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llvm-mirror/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
Chandler Carruth 5b2abcc667 [PM] Rename InstCombine.h to InstCombineInternal.h in preparation for 
creating a non-internal header file for the InstCombine pass.

I thought about calling this InstCombiner.h or in some way more clearly
associating it with the InstCombiner clas that it is primarily defining,
but there are several other utility interfaces defined within this for
InstCombine. If, in the course of refactoring, those end up moving
elsewhere or going away, it might make more sense to make this the
combiner's header alone.

Naturally, this is a bikeshed to a certain degree, so feel free to lobby
for a different shade of paint if this name just doesn't suit you.

llvm-svn: 226783
2015-01-22 05:25:13 +00:00

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//===- InstCombineMulDivRem.cpp -------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the visit functions for mul, fmul, sdiv, udiv, fdiv,
// srem, urem, frem.
//
//===----------------------------------------------------------------------===//
#include "InstCombineInternal.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/PatternMatch.h"
using namespace llvm;
using namespace PatternMatch;
#define DEBUG_TYPE "instcombine"
/// simplifyValueKnownNonZero - The specific integer value is used in a context
/// where it is known to be non-zero. If this allows us to simplify the
/// computation, do so and return the new operand, otherwise return null.
static Value *simplifyValueKnownNonZero(Value *V, InstCombiner &IC,
Instruction *CxtI) {
// If V has multiple uses, then we would have to do more analysis to determine
// if this is safe. For example, the use could be in dynamically unreached
// code.
if (!V->hasOneUse()) return nullptr;
bool MadeChange = false;
// ((1 << A) >>u B) --> (1 << (A-B))
// Because V cannot be zero, we know that B is less than A.
Value *A = nullptr, *B = nullptr, *One = nullptr;
if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(One), m_Value(A))), m_Value(B))) &&
match(One, m_One())) {
A = IC.Builder->CreateSub(A, B);
return IC.Builder->CreateShl(One, A);
}
// (PowerOfTwo >>u B) --> isExact since shifting out the result would make it
// inexact. Similarly for <<.
if (BinaryOperator *I = dyn_cast<BinaryOperator>(V))
if (I->isLogicalShift() &&
isKnownToBeAPowerOfTwo(I->getOperand(0), false, 0,
IC.getAssumptionCache(), CxtI,
IC.getDominatorTree())) {
// We know that this is an exact/nuw shift and that the input is a
// non-zero context as well.
if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC, CxtI)) {
I->setOperand(0, V2);
MadeChange = true;
}
if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
I->setIsExact();
MadeChange = true;
}
if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
I->setHasNoUnsignedWrap();
MadeChange = true;
}
}
// TODO: Lots more we could do here:
// If V is a phi node, we can call this on each of its operands.
// "select cond, X, 0" can simplify to "X".
return MadeChange ? V : nullptr;
}
/// MultiplyOverflows - True if the multiply can not be expressed in an int
/// this size.
static bool MultiplyOverflows(const APInt &C1, const APInt &C2, APInt &Product,
bool IsSigned) {
bool Overflow;
if (IsSigned)
Product = C1.smul_ov(C2, Overflow);
else
Product = C1.umul_ov(C2, Overflow);
return Overflow;
}
/// \brief True if C2 is a multiple of C1. Quotient contains C2/C1.
static bool IsMultiple(const APInt &C1, const APInt &C2, APInt &Quotient,
bool IsSigned) {
assert(C1.getBitWidth() == C2.getBitWidth() &&
"Inconsistent width of constants!");
APInt Remainder(C1.getBitWidth(), /*Val=*/0ULL, IsSigned);
if (IsSigned)
APInt::sdivrem(C1, C2, Quotient, Remainder);
else
APInt::udivrem(C1, C2, Quotient, Remainder);
return Remainder.isMinValue();
}
/// \brief A helper routine of InstCombiner::visitMul().
///
/// If C is a vector of known powers of 2, then this function returns
/// a new vector obtained from C replacing each element with its logBase2.
/// Return a null pointer otherwise.
static Constant *getLogBase2Vector(ConstantDataVector *CV) {
const APInt *IVal;
SmallVector<Constant *, 4> Elts;
for (unsigned I = 0, E = CV->getNumElements(); I != E; ++I) {
Constant *Elt = CV->getElementAsConstant(I);
if (!match(Elt, m_APInt(IVal)) || !IVal->isPowerOf2())
return nullptr;
Elts.push_back(ConstantInt::get(Elt->getType(), IVal->logBase2()));
}
return ConstantVector::get(Elts);
}
/// \brief Return true if we can prove that:
/// (mul LHS, RHS) === (mul nsw LHS, RHS)
bool InstCombiner::WillNotOverflowSignedMul(Value *LHS, Value *RHS,
Instruction *CxtI) {
// Multiplying n * m significant bits yields a result of n + m significant
// bits. If the total number of significant bits does not exceed the
// result bit width (minus 1), there is no overflow.
// This means if we have enough leading sign bits in the operands
// we can guarantee that the result does not overflow.
// Ref: "Hacker's Delight" by Henry Warren
unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
// Note that underestimating the number of sign bits gives a more
// conservative answer.
unsigned SignBits = ComputeNumSignBits(LHS, 0, CxtI) +
ComputeNumSignBits(RHS, 0, CxtI);
// First handle the easy case: if we have enough sign bits there's
// definitely no overflow.
if (SignBits > BitWidth + 1)
return true;
// There are two ambiguous cases where there can be no overflow:
// SignBits == BitWidth + 1 and
// SignBits == BitWidth
// The second case is difficult to check, therefore we only handle the
// first case.
if (SignBits == BitWidth + 1) {
// It overflows only when both arguments are negative and the true
// product is exactly the minimum negative number.
