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