->getArgOperand(1), B.getInt8Ty(), false);
    B.CreateMemSet(CI->getArgOperand(0), Val, CI->getArgOperand(2), 1);
    return CI->getArgOperand(0);
  }
  
  //===----------------------------------------------------------------------===//
  // Math Library Optimizations
  //===----------------------------------------------------------------------===//
  
  /// 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 for unary functions like 'floor'.
  static Value *optimizeUnaryDoubleFP(CallInst *CI, IRBuilder<> &B,
                                      bool CheckRetType) {
    Function *Callee = CI->getCalledFunction();
    // We know this libcall has a valid prototype, but we don't know which.
    if (!CI->getType()->isDoubleTy())
      return nullptr;
  
    if (CheckRetType) {
      // Check if all the uses for function like 'sin' are converted to float.
      for (User *U : CI->users()) {
        FPTruncInst *Cast = dyn_cast<FPTruncInst>(U);
        if (!Cast || !Cast->getType()->isFloatTy())
          return nullptr;
      }
    }
  
    // If this is something like 'floor((double)floatval)', convert to floorf.
    Value *V = valueHasFloatPrecision(CI->getArgOperand(0));
    if (V == nullptr)
      return nullptr;
    
    // Propagate fast-math flags from the existing call to the new call.
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(CI->getFastMathFlags());
  
    // floor((double)floatval) -> (double)floorf(floatval)
    if (Callee->isIntrinsic()) {
      Module *M = CI->getModule();
      Intrinsic::ID IID = Callee->getIntrinsicID();
      Function *F = Intrinsic::getDeclaration(M, IID, B.getFloatTy());
      V = B.CreateCall(F, V);
    } else {
      // The call is a library call rather than an intrinsic.
      V = emitUnaryFloatFnCall(V, Callee->getName(), B, Callee->getAttributes());
    }
  
    return B.CreateFPExt(V, B.getDoubleTy());
  }
  
  /// Shrink double -> float for binary functions like 'fmin/fmax'.
  static Value *optimizeBinaryDoubleFP(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    // We know this libcall has a valid prototype, but we don't know which.
    if (!CI->getType()->isDoubleTy())
      return nullptr;
  
    // If this is something like 'fmin((double)floatval1, (double)floatval2)',
    // or fmin(1.0, (double)floatval), then we convert it to fminf.
    Value *V1 = valueHasFloatPrecision(CI->getArgOperand(0));
    if (V1 == nullptr)
      return nullptr;
    Value *V2 = valueHasFloatPrecision(CI->getArgOperand(1));
    if (V2 == nullptr)
      return nullptr;
  
    // Propagate fast-math flags from the existing call to the new call.
    IRBuilder<>::FastMathFlagGuard Guard(B);
    B.setFastMathFlags(CI->getFastMathFlags());
  
    // fmin((double)floatval1, (double)floatval2)
    //                      -> (double)fminf(floatval1, floatval2)
    // TODO: Handle intrinsics in the same way as in optimizeUnaryDoubleFP().
    Value *V = emitBinaryFloatFnCall(V1, V2, Callee->getName(), B,
                                     Callee->getAttributes());
    return B.CreateFPExt(V, B.getDoubleTy());
  }
  
  Value *LibCallSimplifier::optimizeCos(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Ret = nullptr;
    StringRef Name = Callee->getName();
    if (UnsafeFPShrink && Name == "cos" && hasFloatVersion(Name))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    // cos(-x) -> cos(x)
    Value *Op1 = CI->getArgOperand(0);
    if (BinaryOperator::isFNeg(Op1)) {
      BinaryOperator *BinExpr = cast<BinaryOperator>(Op1);
      return B.CreateCall(Callee, BinExpr->getOperand(1), "cos");
    }
    return Ret;
  }
  
  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];
  }
  
  Value *LibCallSimplifier::optimizePow(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Ret = nullptr;
    StringRef Name = Callee->getName();
    if (UnsafeFPShrink && Name == "pow" && hasFloatVersion(Name))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    Value *Op1 = CI->getArgOperand(0), *Op2 = CI->getArgOperand(1);
  
