//===- InstCombineMulDivRem.cpp -------------------------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This file implements the visit functions for mul, fmul, sdiv, udiv, fdiv, // srem, urem, frem. // //===----------------------------------------------------------------------===// #include "InstCombineInternal.h" #include "llvm/ADT/APInt.h" #include "llvm/ADT/SmallVector.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Analysis/ValueTracking.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/Transforms/InstCombine/InstCombiner.h" #include "llvm/Transforms/Utils/BuildLibCalls.h" #include #define DEBUG_TYPE "instcombine" #include "llvm/Transforms/Utils/InstructionWorklist.h" using namespace llvm; using namespace PatternMatch; /// 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, InstCombinerImpl &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(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)) { IC.replaceOperand(*I, 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; } // TODO: This is a specific form of a much more general pattern. // We could detect a select with any binop identity constant, or we // could use SimplifyBinOp to see if either arm of the select reduces. // But that needs to be done carefully and/or while removing potential // reverse canonicalizations as in InstCombiner::foldSelectIntoOp(). static Value *foldMulSelectToNegate(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { Value *Cond, *OtherOp; // mul (select Cond, 1, -1), OtherOp --> select Cond, OtherOp, -OtherOp // mul OtherOp, (select Cond, 1, -1) --> select Cond, OtherOp, -OtherOp if (match(&I, m_c_Mul(m_OneUse(m_Select(m_Value(Cond), m_One(), m_AllOnes())), m_Value(OtherOp)))) { bool HasAnyNoWrap = I.hasNoSignedWrap() || I.hasNoUnsignedWrap(); Value *Neg = Builder.CreateNeg(OtherOp, "", false, HasAnyNoWrap); return Builder.CreateSelect(Cond, OtherOp, Neg); } // mul (select Cond, -1, 1), OtherOp --> select Cond, -OtherOp, OtherOp // mul OtherOp, (select Cond, -1, 1) --> select Cond, -OtherOp, OtherOp if (match(&I, m_c_Mul(m_OneUse(m_Select(m_Value(Cond), m_AllOnes(), m_One())), m_Value(OtherOp)))) { bool HasAnyNoWrap = I.hasNoSignedWrap() || I.hasNoUnsignedWrap(); Value *Neg = Builder.CreateNeg(OtherOp, "", false, HasAnyNoWrap); return Builder.CreateSelect(Cond, Neg, OtherOp); } // fmul (select Cond, 1.0, -1.0), OtherOp --> select Cond, OtherOp, -OtherOp // fmul OtherOp, (select Cond, 1.0, -1.0) --> select Cond, OtherOp, -OtherOp if (match(&I, m_c_FMul(m_OneUse(m_Select(m_Value(Cond), m_SpecificFP(1.0), m_SpecificFP(-1.0))), m_Value(OtherOp)))) { IRBuilder<>::FastMathFlagGuard FMFGuard(Builder); Builder.setFastMathFlags(I.getFastMathFlags()); return Builder.CreateSelect(Cond, OtherOp, Builder.CreateFNeg(OtherOp)); } // fmul (select Cond, -1.0, 1.0), OtherOp --> select Cond, -OtherOp, OtherOp // fmul OtherOp, (select Cond, -1.0, 1.0) --> select Cond, -OtherOp, OtherOp if (match(&I, m_c_FMul(m_OneUse(m_Select(m_Value(Cond), m_SpecificFP(-1.0), m_SpecificFP(1.0))), m_Value(OtherOp)))) { IRBuilder<>::FastMathFlagGuard FMFGuard(Builder); Builder.setFastMathFlags(I.getFastMathFlags()); return Builder.CreateSelect(Cond, Builder.CreateFNeg(OtherOp), OtherOp); } return nullptr; } /// Reduce integer multiplication patterns that contain a (+/-1 << Z) factor. /// Callers are expected to call this twice to handle commuted patterns. static Value *foldMulShl1(BinaryOperator &Mul, bool CommuteOperands, InstCombiner::BuilderTy &Builder) { Value *X = Mul.getOperand(0), *Y = Mul.getOperand(1); if (CommuteOperands) std::swap(X, Y); const bool HasNSW = Mul.hasNoSignedWrap(); const bool HasNUW = Mul.hasNoUnsignedWrap(); // X * (1 << Z) --> X << Z Value *Z; if (match(Y, m_Shl(m_One(), m_Value(Z)))) { bool PropagateNSW = HasNSW && cast(Y)->hasNoSignedWrap(); return Builder.CreateShl(X, Z, Mul.getName(), HasNUW, PropagateNSW); } // Similar to above, but an increment of the shifted value becomes an add: // X * ((1 << Z) + 1) --> (X * (1 << Z)) + X --> (X << Z) + X // This increases uses of X, so it may require a freeze, but that is still // expected to be an improvement because it removes the multiply. BinaryOperator *Shift; if (match(Y, m_OneUse(m_Add(m_BinOp(Shift), m_One()))) && match(Shift, m_OneUse(m_Shl(m_One(), m_Value(Z))))) { bool PropagateNSW = HasNSW && Shift->hasNoSignedWrap(); Value *FrX = Builder.CreateFreeze(X, X->getName() + ".fr"); Value *Shl = Builder.CreateShl(FrX, Z, "mulshl", HasNUW, PropagateNSW); return Builder.CreateAdd(Shl, FrX, Mul.getName(), HasNUW, PropagateNSW); } // Similar to above, but a decrement of the shifted value is disguised as // 'not' and becomes a sub: // X * (~(-1 << Z)) --> X * ((1 << Z) - 1) --> (X << Z) - X // This increases uses of X, so it may require a freeze, but that is still // expected to be an improvement because it removes the multiply. if (match(Y, m_OneUse(m_Not(m_OneUse(m_Shl(m_AllOnes(), m_Value(Z))))))) { Value *FrX = Builder.CreateFreeze(X, X->getName() + ".fr"); Value *Shl = Builder.CreateShl(FrX, Z, "mulshl"); return Builder.CreateSub(Shl, FrX, Mul.getName()); } return nullptr; } Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = simplifyMulInst(Op0, Op1, I.hasNoSignedWrap(), I.hasNoUnsignedWrap(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (SimplifyAssociativeOrCommutative(I)) return &I; if (Instruction *X = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; if (Value *V = foldUsingDistributiveLaws(I)) return replaceInstUsesWith(I, V); Type *Ty = I.getType(); const unsigned BitWidth = Ty->getScalarSizeInBits(); const bool HasNSW = I.hasNoSignedWrap(); const bool HasNUW = I.hasNoUnsignedWrap(); // X * -1 --> 0 - X if (match(Op1, m_AllOnes())) { return HasNSW ? BinaryOperator::CreateNSWNeg(Op0) : BinaryOperator::CreateNeg(Op0); } // 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(I.getOperand(0)); BinaryOperator *BO = BinaryOperator::CreateMul(NewOp, Shl); if (HasNUW && Mul->hasNoUnsignedWrap()) BO->setHasNoUnsignedWrap(); if (HasNSW && 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 = ConstantExpr::getExactLogBase2(C1)) { BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst); if (HasNUW) Shl->setHasNoUnsignedWrap(); if (HasNSW) { const APInt *V; if (match(NewCst, m_APInt(V)) && *V != V->getBitWidth() - 1) Shl->setHasNoSignedWrap(); } return Shl; } } } if (Op0->hasOneUse() && match(Op1, m_NegatedPower2())) { // Interpret X * (-1<(Op1)), I.getName()); // Try to convert multiply of extended operand to narrow negate and shift // for better analysis. // This is valid if the shift amount (trailing zeros in the multiplier // constant) clears more high bits than the bitwidth difference between // source and destination types: // ({z/s}ext X) * (-1< (zext (-X)) << C const APInt *NegPow2C; Value *X; if (match(Op0, m_ZExtOrSExt(m_Value(X))) && match(Op1, m_APIntAllowUndef(NegPow2C))) { unsigned SrcWidth = X->getType()->getScalarSizeInBits(); unsigned ShiftAmt = NegPow2C->countTrailingZeros(); if (ShiftAmt >= BitWidth - SrcWidth) { Value *N = Builder.CreateNeg(X, X->getName() + ".neg"); Value *Z = Builder.CreateZExt(N, Ty, N->getName() + ".z"); return BinaryOperator::CreateShl(Z, ConstantInt::get(Ty, ShiftAmt)); } } } if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I)) return FoldedMul; if (Value *FoldedMul = foldMulSelectToNegate(I, Builder)) return replaceInstUsesWith(I, FoldedMul); // Simplify mul instructions with a constant RHS. Constant *MulC; if (match(Op1, m_ImmConstant(MulC))) { // Canonicalize (X+C1)*MulC -> X*MulC+C1*MulC. // Canonicalize (X|C1)*MulC -> X*MulC+C1*MulC. Value *X; Constant *C1; if ((match(Op0, m_OneUse(m_Add(m_Value(X), m_ImmConstant(C1))))) || (match(Op0, m_OneUse(m_Or(m_Value(X), m_ImmConstant(C1)))) && haveNoCommonBitsSet(X, C1, DL, &AC, &I, &DT))) { // C1*MulC simplifies to a tidier constant. Value *NewC = Builder.CreateMul(C1, MulC); auto *BOp0 = cast(Op0); bool Op0NUW = (BOp0->getOpcode() == Instruction::Or || BOp0->hasNoUnsignedWrap()); Value *NewMul = Builder.CreateMul(X, MulC); auto *BO = BinaryOperator::CreateAdd(NewMul, NewC); if (HasNUW && Op0NUW) { // If NewMulBO is constant we also can set BO to nuw. if (auto *NewMulBO = dyn_cast(NewMul)) NewMulBO->setHasNoUnsignedWrap(); BO->setHasNoUnsignedWrap(); } return BO; } } // abs(X) * abs(X) -> X * X // nabs(X) * nabs(X) -> X * X if (Op0 == Op1) { Value *X, *Y; SelectPatternFlavor SPF = matchSelectPattern(Op0, X, Y).Flavor; if (SPF == SPF_ABS || SPF == SPF_NABS) return BinaryOperator::CreateMul(X, X); if (match(Op0, m_Intrinsic(m_Value(X)))) return BinaryOperator::CreateMul(X, X); } // -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 (HasNSW && cast(Op0)->hasNoSignedWrap() && cast(Op1)->hasNoSignedWrap()) NewMul->setHasNoSignedWrap(); return NewMul; } // -X * Y --> -(X * Y) // X * -Y --> -(X * Y) if (match(&I, m_c_Mul(m_OneUse(m_Neg(m_Value(X))), m_Value(Y)))) return BinaryOperator::CreateNeg(Builder.CreateMul(X, Y)); // (X / Y) * Y = X - (X % Y) // (X / Y) * -Y = (X % Y) - X { Value *Y = Op1; BinaryOperator *Div = dyn_cast(Op0); if (!Div || (Div->getOpcode() != Instruction::UDiv && Div->getOpcode() != Instruction::SDiv)) { Y = Op0; Div = dyn_cast(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; // X must be frozen because we are increasing its number of uses. Value *XFreeze = Builder.CreateFreeze(X, X->getName() + ".fr"); Value *Rem = Builder.CreateBinOp(RemOpc, XFreeze, DivOp1); if (DivOp1 == Y) return BinaryOperator::CreateSub(XFreeze, Rem); return BinaryOperator::CreateSub(Rem, XFreeze); } } // Fold the following two scenarios: // 1) i1 mul -> i1 and. // 2) X * Y --> X & Y, iff X, Y can be only {0,1}. // Note: We could use known bits to generalize this and related patterns with // shifts/truncs if (Ty->isIntOrIntVectorTy(1) || (match(Op0, m_And(m_Value(), m_One())) && match(Op1, m_And(m_Value(), m_One())))) return BinaryOperator::CreateAnd(Op0, Op1); if (Value *R = foldMulShl1(I, /* CommuteOperands */ false, Builder)) return replaceInstUsesWith(I, R); if (Value *R = foldMulShl1(I, /* CommuteOperands */ true, Builder)) return replaceInstUsesWith(I, R); // (zext bool X) * (zext bool Y) --> zext (and X, Y) // (sext bool X) * (sext bool Y) --> zext (and X, Y) // Note: -1 * -1 == 1 * 1 == 1 (if the extends match, the result is the same) if (((match(Op0, m_ZExt(m_Value(X))) && match(Op1, m_ZExt(m_Value(Y)))) || (match(Op0, m_SExt(m_Value(X))) && match(Op1, m_SExt(m_Value(Y))))) && X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType() && (Op0->hasOneUse() || Op1->hasOneUse() || X == Y)) { Value *And = Builder.CreateAnd(X, Y, "mulbool"); return CastInst::Create(Instruction::ZExt, And, Ty); } // (sext bool X) * (zext bool Y) --> sext (and X, Y) // (zext bool X) * (sext bool