// E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
// For simplicity we just check if at least one side is not negative.
bool LHSNonNegative, LHSNegative;
bool RHSNonNegative, RHSNegative;
ComputeSignBit(LHS, LHSNonNegative, LHSNegative, /*Depth=*/0, CxtI);
ComputeSignBit(RHS, RHSNonNegative, RHSNegative, /*Depth=*/0, CxtI);
if (LHSNonNegative || RHSNonNegative)
return true;
}
return false;
}
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
bool Changed = SimplifyAssociativeOrCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifyMulInst(Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifyUsingDistributiveLaws(I))
return ReplaceInstUsesWith(I, V);
// X * -1 == 0 - X
if (match(Op1, m_AllOnes())) {
BinaryOperator *BO = BinaryOperator::CreateNeg(Op0, I.getName());
if (I.hasNoSignedWrap())
BO->setHasNoSignedWrap();
return BO;
}
// Also allow combining multiply instructions on vectors.
{
Value *NewOp;
Constant *C1, *C2;
const APInt *IVal;
if (match(&I, m_Mul(m_Shl(m_Value(NewOp), m_Constant(C2)),
m_Constant(C1))) &&
match(C1, m_APInt(IVal))) {
// ((X << C2)*C1) == (X * (C1 << C2))
Constant *Shl = ConstantExpr::getShl(C1, C2);
BinaryOperator *Mul = cast<BinaryOperator>(I.getOperand(0));
BinaryOperator *BO = BinaryOperator::CreateMul(NewOp, Shl);
if (I.hasNoUnsignedWrap() && Mul->hasNoUnsignedWrap())
BO->setHasNoUnsignedWrap();
if (I.hasNoSignedWrap() && Mul->hasNoSignedWrap() &&
Shl->isNotMinSignedValue())
BO->setHasNoSignedWrap();
return BO;
}
if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
Constant *NewCst = nullptr;
if (match(C1, m_APInt(IVal)) && IVal->isPowerOf2())
// Replace X*(2^C) with X << C, where C is either a scalar or a splat.
NewCst = ConstantInt::get(NewOp->getType(), IVal->logBase2());
else if (ConstantDataVector *CV = dyn_cast<ConstantDataVector>(C1))
// Replace X*(2^C) with X << C, where C is a vector of known
// constant powers of 2.
NewCst = getLogBase2Vector(CV);
if (NewCst) {
BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
if (I.hasNoUnsignedWrap())
Shl->setHasNoUnsignedWrap();
if (I.hasNoSignedWrap() && NewCst->isNotMinSignedValue())
Shl->setHasNoSignedWrap();
return Shl;
}
}
}
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
// (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
// (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
// The "* (2**n)" thus becomes a potential shifting opportunity.
{
const APInt & Val = CI->getValue();
const APInt &PosVal = Val.abs();
if (Val.isNegative() && PosVal.isPowerOf2()) {
Value *X = nullptr, *Y = nullptr;
if (Op0->hasOneUse()) {
ConstantInt *C1;
Value *Sub = nullptr;
if (match(Op0, m_Sub(m_Value(Y), m_Value(X))))
Sub = Builder->CreateSub(X, Y, "suba");
else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))
Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
if (Sub)
return
BinaryOperator::CreateMul(Sub,
ConstantInt::get(Y->getType(), PosVal));
}
}
}
}
// Simplify mul instructions with a constant RHS.
if (isa<Constant>(Op1)) {
// Try to fold constant mul into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
// Canonicalize (X+C1)*CI -> X*CI+C1*CI.
{
Value *X;
Constant *C1;
if (match(Op0, m_OneUse(m_Add(m_Value(X), m_Constant(C1))))) {
Value *Mul = Builder->CreateMul(C1, Op1);
// Only go forward with the transform if C1*CI simplifies to a tidier
// constant.
if (!match(Mul, m_Mul(m_Value(), m_Value())))
return BinaryOperator::CreateAdd(Builder->CreateMul(X, Op1), Mul);
}
}
}
if (Value *Op0v = dyn_castNegVal(Op0)) { // -X * -Y = X*Y
if (Value *Op1v = dyn_castNegVal(Op1)) {
BinaryOperator *BO = BinaryOperator::CreateMul(Op0v, Op1v);
if (I.hasNoSignedWrap() &&
match(Op0, m_NSWSub(m_Value(), m_Value())) &&
match(Op1, m_NSWSub(m_Value(), m_Value())))
BO->setHasNoSignedWrap();
return BO;
}
}
// (X / Y) * Y = X - (X % Y)
// (X / Y) * -Y = (X % Y) - X
{
Value *Op1C = Op1;
BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0);
if (!BO ||
(BO->getOpcode() != Instruction::UDiv &&
BO->getOpcode() != Instruction::SDiv)) {
Op1C = Op0;
BO = dyn_cast<BinaryOperator>(Op1);
}
Value *Neg = dyn_castNegVal(Op1C);
if (BO && BO->hasOneUse() &&
(BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) &&
(BO->getOpcode() == Instruction::UDiv ||
BO->getOpcode() == Instruction::SDiv)) {
Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
// If the division is exact, X % Y is zero, so we end up with X or -X.
if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO))
if (SDiv->isExact()) {
if (Op1BO == Op1C)
return ReplaceInstUsesWith(I, Op0BO);
return BinaryOperator::CreateNeg(Op0BO);
}
Value *Rem;
if (BO->getOpcode() == Instruction::UDiv)
Rem = Builder->CreateURem(Op0BO, Op1BO);
else
Rem = Builder->CreateSRem(Op0BO, Op1BO);
Rem->takeName(BO);
if (Op1BO == Op1C)
return BinaryOperator::CreateSub(Op0BO, Rem);
return BinaryOperator::CreateSub(Rem, Op0BO);
}
}
/// i1 mul -> i1 and.
if (I.getType()->getScalarType()->isIntegerTy(1))
return BinaryOperator::CreateAnd(Op0, Op1);
// X*(1 << Y) --> X << Y
// (1 << Y)*X --> X << Y
{
Value *Y;
BinaryOperator *BO = nullptr;
bool ShlNSW = false;
if (match(Op0, m_Shl(m_One(), m_Value(Y)))) {
BO = BinaryOperator::CreateShl(Op1, Y);
ShlNSW = cast<ShlOperator>(Op0)->hasNoSignedWrap();
} else if (match(Op1, m_Shl(m_One(), m_Value(Y)))) {
BO = BinaryOperator::CreateShl(Op0, Y);
ShlNSW = cast<ShlOperator>(Op1)->hasNoSignedWrap();
}
if (BO) {
if (I.hasNoUnsignedWrap())
BO->setHasNoUnsignedWrap();
if (I.hasNoSignedWrap() && ShlNSW)
BO->setHasNoSignedWrap();
return BO;
}
}
// If one of the operands of the multiply is a cast from a boolean value, then
// we know the bool is either zero or one, so this is a 'masking' multiply.
