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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/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Transforms/InstCombine/InstCombineWorklist.h"
#include "llvm/Transforms/Utils/BuildLibCalls.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <utility>
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() &&
IC.isKnownToBeAPowerOfTwo(I->getOperand(0), false, 0, &CxtI)) {
// 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;
}
/// A helper routine of InstCombiner::visitMul().
///
/// If C is a scalar/vector of known powers of 2, then this function returns
/// a new scalar/vector obtained from logBase2 of C.
/// Return a null pointer otherwise.
static Constant *getLogBase2(Type *Ty, Constant *C) {
const APInt *IVal;
if (match(C, m_APInt(IVal)) && IVal->isPowerOf2())
return ConstantInt::get(Ty, IVal->logBase2());
if (!Ty->isVectorTy())
return nullptr;
SmallVector<Constant *, 4> Elts;
for (unsigned I = 0, E = Ty->getVectorNumElements(); I != E; ++I) {
Constant *Elt = C->getAggregateElement(I);
if (!Elt)
return nullptr;
if (isa<UndefValue>(Elt)) {
Elts.push_back(UndefValue::get(Ty->getScalarType()));
continue;
}
if (!match(Elt, m_APInt(IVal)) || !IVal->isPowerOf2())
return nullptr;
Elts.push_back(ConstantInt::get(Ty->getScalarType(), IVal->logBase2()));
}
return ConstantVector::get(Elts);
}
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
if (Value *V = SimplifyMulInst(I.getOperand(0), I.getOperand(1),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (SimplifyAssociativeOrCommutative(I))
return &I;
if (Instruction *X = foldShuffledBinop(I))
return X;
if (Value *V = SimplifyUsingDistributiveLaws(I))
return replaceInstUsesWith(I, V);
// X * -1 == 0 - X
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
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)))) {
// Replace X*(2^C) with X << C, where C is either a scalar or a vector.
if (Constant *NewCst = getLogBase2(NewOp->getType(), C1)) {
unsigned Width = NewCst->getType()->getPrimitiveSizeInBits();
BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
if (I.hasNoUnsignedWrap())
Shl->setHasNoUnsignedWrap();
if (I.hasNoSignedWrap()) {
const APInt *V;
if (match(NewCst, m_APInt(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));
}
}
}
}
if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I))
return FoldedMul;
// Simplify mul instructions with a constant RHS.
if (isa<Constant>(Op1)) {
// 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);
}
}
// -X * C --> X * -C
Value *X, *Y;
Constant *Op1C;
if (match(Op0, m_Neg(m_Value(X))) && match(Op1, m_Constant(Op1C)))
return BinaryOperator::CreateMul(X, ConstantExpr::getNeg(Op1C));
// -X * -Y --> X * Y
if (match(Op0, m_Neg(m_Value(X))) && match(Op1, m_Neg(m_Value(Y)))) {
auto *NewMul = BinaryOperator::CreateMul(X, Y);
if (I.hasNoSignedWrap() &&
cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap() &&
cast<OverflowingBinaryOperator>(Op1)->hasNoSignedWrap())
NewMul->setHasNoSignedWrap();
return NewMul;
}
// (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()->isIntOrIntVectorTy(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;
}
}
// (bool X) * Y --> X ? Y : 0
// Y * (bool X) --> X ? Y : 0
if (match(Op0, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1))
return SelectInst::Create(X, Op1, ConstantInt::get(I.getType(), 0));
if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1))
return SelectInst::Create(X, Op0, ConstantInt::get(I.getType(), 0));
// (lshr X, 31) * Y --> (ashr X, 31) & Y
// Y * (lshr X, 31) --> (ashr X, 31) & Y
// TODO: We are not checking one-use because the elimination of the multiply
// is better for analysis?