Y) --> sext (and X, Y) // Note: -1 * 1 == 1 * -1 == -1 if (((match(Op0, m_SExt(m_Value(X))) && match(Op1, m_ZExt(m_Value(Y)))) || (match(Op0, m_ZExt(m_Value(X))) && match(Op1, m_SExt(m_Value(Y))))) && X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType() && (Op0->hasOneUse() || Op1->hasOneUse())) { Value *And = Builder.CreateAnd(X, Y, "mulbool"); return CastInst::Create(Instruction::SExt, And, Ty); } // (zext bool X) * Y --> X ? Y : 0 // Y * (zext bool X) --> X ? Y : 0 if (match(Op0, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) return SelectInst::Create(X, Op1, ConstantInt::getNullValue(Ty)); if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) return SelectInst::Create(X, Op0, ConstantInt::getNullValue(Ty)); Constant *ImmC; if (match(Op1, m_ImmConstant(ImmC))) { // (sext bool X) * C --> X ? -C : 0 if (match(Op0, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) { Constant *NegC = ConstantExpr::getNeg(ImmC); return SelectInst::Create(X, NegC, ConstantInt::getNullValue(Ty)); } // (ashr i32 X, 31) * C --> (X < 0) ? -C : 0 const APInt *C; if (match(Op0, m_OneUse(m_AShr(m_Value(X), m_APInt(C)))) && *C == C->getBitWidth() - 1) { Constant *NegC = ConstantExpr::getNeg(ImmC); Value *IsNeg = Builder.CreateIsNeg(X, "isneg"); return SelectInst::Create(IsNeg, NegC, ConstantInt::getNullValue(Ty)); } } // (lshr X, 31) * Y --> (X < 0) ? Y : 0 // TODO: We are not checking one-use because the elimination of the multiply // is better for analysis? const APInt *C; if (match(&I, m_c_BinOp(m_LShr(m_Value(X), m_APInt(C)), m_Value(Y))) && *C == C->getBitWidth() - 1) { Value *IsNeg = Builder.CreateIsNeg(X, "isneg"); return SelectInst::Create(IsNeg, Y, ConstantInt::getNullValue(Ty)); } // (and X, 1) * Y --> (trunc X) ? Y : 0 if (match(&I, m_c_BinOp(m_OneUse(m_And(m_Value(X), m_One())), m_Value(Y)))) { Value *Tr = Builder.CreateTrunc(X, CmpInst::makeCmpResultType(Ty)); return SelectInst::Create(Tr, Y, ConstantInt::getNullValue(Ty)); } // ((ashr X, 31) | 1) * X --> abs(X) // X * ((ashr X, 31) | 1) --> abs(X) if (match(&I, m_c_BinOp(m_Or(m_AShr(m_Value(X), m_SpecificIntAllowUndef(BitWidth - 1)), m_One()), m_Deferred(X)))) { Value *Abs = Builder.CreateBinaryIntrinsic( Intrinsic::abs, X, ConstantInt::getBool(I.getContext(), HasNSW)); Abs->takeName(&I); return replaceInstUsesWith(I, Abs); } if (Instruction *Ext = narrowMathIfNoOverflow(I)) return Ext; bool Changed = false; if (!HasNSW && willNotOverflowSignedMul(Op0, Op1, I)) { Changed = true; I.setHasNoSignedWrap(true); } if (!HasNUW && willNotOverflowUnsignedMul(Op0, Op1, I)) { Changed = true; I.setHasNoUnsignedWrap(true); } return Changed ? &I : nullptr; } Instruction *InstCombinerImpl::foldFPSignBitOps(BinaryOperator &I) { BinaryOperator::BinaryOps Opcode = I.getOpcode(); assert((Opcode == Instruction::FMul || Opcode == Instruction::FDiv) && "Expected fmul or fdiv"); Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); Value *X, *Y; // -X * -Y --> X * Y // -X / -Y --> X / Y if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y)))) return BinaryOperator::CreateWithCopiedFlags(Opcode, X, Y, &I); // fabs(X) * fabs(X) -> X * X // fabs(X) / fabs(X) -> X / X if (Op0 == Op1 && match(Op0, m_FAbs(m_Value(X)))) return BinaryOperator::CreateWithCopiedFlags(Opcode, X, X, &I); // fabs(X) * fabs(Y) --> fabs(X * Y) // fabs(X) / fabs(Y) --> fabs(X / Y) if (match(Op0, m_FAbs(m_Value(X))) && match(Op1, m_FAbs(m_Value(Y))) && (Op0->hasOneUse() || Op1->hasOneUse())) { IRBuilder<>::FastMathFlagGuard FMFGuard(Builder); Builder.setFastMathFlags(I.getFastMathFlags()); Value *XY = Builder.CreateBinOp(Opcode, X, Y); Value *Fabs = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, XY); Fabs->takeName(&I); return replaceInstUsesWith(I, Fabs); } return nullptr; } Instruction *InstCombinerImpl::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 = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I)) return FoldedMul; if (Value *FoldedMul = foldMulSelectToNegate(I, Builder)) return replaceInstUsesWith(I, FoldedMul); if (Instruction *R = foldFPSignBitOps(I)) return R; // X * -1.0 --> -X Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (match(Op1, m_SpecificFP(-1.0))) return UnaryOperator::CreateFNegFMF(Op0, &I); // With no-nans: X * 0.0 --> copysign(0.0, X) if (I.hasNoNaNs() && match(Op1, m_PosZeroFP())) { CallInst *CopySign = Builder.CreateIntrinsic(Intrinsic::copysign, {I.getType()}, {Op1, Op0}, &I); return replaceInstUsesWith(I, CopySign); } // -X * C --> X * -C Value *X, *Y; Constant *C; if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_Constant(C))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) return BinaryOperator::CreateFMulFMF(X, NegC, &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 = ConstantFoldBinaryOpOperands(Instruction::FMul, C, C1, DL); if (CC1 && 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 = ConstantFoldBinaryOpOperands(Instruction::FDiv, C, C1, DL); if (CDivC1 && 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 = ConstantFoldBinaryOpOperands(Instruction::FDiv, C1, C, DL); if (C1DivC && 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) if (Constant *CC1 = ConstantFoldBinaryOpOperands( Instruction::FMul, C, C1, DL)) { 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) if (Constant *CC1 = ConstantFoldBinaryOpOperands( Instruction::FMul, C, C1, DL)) { Value *XC = Builder.CreateFMulFMF(X, C, &I); return