// X * Y (where Y is 0 or 1) -> X & (0-Y)
if (!I.getType()->isVectorTy()) {
// -2 is "-1 << 1" so it is all bits set except the low one.
APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true);
Value *BoolCast = nullptr, *OtherOp = nullptr;
if (MaskedValueIsZero(Op0, Negative2, 0, &I))
BoolCast = Op0, OtherOp = Op1;
else if (MaskedValueIsZero(Op1, Negative2, 0, &I))
BoolCast = Op1, OtherOp = Op0;
if (BoolCast) {
Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()),
BoolCast);
return BinaryOperator::CreateAnd(V, OtherOp);
}
}
if (!I.hasNoSignedWrap() && WillNotOverflowSignedMul(Op0, Op1, &I)) {
Changed = true;
I.setHasNoSignedWrap(true);
}
if (!I.hasNoUnsignedWrap() &&
computeOverflowForUnsignedMul(Op0, Op1, &I) ==
OverflowResult::NeverOverflows) {
Changed = true;
I.setHasNoUnsignedWrap(true);
}
return Changed ? &I : nullptr;
}
/// Detect pattern log2(Y * 0.5) with corresponding fast math flags.
static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
if (!Op->hasOneUse())
return;
IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
if (!II)
return;
if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra())
return;
Log2 = II;
Value *OpLog2Of = II->getArgOperand(0);
if (!OpLog2Of->hasOneUse())
return;
Instruction *I = dyn_cast<Instruction>(OpLog2Of);
if (!I)
return;
if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
return;
if (match(I->getOperand(0), m_SpecificFP(0.5)))
Y = I->getOperand(1);
else if (match(I->getOperand(1), m_SpecificFP(0.5)))
Y = I->getOperand(0);
}
static bool isFiniteNonZeroFp(Constant *C) {
if (C->getType()->isVectorTy()) {
for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
++I) {
ConstantFP *CFP = dyn_cast<ConstantFP>(C->getAggregateElement(I));
if (!CFP || !CFP->getValueAPF().isFiniteNonZero())
return false;
}
return true;
}
return isa<ConstantFP>(C) &&
cast<ConstantFP>(C)->getValueAPF().isFiniteNonZero();
}
static bool isNormalFp(Constant *C) {
if (C->getType()->isVectorTy()) {
for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
++I) {
ConstantFP *CFP = dyn_cast<ConstantFP>(C->getAggregateElement(I));
if (!CFP || !CFP->getValueAPF().isNormal())
return false;
}
return true;
}
return isa<ConstantFP>(C) && cast<ConstantFP>(C)->getValueAPF().isNormal();
}
/// Helper function of InstCombiner::visitFMul(BinaryOperator(). It returns
/// true iff the given value is FMul or FDiv with one and only one operand
/// being a normal constant (i.e. not Zero/NaN/Infinity).
static bool isFMulOrFDivWithConstant(Value *V) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I || (I->getOpcode() != Instruction::FMul &&
I->getOpcode() != Instruction::FDiv))
return false;
Constant *C0 = dyn_cast<Constant>(I->getOperand(0));
Constant *C1 = dyn_cast<Constant>(I->getOperand(1));
if (C0 && C1)
return false;
return (C0 && isFiniteNonZeroFp(C0)) || (C1 && isFiniteNonZeroFp(C1));
}
/// foldFMulConst() is a helper routine of InstCombiner::visitFMul().
/// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand
/// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true).
/// This function is to simplify "FMulOrDiv * C" and returns the
/// resulting expression. Note that this function could return NULL in
/// case the constants cannot be folded into a normal floating-point.
///
Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, Constant *C,
Instruction *InsertBefore) {
assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid");
Value *Opnd0 = FMulOrDiv->getOperand(0);
Value *Opnd1 = FMulOrDiv->getOperand(1);
Constant *C0 = dyn_cast<Constant>(Opnd0);
Constant *C1 = dyn_cast<Constant>(Opnd1);
BinaryOperator *R = nullptr;
// (X * C0) * C => X * (C0*C)
if (FMulOrDiv->getOpcode() == Instruction::FMul) {
Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C);
if (isNormalFp(F))
R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F);
} else {
if (C0) {
// (C0 / X) * C => (C0 * C) / X
if (FMulOrDiv->hasOneUse()) {
// It would otherwise introduce another div.
Constant *F = ConstantExpr::getFMul(C0, C);
if (isNormalFp(F))
R = BinaryOperator::CreateFDiv(F, Opnd1);
}
} else {
// (X / C1) * C => X * (C/C1) if C/C1 is not a denormal
Constant *F = ConstantExpr::getFDiv(C, C1);
if (isNormalFp(F)) {
R = BinaryOperator::CreateFMul(Opnd0, F);
} else {
// (X / C1) * C => X / (C1/C)
Constant *F = ConstantExpr::getFDiv(C1, C);
if (isNormalFp(F))
R = BinaryOperator::CreateFDiv(Opnd0, F);
}
}
}
if (R) {
R->setHasUnsafeAlgebra(true);
InsertNewInstWith(R, *InsertBefore);
}
return R;
}
Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
bool Changed = SimplifyAssociativeOrCommutative(I);
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (isa<Constant>(Op0))
std::swap(Op0, Op1);
if (Value *V =
SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(), DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
bool AllowReassociate = I.hasUnsafeAlgebra();
// Simplify mul instructions with a constant RHS.
if (isa<Constant>(Op1)) {
// Try to fold constant mul into select arguments.