// TODO: Should we canonicalize to '(X < 0) ? Y : 0' instead? That would be
// more similar to what we're doing above.
const APInt *C;
if (match(Op0, m_LShr(m_Value(X), m_APInt(C))) && *C == C->getBitWidth() - 1)
return BinaryOperator::CreateAnd(Builder.CreateAShr(X, *C), Op1);
if (match(Op1, m_LShr(m_Value(X), m_APInt(C))) && *C == C->getBitWidth() - 1)
return BinaryOperator::CreateAnd(Builder.CreateAShr(X, *C), Op0);
// 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 &&
willNotOverflowUnsignedMul(Op0Conv->getOperand(0), CI, I)) {
// 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()) &&
willNotOverflowUnsignedMul(Op0Conv->getOperand(0),
Op1Conv->getOperand(0), I)) {
// Insert the new integer mul.
Value *NewMul = Builder.CreateNUWMul(
Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
return new ZExtInst(NewMul, I.getType());
}
}
}
bool Changed = false;
if (!I.hasNoSignedWrap() && willNotOverflowSignedMul(Op0, Op1, I)) {
Changed = true;
I.setHasNoSignedWrap(true);
}
if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedMul(Op0, Op1, I)) {
Changed = true;
I.setHasNoUnsignedWrap(true);
}
return Changed ? &I : nullptr;
}
Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
if (Value *V = SimplifyFMulInst(I.getOperand(0), I.getOperand(1),
I.getFastMathFlags(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (SimplifyAssociativeOrCommutative(I))
return &I;
if (Instruction *X = foldShuffledBinop(I))
return X;
if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I))
return FoldedMul;
// X * -1.0 --> -X
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (match(Op1, m_SpecificFP(-1.0)))
return BinaryOperator::CreateFNegFMF(Op0, &I);
// -X * -Y --> X * Y
Value *X, *Y;
if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
return BinaryOperator::CreateFMulFMF(X, Y, &I);
// -X * C --> X * -C
Constant *C;
if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_Constant(C)))
return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I);
// Sink negation: -X * Y --> -(X * Y)
if (match(Op0, m_OneUse(m_FNeg(m_Value(X)))))
return BinaryOperator::CreateFNegFMF(Builder.CreateFMulFMF(X, Op1, &I), &I);
// Sink negation: Y * -X --> -(X * Y)
if (match(Op1, m_OneUse(m_FNeg(m_Value(X)))))
return BinaryOperator::CreateFNegFMF(Builder.CreateFMulFMF(X, Op0, &I), &I);
// fabs(X) * fabs(X) -> X * X
if (Op0 == Op1 && match(Op0, m_Intrinsic<Intrinsic::fabs>(m_Value(X))))
return BinaryOperator::CreateFMulFMF(X, X, &I);
// (select A, B, C) * (select A, D, E) --> select A, (B*D), (C*E)
if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1))
return replaceInstUsesWith(I, V);
if (I.hasAllowReassoc()) {
// Reassociate constant RHS with another constant to form constant
// expression.
if (match(Op1, m_Constant(C)) && C->isFiniteNonZeroFP()) {
Constant *C1;
if (match(Op0, m_OneUse(m_FDiv(m_Constant(C1), m_Value(X))))) {
// (C1 / X) * C --> (C * C1) / X
Constant *CC1 = ConstantExpr::getFMul(C, C1);
if (CC1->isNormalFP())
return BinaryOperator::CreateFDivFMF(CC1, X, &I);
}
if (match(Op0, m_FDiv(m_Value(X), m_Constant(C1)))) {
// (X / C1) * C --> X * (C / C1)
Constant *CDivC1 = ConstantExpr::getFDiv(C, C1);
if (CDivC1->isNormalFP())
return BinaryOperator::CreateFMulFMF(X, CDivC1, &I);
// If the constant was a denormal, try reassociating differently.