BinaryOperator::CreateFSubFMF(CC1, XC, &I); } } } Value *Z; if (match(&I, m_c_FMul(m_OneUse(m_FDiv(m_Value(X), m_Value(Y))), m_Value(Z)))) { // Sink division: (X / Y) * Z --> (X * Z) / Y Value *NewFMul = Builder.CreateFMulFMF(X, Z, &I); return BinaryOperator::CreateFDivFMF(NewFMul, Y, &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_Sqrt(m_Value(X)))) && match(Op1, m_OneUse(m_Sqrt(m_Value(Y))))) { Value *XY = Builder.CreateFMulFMF(X, Y, &I); Value *Sqrt = Builder.CreateUnaryIntrinsic(Intrinsic::sqrt, XY, &I); return replaceInstUsesWith(I, Sqrt); } // The following transforms are done irrespective of the number of uses // for the expression "1.0/sqrt(X)". // 1) 1.0/sqrt(X) * X -> X/sqrt(X) // 2) X * 1.0/sqrt(X) -> X/sqrt(X) // We always expect the backend to reduce X/sqrt(X) to sqrt(X), if it // has the necessary (reassoc) fast-math-flags. if (I.hasNoSignedZeros() && match(Op0, (m_FDiv(m_SpecificFP(1.0), m_Value(Y)))) && match(Y, m_Sqrt(m_Value(X))) && Op1 == X) return BinaryOperator::CreateFDivFMF(X, Y, &I); if (I.hasNoSignedZeros() && match(Op1, (m_FDiv(m_SpecificFP(1.0), m_Value(Y)))) && match(Y, m_Sqrt(m_Value(X))) && Op0 == X) return BinaryOperator::CreateFDivFMF(X, Y, &I); // Like the similar transform in instsimplify, this requires 'nsz' because // sqrt(-0.0) = -0.0, and -0.0 * -0.0 does not simplify to -0.0. if (I.hasNoNaNs() && I.hasNoSignedZeros() && Op0 == Op1 && Op0->hasNUses(2)) { // Peek through fdiv to find squaring of square root: // (X / sqrt(Y)) * (X / sqrt(Y)) --> (X * X) / Y if (match(Op0, m_FDiv(m_Value(X), m_Sqrt(m_Value(Y))))) { Value *XX = Builder.CreateFMulFMF(X, X, &I); return BinaryOperator::CreateFDivFMF(XX, Y, &I); } // (sqrt(Y) / X) * (sqrt(Y) / X) --> Y / (X * X) if (match(Op0, m_FDiv(m_Sqrt(m_Value(Y)), m_Value(X)))) { Value *XX = Builder.CreateFMulFMF(X, X, &I); return BinaryOperator::CreateFDivFMF(Y, XX, &I); } } // pow(X, Y) * X --> pow(X, Y+1) // X * pow(X, Y) --> pow(X, Y+1) if (match(&I, m_c_FMul(m_OneUse(m_Intrinsic(m_Value(X), m_Value(Y))), m_Deferred(X)))) { Value *Y1 = Builder.CreateFAddFMF(Y, ConstantFP::get(I.getType(), 1.0), &I); Value *Pow = Builder.CreateBinaryIntrinsic(Intrinsic::pow, X, Y1, &I); return replaceInstUsesWith(I, Pow); } if (I.isOnlyUserOfAnyOperand()) { // pow(X, Y) * pow(X, Z) -> pow(X, Y + Z) if (match(Op0, m_Intrinsic(m_Value(X), m_Value(Y))) && match(Op1, m_Intrinsic(m_Specific(X), m_Value(Z)))) { auto *YZ = Builder.CreateFAddFMF(Y, Z, &I); auto *NewPow = Builder.CreateBinaryIntrinsic(Intrinsic::pow, X, YZ, &I); return replaceInstUsesWith(I, NewPow); } // pow(X, Y) * pow(Z, Y) -> pow(X * Z, Y) if (match(Op0, m_Intrinsic(m_Value(X), m_Value(Y))) && match(Op1, m_Intrinsic(m_Value(Z), m_Specific(Y)))) { auto *XZ = Builder.CreateFMulFMF(X, Z, &I); auto *NewPow = Builder.CreateBinaryIntrinsic(Intrinsic::pow, XZ, Y, &I); return replaceInstUsesWith(I, NewPow); } // powi(x, y) * powi(x, z) -> powi(x, y + z) if (match(Op0, m_Intrinsic(m_Value(X), m_Value(Y))) && match(Op1, m_Intrinsic(m_Specific(X), m_Value(Z))) && Y->getType() == Z->getType()) { auto *YZ = Builder.CreateAdd(Y, Z); auto *NewPow = Builder.CreateIntrinsic( Intrinsic::powi, {X->getType(), YZ->getType()}, {X, YZ}, &I); return replaceInstUsesWith(I, NewPow); } // exp(X) * exp(Y) -> exp(X + Y) if (match(Op0, m_Intrinsic(m_Value(X))) && match(Op1, m_Intrinsic(m_Value(Y)))) { Value *XY = Builder.CreateFAddFMF(X, Y, &I); Value *Exp = Builder.CreateUnaryIntrinsic(Intrinsic::exp, XY, &I); return replaceInstUsesWith(I, Exp); } // exp2(X) * exp2(Y) -> exp2(X + Y) if (match(Op0, m_Intrinsic(m_Value(X))) && match(Op1, m_Intrinsic(m_Value(Y)))) { Value *XY = Builder.CreateFAddFMF(X, Y, &I); Value *Exp2 = Builder.CreateUnaryIntrinsic(Intrinsic::exp2, XY, &I); return replaceInstUsesWith(I, Exp2); } } // (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( m_OneUse(m_FMul(m_Value(X), m_SpecificFP(0.5))))))) { Log2 = cast(Op0); Y = Op1; } if (match(Op1, m_OneUse(m_Intrinsic( m_OneUse(m_FMul(m_Value(X), m_SpecificFP(0.5))))))) { Log2 = cast(Op1); Y = Op0; } if (Log2) { Value *Log2 = Builder.CreateUnaryIntrinsic(Intrinsic::log2, X, &I); Value *LogXTimesY = Builder.CreateFMulFMF(Log2, Y, &I); return BinaryOperator::CreateFSubFMF(LogXTimesY, Y, &I); } } // Simplify FMUL recurrences starting with 0.0 to 0.0 if nnan and nsz are set. // Given a phi node with entry value as 0 and it used in fmul operation, // we can replace fmul with 0 safely and eleminate loop operation. PHINode *PN = nullptr; Value *Start = nullptr, *Step = nullptr; if (matchSimpleRecurrence(&I, PN, Start, Step) && I.hasNoNaNs() && I.hasNoSignedZeros() && match(Start, m_Zero())) return replaceInstUsesWith(I, Start); 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 InstCombinerImpl::simplifyDivRemOfSelectWithZeroOp(BinaryOperator &I) { SelectInst *SI = dyn_cast(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. replaceOperand(I, 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 (Use &Op : BBI->operands()) { if (Op == SI) { replaceUse(Op, SI->getOperand(NonNullOperand)); Worklist.push(&*BBI); } else if (Op == SelectCond) { replaceUse(Op, NonNullOperand == 1 ? ConstantInt::getTrue(CondTy) : ConstantInt::getFalse(CondTy)); Worklist.push(&*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.isZero()) return false; // Bail if we would divide INT_MIN by -1. if (IsSigned && C1.isMinSignedValue() && C2.isAllOnes()) 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(); } static Instruction *foldIDivShl(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { assert((I.getOpcode() == Instruction::SDiv || I.getOpcode() == Instruction::UDiv) && "Expected integer divide"); bool IsSigned = I.getOpcode() == Instruction::SDiv; Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); Type *Ty = I.getType(); Instruction *Ret = nullptr; Value *X, *Y, *Z; // With appropriate no-wrap constraints, remove a common factor in the // dividend and divisor that is disguised as a left-shifted value. if (match(Op1, m_Shl(m_Value(X), m_Value(Z))) && match(Op0, m_c_Mul(m_Specific(X), m_Value(Y)))) { // Both operands must have the matching no-wrap for this kind of division. auto *Mul = cast(Op0); auto *Shl = cast(Op1); bool HasNUW = Mul->hasNoUnsignedWrap() && Shl->hasNoUnsignedWrap(); bool HasNSW = Mul->hasNoSignedWrap() && Shl->hasNoSignedWrap(); // (X * Y) u/ (X << Z) --> Y u>> Z if (!IsSigned && HasNUW) Ret = BinaryOperator::CreateLShr(Y, Z); // (X * Y) s/ (X << Z) --> Y s/ (1 << Z) if (IsSigned && HasNSW && (Op0->hasOneUse() || Op1->hasOneUse())) { Value *Shl = Builder.CreateShl(ConstantInt::get(Ty, 1), Z); Ret = BinaryOperator::CreateSDiv(Y, Shl); } } // With appropriate no-wrap constraints, remove a common factor in the // dividend and divisor that is disguised as a left-shift amount. if (match(Op0, m_Shl(m_Value(X), m_Value(Z))) && match(Op1, m_Shl(m_Value(Y), m_Specific(Z)))) { auto *Shl0 = cast(Op0); auto *Shl1 = cast(Op1); // For unsigned div, we need 'nuw' on both shifts or // 'nsw' on both shifts + 'nuw' on the dividend. // (X << Z) / (Y << Z) --> X / Y if (!IsSigned && ((Shl0->hasNoUnsignedWrap() && Shl1->hasNoUnsignedWrap()) || (Shl0->hasNoUnsignedWrap() && Shl0->hasNoSignedWrap() && Shl1->hasNoSignedWrap()))) Ret = BinaryOperator::CreateUDiv(X, Y); // For signed div, we need 'nsw' on both shifts + 'nuw' on the divisor. // (X << Z) / (Y << Z) --> X / Y if (IsSigned && Shl0->hasNoSignedWrap() && Shl1->hasNoSignedWrap() && Shl1->hasNoUnsignedWrap()) Ret = BinaryOperator::CreateSDiv(X, Y); } if (!Ret) return nullptr; Ret->setIsExact(I.isExact()); return Ret; } /// 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 *InstCombinerImpl::commonIDivTransforms(BinaryOperator &I) { if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; 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)) return replaceOperand(I, 1, V); // Handle cases involving: [su]div X, (select Cond, Y, Z) // This does not apply for fdiv. if (simplifyDivRemOfSelectWithZeroOp(I)) return &I; // If the divisor is a select-of-constants, try to constant fold all div ops: // C / (select Cond, TrueC, FalseC) --> select Cond, (C / TrueC), (C / FalseC) // TODO: Adapt simplifyDivRemOfSelectWithZeroOp to allow this and other folds. if (match(Op0, m_ImmConstant()) && match(Op1, m_Select(m_Value(), m_ImmConstant(), m_ImmConstant()))) { if (Instruction *R = FoldOpIntoSelect(I, cast(Op1), /*FoldWithMultiUse*/ true)) return R; } 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(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->ult(C1->getBitWidth() - 1)) || (!IsSigned && match(Op0, m_NUWShl(m_Value(X), m_APInt(C1))) && C1->ult(C1->getBitWidth()))) { APInt Quotient(C1->getBitWidth(), /*val=*/0ULL, IsSigned); APInt C1Shifted = APInt::getOneBitSet( C1->getBitWidth(), static_cast(C1->getZExtValue())); // (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(Op0); Mul->setHasNoUnsignedWrap(!IsSigned && OBO->hasNoUnsignedWrap()); Mul->setHasNoSignedWrap(OBO->hasNoSignedWrap()); return Mul; } } if (!C2->isZero()) // 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) { // 1 / 0 --> undef ; 1 / 1 --> 1 ; 1 / -1 --> -1 ; 1 / anything else --> 0 // (Op1 + 1) u< 3 ? Op1 : 0 // Op1 must be frozen because we are increasing its number of uses. Value *F1 = Builder.CreateFreeze(Op1, Op1->getName() + ".fr"); Value *Inc = Builder.CreateAdd(F1, Op0); Value *Cmp = Builder.CreateICmpULT(Inc, ConstantInt::get(Ty, 3)); return SelectInst::Create(Cmp, F1, 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(Op1)->hasNoSignedWrap(); bool HasNUW = cast(Op1)->hasNoUnsignedWrap(); if ((IsSigned && HasNSW) || (!IsSigned && HasNUW)) { replaceOperand(I, 0, ConstantInt::get(Ty, 1)); replaceOperand(I, 1, Y); return &I; } } // (X << Z) / (X * Y) -> (1 << Z) / Y // TODO: Handle sdiv. if (!IsSigned && Op1->hasOneUse() && match(Op0, m_NUWShl(m_Value(X), m_Value(Z))) && match(Op1, m_c_Mul(m_Specific(X), m_Value(Y)))) if (cast(Op1)->hasNoUnsignedWrap()) { Instruction *NewDiv = BinaryOperator::CreateUDiv( Builder.CreateShl(ConstantInt::get(Ty, 1), Z, "", /*NUW*/ true), Y); NewDiv->setIsExact(I.isExact()); return NewDiv; } if (Instruction *R = foldIDivShl(I, Builder)) return R; // With the appropriate no-wrap constraint, remove a multiply by the divisor // after peeking through another divide: // ((Op1 * X) / Y) / Op1 --> X / Y if (match(Op0, m_BinOp(I.getOpcode(), m_c_Mul(m_Specific(Op1), m_Value(X)), m_Value(Y)))) { auto *InnerDiv = cast(Op0); auto *Mul = cast(InnerDiv->getOperand(0)); Instruction *NewDiv = nullptr; if (!IsSigned && Mul->hasNoUnsignedWrap()) NewDiv = BinaryOperator::CreateUDiv(X, Y); else if (IsSigned && Mul->hasNoSignedWrap()) NewDiv = BinaryOperator::CreateSDiv(X, Y); // Exact propagates only if both of the original divides