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llvm-project/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

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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"
/// 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 <<.
BinaryOperator *I = dyn_cast<BinaryOperator>(V);
if (I && I->isLogicalShift() &&
isKnownToBeAPowerOfTwo(I->getOperand(0), IC.getDataLayout(), 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;
}
/// 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!");
// Bail if we will divide by zero.
if (C2.isMinValue())
return false;
// Bail if we would divide INT_MIN by -1.
if (IsSigned && C1.isMinSignedValue() && C2.isAllOnesValue())
return false;
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, SQ))
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) {
unsigned Width = NewCst->getType()->getPrimitiveSizeInBits();
BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
if (I.hasNoUnsignedWrap())
Shl->setHasNoUnsignedWrap();
if (I.hasNoSignedWrap()) {
uint64_t V;
if (match(NewCst, m_ConstantInt(V)) && V != Width - 1)
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)) {
if (Instruction *FoldedMul = foldOpWithConstantIntoOperand(I))
return FoldedMul;
// 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 *Y = Op1;
BinaryOperator *Div = dyn_cast<BinaryOperator>(Op0);
if (!Div || (Div->getOpcode() != Instruction::UDiv &&
Div->getOpcode() != Instruction::SDiv)) {
Y = Op0;
Div = dyn_cast<BinaryOperator>(Op1);
}
Value *Neg = dyn_castNegVal(Y);
if (Div && Div->hasOneUse() &&
(Div->getOperand(1) == Y || Div->getOperand(1) == Neg) &&
(Div->getOpcode() == Instruction::UDiv ||
Div->getOpcode() == Instruction::SDiv)) {
Value *X = Div->getOperand(0), *DivOp1 = Div->getOperand(1);
// If the division is exact, X % Y is zero, so we end up with X or -X.
if (Div->isExact()) {
if (DivOp1 == Y)
return replaceInstUsesWith(I, X);
return BinaryOperator::CreateNeg(X);
}
auto RemOpc = Div->getOpcode() == Instruction::UDiv ? Instruction::URem
: Instruction::SRem;
Value *Rem = Builder->CreateBinOp(RemOpc, X, DivOp1);
if (DivOp1 == Y)
return BinaryOperator::CreateSub(X, Rem);
return BinaryOperator::CreateSub(Rem, X);
}
}
/// 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);
}
}
// Check for (mul (sext x), y), see if we can merge this into an
// integer mul followed by a sext.
if (SExtInst *Op0Conv = dyn_cast<SExtInst>(Op0)) {
// (mul (sext x), cst) --> (sext (mul x, cst'))
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
if (Op0Conv->hasOneUse()) {
Constant *CI =
ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
if (ConstantExpr::getSExt(CI, I.getType()) == Op1C &&
WillNotOverflowSignedMul(Op0Conv->getOperand(0), CI, I)) {
// Insert the new, smaller mul.
Value *NewMul =
Builder->CreateNSWMul(Op0Conv->getOperand(0), CI, "mulconv");
return new SExtInst(NewMul, I.getType());
}
}
}
// (mul (sext x), (sext y)) --> (sext (mul int x, y))
if (SExtInst *Op1Conv = dyn_cast<SExtInst>(Op1)) {
// Only do this if x/y have the same type, if at last one of them has a
// single use (so we don't increase the number of sexts), and if the
// integer mul will not overflow.
if (Op0Conv->getOperand(0)->getType() ==
Op1Conv->getOperand(0)->getType() &&
(Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
WillNotOverflowSignedMul(Op0Conv->getOperand(0),
Op1Conv->getOperand(0), I)) {
// Insert the new integer mul.
Value *NewMul = Builder->CreateNSWMul(
Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
return new SExtInst(NewMul, I.getType());
}
}
}
// Check for (mul (zext x), y), see if we can merge this into an
// integer mul followed by a zext.
if (auto *Op0Conv = dyn_cast<ZExtInst>(Op0)) {
// (mul (zext x), cst) --> (zext (mul x, cst'))
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
if (Op0Conv->hasOneUse()) {
Constant *CI =
ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
if (ConstantExpr::getZExt(CI, I.getType()) == Op1C &&
computeOverflowForUnsignedMul(Op0Conv->getOperand(0), CI, &I) ==
OverflowResult::NeverOverflows) {
// Insert the new, smaller mul.
Value *NewMul =
Builder->CreateNUWMul(Op0Conv->getOperand(0), CI, "mulconv");
return new ZExtInst(NewMul, I.getType());
}
}
}
// (mul (zext x), (zext y)) --> (zext (mul int x, y))
if (auto *Op1Conv = dyn_cast<ZExtInst>(Op1)) {
// Only do this if x/y have the same type, if at last one of them has a
// single use (so we don't increase the number of zexts), and if the
// integer mul will not overflow.
if (Op0Conv->getOperand(0)->getType() ==
Op1Conv->getOperand(0)->getType() &&
(Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
computeOverflowForUnsignedMul(Op0Conv->getOperand(0),
Op1Conv->getOperand(0),
&I) == OverflowResult::NeverOverflows) {
// Insert the new integer mul.