// (X / C1) * C --> X / (C1 / C)
Constant *C1DivC = ConstantExpr::getFDiv(C1, C);
if (Op0->hasOneUse() && C1DivC->isNormalFP())
return BinaryOperator::CreateFDivFMF(X, C1DivC, &I);
}
// We do not need to match 'fadd C, X' and 'fsub X, C' because they are
// canonicalized to 'fadd X, C'. Distributing the multiply may allow
// further folds and (X * C) + C2 is 'fma'.
if (match(Op0, m_OneUse(m_FAdd(m_Value(X), m_Constant(C1))))) {
// (X + C1) * C --> (X * C) + (C * C1)
Constant *CC1 = ConstantExpr::getFMul(C, C1);
Value *XC = Builder.CreateFMulFMF(X, C, &I);
return BinaryOperator::CreateFAddFMF(XC, CC1, &I);
}
if (match(Op0, m_OneUse(m_FSub(m_Constant(C1), m_Value(X))))) {
// (C1 - X) * C --> (C * C1) - (X * C)
Constant *CC1 = ConstantExpr::getFMul(C, C1);
Value *XC = Builder.CreateFMulFMF(X, C, &I);
return BinaryOperator::CreateFSubFMF(CC1, XC, &I);
}
}
// sqrt(X) * sqrt(Y) -> sqrt(X * Y)
// nnan disallows the possibility of returning a number if both operands are
// negative (in that case, we should return NaN).
if (I.hasNoNaNs() &&
match(Op0, m_OneUse(m_Intrinsic<Intrinsic::sqrt>(m_Value(X)))) &&
match(Op1, m_OneUse(m_Intrinsic<Intrinsic::sqrt>(m_Value(Y))))) {
Value *XY = Builder.CreateFMulFMF(X, Y, &I);
Value *Sqrt = Builder.CreateIntrinsic(Intrinsic::sqrt, { XY }, &I);
return replaceInstUsesWith(I, Sqrt);
}
// (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 (match(Op0, m_OneUse(m_c_FMul(m_Specific(Op1), m_Value(Y)))) &&
Op1 != Y) {
Value *XX = Builder.CreateFMulFMF(Op1, Op1, &I);
return BinaryOperator::CreateFMulFMF(XX, Y, &I);
}
if (match(Op1, m_OneUse(m_c_FMul(m_Specific(Op0), m_Value(Y)))) &&
Op0 != Y) {
Value *XX = Builder.CreateFMulFMF(Op0, Op0, &I);
return BinaryOperator::CreateFMulFMF(XX, Y, &I);
}
}
// log2(X * 0.5) * Y = log2(X) * Y - Y
if (I.isFast()) {
IntrinsicInst *Log2 = nullptr;
if (match(Op0, m_OneUse(m_Intrinsic<Intrinsic::log2>(
m_OneUse(m_FMul(m_Value(X), m_SpecificFP(0.5))))))) {
Log2 = cast<IntrinsicInst>(Op0);
Y = Op1;
}
if (match(Op1, m_OneUse(m_Intrinsic<Intrinsic::log2>(
m_OneUse(m_FMul(m_Value(X), m_SpecificFP(0.5))))))) {
Log2 = cast<IntrinsicInst>(Op1);
Y = Op0;
}
if (Log2) {
Log2->setArgOperand(0, X);
Log2->copyFastMathFlags(&I);
Value *LogXTimesY = Builder.CreateFMulFMF(Log2, Y, &I);
return BinaryOperator::CreateFSubFMF(LogXTimesY, Y, &I);
}
}
return nullptr;
}
/// Fold a divide or remainder with a select instruction divisor when one of the
/// select operands is zero. In that case, we can use the other select operand
/// because div/rem by zero is undefined.
bool InstCombiner::simplifyDivRemOfSelectWithZeroOp(BinaryOperator &I) {
SelectInst *SI = dyn_cast<SelectInst>(I.getOperand(1));
if (!SI)
return false;
int NonNullOperand;
if (match(SI->getTrueValue(), m_Zero()))
// div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
NonNullOperand = 2;
else if (match(SI->getFalseValue(), m_Zero()))
// div/rem X, (Cond ? Y : 0) -> div/rem X, Y
NonNullOperand = 1;
else
return false;
// 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.