are exact. if (NewDiv) { NewDiv->setIsExact(I.isExact() && InnerDiv->isExact()); return NewDiv; } } return nullptr; } static const unsigned MaxDepth = 6; // Take the exact integer log2 of the value. If DoFold is true, create the // actual instructions, otherwise return a non-null dummy value. Return nullptr // on failure. static Value *takeLog2(IRBuilderBase &Builder, Value *Op, unsigned Depth, bool DoFold) { auto IfFold = [DoFold](function_ref Fn) { if (!DoFold) return reinterpret_cast(-1); return Fn(); }; // FIXME: assert that Op1 isn't/doesn't contain undef. // log2(2^C) -> C if (match(Op, m_Power2())) return IfFold([&]() { Constant *C = ConstantExpr::getExactLogBase2(cast(Op)); if (!C) llvm_unreachable("Failed to constant fold udiv -> logbase2"); return C; }); // The remaining tests are all recursive, so bail out if we hit the limit. if (Depth++ == MaxDepth) return nullptr; // log2(zext X) -> zext log2(X) // FIXME: Require one use? Value *X, *Y; if (match(Op, m_ZExt(m_Value(X)))) if (Value *LogX = takeLog2(Builder, X, Depth, DoFold)) return IfFold([&]() { return Builder.CreateZExt(LogX, Op->getType()); }); // log2(X << Y) -> log2(X) + Y // FIXME: Require one use unless X is 1? if (match(Op, m_Shl(m_Value(X), m_Value(Y)))) if (Value *LogX = takeLog2(Builder, X, Depth, DoFold)) return IfFold([&]() { return Builder.CreateAdd(LogX, Y); }); // log2(Cond ? X : Y) -> Cond ? log2(X) : log2(Y) // FIXME: missed optimization: if one of the hands of select is/contains // undef, just directly pick the other one. // FIXME: can both hands contain undef? // FIXME: Require one use? if (SelectInst *SI = dyn_cast(Op)) if (Value *LogX = takeLog2(Builder, SI->getOperand(1), Depth, DoFold)) if (Value *LogY = takeLog2(Builder, SI->getOperand(2), Depth, DoFold)) return IfFold([&]() { return Builder.CreateSelect(SI->getOperand(0), LogX, LogY); }); // log2(umin(X, Y)) -> umin(log2(X), log2(Y)) // log2(umax(X, Y)) -> umax(log2(X), log2(Y)) auto *MinMax = dyn_cast(Op); if (MinMax && MinMax->hasOneUse() && !MinMax->isSigned()) if (Value *LogX = takeLog2(Builder, MinMax->getLHS(), Depth, DoFold)) if (Value *LogY = takeLog2(Builder, MinMax->getRHS(), Depth, DoFold)) return IfFold([&]() { return Builder.CreateBinaryIntrinsic( MinMax->getIntrinsicID(), LogX, LogY); }); return nullptr; } /// 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 (isa(N) && match(N, m_OneUse(m_ZExt(m_Value(X)))) && match(D, 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') return new ZExtInst(Builder.CreateBinOp(Opcode, X, TruncC), Ty); } if (isa(D) && 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 C, (zext X) --> zext (udiv C', X) // urem C, (zext X) --> zext (urem C', X) return new ZExtInst(Builder.CreateBinOp(Opcode, TruncC, X), Ty); } return nullptr; } Instruction *InstCombinerImpl::visitUDiv(BinaryOperator &I) { if (Value *V = simplifyUDivInst(I.getOperand(0), I.getOperand(1), I.isExact(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(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); } // Look through a right-shift to find the common factor: // ((Op1 *nuw A) >> B) / Op1 --> A >> B if (match(Op0, m_LShr(m_NUWMul(m_Specific(Op1), m_Value(A)), m_Value(B))) || match(Op0, m_LShr(m_NUWMul(m_Value(A), m_Specific(Op1)), m_Value(B)))) { Instruction *Lshr = BinaryOperator::CreateLShr(A, B); if (I.isExact() && cast(Op0)->isExact()) Lshr->setIsExact(); return Lshr; } // Op1 udiv Op2 -> Op1 lshr log2(Op2), if log2() folds away. if (takeLog2(Builder, Op1, /*Depth*/0, /*DoFold*/false)) { Value *Res = takeLog2(Builder, Op1, /*Depth*/0, /*DoFold*/true); return replaceInstUsesWith( I, Builder.CreateLShr(Op0, Res, I.getName(), I.isExact())); } return nullptr; } Instruction *InstCombinerImpl::visitSDiv(BinaryOperator &I) { if (Value *V = simplifySDivInst(I.getOperand(0), I.getOperand(1), I.isExact(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(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); Type *Ty = I.getType(); 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); // X / INT_MIN --> X == INT_MIN if (match(Op1, m_SignMask())) return new ZExtInst(Builder.CreateICmpEQ(Op0, Op1), Ty); if (I.isExact()) { // sdiv exact X, 1< ashr exact X, C iff 1<(Op1)); return BinaryOperator::CreateExactAShr(Op0, C); } // sdiv exact X, (1< ashr exact X, ShAmt (if shl is non-negative) Value *ShAmt; if (match(Op1, m_NSWShl(m_One(), m_Value(ShAmt)))) return BinaryOperator::CreateExactAShr(Op0, ShAmt); // sdiv exact X, -1< -(ashr exact X, C) if (match(Op1, m_NegatedPower2())) { Constant *NegPow2C = ConstantExpr::getNeg(cast(Op1)); Constant *C = ConstantExpr::getExactLogBase2(NegPow2C); Value *Ashr = Builder.CreateAShr(Op0, C, I.getName() + ".neg", true); return BinaryOperator::CreateNeg(Ashr); } } const APInt *Op1C; if (match(Op1, m_APInt(Op1C))) { // 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(Op1), Op0Src->getType()); Value *NarrowOp = Builder.CreateSDiv(Op0Src, NarrowDivisor); return new SExtInst(NarrowOp, Ty); } // -X / C --> X / -C (if the negation doesn't overflow). // TODO: This could be enhanced to handle arbitrary vector constants by // checking if all elements are not the min-signed-val. if (!Op1C->isMinSignedValue() && match(Op0, m_NSWSub(m_Zero(), m_Value(X)))) { Constant *NegC = ConstantInt::get(Ty, -(*Op1C)); Instruction *BO = BinaryOperator::CreateSDiv(X, NegC); BO->setIsExact(I.isExact()); return BO; } } // -X / Y --> -(X / Y) Value *Y; if (match(&I, m_SDiv(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y)))) return BinaryOperator::CreateNSWNeg( Builder.CreateSDiv(X, Y, I.getName(), I.isExact())); // abs(X) / X --> X > -1 ? 