    // pow(1.0, x) -> 1.0
    if (match(Op1, m_SpecificFP(1.0)))
      return Op1;
    // pow(2.0, x) -> llvm.exp2(x)
    if (match(Op1, m_SpecificFP(2.0))) {
      Value *Exp2 = Intrinsic::getDeclaration(CI->getModule(), Intrinsic::exp2,
                                              CI->getType());
      return B.CreateCall(Exp2, Op2, "exp2");
    }
  
    // There's no llvm.exp10 intrinsic yet, but, maybe, some day there will
    // be one.
    if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
      // pow(10.0, x) -> exp10(x)
      if (Op1C->isExactlyValue(10.0) &&
          hasUnaryFloatFn(TLI, Op1->getType(), LibFunc::exp10, LibFunc::exp10f,
                          LibFunc::exp10l))
        return emitUnaryFloatFnCall(Op2, TLI->getName(LibFunc::exp10), B,
                                    Callee->getAttributes());
    }
  
    // pow(exp(x), y) -> exp(x * y)
    // pow(exp2(x), y) -> exp2(x * y)
    // We enable these only with fast-math. Besides rounding differences, the
    // transformation changes overflow and underflow behavior quite dramatically.
    // Example: x = 1000, y = 0.001.
    // pow(exp(x), y) = pow(inf, 0.001) = inf, whereas exp(x*y) = exp(1).
    auto *OpC = dyn_cast<CallInst>(Op1);
    if (OpC && OpC->hasUnsafeAlgebra() && CI->hasUnsafeAlgebra()) {
      LibFunc::Func Func;
      Function *OpCCallee = OpC->getCalledFunction();
      if (OpCCallee && TLI->getLibFunc(OpCCallee->getName(), Func) &&
          TLI->has(Func) && (Func == LibFunc::exp || Func == LibFunc::exp2)) {
        IRBuilder<>::FastMathFlagGuard Guard(B);
        B.setFastMathFlags(CI->getFastMathFlags());
        Value *FMul = B.CreateFMul(OpC->getArgOperand(0), Op2, "mul");
        return emitUnaryFloatFnCall(FMul, OpCCallee->getName(), B,
                                    OpCCallee->getAttributes());
      }
    }
  
    ConstantFP *Op2C = dyn_cast<ConstantFP>(Op2);
    if (!Op2C)
      return Ret;
  
    if (Op2C->getValueAPF().isZero()) // pow(x, 0.0) -> 1.0
      return ConstantFP::get(CI->getType(), 1.0);
  
    if (Op2C->isExactlyValue(-0.5) &&
        hasUnaryFloatFn(TLI, Op2->getType(), LibFunc::sqrt, LibFunc::sqrtf,
                        LibFunc::sqrtl)) {
      // If -ffast-math:
      // pow(x, -0.5) -> 1.0 / sqrt(x)
      if (CI->hasUnsafeAlgebra()) {
        IRBuilder<>::FastMathFlagGuard Guard(B);
        B.setFastMathFlags(CI->getFastMathFlags());
  
        // Here we cannot lower to an intrinsic because C99 sqrt() and llvm.sqrt
        // are not guaranteed to have the same semantics.
        Value *Sqrt = emitUnaryFloatFnCall(Op1, TLI->getName(LibFunc::sqrt), B,
                                           Callee->getAttributes());
  
        return B.CreateFDiv(ConstantFP::get(CI->getType(), 1.0), Sqrt, "sqrtrecip");
      }
    }
  
    if (Op2C->isExactlyValue(0.5) &&
        hasUnaryFloatFn(TLI, Op2->getType(), LibFunc::sqrt, LibFunc::sqrtf,
                        LibFunc::sqrtl) &&
        hasUnaryFloatFn(TLI, Op2->getType(), LibFunc::fabs, LibFunc::fabsf,
                        LibFunc::fabsl)) {
  
      // In -ffast-math, pow(x, 0.5) -> sqrt(x).
      if (CI->hasUnsafeAlgebra()) {
        IRBuilder<>::FastMathFlagGuard Guard(B);
        B.setFastMathFlags(CI->getFastMathFlags());
  
        // Unlike other math intrinsics, sqrt has differerent semantics
        // from the libc function. See LangRef for details.
        return emitUnaryFloatFnCall(Op1, TLI->getName(LibFunc::sqrt), B,
                                    Callee->getAttributes());
      }
  