Value *SelectCond = SI->getCondition();
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();
Type *CondTy = SelectCond->getType();
while (BBI != BBFront) {
--BBI;
// If we found an instruction that we can't assume will return, so
// information from below it cannot be propagated above it.
if (!isGuaranteedToTransferExecutionToSuccessor(&*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 = NonNullOperand == 1 ? ConstantInt::getTrue(CondTy)
: ConstantInt::getFalse(CondTy);
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;
}
/// 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;
Product = IsSigned ? C1.smul_ov(C2, Overflow) : C1.umul_ov(C2, Overflow);
return Overflow;
}
/// True if C1 is a multiple of C2. Quotient contains C1/C2.
static bool isMultiple(const APInt &C1, const APInt &C2, APInt &Quotient,
bool IsSigned) {
assert(C1.getBitWidth() == C2.getBitWidth() && "Constant widths not equal");
// Bail if we will divide by zero.
if (C2.isNullValue())
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();
}
/// 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.
/// Common integer divide transforms
Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
bool IsSigned = I.getOpcode() == Instruction::SDiv;
Type *Ty = I.getType();
// 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 (simplifyDivRemOfSelectWithZeroOp(I))
return &I;
const APInt *C2;
if (match(Op1, m_APInt(C2))) {
Value *X;
const APInt *C1;
// (X / C1) / C2 -> X / (C1*C2)
if ((IsSigned && match(Op0, m_SDiv(m_Value(X), m_APInt(C1)))) ||
(!IsSigned && match(Op0, 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(Ty, Product));
}
if ((IsSigned && match(Op0, m_NSWMul(m_Value(X), m_APInt(C1)))) ||
(!IsSigned && match(Op0, 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)) {
auto *NewDiv = BinaryOperator::Create(I.getOpcode(), X,
ConstantInt::get(Ty, Quotient));
NewDiv->setIsExact(I.isExact());
return NewDiv;
}
// (X * C1) / C2 -> X * (C1 / C2) if C1 is a multiple of C2.
if (isMultiple(*C1, *C2, Quotient, IsSigned)) {
auto *Mul = BinaryOperator::Create(Instruction::Mul, X,
ConstantInt::get(Ty, Quotient));
auto *OBO = cast<OverflowingBinaryOperator>(Op0);
Mul->setHasNoUnsignedWrap(!IsSigned && OBO->hasNoUnsignedWrap());
Mul->setHasNoSignedWrap(OBO->hasNoSignedWrap());
return Mul;
}
}
if ((IsSigned && match(Op0, m_NSWShl(m_Value(X), m_APInt(C1))) &&
*C1 != C1->getBitWidth() - 1) ||
(!IsSigned && match(Op0, 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 1 << C1.
if (isMultiple(*C2, C1Shifted, Quotient, IsSigned)) {
auto *BO = BinaryOperator::Create(I.getOpcode(), X,
ConstantInt::get(Ty, Quotient));
BO->setIsExact(I.isExact());
return BO;
}
// (X << C1) / C2 -> X * ((1 << C1) / C2) if 1 << C1 is a multiple of C2.
if (isMultiple(C1Shifted, *C2, Quotient, IsSigned)) {
auto *Mul = BinaryOperator::Create(Instruction::Mul, X,
ConstantInt::get(Ty, Quotient));
auto *OBO = cast<OverflowingBinaryOperator>(Op0);
Mul->setHasNoUnsignedWrap(!IsSigned && OBO->hasNoUnsignedWrap());
Mul->setHasNoSignedWrap(OBO->hasNoSignedWrap());
return Mul;
}
}
if (!C2->isNullValue()) // avoid X udiv 0
if (Instruction *FoldedDiv = foldBinOpIntoSelectOrPhi(I))
return FoldedDiv;
}
if (match(Op0, m_One())) {
assert(!Ty->isIntOrIntVectorTy(1) && "i1 divide not removed?");
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, Op0);
Value *Cmp = Builder.CreateICmpULT(Inc, ConstantInt::get(Ty, 3));
return SelectInst::Create(Cmp, Op1, ConstantInt::get(Ty, 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), Ty);
}
}
// 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, *Z;
if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) // (X - Z) / Y; Y = Op1
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);
// (X << Y) / X -> 1 << Y
Value *Y;
if (IsSigned && match(Op0, m_NSWShl(m_Specific(Op1), m_Value(Y))))
return BinaryOperator::CreateNSWShl(ConstantInt::get(Ty, 1), Y);
if (!IsSigned && match(Op0, m_NUWShl(m_Specific(Op1), m_Value(Y))))
return BinaryOperator::CreateNUWShl(ConstantInt::get(Ty, 1), Y);
// X / (X * Y) -> 1 / Y if the multiplication does not overflow.
