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llvm-project/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

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//===------ 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;
}
/// 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) &&
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;
// 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);
// TODO: Should the new instructions propagate the 'fast' flag of the pow()?
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();
Value *Ret = nullptr;
StringRef Name = Callee->getName();
if (Name == "fabs" && hasFloatVersion(Name))
Ret = optimizeUnaryDoubleFP(CI, B, false);
Value *Op = CI->getArgOperand(0);
if (Instruction *I = dyn_cast<Instruction>(Op)) {
// Fold fabs(x * x) -> x * x; any squared FP value must already be positive.
if (I->getOpcode() == Instruction::FMul)
if (I->getOperand(0) == I->getOperand(1))
return Op;
}
return Ret;
}
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);
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);
}
}
void LibCallSimplifier::replaceTrigInsts(SmallVectorImpl<CallInst *> &Calls,
Value *Res) {
for (CallInst *C : Calls)
replaceAllUsesWith(C, Res);
}
//===----------------------------------------------------------------------===//
// Integer Library Call Optimizations
//===----------------------------------------------------------------------===//
Value *LibCallSimplifier::optimizeFFS(CallInst *CI, IRBuilder<> &B) {
Function *Callee = CI->getCalledFunction();
Value *Op = CI->getArgOperand(0);
// Constant fold.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
if (CI->isZero()) // ffs(0) -> 0.
return B.getInt32(0);
// ffs(c) -> cttz(c)+1
return B.getInt32(CI->getValue().countTrailingZeros() + 1);
}
// ffs(x) -> x != 0 ? (i32)llvm.cttz(x)+1 : 0
Type *ArgType = Op->getType();
Value *F =
Intrinsic::getDeclaration(Callee->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::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) ||
CI->getCallingConv() == llvm::CallingConv::C) &&
"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 = CI->getCallingConv() == llvm::CallingConv::C;
// 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::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 = CI->getCallingConv() == llvm::CallingConv::C;
// 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) {}
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