      // Expand pow(x, 0.5) to (x == -infinity ? +infinity : fabs(sqrt(x))).
      // This is faster than calling pow, and still handles negative zero
      // and negative infinity correctly.
      // TODO: In finite-only mode, this could be just fabs(sqrt(x)).
      Value *Inf = ConstantFP::getInfinity(CI->getType());
      Value *NegInf = ConstantFP::getInfinity(CI->getType(), true);
      Value *Sqrt = emitUnaryFloatFnCall(Op1, "sqrt", B, Callee->getAttributes());
      Value *FAbs =
          emitUnaryFloatFnCall(Sqrt, "fabs", B, Callee->getAttributes());
      Value *FCmp = B.CreateFCmpOEQ(Op1, NegInf);
      Value *Sel = B.CreateSelect(FCmp, Inf, FAbs);
      return Sel;
    }
  
    if (Op2C->isExactlyValue(1.0)) // pow(x, 1.0) -> x
      return Op1;
    if (Op2C->isExactlyValue(2.0)) // pow(x, 2.0) -> x*x
      return B.CreateFMul(Op1, Op1, "pow2");
    if (Op2C->isExactlyValue(-1.0)) // pow(x, -1.0) -> 1.0/x
      return B.CreateFDiv(ConstantFP::get(CI->getType(), 1.0), Op1, "powrecip");
  
    // In -ffast-math, generate repeated fmul instead of generating pow(x, n).
    if (CI->hasUnsafeAlgebra()) {
      APFloat V = abs(Op2C->getValueAPF());
      // We limit to a max of 7 fmul(s). Thus max exponent is 32.
      // This transformation applies to integer exponents only.
      if (V.compare(APFloat(V.getSemantics(), 32.0)) == APFloat::cmpGreaterThan ||
          !V.isInteger())
        return nullptr;
  
      // Propagate fast math flags.
      IRBuilder<>::FastMathFlagGuard Guard(B);
      B.setFastMathFlags(CI->getFastMathFlags());
  
      // We will memoize intermediate products of the Addition Chain.
      Value *InnerChain[33] = {nullptr};
      InnerChain[1] = Op1;
      InnerChain[2] = B.CreateFMul(Op1, Op1);
  
      // We cannot readily convert a non-double type (like float) to a double.
      // So we first convert V to something which could be converted to double.
      bool ignored;
      V.convert(APFloat::IEEEdouble(), APFloat::rmTowardZero, &ignored);
      
      Value *FMul = getPow(InnerChain, V.convertToDouble(), B);
      // For negative exponents simply compute the reciprocal.
      if (Op2C->isNegative())
        FMul = B.CreateFDiv(ConstantFP::get(CI->getType(), 1.0), FMul);
      return FMul;
    }
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeExp2(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Ret = nullptr;
    StringRef Name = Callee->getName();
    if (UnsafeFPShrink && Name == "exp2" && hasFloatVersion(Name))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    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
    LibFunc::Func LdExp = LibFunc::ldexpl;
    if (Op->getType()->isFloatTy())
      LdExp = LibFunc::ldexpf;
    else if (Op->getType()->isDoubleTy())
      LdExp = LibFunc::ldexp;
  
    if (TLI->has(LdExp)) {
      Value *LdExpArg = nullptr;
      if (SIToFPInst *OpC = dyn_cast<SIToFPInst>(Op)) {
        if (OpC->getOperand(0)->getType()->getPrimitiveSizeInBits() <= 32)
          LdExpArg = B.CreateSExt(OpC->getOperand(0), B.getInt32Ty());
      } else if (UIToFPInst *OpC = dyn_cast<UIToFPInst>(Op)) {
        if (OpC->getOperand(0)->getType()->getPrimitiveSizeInBits() < 32)
          LdExpArg = B.CreateZExt(OpC->getOperand(0), B.getInt32Ty());
      }
  
      if (LdExpArg) {
        Constant *One = ConstantFP::get(CI->getContext(), APFloat(1.0f));
        if (!Op->getType()->isFloatTy())
          One = ConstantExpr::getFPExtend(One, Op->getType());
  