if (match(Op1, m_c_Mul(m_Specific(Op0), m_Value(Y)))) {
bool HasNSW = cast<OverflowingBinaryOperator>(Op1)->hasNoSignedWrap();
bool HasNUW = cast<OverflowingBinaryOperator>(Op1)->hasNoUnsignedWrap();
if ((IsSigned && HasNSW) || (!IsSigned && HasNUW)) {
I.setOperand(0, ConstantInt::get(Ty, 1));
I.setOperand(1, Y);
return &I;
}
}
return nullptr;
}
static const unsigned MaxDepth = 6;
namespace {
using FoldUDivOperandCb = Instruction *(*)(Value *Op0, Value *Op1,
const BinaryOperator &I,
InstCombiner &IC);
/// Used to maintain state for visitUDivOperand().
struct UDivFoldAction {
/// Informs visitUDiv() how to fold this operand. This can be zero if this
/// action joins two actions together.
FoldUDivOperandCb FoldAction;
/// Which operand to fold.
Value *OperandToFold;
union {
/// The instruction returned when FoldAction is invoked.
Instruction *FoldResult;
/// Stores the LHS action index if this action joins two actions together.
size_t SelectLHSIdx;
};
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) {}
};
} // end anonymous namespace
// X udiv 2^C -> X >> C
static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
const BinaryOperator &I, InstCombiner &IC) {
Constant *C1 = getLogBase2(Op0->getType(), cast<Constant>(Op1));
if (!C1)
llvm_unreachable("Failed to constant fold udiv -> logbase2");
BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, C1);
if (I.isExact())
LShr->setIsExact();
return LShr;
}
// 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;
Constant *CI;
Value *N;
if (!match(ShiftLeft, m_Shl(m_Constant(CI), m_Value(N))))
llvm_unreachable("match should never fail here!");
Constant *Log2Base = getLogBase2(N->getType(), CI);
if (!Log2Base)
llvm_unreachable("getLogBase2 should never fail here!");
N = IC.Builder.CreateAdd(N, Log2Base);
if (Op1 != ShiftLeft)
N = IC.Builder.CreateZExt(N, Op1->getType());
BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
if (I.isExact())
LShr->setIsExact();
return LShr;
}
// 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();
}
// 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;
}
/// If we have zero-extended operands of an unsigned div or rem, we may be able
/// to narrow the operation (sink the zext below the math).
static Instruction *narrowUDivURem(BinaryOperator &I,
InstCombiner::BuilderTy &Builder) {
Instruction::BinaryOps Opcode = I.getOpcode();
Value *N = I.getOperand(0);
Value *D = I.getOperand(1);
Type *Ty = I.getType();
Value *X, *Y;
if (match(N, m_ZExt(m_Value(X))) && match(D, m_ZExt(m_Value(Y))) &&
X->getType() == Y->getType() && (N->hasOneUse() || D->hasOneUse())) {
// udiv (zext X), (zext Y) --> zext (udiv X, Y)
// urem (zext X), (zext Y) --> zext (urem X, Y)
Value *NarrowOp = Builder.CreateBinOp(Opcode, X, Y);
return new ZExtInst(NarrowOp, Ty);
}
Constant *C;
if ((match(N, m_OneUse(m_ZExt(m_Value(X)))) && match(D, m_Constant(C))) ||
(match(D, m_OneUse(m_ZExt(m_Value(X)))) && match(N, m_Constant(C)))) {
// If the constant is the same in the smaller type, use the narrow version.
