//===- 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/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 #include #include #include 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(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 Elts; for (unsigned I = 0, E = Ty->getVectorNumElements(); I != E; ++I) { Constant *Elt = C->getAggregateElement(I); if (!Elt) return nullptr; if (isa(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); } // 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)))) return Builder.CreateSelect(Cond, OtherOp, Builder.CreateNeg(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_AllOnes(), m_One())), m_Value(OtherOp)))) return Builder.CreateSelect(Cond, Builder.CreateNeg(OtherOp), 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; } 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 = foldVectorBinop(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(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)) { BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst); if (I.hasNoUnsignedWrap()) Shl->setHasNoUnsignedWrap(); if (I.hasNoSignedWrap()) { const APInt *V; if (match(NewCst, m_APInt(V)) && *V != V->getBitWidth() - 1) Shl->setHasNoSignedWrap(); } return Shl; } } } if (ConstantInt *CI = dyn_cast(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; if (Value *FoldedMul = foldMulSelectToNegate(I, Builder)) return replaceInstUsesWith(I, FoldedMul); // Simplify mul instructions with a constant RHS. if (isa(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(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; 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(Op0)->hasNoSignedWrap(); } else if (match(Op1, m_Shl(m_One(), m_Value(Y)))) { BO = BinaryOperator::CreateShl(Op0, Y); ShlNSW = cast(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); if (Instruction *Ext = narrowMathIfNoOverflow(I)) return Ext; 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 = foldVectorBinop(I)) return X; if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I)) return FoldedMul; if (Value *FoldedMul = foldMulSelectToNegate(I, Builder)) return replaceInstUsesWith(I, 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); // fabs(X) * fabs(X) -> X * X if (Op0 == Op1 && match(Op0, m_Intrinsic(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); } } 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_Intrinsic(m_Value(X)))) && match(Op1, m_OneUse(m_Intrinsic(m_Value(Y))))) { Value *XY = Builder.CreateFMulFMF(X, Y, &I); Value *Sqrt = Builder.CreateUnaryIntrinsic(Intrinsic::sqrt, XY, &I); return replaceInstUsesWith(I, Sqrt); } // 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_Intrinsic(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_Intrinsic(m_Value(Y)), m_Value(X)))) { Value *XX = Builder.CreateFMulFMF(X, X, &I); return BinaryOperator::CreateFDivFMF(Y, XX, &I); } } // exp(X) * exp(Y) -> exp(X + Y) // Match as long as at least one of exp has only one use. if (match(Op0, m_Intrinsic(m_Value(X))) && match(Op1, m_Intrinsic(m_Value(Y))) && (Op0->hasOneUse() || Op1->hasOneUse())) { 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) // Match as long as at least one of exp2 has only one use. if (match(Op0, m_Intrinsic(m_Value(X))) && match(Op1, m_Intrinsic(m_Value(Y))) && (Op0->hasOneUse() || Op1->hasOneUse())) { 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) { 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(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(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(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(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(Op1)->hasNoSignedWrap(); bool HasNUW = cast(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(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< X >> (N+C2) // X udiv (zext (C1 << N)), where C1 is "1< 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 &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< 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(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(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 = 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); } // (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...)))) SmallVector 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(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 = 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; // 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), I.getType()); 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(Op1), Op0Src->getType()); Value *NarrowOp = Builder.CreateSDiv(Op0Src, NarrowDivisor); return new SExtInst(NarrowOp, Op0->getType()); } // -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(I.getType(), -(*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())); // 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 = foldVectorBinop(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(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(&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 / -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; } // 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_Intrinsic(m_Deferred(X)))) || match(&I, m_FDiv(m_Intrinsic(m_Value(X)), m_Deferred(X))))) { Value *V = Builder.CreateBinaryIntrinsic( Intrinsic::copysign, ConstantFP::get(I.getType(), 1.0), X, &I); return replaceInstUsesWith(I, V); } 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(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 *InstCombiner::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); } // 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 = 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()) { Worklist.AddValue(I.getOperand(1)); I.setOperand(1, ConstantInt::get(I.getType(), -*Y)); return &I; } } // -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 = 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(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 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 = foldVectorBinop(I)) return X; return nullptr; }