Value *NewMul = Builder->CreateNUWMul(
Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
return new ZExtInst(NewMul, I.getType());
}
}
}
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_or_null<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_or_null<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(), SQ))
return replaceInstUsesWith(I, V);
bool AllowReassociate = I.hasUnsafeAlgebra();
// Simplify mul instructions with a constant RHS.
if (isa<Constant>(Op1)) {
if (Instruction *FoldedMul = foldOpWithConstantIntoOperand(I))
return FoldedMul;
// (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;
}
}
}
}
}
if (Op0 == Op1) {
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0)) {
// sqrt(X) * sqrt(X) -> X
if (AllowReassociate && II->getIntrinsicID() == Intrinsic::sqrt)
return replaceInstUsesWith(I, II->getOperand(0));
// fabs(X) * fabs(X) -> X * X
if (II->getIntrinsicID() == Intrinsic::fabs) {
Instruction *FMulVal = BinaryOperator::CreateFMul(II->getOperand(0),
II->getOperand(0),
I.getName());
FMulVal->copyFastMathFlags(&I);
return FMulVal;
}
}
}
// 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;
}
/// 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.getIterator(), 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 (Instruction *FoldedDiv = foldOpWithConstantIntoOperand(I))
return FoldedDiv;
}
}
if (match(Op0, m_One())) {
assert(!I.getType()->getScalarType()->isIntegerTy(1) &&
"i1 divide not removed?");
if (I.getOpcode() == Instruction::SDiv) {
// 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, Op0);
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, Op0), 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)
// X udiv (zext (C1 << N)), where C1 is "1<<C2" --> X >> (N+C2)
static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
InstCombiner &IC) {
Value *ShiftLeft;
if (!match(Op1, m_ZExt(m_Value(ShiftLeft))))
ShiftLeft = Op1;
const APInt *CI;
Value *N;
if (!match(ShiftLeft, m_Shl(m_APInt(CI), m_Value(N))))
llvm_unreachable("match should never fail here!");
if (*CI != 1)
N = IC.Builder->CreateAdd(N,
ConstantInt::get(N->getType(), CI->logBase2()));
if (Op1 != ShiftLeft)
N = IC.Builder->CreateZExt(N, Op1->getType());
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, SQ))
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, SQ))
return replaceInstUsesWith(I, V);
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
const APInt *Op1C;
if (match(Op1, m_APInt(Op1C))) {
// sdiv X, -1 == -X
if (Op1C->isAllOnesValue())
return BinaryOperator::CreateNeg(Op0);
// sdiv exact X, C --> ashr exact X, log2(C)
if (I.isExact() && Op1C->isNonNegative() && Op1C->isPowerOf2()) {
Value *ShAmt = ConstantInt::get(Op1->getType(), Op1C->exactLogBase2());
return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
}
// If the dividend is sign-extended and the constant divisor is small enough
// to fit in the source type, shrink the division to the narrower type:
// (sext X) sdiv C --> sext (X sdiv C)
Value *Op0Src;
if (match(Op0, m_OneUse(m_SExt(m_Value(Op0Src)))) &&
Op0Src->getType()->getScalarSizeInBits() >= Op1C->getMinSignedBits()) {
// In the general case, we need to make sure that the dividend is not the
// minimum signed value because dividing that by -1 is UB. But here, we
// know that the -1 divisor case is already handled above.
Constant *NarrowDivisor =
ConstantExpr::getTrunc(cast<Constant>(Op1), Op0Src->getType());
Value *NarrowOp = Builder->CreateSDiv(Op0Src, NarrowDivisor);
return new SExtInst(NarrowOp, Op0->getType());
}
}
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.
APInt Mask(APInt::getSignMask(I.getType()->getScalarSizeInBits()));
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, DL, /*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, I.getFastMathFlags(), SQ))
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;
}
}
Value *LHS;
Value *RHS;
// -x / -y -> x / y
if (match(Op0, m_FNeg(m_Value(LHS))) && match(Op1, m_FNeg(m_Value(RHS)))) {
I.setOperand(0, LHS);
I.setOperand(1, RHS);
return &I;
}
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 (auto *PN = dyn_cast<PHINode>(Op0I)) {
using namespace llvm::PatternMatch;
const APInt *Op1Int;
if (match(Op1, m_APInt(Op1Int)) && !Op1Int->isMinValue() &&
(I.getOpcode() == Instruction::URem ||
!Op1Int->isMinSignedValue())) {
// foldOpIntoPhi will speculate instructions to the end of the PHI's
// predecessor blocks, so do this only if we know the srem or urem
// will not fault.
if (Instruction *NV = foldOpIntoPhi(I, PN))
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, SQ))
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, DL, /*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);
}
// X urem C -> X < C ? X : X - C, where C >= signbit.
const APInt *DivisorC;
if (match(Op1, m_APInt(DivisorC)) && DivisorC->isNegative()) {
Value *Cmp = Builder->CreateICmpULT(Op0, Op1);
Value *Sub = Builder->CreateSub(Op0, Op1);
return SelectInst::Create(Cmp, Op0, Sub);
}
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, SQ))
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.
APInt Mask(APInt::getSignMask(I.getType()->getScalarSizeInBits()));
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, I.getFastMathFlags(), SQ))
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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