Constant *TruncC = ConstantExpr::getTrunc(C, X->getType());
if (ConstantExpr::getZExt(TruncC, Ty) != C)
return nullptr;
// udiv (zext X), C --> zext (udiv X, C')
// urem (zext X), C --> zext (urem X, C')
// udiv C, (zext X) --> zext (udiv C', X)
// urem C, (zext X) --> zext (urem C', X)
Value *NarrowOp = isa<Constant>(D) ? Builder.CreateBinOp(Opcode, X, TruncC)
: Builder.CreateBinOp(Opcode, TruncC, X);
return new ZExtInst(NarrowOp, Ty);
}
return nullptr;
}
Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
if (Value *V = SimplifyUDivInst(I.getOperand(0), I.getOperand(1),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldShuffledBinop(I))
return X;
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
Value *X;
const APInt *C1, *C2;
if (match(Op0, m_LShr(m_Value(X), m_APInt(C1))) && match(Op1, m_APInt(C2))) {
// (X lshr C1) udiv C2 --> X udiv (C2 << C1)
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;
}
}
// Op0 / C where C is large (negative) --> zext (Op0 >= C)
// TODO: Could use isKnownNegative() to handle non-constant values.
Type *Ty = I.getType();
if (match(Op1, m_Negative())) {
Value *Cmp = Builder.CreateICmpUGE(Op0, Op1);
return CastInst::CreateZExtOrBitCast(Cmp, Ty);
}
// Op0 / (sext i1 X) --> zext (Op0 == -1) (if X is 0, the div is undefined)
if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
Value *Cmp = Builder.CreateICmpEQ(Op0, ConstantInt::getAllOnesValue(Ty));
return CastInst::CreateZExtOrBitCast(Cmp, Ty);
}
if (Instruction *NarrowDiv = narrowUDivURem(I, Builder))
return NarrowDiv;
// If the udiv operands are non-overflowing multiplies with a common operand,
// then eliminate the common factor:
// (A * B) / (A * X) --> B / X (and commuted variants)
// TODO: The code would be reduced if we had m_c_NUWMul pattern matching.
// TODO: If -reassociation handled this generally, we could remove this.
Value *A, *B;
if (match(Op0, m_NUWMul(m_Value(A), m_Value(B)))) {
if (match(Op1, m_NUWMul(m_Specific(A), m_Value(X))) ||
match(Op1, m_NUWMul(m_Value(X), m_Specific(A))))
return BinaryOperator::CreateUDiv(B, X);
if (match(Op1, m_NUWMul(m_Specific(B), m_Value(X))) ||
match(Op1, m_NUWMul(m_Value(X), m_Specific(B))))
return BinaryOperator::CreateUDiv(A, X);
}
// (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) {
if (Value *V = SimplifySDivInst(I.getOperand(0), I.getOperand(1),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldShuffledBinop(I))
return X;
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
Value *X;
// sdiv Op0, -1 --> -Op0
// sdiv Op0, (sext i1 X) --> -Op0 (because if X is 0, the op is undefined)
if (match(Op1, m_AllOnes()) ||
(match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)))
return BinaryOperator::CreateNeg(Op0);
const APInt *Op1C;
if (match(Op1, m_APInt(Op1C))) {
// 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, /*OrZero*/ true, 0, &I)) {
// 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;
}
/// Remove negation and try to convert division into multiplication.
static Instruction *foldFDivConstantDivisor(BinaryOperator &I) {
Constant *C;
if (!match(I.getOperand(1), m_Constant(C)))
return nullptr;
// -X / C --> X / -C
Value *X;
if (match(I.getOperand(0), m_FNeg(m_Value(X))))
return BinaryOperator::CreateFDivFMF(X, ConstantExpr::getFNeg(C), &I);
// If the constant divisor has an exact inverse, this is always safe. If not,
// then we can still create a reciprocal if fast-math-flags allow it and the
// constant is a regular number (not zero, infinite, or denormal).
if (!(C->hasExactInverseFP() || (I.hasAllowReciprocal() && C->isNormalFP())))
return nullptr;
// Disallow denormal constants because we don't know what would happen
// on all targets.