        Module *M = CI->getModule();
        Value *NewCallee =
            M->getOrInsertFunction(TLI->getName(LdExp), Op->getType(),
                                   Op->getType(), B.getInt32Ty(), nullptr);
        CallInst *CI = B.CreateCall(NewCallee, {One, LdExpArg});
        if (const Function *F = dyn_cast<Function>(Callee->stripPointerCasts()))
          CI->setCallingConv(F->getCallingConv());
  
        return CI;
      }
    }
    return Ret;
  }
  
  Value *LibCallSimplifier::optimizeFabs(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    StringRef Name = Callee->getName();
    if (Name == "fabs" && hasFloatVersion(Name))
      return optimizeUnaryDoubleFP(CI, B, false);
  
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeFMinFMax(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    // If we can shrink the call to a float function rather than a double
    // function, do that first.
    StringRef Name = Callee->getName();
    if ((Name == "fmin" || Name == "fmax") && hasFloatVersion(Name))
      if (Value *Ret = optimizeBinaryDoubleFP(CI, B))
        return Ret;
  
    IRBuilder<>::FastMathFlagGuard Guard(B);
    FastMathFlags FMF;
    if (CI->hasUnsafeAlgebra()) {
      // Unsafe algebra sets all fast-math-flags to true.
      FMF.setUnsafeAlgebra();
    } else {
      // At a minimum, no-nans-fp-math must be true.
      if (!CI->hasNoNaNs())
        return nullptr;
      // No-signed-zeros is implied by the definitions of fmax/fmin themselves:
      // "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."
      FMF.setNoSignedZeros();
      FMF.setNoNaNs();
    }
    B.setFastMathFlags(FMF);
  
    // We have a relaxed floating-point environment. We can ignore NaN-handling
    // and transform to a compare and select. We do not have to consider errno or
    // exceptions, because fmin/fmax do not have those.
    Value *Op0 = CI->getArgOperand(0);
    Value *Op1 = CI->getArgOperand(1);
    Value *Cmp = Callee->getName().startswith("fmin") ?
      B.CreateFCmpOLT(Op0, Op1) : B.CreateFCmpOGT(Op0, Op1);
    return B.CreateSelect(Cmp, Op0, Op1);
  }
  
  Value *LibCallSimplifier::optimizeLog(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Ret = nullptr;
    StringRef Name = Callee->getName();
    if (UnsafeFPShrink && hasFloatVersion(Name))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    if (!CI->hasUnsafeAlgebra())
      return Ret;
    Value *Op1 = CI->getArgOperand(0);
    auto *OpC = dyn_cast<CallInst>(Op1);
  
    // The earlier call must also be unsafe in order to do these transforms.
    if (!OpC || !OpC->hasUnsafeAlgebra())
      return Ret;
  
    // log(pow(x,y)) -> y*log(x)
    // This is only applicable to log, log2, log10.
    if (Name != "log" && Name != "log2" && Name != "log10")
      return Ret;
  
    IRBuilder<>::FastMathFlagGuard Guard(B);
    FastMathFlags FMF;
    FMF.setUnsafeAlgebra();
    B.setFastMathFlags(FMF);
  
    LibFunc::Func Func;
    Function *F = OpC->getCalledFunction();
    if (F && ((TLI->getLibFunc(F->getName(), Func) && TLI->has(Func) &&
        Func == LibFunc::pow) || F->getIntrinsicID() == Intrinsic::pow))
      return B.CreateFMul(OpC->getArgOperand(1),
        emitUnaryFloatFnCall(OpC->getOperand(0), Callee->getName(), B,
                             Callee->getAttributes()), "mul");
  
    // log(exp2(y)) -> y*log(2)
    if (F && Name == "log" && TLI->getLibFunc(F->getName(), Func) &&
        TLI->has(Func) && Func == LibFunc::exp2)
      return B.CreateFMul(
          OpC->getArgOperand(0),
          emitUnaryFloatFnCall(ConstantFP::get(CI->getType(), 2.0),
                               Callee->getName(), B, Callee->getAttributes()),
          "logmul");
    return Ret;
  }
  
  Value *LibCallSimplifier::optimizeSqrt(CallInst *CI, IRBuilder<> &B) {
    Function *Callee = CI->getCalledFunction();
    Value *Ret = nullptr;
    if (TLI->has(LibFunc::sqrtf) && (Callee->getName() == "sqrt" ||
                                     Callee->getIntrinsicID() == Intrinsic::sqrt))
      Ret = optimizeUnaryDoubleFP(CI, B, true);
  
    if (!CI->hasUnsafeAlgebra())
      return Ret;
  