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
// (fmul X, -1.0) --> (fsub -0.0, X)
if (match(Op1, m_SpecificFP(-1.0))) {
Constant *NegZero = ConstantFP::getNegativeZero(Op1->getType());
Instruction *RI = BinaryOperator::CreateFSub(NegZero, Op0);
RI->copyFastMathFlags(&I);
return RI;
}
Constant *C = cast<Constant>(Op1);
if (AllowReassociate && isFiniteNonZeroFp(C)) {
// Let MDC denote an expression in one of these forms:
// X * C, C/X, X/C, where C is a constant.
//
// Try to simplify "MDC * Constant"
if (isFMulOrFDivWithConstant(Op0))
if (Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I))
return ReplaceInstUsesWith(I, V);
// (MDC +/- C1) * C => (MDC * C) +/- (C1 * C)
Instruction *FAddSub = dyn_cast<Instruction>(Op0);
if (FAddSub &&
(FAddSub->getOpcode() == Instruction::FAdd ||
FAddSub->getOpcode() == Instruction::FSub)) {
Value *Opnd0 = FAddSub->getOperand(0);
Value *Opnd1 = FAddSub->getOperand(1);
Constant *C0 = dyn_cast<Constant>(Opnd0);
Constant *C1 = dyn_cast<Constant>(Opnd1);
bool Swap = false;
if (C0) {
std::swap(C0, C1);
std::swap(Opnd0, Opnd1);
Swap = true;
}
if (C1 && isFiniteNonZeroFp(C1) && isFMulOrFDivWithConstant(Opnd0)) {
Value *M1 = ConstantExpr::getFMul(C1, C);
Value *M0 = isNormalFp(cast<Constant>(M1)) ?
foldFMulConst(cast<Instruction>(Opnd0), C, &I) :
nullptr;
if (M0 && M1) {
if (Swap && FAddSub->getOpcode() == Instruction::FSub)
std::swap(M0, M1);
Instruction *RI = (FAddSub->getOpcode() == Instruction::FAdd)
? BinaryOperator::CreateFAdd(M0, M1)
: BinaryOperator::CreateFSub(M0, M1);
RI->copyFastMathFlags(&I);
return RI;
}
}
}
}
}
// sqrt(X) * sqrt(X) -> X
if (AllowReassociate && (Op0 == Op1))
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0))
if (II->getIntrinsicID() == Intrinsic::sqrt)
return ReplaceInstUsesWith(I, II->getOperand(0));
// Under unsafe algebra do:
// X * log2(0.5*Y) = X*log2(Y) - X
if (AllowReassociate) {
Value *OpX = nullptr;
Value *OpY = nullptr;
IntrinsicInst *Log2;
detectLog2OfHalf(Op0, OpY, Log2);
if (OpY) {
OpX = Op1;
} else {
detectLog2OfHalf(Op1, OpY, Log2);
if (OpY) {
OpX = Op0;
}
}
// if pattern detected emit alternate sequence
if (OpX && OpY) {
BuilderTy::FastMathFlagGuard Guard(*Builder);
Builder->SetFastMathFlags(Log2->getFastMathFlags());
Log2->setArgOperand(0, OpY);
Value *FMulVal = Builder->CreateFMul(OpX, Log2);
Value *FSub = Builder->CreateFSub(FMulVal, OpX);
FSub->takeName(&I);
return ReplaceInstUsesWith(I, FSub);
}
}
// Handle symmetric situation in a 2-iteration loop
Value *Opnd0 = Op0;
Value *Opnd1 = Op1;
for (int i = 0; i < 2; i++) {
bool IgnoreZeroSign = I.hasNoSignedZeros();
if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) {
BuilderTy::FastMathFlagGuard Guard(*Builder);
Builder->SetFastMathFlags(I.getFastMathFlags());
Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign);
Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign);
// -X * -Y => X*Y
if (N1) {
Value *FMul = Builder->CreateFMul(N0, N1);
FMul->takeName(&I);
return ReplaceInstUsesWith(I, FMul);
}
if (Opnd0->hasOneUse()) {
// -X * Y => -(X*Y) (Promote negation as high as possible)
Value *T = Builder->CreateFMul(N0, Opnd1);
Value *Neg = Builder->CreateFNeg(T);
Neg->takeName(&I);
return ReplaceInstUsesWith(I, Neg);
}
}
// (X*Y) * X => (X*X) * Y where Y != X
// The purpose is two-fold:
// 1) to form a power expression (of X).
// 2) potentially shorten the critical path: After transformation, the
// latency of the instruction Y is amortized by the expression of X*X,
// and therefore Y is in a "less critical" position compared to what it
// was before the transformation.
//
if (AllowReassociate) {
Value *Opnd0_0, *Opnd0_1;
if (Opnd0->hasOneUse() &&
match(Opnd0, m_FMul(m_Value(Opnd0_0), m_Value(Opnd0_1)))) {
Value *Y = nullptr;
if (Opnd0_0 == Opnd1 && Opnd0_1 != Opnd1)
Y = Opnd0_1;
else if (Opnd0_1 == Opnd1 && Opnd0_0 != Opnd1)
Y = Opnd0_0;
if (Y) {
BuilderTy::FastMathFlagGuard Guard(*Builder);
Builder->SetFastMathFlags(I.getFastMathFlags());
Value *T = Builder->CreateFMul(Opnd1, Opnd1);
Value *R = Builder->CreateFMul(T, Y);
R->takeName(&I);
return ReplaceInstUsesWith(I, R);
}
}
}
if (!isa<Constant>(Op1))
std::swap(Opnd0, Opnd1);
else
break;
}
return Changed ? &I : nullptr;
}
/// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
/// instruction.
bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
SelectInst *SI = cast<SelectInst>(I.getOperand(1));
// div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
int NonNullOperand = -1;
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
if (ST->isNullValue())
NonNullOperand = 2;
// div/rem X, (Cond ? Y : 0) -> div/rem X, Y
if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
if (ST->isNullValue())
NonNullOperand = 1;
if (NonNullOperand == -1)
return false;
Value *SelectCond = SI->getOperand(0);
// Change the div/rem to use 'Y' instead of the select.