// TODO: Use Intrinsic::canonicalize or let function attributes tell us that
// denorms are flushed?
auto *RecipC = ConstantExpr::getFDiv(ConstantFP::get(I.getType(), 1.0), C);
if (!RecipC->isNormalFP())
return nullptr;
// X / C --> X * (1 / C)
return BinaryOperator::CreateFMulFMF(I.getOperand(0), RecipC, &I);
}
/// Remove negation and try to reassociate constant math.
static Instruction *foldFDivConstantDividend(BinaryOperator &I) {
Constant *C;
if (!match(I.getOperand(0), m_Constant(C)))
return nullptr;
// C / -X --> -C / X
Value *X;
if (match(I.getOperand(1), m_FNeg(m_Value(X))))
return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I);
if (!I.hasAllowReassoc() || !I.hasAllowReciprocal())
return nullptr;
// Try to reassociate C / X expressions where X includes another constant.
Constant *C2, *NewC = nullptr;
if (match(I.getOperand(1), m_FMul(m_Value(X), m_Constant(C2)))) {
// C / (X * C2) --> (C / C2) / X
NewC = ConstantExpr::getFDiv(C, C2);
} else if (match(I.getOperand(1), m_FDiv(m_Value(X), m_Constant(C2)))) {
// C / (X / C2) --> (C * C2) / X
NewC = ConstantExpr::getFMul(C, C2);
}
// Disallow denormal constants because we don't know what would happen
// on all targets.
// TODO: Use Intrinsic::canonicalize or let function attributes tell us that
// denorms are flushed?
if (!NewC || !NewC->isNormalFP())
return nullptr;
return BinaryOperator::CreateFDivFMF(NewC, X, &I);
}
Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
if (Value *V = SimplifyFDivInst(I.getOperand(0), I.getOperand(1),
I.getFastMathFlags(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldShuffledBinop(I))
return X;
if (Instruction *R = foldFDivConstantDivisor(I))
return R;
if (Instruction *R = foldFDivConstantDividend(I))
return R;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (isa<Constant>(Op0))
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
if (isa<Constant>(Op1))
if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *R = FoldOpIntoSelect(I, SI))
return R;
if (I.hasAllowReassoc() && I.hasAllowReciprocal()) {
Value *X, *Y;
if (match(Op0, m_OneUse(m_FDiv(m_Value(X), m_Value(Y)))) &&
(!isa<Constant>(Y) || !isa<Constant>(Op1))) {
// (X / Y) / Z => X / (Y * Z)
Value *YZ = Builder.CreateFMulFMF(Y, Op1, &I);
return BinaryOperator::CreateFDivFMF(X, YZ, &I);
}
if (match(Op1, m_OneUse(m_FDiv(m_Value(X), m_Value(Y)))) &&
(!isa<Constant>(Y) || !isa<Constant>(Op0))) {
// Z / (X / Y) => (Y * Z) / X
Value *YZ = Builder.CreateFMulFMF(Y, Op0, &I);
return BinaryOperator::CreateFDivFMF(YZ, X, &I);
}
}
if (I.hasAllowReassoc() && Op0->hasOneUse() && Op1->hasOneUse()) {
// sin(X) / cos(X) -> tan(X)
// cos(X) / sin(X) -> 1/tan(X) (cotangent)
Value *X;
bool IsTan = match(Op0, m_Intrinsic<Intrinsic::sin>(m_Value(X))) &&
match(Op1, m_Intrinsic<Intrinsic::cos>(m_Specific(X)));
bool IsCot =
!IsTan && match(Op0, m_Intrinsic<Intrinsic::cos>(m_Value(X))) &&
match(Op1, m_Intrinsic<Intrinsic::sin>(m_Specific(X)));
if ((IsTan || IsCot) && hasUnaryFloatFn(&TLI, I.getType(), LibFunc_tan,
LibFunc_tanf, LibFunc_tanl)) {
IRBuilder<> B(&I);
IRBuilder<>::FastMathFlagGuard FMFGuard(B);
B.setFastMathFlags(I.getFastMathFlags());