    Instruction *I = dyn_cast<Instruction>(CI->getArgOperand(0));
    if (!I || I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
      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)->hasUnsafeAlgebra()) {
          // 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();
    Value *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.
      Value *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 allow unsafe optimizations in order to remove them.
    if (!CI->hasUnsafeAlgebra() || !OpC->hasUnsafeAlgebra())
      return Ret;
  
    // tan(atan(x)) -> x
    // tanf(atanf(x)) -> x
    // tanl(atanl(x)) -> x
    LibFunc::Func 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, nullptr));
    } else {
      Name = "__sincospi_stret";
      ResTy = StructType::get(ArgTy, ArgTy, nullptr);
    }
  
    Module *M = OrigCallee->getParent();
    Value *Callee = M->getOrInsertFunction(Name, OrigCallee->getAttributes(),
                                           ResTy, ArgTy, nullptr);
  
    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 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();
    Value *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();
    Value *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 -1 ? x : -x
    Value *Op = CI->getArgOperand(0);
    Value *Pos =
        B.CreateICmpSGT(Op, Constant::getAllOnesValue(Op->getType()), "ispos");
    Value *Neg = B.CreateNeg(Op, "neg");
    return B.CreateSelect(Pos, Op, Neg);
  }
  
  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));
  }
  
  //===----------------------------------------------------------------------===//
  // 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(AttributeSet::FunctionIndex, Attribute::Cold);
    }
  
    return nullptr;
  }
  
  static bool isReportingError(Function *Callee, CallInst *CI, int StreamArg) {
    if (!ColdErrorCalls || !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();
      Constant *IPrintFFn =
          M->getOrInsertFunction("iprintf", FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(IPrintFFn);
      B.Insert(New);
      return New;
    }
    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.
      for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
        if (FormatStr[i] == '%')
          return nullptr; // we found a format specifier, bail out.
  
      // sprintf(str, fmt) -> llvm.memcpy(str, fmt, strlen(fmt)+1, 1)
      B.CreateMemCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                     ConstantInt::get(DL.getIntPtrType(CI->getContext()),
                                      FormatStr.size() + 1),
                     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(dest, str, strlen(str)+1, 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), CI->getArgOperand(2), IncLen, 1);
  
      // 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();
      Constant *SIPrintFFn =
          M->getOrInsertFunction("siprintf", FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(SIPrintFFn);
      B.Insert(New);
      return New;
    }
    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) {
      for (unsigned i = 0, e = FormatStr.size(); i != e; ++i)
        if (FormatStr[i] == '%') // Could handle %% -> % if we cared.
          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();
      Constant *FIPrintFFn =
          M->getOrInsertFunction("fiprintf", FT, Callee->getAttributes());
      CallInst *New = cast<CallInst>(CI->clone());
      New->setCalledFunction(FIPrintFFn);
      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)
      return nullptr;
    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(castToCStr(CI->getArgOperand(0), B), "char");
      Value *NewCI = emitFPutC(Char, CI->getArgOperand(3), B, TLI);
      return NewCI ? ConstantInt::get(CI->getType(), 1) : nullptr;
    }
  
    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.
    if (CI->getParent()->getParent()->optForSize())
      return nullptr;
  
    // We can't optimize if return value is used.
    if (!CI->use_empty())
      return nullptr;
  
    // fputs(s,F) --> fwrite(s,1,strlen(s),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::optimizePuts(CallInst *CI, IRBuilder<> &B) {
    // Check for a constant string.
    StringRef Str;
    if (!getConstantStringInfo(CI->getArgOperand(0), Str))
      return nullptr;
  
    if (Str.empty() && CI->use_empty()) {
      // puts("") -> putchar('\n')
      Value *Res = emitPutChar(B.getInt32('\n'), B, TLI);
      if (CI->use_empty() || !Res)
        return Res;
      return B.CreateIntCast(Res, CI->getType(), true);
    }
  
    return nullptr;
  }
  
  bool LibCallSimplifier::hasFloatVersion(StringRef FuncName) {
    LibFunc::Func 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 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::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::memcmp:
        return optimizeMemCmp(CI, Builder);
      case LibFunc::memcpy:
        return optimizeMemCpy(CI, Builder);
      case LibFunc::memmove:
        return optimizeMemMove(CI, Builder);
      case LibFunc::memset:
        return optimizeMemSet(CI, Builder);
      default:
        break;
      }
    }
    return nullptr;
  }
  