1 : -1 // X / abs(X) --> X > -1 ? 1 : -1 if (match(&I, m_c_BinOp( m_OneUse(m_Intrinsic(m_Value(X), m_One())), m_Deferred(X)))) { Value *Cond = Builder.CreateIsNotNeg(X); return SelectInst::Create(Cond, ConstantInt::get(Ty, 1), ConstantInt::getAllOnesValue(Ty)); } KnownBits KnownDividend = computeKnownBits(Op0, 0, &I); if (!I.isExact() && (match(Op1, m_Power2(Op1C)) || match(Op1, m_NegatedPower2(Op1C))) && KnownDividend.countMinTrailingZeros() >= Op1C->countTrailingZeros()) { I.setIsExact(); return &I; } if (KnownDividend.isNonNegative()) { // If both operands are unsigned, turn this into a udiv. if (isKnownNonNegative(Op1, DL, 0, &AC, &I, &DT)) { auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName()); BO->setIsExact(I.isExact()); return BO; } if (match(Op1, m_NegatedPower2())) { // X sdiv (-(1 << C)) -> -(X sdiv (1 << C)) -> // -> -(X udiv (1 << C)) -> -(X u>> C) Constant *CNegLog2 = ConstantExpr::getExactLogBase2( ConstantExpr::getNeg(cast(Op1))); Value *Shr = Builder.CreateLShr(Op0, CNegLog2, I.getName(), I.isExact()); return BinaryOperator::CreateNeg(Shr); } 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. Instruction *InstCombinerImpl::foldFDivConstantDivisor(BinaryOperator &I) { Constant *C; if (!match(I.getOperand(1), m_Constant(C))) return nullptr; // -X / C --> X / -C Value *X; const DataLayout &DL = I.getModule()->getDataLayout(); if (match(I.getOperand(0), m_FNeg(m_Value(X)))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) return BinaryOperator::CreateFDivFMF(X, NegC, &I); // nnan X / +0.0 -> copysign(inf, X) if (I.hasNoNaNs() && match(I.getOperand(1), m_Zero())) { IRBuilder<> B(&I); // TODO: nnan nsz X / -0.0 -> copysign(inf, X) CallInst *CopySign = B.CreateIntrinsic( Intrinsic::copysign, {C->getType()}, {ConstantFP::getInfinity(I.getType()), I.getOperand(0)}, &I); CopySign->takeName(&I); return replaceInstUsesWith(I, CopySign); } // 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 = ConstantFoldBinaryOpOperands( Instruction::FDiv, ConstantFP::get(I.getType(), 1.0), C, DL); if (!RecipC || !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; const DataLayout &DL = I.getModule()->getDataLayout(); if (match(I.getOperand(1), m_FNeg(m_Value(X)))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) return BinaryOperator::CreateFDivFMF(NegC, 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 = ConstantFoldBinaryOpOperands(Instruction::FDiv, C, C2, DL); } else if (match(I.getOperand(1), m_FDiv(m_Value(X), m_Constant(C2)))) { // C / (X / C2) --> (C * C2) / X NewC = ConstantFoldBinaryOpOperands(Instruction::FMul, C, C2, DL); } // 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); } /// Negate the exponent of pow/exp to fold division-by-pow() into multiply. static Instruction *foldFDivPowDivisor(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); auto *II = dyn_cast(Op1); if (!II || !II->hasOneUse() || !I.hasAllowReassoc() || !I.hasAllowReciprocal()) return nullptr; // Z / pow(X, Y) --> Z * pow(X, -Y) // Z / exp{2}(Y) --> Z * exp{2}(-Y) // In the general case, this creates an extra instruction, but fmul allows // for better canonicalization and optimization than fdiv. Intrinsic::ID IID = II->getIntrinsicID(); SmallVector Args; switch (IID) { case Intrinsic::pow: Args.push_back(II->getArgOperand(0)); Args.push_back(Builder.CreateFNegFMF(II->getArgOperand(1), &I)); break; case Intrinsic::powi: { // Require 'ninf' assuming that makes powi(X, -INT_MIN) acceptable. // That is, X ** (huge negative number) is 0.0, ~1.0, or INF and so // dividing by that is INF, ~1.0, or 0.0. Code that uses powi allows // non-standard results, so this corner case should be acceptable if the // code rules out INF values. if (!I.hasNoInfs()) return nullptr; Args.push_back(II->getArgOperand(0)); Args.push_back(Builder.CreateNeg(II->getArgOperand(1))); Type *Tys[] = {I.getType(), II->getArgOperand(1)->getType()}; Value *Pow = Builder.CreateIntrinsic(IID, Tys, Args, &I); return BinaryOperator::CreateFMulFMF(Op0, Pow, &I); } case Intrinsic::exp: case Intrinsic::exp2: Args.push_back(Builder.CreateFNegFMF(II->getArgOperand(0), &I)); break; default: return nullptr; } Value *Pow = Builder.CreateIntrinsic(IID, I.getType(), Args, &I); return BinaryOperator::CreateFMulFMF(Op0, Pow, &I); } Instruction *InstCombinerImpl::visitFDiv(BinaryOperator &I) { Module *M = I.getModule(); if (Value *V = simplifyFDivInst(I.getOperand(0), I.getOperand(1), I.getFastMathFlags(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; if (Instruction *R = foldFDivConstantDivisor(I)) return R; if (Instruction *R = foldFDivConstantDividend(I)) return R; if (Instruction *R = foldFPSignBitOps(I)) return R; Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (isa(Op0)) if (SelectInst *SI = dyn_cast(Op1)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; if (isa(Op1)) if (SelectInst *SI = dyn_cast(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(Y) || !isa(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(Y) || !isa(Op0))) { // Z / (X / Y) => (Y * Z) / X Value *YZ = Builder.CreateFMulFMF(Y, Op0, &I); return BinaryOperator::CreateFDivFMF(YZ, X, &I); } // Z / (1.0 / Y) => (Y * Z) // // This is a special case of Z / (X / Y) => (Y * Z) / X, with X = 1.0. The // m_OneUse check is avoided because even in the case of the multiple uses // for 1.0/Y, the number of instructions remain the same and a division is // replaced by a multiplication. if (match(Op1, m_FDiv(m_SpecificFP(1.0), m_Value(Y)))) return BinaryOperator::CreateFMulFMF(Y, Op0, &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(m_Value(X))) && match(Op1, m_Intrinsic(m_Specific(X))); bool IsCot = !IsTan && match(Op0, m_Intrinsic(m_Value(X))) && match(Op1, m_Intrinsic(m_Specific(X))); if ((IsTan || IsCot) && hasFloatFn(M, &TLI, I.getType(), LibFunc_tan, LibFunc_tanf, LibFunc_tanl)) { IRBuilder<> B(&I); IRBuilder<>::FastMathFlagGuard FMFGuard(B); B.setFastMathFlags(I.getFastMathFlags()); AttributeList Attrs = cast(Op0)->getCalledFunction()->getAttributes(); Value *Res = emitUnaryFloatFnCall(X, &TLI, LibFunc_tan, LibFunc_tanf, LibFunc_tanl, B, Attrs); if (IsCot) Res = B.CreateFDiv(ConstantFP::get(I.getType(), 1.0), Res); return replaceInstUsesWith(I, Res); } } // 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. Value *X, *Y; if (I.hasNoNaNs() && I.hasAllowReassoc() && match(Op1, m_c_FMul(m_Specific(Op0), m_Value(Y)))) { replaceOperand(I, 0, ConstantFP::get(I.getType(), 1.0)); replaceOperand(I, 1, Y); return &I; } // X / fabs(X) -> copysign(1.0, X) // fabs(X) / X -> copysign(1.0, X) if (I.hasNoNaNs() && I.hasNoInfs() && (match(&I, m_FDiv(m_Value(X), m_FAbs(m_Deferred(X)))) || match(&I, m_FDiv(m_FAbs(m_Value(X)), m_Deferred(X))))) { Value *V = Builder.CreateBinaryIntrinsic( Intrinsic::copysign, ConstantFP::get(I.getType(), 1.0), X, &I); return replaceInstUsesWith(I, V); } if (Instruction *Mul = foldFDivPowDivisor(I, Builder)) return Mul; // pow(X, Y) / X --> pow(X, Y-1) if (I.hasAllowReassoc() && match(Op0, m_OneUse(m_Intrinsic(m_Specific(Op1), m_Value(Y))))) { Value *Y1 = Builder.CreateFAddFMF(Y, ConstantFP::get(I.getType(), -1.0), &I); Value *Pow = Builder.CreateBinaryIntrinsic(Intrinsic::pow, Op1, Y1, &I); return replaceInstUsesWith(I, Pow); } 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 *InstCombinerImpl::commonIRemTransforms(BinaryOperator &I) { if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); // The RHS is known non-zero. if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I)) return replaceOperand(I, 1, V); // Handle cases involving: rem X, (select Cond, Y, Z) if (simplifyDivRemOfSelectWithZeroOp(I)) return &I; // If the divisor is a select-of-constants, try to constant fold all rem ops: // C % (select Cond, TrueC, FalseC) --> select Cond, (C % TrueC), (C % FalseC) // TODO: Adapt simplifyDivRemOfSelectWithZeroOp to allow this and other folds. if (match(Op0, m_ImmConstant()) && match(Op1, m_Select(m_Value(), m_ImmConstant(), m_ImmConstant()))) { if (Instruction *R = FoldOpIntoSelect(I, cast(Op1), /*FoldWithMultiUse*/ true)) return R; } if (isa(Op1)) { if (Instruction *Op0I = dyn_cast(Op0)) { if (SelectInst *SI = dyn_cast(Op0I)) { if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; } else if (auto *PN = dyn_cast(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 *InstCombinerImpl::visitURem(BinaryOperator &I) { if (Value *V = simplifyURemInst(I.getOperand(0), I.getOperand(1), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(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)) { // This may increase instruction count, we don't enforce that Y is a // constant. 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())) { Value *Cmp = Builder.CreateICmpNE(Op1, ConstantInt::get(Ty, 1)); return CastInst::CreateZExtOrBitCast(Cmp, Ty); } // Op0 urem C -> Op0 < C ? Op0 : Op0 - C, where C >= signbit. // Op0 must be frozen because we are increasing its number of uses. if (match(Op1, m_Negative())) { Value *F0 = Builder.CreateFreeze(Op0, Op0->getName() + ".fr"); Value *Cmp = Builder.CreateICmpULT(F0, Op1); Value *Sub = Builder.CreateSub(F0, Op1); return SelectInst::Create(Cmp, F0, 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 *InstCombinerImpl::visitSRem(BinaryOperator &I) { if (Value *V = simplifySRemInst(I.getOperand(0), I.getOperand(1), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(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()) return replaceOperand(I, 1, ConstantInt::get(I.getType(), -*Y)); } // -X srem Y --> -(X srem Y) Value *X, *Y; if (match(&I, m_SRem(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y)))) return BinaryOperator::CreateNSWNeg(Builder.CreateSRem(X, Y)); // 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(Op1) || isa(Op1)) { Constant *C = cast(Op1); unsigned VWidth = cast(C->getType())->getNumElements(); 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(Elt)) if (RHS->isNegative()) hasNegative = true; } if (hasNegative && !hasMissing) { SmallVector Elts(VWidth); for (unsigned i = 0; i != VWidth; ++i) { Elts[i] = C->getAggregateElement(i); // Handle undef, etc. if (ConstantInt *RHS = dyn_cast(Elts[i])) { if (RHS->isNegative()) Elts[i] = cast(ConstantExpr::getNeg(RHS)); } } Constant *NewRHSV = ConstantVector::get(Elts); if (NewRHSV != C) // Don't loop on -MININT return replaceOperand(I, 1, NewRHSV); } } return nullptr; } Instruction *InstCombinerImpl::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 = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; return nullptr; }