I.setOperand(1, SI->getOperand(NonNullOperand));
// Okay, we know we replace the operand of the div/rem with 'Y' with no
// problem. However, the select, or the condition of the select may have
// multiple uses. Based on our knowledge that the operand must be non-zero,
// propagate the known value for the select into other uses of it, and
// propagate a known value of the condition into its other users.
// If the select and condition only have a single use, don't bother with this,
// early exit.
if (SI->use_empty() && SelectCond->hasOneUse())
return true;
// Scan the current block backward, looking for other uses of SI.
BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
while (BBI != BBFront) {
--BBI;
// If we found a call to a function, we can't assume it will return, so
// information from below it cannot be propagated above it.
if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
break;
// Replace uses of the select or its condition with the known values.
for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
I != E; ++I) {
if (*I == SI) {
*I = SI->getOperand(NonNullOperand);
Worklist.Add(BBI);
} else if (*I == SelectCond) {
*I = Builder->getInt1(NonNullOperand == 1);
Worklist.Add(BBI);
}
}
// If we past the instruction, quit looking for it.
if (&*BBI == SI)
SI = nullptr;
if (&*BBI == SelectCond)
SelectCond = nullptr;
// If we ran out of things to eliminate, break out of the loop.
if (!SelectCond && !SI)
break;
}
return true;
}
/// This function implements the transforms common to both integer division
/// instructions (udiv and sdiv). It is called by the visitors to those integer
/// division instructions.
/// @brief Common integer divide transforms
Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// The RHS is known non-zero.
if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, &I)) {
I.setOperand(1, V);
return &I;
}
// Handle cases involving: [su]div X, (select Cond, Y, Z)
// This does not apply for fdiv.
if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
return &I;
if (Instruction *LHS = dyn_cast<Instruction>(Op0)) {
const APInt *C2;
if (match(Op1, m_APInt(C2))) {
Value *X;
const APInt *C1;
bool IsSigned = I.getOpcode() == Instruction::SDiv;
// (X / C1) / C2 -> X / (C1*C2)
if ((IsSigned && match(LHS, m_SDiv(m_Value(X), m_APInt(C1)))) ||
(!IsSigned && match(LHS, m_UDiv(m_Value(X), m_APInt(C1))))) {
APInt Product(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
if (!MultiplyOverflows(*C1, *C2, Product, IsSigned))
return BinaryOperator::Create(I.getOpcode(), X,
ConstantInt::get(I.getType(), Product));
}
if ((IsSigned && match(LHS, m_NSWMul(m_Value(X), m_APInt(C1)))) ||
(!IsSigned && match(LHS, m_NUWMul(m_Value(X), m_APInt(C1))))) {
APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
// (X * C1) / C2 -> X / (C2 / C1) if C2 is a multiple of C1.
if (IsMultiple(*C2, *C1, Quotient, IsSigned)) {
BinaryOperator *BO = BinaryOperator::Create(
I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
BO->setIsExact(I.isExact());
return BO;
}
// (X * C1) / C2 -> X * (C1 / C2) if C1 is a multiple of C2.
if (IsMultiple(*C1, *C2, Quotient, IsSigned)) {
BinaryOperator *BO = BinaryOperator::Create(
Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
BO->setHasNoUnsignedWrap(
!IsSigned &&
cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
BO->setHasNoSignedWrap(
cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
return BO;
}
}
if ((IsSigned && match(LHS, m_NSWShl(m_Value(X), m_APInt(C1))) &&
*C1 != C1->getBitWidth() - 1) ||
(!IsSigned && match(LHS, m_NUWShl(m_Value(X), m_APInt(C1))))) {
APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
APInt C1Shifted = APInt::getOneBitSet(
C1->getBitWidth(), static_cast<unsigned>(C1->getLimitedValue()));
// (X << C1) / C2 -> X / (C2 >> C1) if C2 is a multiple of C1.
if (IsMultiple(*C2, C1Shifted, Quotient, IsSigned)) {
BinaryOperator *BO = BinaryOperator::Create(
I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
BO->setIsExact(I.isExact());
return BO;
}
// (X << C1) / C2 -> X * (C2 >> C1) if C1 is a multiple of C2.
if (IsMultiple(C1Shifted, *C2, Quotient, IsSigned)) {
BinaryOperator *BO = BinaryOperator::Create(
Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
BO->setHasNoUnsignedWrap(
!IsSigned &&
cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
BO->setHasNoSignedWrap(
cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
return BO;
}
}
if (*C2 != 0) { // avoid X udiv 0
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
if (isa<PHINode>(Op0))
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
}
}
if (ConstantInt *One = dyn_cast<ConstantInt>(Op0)) {
if (One->isOne() && !I.getType()->isIntegerTy(1)) {
bool isSigned = I.getOpcode() == Instruction::SDiv;
if (isSigned) {
// If Op1 is 0 then it's undefined behaviour, if Op1 is 1 then the
// result is one, if Op1 is -1 then the result is minus one, otherwise
// it's zero.