  Value *LibCallSimplifier::optimizeCall(CallInst *CI) {
    if (CI->isNoBuiltin())
      return nullptr;
  
    LibFunc::Func Func;
    Function *Callee = CI->getCalledFunction();
    StringRef FuncName = Callee->getName();
  
    SmallVector<OperandBundleDef, 2> OpBundles;
    CI->getOperandBundlesAsDefs(OpBundles);
    IRBuilder<> Builder(CI, /*FPMathTag=*/nullptr, OpBundles);
    bool isCallingConvC = isCallingConvCCompatible(CI);
  
    // Command-line parameter overrides instruction attribute.
    if (EnableUnsafeFPShrink.getNumOccurrences() > 0)
      UnsafeFPShrink = EnableUnsafeFPShrink;
    else if (isa<FPMathOperator>(CI) && CI->hasUnsafeAlgebra())
      UnsafeFPShrink = true;
  
    // First, check for intrinsics.
    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
      if (!isCallingConvC)
        return nullptr;
      switch (II->getIntrinsicID()) {
      case Intrinsic::pow:
        return optimizePow(CI, Builder);
      case Intrinsic::exp2:
        return optimizeExp2(CI, Builder);
      case Intrinsic::fabs:
        return optimizeFabs(CI, Builder);
      case Intrinsic::log:
        return optimizeLog(CI, Builder);
      case Intrinsic::sqrt:
        return optimizeSqrt(CI, Builder);
      // TODO: Use foldMallocMemset() with memset intrinsic.
      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.
          SimplifiedCI->replaceAllUsesWith(V);
          SimplifiedCI->eraseFromParent();
          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;
      switch (Func) {
      case LibFunc::cosf:
      case LibFunc::cos:
      case LibFunc::cosl:
        return optimizeCos(CI, Builder);
      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 optimizeFabs(CI, Builder);
      case LibFunc::sqrtf:
      case LibFunc::sqrt:
      case LibFunc::sqrtl:
        return optimizeSqrt(CI, Builder);
      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::printf:
        return optimizePrintF(CI, Builder);
      case LibFunc::sprintf:
        return optimizeSPrintF(CI, Builder);
      case LibFunc::fprintf:
        return optimizeFPrintF(CI, Builder);
      case LibFunc::fwrite:
        return optimizeFWrite(CI, Builder);
      case LibFunc::fputs:
        return optimizeFPuts(CI, Builder);
      case LibFunc::log:
      case LibFunc::log10:
      case LibFunc::log1p:
      case LibFunc::log2:
      case LibFunc::logb:
        return optimizeLog(CI, Builder);
      case LibFunc::puts:
        return optimizePuts(CI, Builder);
      case LibFunc::tan:
      case LibFunc::tanf:
      case LibFunc::tanl:
        return optimizeTan(CI, Builder);
      case LibFunc::perror:
        return optimizeErrorReporting(CI, Builder);
      case LibFunc::vfprintf:
      case LibFunc::fiprintf:
        return optimizeErrorReporting(CI, Builder, 0);
      case LibFunc::fputc:
        return optimizeErrorReporting(CI, Builder, 1);
      case LibFunc::ceil:
      case LibFunc::floor:
      case LibFunc::rint:
      case LibFunc::round:
      case LibFunc::nearbyint:
      case LibFunc::trunc:
        if (hasFloatVersion(FuncName))
          return optimizeUnaryDoubleFP(CI, Builder, false);
        return nullptr;
      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::sin:
      case LibFunc::sinh:
      case LibFunc::tanh:
        if (UnsafeFPShrink && hasFloatVersion(FuncName))
          return optimizeUnaryDoubleFP(CI, Builder, true);
        return nullptr;
      case LibFunc::copysign:
        if (hasFloatVersion(FuncName))
          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);
      default:
        return nullptr;
      }
    }
    return nullptr;
  }
  