AttributeList Attrs = CallSite(Op0).getCalledFunction()->getAttributes();
Value *Res = emitUnaryFloatFnCall(X, TLI.getName(LibFunc_tan), B, Attrs);
if (IsCot)
Res = B.CreateFDiv(ConstantFP::get(I.getType(), 1.0), Res);
return replaceInstUsesWith(I, Res);
}
}
// -X / -Y -> X / Y
Value *X, *Y;
if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y)))) {
I.setOperand(0, X);
I.setOperand(1, Y);
return &I;
}
// X / (X * Y) --> 1.0 / Y
// Reassociate to (X / X -> 1.0) is legal when NaNs are not allowed.
// We can ignore the possibility that X is infinity because INF/INF is NaN.
if (I.hasNoNaNs() && I.hasAllowReassoc() &&
match(Op1, m_c_FMul(m_Specific(Op0), m_Value(Y)))) {
I.setOperand(0, ConstantFP::get(I.getType(), 1.0));
I.setOperand(1, Y);
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.
/// 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 (simplifyDivRemOfSelectWithZeroOp(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)) {
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) {
if (Value *V = SimplifyURemInst(I.getOperand(0), I.getOperand(1),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldShuffledBinop(I))
return X;
if (Instruction *common = commonIRemTransforms(I))
return common;
if (Instruction *NarrowRem = narrowUDivURem(I, Builder))
return NarrowRem;
// X urem Y -> X and Y-1, where Y is a power of 2,
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
Type *Ty = I.getType();
if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, &I)) {
Constant *N1 = Constant::getAllOnesValue(Ty);
Value *Add = Builder.CreateAdd(Op1, N1);
return BinaryOperator::CreateAnd(Op0, Add);
}
// 1 urem X -> zext(X != 1)
if (match(Op0, m_One()))
return CastInst::CreateZExtOrBitCast(Builder.CreateICmpNE(Op1, Op0), Ty);
// X urem C -> X < C ? X : X - C, where C >= signbit.
if (match(Op1, m_Negative())) {
Value *Cmp = Builder.CreateICmpULT(Op0, Op1);
Value *Sub = Builder.CreateSub(Op0, Op1);
return SelectInst::Create(Cmp, Op0, Sub);
}
// If the divisor is a sext of a boolean, then the divisor must be max
// unsigned value (-1). Therefore, the remainder is Op0 unless Op0 is also
// max unsigned value. In that case, the remainder is 0:
// urem Op0, (sext i1 X) --> (Op0 == -1) ? 0 : Op0
Value *X;
if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
Value *Cmp = Builder.CreateICmpEQ(Op0, ConstantInt::getAllOnesValue(Ty));
return SelectInst::Create(Cmp, ConstantInt::getNullValue(Ty), Op0);
}
return nullptr;
}
Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
if (Value *V = SimplifySRemInst(I.getOperand(0), I.getOperand(1),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldShuffledBinop(I))
return X;
// Handle the integer rem common cases
if (Instruction *Common = commonIRemTransforms(I))
return Common;
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
{
const APInt *Y;
// X % -Y -> X % Y
if (match(Op1, m_Negative(Y)) && !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) {
if (Value *V = SimplifyFRemInst(I.getOperand(0), I.getOperand(1),
I.getFastMathFlags(),
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
if (Instruction *X = foldShuffledBinop(I))
return X;
return nullptr;
}
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