Value *Inc = Builder->CreateAdd(Op1, One);
Value *Cmp = Builder->CreateICmpULT(
Inc, ConstantInt::get(I.getType(), 3));
return SelectInst::Create(Cmp, Op1, ConstantInt::get(I.getType(), 0));
} else {
// If Op1 is 0 then it's undefined behaviour. If Op1 is 1 then the
// result is one, otherwise it's zero.
return new ZExtInst(Builder->CreateICmpEQ(Op1, One), I.getType());
}
}
}
// See if we can fold away this div instruction.
if (SimplifyDemandedInstructionBits(I))
return &I;
// (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
Value *X = nullptr, *Z = nullptr;
if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
bool isSigned = I.getOpcode() == Instruction::SDiv;
if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
(!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
return BinaryOperator::Create(I.getOpcode(), X, Op1);
}
return nullptr;
}
/// dyn_castZExtVal - Checks if V is a zext or constant that can
/// be truncated to Ty without losing bits.
static Value *dyn_castZExtVal(Value *V, Type *Ty) {
if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) {
if (Z->getSrcTy() == Ty)
return Z->getOperand(0);
} else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) {
if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth())
return ConstantExpr::getTrunc(C, Ty);
}
return nullptr;
}
namespace {
const unsigned MaxDepth = 6;
typedef Instruction *(*FoldUDivOperandCb)(Value *Op0, Value *Op1,
const BinaryOperator &I,
InstCombiner &IC);
/// \brief Used to maintain state for visitUDivOperand().
struct UDivFoldAction {
FoldUDivOperandCb FoldAction; ///< Informs visitUDiv() how to fold this
///< operand. This can be zero if this action
///< joins two actions together.
Value *OperandToFold; ///< Which operand to fold.
union {
Instruction *FoldResult; ///< The instruction returned when FoldAction is
///< invoked.
size_t SelectLHSIdx; ///< Stores the LHS action index if this action
///< joins two actions together.
};
UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand)
: FoldAction(FA), OperandToFold(InputOperand), FoldResult(nullptr) {}
UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand, size_t SLHS)
: FoldAction(FA), OperandToFold(InputOperand), SelectLHSIdx(SLHS) {}
};
}
// X udiv 2^C -> X >> C
static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
const BinaryOperator &I, InstCombiner &IC) {
const APInt &C = cast<Constant>(Op1)->getUniqueInteger();
BinaryOperator *LShr = BinaryOperator::CreateLShr(
Op0, ConstantInt::get(Op0->getType(), C.logBase2()));
if (I.isExact())
LShr->setIsExact();
return LShr;
}
// X udiv C, where C >= signbit
static Instruction *foldUDivNegCst(Value *Op0, Value *Op1,
const BinaryOperator &I, InstCombiner &IC) {
Value *ICI = IC.Builder->CreateICmpULT(Op0, cast<ConstantInt>(Op1));
return SelectInst::Create(ICI, Constant::getNullValue(I.getType()),
ConstantInt::get(I.getType(), 1));
}
// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
InstCombiner &IC) {
Instruction *ShiftLeft = cast<Instruction>(Op1);
if (isa<ZExtInst>(ShiftLeft))
ShiftLeft = cast<Instruction>(ShiftLeft->getOperand(0));
const APInt &CI =
cast<Constant>(ShiftLeft->getOperand(0))->getUniqueInteger();
Value *N = ShiftLeft->getOperand(1);
if (CI != 1)
N = IC.Builder->CreateAdd(N, ConstantInt::get(N->getType(), CI.logBase2()));
if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
N = IC.Builder->CreateZExt(N, Z->getDestTy());
BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
if (I.isExact())
LShr->setIsExact();
return LShr;
}
// \brief Recursively visits the possible right hand operands of a udiv
// instruction, seeing through select instructions, to determine if we can
// replace the udiv with something simpler. If we find that an operand is not
// able to simplify the udiv, we abort the entire transformation.
static size_t visitUDivOperand(Value *Op0, Value *Op1, const BinaryOperator &I,
SmallVectorImpl<UDivFoldAction> &Actions,
unsigned Depth = 0) {
// Check to see if this is an unsigned division with an exact power of 2,
// if so, convert to a right shift.
if (match(Op1, m_Power2())) {
Actions.push_back(UDivFoldAction(foldUDivPow2Cst, Op1));
return Actions.size();
}
if (ConstantInt *C = dyn_cast<ConstantInt>(Op1))
// X udiv C, where C >= signbit
if (C->getValue().isNegative()) {
Actions.push_back(UDivFoldAction(foldUDivNegCst, C));
return Actions.size();
}
// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
if (match(Op1, m_Shl(m_Power2(), m_Value())) ||
match(Op1, m_ZExt(m_Shl(m_Power2(), m_Value())))) {
Actions.push_back(UDivFoldAction(foldUDivShl, Op1));
return Actions.size();
}
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth++ == MaxDepth)
return 0;
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (size_t LHSIdx =
visitUDivOperand(Op0, SI->getOperand(1), I, Actions, Depth))
if (visitUDivOperand(Op0, SI->getOperand(2), I, Actions, Depth)) {
Actions.push_back(UDivFoldAction(nullptr, Op1, LHSIdx - 1));
return Actions.size();
}
return 0;
}
Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifyUDivInst(Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
// (x lshr C1) udiv C2 --> x udiv (C2 << C1)
{
Value *X;
const APInt *C1, *C2;
if (match(Op0, m_LShr(m_Value(X), m_APInt(C1))) &&
match(Op1, m_APInt(C2))) {
bool Overflow;
APInt C2ShlC1 = C2->ushl_ov(*C1, Overflow);
if (!Overflow) {
bool IsExact = I.isExact() && match(Op0, m_Exact(m_Value()));
BinaryOperator *BO = BinaryOperator::CreateUDiv(
X, ConstantInt::get(X->getType(), C2ShlC1));
if (IsExact)
BO->setIsExact();
return BO;
}
}
}
// (zext A) udiv (zext B) --> zext (A udiv B)
if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
return new ZExtInst(
Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div", I.isExact()),
I.getType());
// (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...))))