  LibCallSimplifier::LibCallSimplifier(
      const DataLayout &DL, const TargetLibraryInfo *TLI,
      function_ref<void(Instruction *, Value *)> Replacer)
      : FortifiedSimplifier(TLI), DL(DL), TLI(TLI), UnsafeFPShrink(false),
        Replacer(Replacer) {}
  
  void LibCallSimplifier::replaceAllUsesWith(Instruction *I, Value *With) {
    // Indirect through the replacer used in this instance.
    Replacer(I, With);
  }
  
  // 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)
  //
  // lround, lroundf, lroundl:
  //   * lround(cnst) -> cnst'
  //
  // pow, powf, powl:
  //   * pow(sqrt(x),y) -> pow(x,y*0.5)
  //   * pow(pow(x,y),z)-> pow(x,y*z)
  //
  // round, roundf, roundl:
  //   * round(cnst) -> cnst'
  //
  // 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)
  //
  // trunc, truncf, truncl:
  //   * trunc(cnst) -> cnst'
  //
  //
  
  //===----------------------------------------------------------------------===//
  // Fortified Library Call Optimizations
  //===----------------------------------------------------------------------===//
  
  bool FortifiedLibCallSimplifier::isFortifiedCallFoldable(CallInst *CI,
                                                           unsigned ObjSizeOp,
                                                           unsigned SizeOp,
                                                           bool isString) {
    if (CI->getArgOperand(ObjSizeOp) == CI->getArgOperand(SizeOp))
      return true;
    if (ConstantInt *ObjSizeCI =
            dyn_cast<ConstantInt>(CI->getArgOperand(ObjSizeOp))) {
      if (ObjSizeCI->isAllOnesValue())
        return true;
      // If the object size wasn't -1 (unknown), bail out if we were asked to.
      if (OnlyLowerUnknownSize)
        return false;
      if (isString) {
        uint64_t Len = GetStringLength(CI->getArgOperand(SizeOp));
        // If the length is 0 we don't know how long it is and so we can't
        // remove the check.
        if (Len == 0)
          return false;
        return ObjSizeCI->getZExtValue() >= Len;
      }
      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, false)) {
      B.CreateMemCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                     CI->getArgOperand(2), 1);
      return CI->getArgOperand(0);
    }
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeMemMoveChk(CallInst *CI,
                                                        IRBuilder<> &B) {
    if (isFortifiedCallFoldable(CI, 3, 2, false)) {
      B.CreateMemMove(CI->getArgOperand(0), CI->getArgOperand(1),
                      CI->getArgOperand(2), 1);
      return CI->getArgOperand(0);
    }
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeMemSetChk(CallInst *CI,
                                                       IRBuilder<> &B) {
    // TODO: Try foldMallocMemset() here.
  
    if (isFortifiedCallFoldable(CI, 3, 2, false)) {
      Value *Val = B.CreateIntCast(CI->getArgOperand(1), B.getInt8Ty(), false);
      B.CreateMemSet(CI->getArgOperand(0), Val, CI->getArgOperand(2), 1);
      return CI->getArgOperand(0);
    }
    return nullptr;
  }
  
  Value *FortifiedLibCallSimplifier::optimizeStrpCpyChk(CallInst *CI,
                                                        IRBuilder<> &B,
                                                        LibFunc::Func Func) {
    Function *Callee = CI->getCalledFunction();
    StringRef Name = Callee->getName();
    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, 1, true))
      return emitStrCpy(Dst, Src, B, TLI, Name.substr(2, 6));
  
    if (OnlyLowerUnknownSize)
      return nullptr;
  
    // Maybe we can stil fold __st[rp]cpy_chk to __memcpy_chk.
    uint64_t Len = GetStringLength(Src);
    if (Len == 0)
      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 Func) {
    Function *Callee = CI->getCalledFunction();
    StringRef Name = Callee->getName();
    if (isFortifiedCallFoldable(CI, 3, 2, false)) {
      Value *Ret = emitStrNCpy(CI->getArgOperand(0), CI->getArgOperand(1),
                               CI->getArgOperand(2), B, TLI, Name.substr(2, 7));
      return Ret;
    }
    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 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);
    default:
      break;
    }
    return nullptr;
  }
  
  FortifiedLibCallSimplifier::FortifiedLibCallSimplifier(
      const TargetLibraryInfo *TLI, bool OnlyLowerUnknownSize)
      : TLI(TLI), OnlyLowerUnknownSize(OnlyLowerUnknownSize) {}
  