SmallVector<UDivFoldAction, 6> UDivActions;
if (visitUDivOperand(Op0, Op1, I, UDivActions))
for (unsigned i = 0, e = UDivActions.size(); i != e; ++i) {
FoldUDivOperandCb Action = UDivActions[i].FoldAction;
Value *ActionOp1 = UDivActions[i].OperandToFold;
Instruction *Inst;
if (Action)
Inst = Action(Op0, ActionOp1, I, *this);
else {
// This action joins two actions together. The RHS of this action is
// simply the last action we processed, we saved the LHS action index in
// the joining action.
size_t SelectRHSIdx = i - 1;
Value *SelectRHS = UDivActions[SelectRHSIdx].FoldResult;
size_t SelectLHSIdx = UDivActions[i].SelectLHSIdx;
Value *SelectLHS = UDivActions[SelectLHSIdx].FoldResult;
Inst = SelectInst::Create(cast<SelectInst>(ActionOp1)->getCondition(),
SelectLHS, SelectRHS);
}
// If this is the last action to process, return it to the InstCombiner.
// Otherwise, we insert it before the UDiv and record it so that we may
// use it as part of a joining action (i.e., a SelectInst).
if (e - i != 1) {
Inst->insertBefore(&I);
UDivActions[i].FoldResult = Inst;
} else
return Inst;
}
return nullptr;
}
Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifySDivInst(Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
// sdiv X, -1 == -X
if (match(Op1, m_AllOnes()))
return BinaryOperator::CreateNeg(Op0);
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
// sdiv X, C --> ashr exact X, log2(C)
if (I.isExact() && RHS->getValue().isNonNegative() &&
RHS->getValue().isPowerOf2()) {
Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
RHS->getValue().exactLogBase2());
return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
}
}
if (Constant *RHS = dyn_cast<Constant>(Op1)) {
// X/INT_MIN -> X == INT_MIN
if (RHS->isMinSignedValue())
return new ZExtInst(Builder->CreateICmpEQ(Op0, Op1), I.getType());
// -X/C --> X/-C provided the negation doesn't overflow.
Value *X;
if (match(Op0, m_NSWSub(m_Zero(), m_Value(X)))) {
auto *BO = BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(RHS));
BO->setIsExact(I.isExact());
return BO;
}
}
// If the sign bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a udiv.
if (I.getType()->isIntegerTy()) {
APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
if (MaskedValueIsZero(Op0, Mask, 0, &I)) {
if (MaskedValueIsZero(Op1, Mask, 0, &I)) {
// X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
BO->setIsExact(I.isExact());
return BO;
}
if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, AC, &I, DT)) {
// X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
// Safe because the only negative value (1 << Y) can take on is
// INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
// the sign bit set.
auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
BO->setIsExact(I.isExact());
return BO;
}
}
}
return nullptr;
}
/// CvtFDivConstToReciprocal tries to convert X/C into X*1/C if C not a special
/// FP value and:
/// 1) 1/C is exact, or
/// 2) reciprocal is allowed.
/// If the conversion was successful, the simplified expression "X * 1/C" is
/// returned; otherwise, NULL is returned.
///
static Instruction *CvtFDivConstToReciprocal(Value *Dividend, Constant *Divisor,
bool AllowReciprocal) {
if (!isa<ConstantFP>(Divisor)) // TODO: handle vectors.
return nullptr;
const APFloat &FpVal = cast<ConstantFP>(Divisor)->getValueAPF();
APFloat Reciprocal(FpVal.getSemantics());
bool Cvt = FpVal.getExactInverse(&Reciprocal);
if (!Cvt && AllowReciprocal && FpVal.isFiniteNonZero()) {
Reciprocal = APFloat(FpVal.getSemantics(), 1.0f);
(void)Reciprocal.divide(FpVal, APFloat::rmNearestTiesToEven);
Cvt = !Reciprocal.isDenormal();
}
if (!Cvt)
return nullptr;
ConstantFP *R;
R = ConstantFP::get(Dividend->getType()->getContext(), Reciprocal);
return BinaryOperator::CreateFMul(Dividend, R);
}
Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifyFDivInst(Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
if (isa<Constant>(Op0))
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
bool AllowReassociate = I.hasUnsafeAlgebra();
bool AllowReciprocal = I.hasAllowReciprocal();
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
if (AllowReassociate) {
Constant *C1 = nullptr;
Constant *C2 = Op1C;
Value *X;
Instruction *Res = nullptr;
if (match(Op0, m_FMul(m_Value(X), m_Constant(C1)))) {
// (X*C1)/C2 => X * (C1/C2)
//
Constant *C = ConstantExpr::getFDiv(C1, C2);
if (isNormalFp(C))
Res = BinaryOperator::CreateFMul(X, C);
} else if (match(Op0, m_FDiv(m_Value(X), m_Constant(C1)))) {
// (X/C1)/C2 => X /(C2*C1) [=> X * 1/(C2*C1) if reciprocal is allowed]
//
Constant *C = ConstantExpr::getFMul(C1, C2);
if (isNormalFp(C)) {
Res = CvtFDivConstToReciprocal(X, C, AllowReciprocal);
if (!Res)
Res = BinaryOperator::CreateFDiv(X, C);
}
}
if (Res) {
Res->setFastMathFlags(I.getFastMathFlags());
return Res;
}
}
// X / C => X * 1/C
if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal)) {
T->copyFastMathFlags(&I);
return T;
}
return nullptr;
}
if (AllowReassociate && isa<Constant>(Op0)) {
Constant *C1 = cast<Constant>(Op0), *C2;
Constant *Fold = nullptr;
Value *X;
bool CreateDiv = true;
// C1 / (X*C2) => (C1/C2) / X
if (match(Op1, m_FMul(m_Value(X), m_Constant(C2))))
Fold = ConstantExpr::getFDiv(C1, C2);
else if (match(Op1, m_FDiv(m_Value(X), m_Constant(C2)))) {
// C1 / (X/C2) => (C1*C2) / X
Fold = ConstantExpr::getFMul(C1, C2);
} else if (match(Op1, m_FDiv(m_Constant(C2), m_Value(X)))) {
// C1 / (C2/X) => (C1/C2) * X
Fold = ConstantExpr::getFDiv(C1, C2);
CreateDiv = false;
}
if (Fold && isNormalFp(Fold)) {
Instruction *R = CreateDiv ? BinaryOperator::CreateFDiv(Fold, X)
: BinaryOperator::CreateFMul(X, Fold);
R->setFastMathFlags(I.getFastMathFlags());
return R;
}
return nullptr;
}
if (AllowReassociate) {
Value *X, *Y;
Value *NewInst = nullptr;
Instruction *SimpR = nullptr;
if (Op0->hasOneUse() && match(Op0, m_FDiv(m_Value(X), m_Value(Y)))) {
// (X/Y) / Z => X / (Y*Z)
//
if (!isa<Constant>(Y) || !isa<Constant>(Op1)) {
NewInst = Builder->CreateFMul(Y, Op1);
if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
FastMathFlags Flags = I.getFastMathFlags();
Flags &= cast<Instruction>(Op0)->getFastMathFlags();
RI->setFastMathFlags(Flags);
}
SimpR = BinaryOperator::CreateFDiv(X, NewInst);
}
} else if (Op1->hasOneUse() && match(Op1, m_FDiv(m_Value(X), m_Value(Y)))) {
// Z / (X/Y) => Z*Y / X
//
if (!isa<Constant>(Y) || !isa<Constant>(Op0)) {
NewInst = Builder->CreateFMul(Op0, Y);
if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
FastMathFlags Flags = I.getFastMathFlags();
Flags &= cast<Instruction>(Op1)->getFastMathFlags();
RI->setFastMathFlags(Flags);
}
SimpR = BinaryOperator::CreateFDiv(NewInst, X);
}
}
if (NewInst) {
if (Instruction *T = dyn_cast<Instruction>(NewInst))
T->setDebugLoc(I.getDebugLoc());
SimpR->setFastMathFlags(I.getFastMathFlags());
return SimpR;
}
}
return nullptr;
}
/// This function implements the transforms common to both integer remainder
/// instructions (urem and srem). It is called by the visitors to those integer
/// remainder instructions.
/// @brief Common integer remainder transforms
Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
// The RHS is known non-zero.
if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, &I)) {
I.setOperand(1, V);
return &I;
}
// Handle cases involving: rem X, (select Cond, Y, Z)
if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
return &I;
if (isa<Constant>(Op1)) {
if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
} else if (isa<PHINode>(Op0I)) {
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
}
// See if we can fold away this rem instruction.
if (SimplifyDemandedInstructionBits(I))
return &I;
}
}
return nullptr;
}
Instruction *InstCombiner::visitURem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifyURemInst(Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
if (Instruction *common = commonIRemTransforms(I))
return common;
// (zext A) urem (zext B) --> zext (A urem B)
if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
I.getType());
// X urem Y -> X and Y-1, where Y is a power of 2,
if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, AC, &I, DT)) {
Constant *N1 = Constant::getAllOnesValue(I.getType());
Value *Add = Builder->CreateAdd(Op1, N1);
return BinaryOperator::CreateAnd(Op0, Add);
}
// 1 urem X -> zext(X != 1)
if (match(Op0, m_One())) {
Value *Cmp = Builder->CreateICmpNE(Op1, Op0);
Value *Ext = Builder->CreateZExt(Cmp, I.getType());
return ReplaceInstUsesWith(I, Ext);
}
return nullptr;
}
Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifySRemInst(Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
// Handle the integer rem common cases
if (Instruction *Common = commonIRemTransforms(I))
return Common;
{
const APInt *Y;
// X % -Y -> X % Y
if (match(Op1, m_APInt(Y)) && Y->isNegative() && !Y->isMinSignedValue()) {
Worklist.AddValue(I.getOperand(1));
I.setOperand(1, ConstantInt::get(I.getType(), -*Y));
return &I;
}
}
// If the sign bits of both operands are zero (i.e. we can prove they are
// unsigned inputs), turn this into a urem.
if (I.getType()->isIntegerTy()) {
APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
if (MaskedValueIsZero(Op1, Mask, 0, &I) &&
MaskedValueIsZero(Op0, Mask, 0, &I)) {
// X srem Y -> X urem Y, iff X and Y don't have sign bit set
return BinaryOperator::CreateURem(Op0, Op1, I.getName());
}
}
// If it's a constant vector, flip any negative values positive.
if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) {
Constant *C = cast<Constant>(Op1);
unsigned VWidth = C->getType()->getVectorNumElements();
bool hasNegative = false;
bool hasMissing = false;
for (unsigned i = 0; i != VWidth; ++i) {
Constant *Elt = C->getAggregateElement(i);
if (!Elt) {
hasMissing = true;
break;
}
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt))
if (RHS->isNegative())
hasNegative = true;
}
if (hasNegative && !hasMissing) {
SmallVector<Constant *, 16> Elts(VWidth);
for (unsigned i = 0; i != VWidth; ++i) {
Elts[i] = C->getAggregateElement(i); // Handle undef, etc.
if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) {
if (RHS->isNegative())
Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
}
}
Constant *NewRHSV = ConstantVector::get(Elts);
if (NewRHSV != C) { // Don't loop on -MININT
Worklist.AddValue(I.getOperand(1));
I.setOperand(1, NewRHSV);
return &I;
}
}
}
return nullptr;
}
Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (Value *V = SimplifyVectorOp(I))
return ReplaceInstUsesWith(I, V);
if (Value *V = SimplifyFRemInst(Op0, Op1, DL, TLI, DT, AC))
return ReplaceInstUsesWith(I, V);
// Handle cases involving: rem X, (select Cond, Y, Z)
if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
return &I;
return nullptr;
}
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