//===- 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 "InstCombine.h" #include "llvm/IntrinsicInst.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Support/PatternMatch.h" using namespace llvm; using namespace PatternMatch; /// 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) { // 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 0; 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 = 0, *B = 0, *PowerOf2 = 0; if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(PowerOf2), m_Value(A))), m_Value(B))) && // The "1" can be any value known to be a power of 2. isPowerOfTwo(PowerOf2, IC.getTargetData())) { A = IC.Builder->CreateSub(A, B); return IC.Builder->CreateShl(PowerOf2, A); } // (PowerOfTwo >>u B) --> isExact since shifting out the result would make it // inexact. Similarly for <<. if (BinaryOperator *I = dyn_cast(V)) if (I->isLogicalShift() && isPowerOfTwo(I->getOperand(0), IC.getTargetData())) { // 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)) { 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 : 0; } /// MultiplyOverflows - True if the multiply can not be expressed in an int /// this size. static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) { uint32_t W = C1->getBitWidth(); APInt LHSExt = C1->getValue(), RHSExt = C2->getValue(); if (sign) { LHSExt = LHSExt.sext(W * 2); RHSExt = RHSExt.sext(W * 2); } else { LHSExt = LHSExt.zext(W * 2); RHSExt = RHSExt.zext(W * 2); } APInt MulExt = LHSExt * RHSExt; if (!sign) return MulExt.ugt(APInt::getLowBitsSet(W * 2, W)); APInt Min = APInt::getSignedMinValue(W).sext(W * 2); APInt Max = APInt::getSignedMaxValue(W).sext(W * 2); return MulExt.slt(Min) || MulExt.sgt(Max); } Instruction *InstCombiner::visitMul(BinaryOperator &I) { bool Changed = SimplifyAssociativeOrCommutative(I); Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifyMulInst(Op0, Op1, TD)) return ReplaceInstUsesWith(I, V); if (Value *V = SimplifyUsingDistributiveLaws(I)) return ReplaceInstUsesWith(I, V); if (match(Op1, m_AllOnes())) // X * -1 == 0 - X return BinaryOperator::CreateNeg(Op0, I.getName()); if (ConstantInt *CI = dyn_cast(Op1)) { // ((X << C1)*C2) == (X * (C2 << C1)) if (BinaryOperator *SI = dyn_cast(Op0)) if (SI->getOpcode() == Instruction::Shl) if (Constant *ShOp = dyn_cast(SI->getOperand(1))) return BinaryOperator::CreateMul(SI->getOperand(0), ConstantExpr::getShl(CI, ShOp)); const APInt &Val = CI->getValue(); if (Val.isPowerOf2()) { // Replace X*(2^C) with X << C Constant *NewCst = ConstantInt::get(Op0->getType(), Val.logBase2()); BinaryOperator *Shl = BinaryOperator::CreateShl(Op0, NewCst); if (I.hasNoSignedWrap()) Shl->setHasNoSignedWrap(); if (I.hasNoUnsignedWrap()) Shl->setHasNoUnsignedWrap(); return Shl; } // Canonicalize (X+C1)*CI -> X*CI+C1*CI. { Value *X; ConstantInt *C1; if (Op0->hasOneUse() && match(Op0, m_Add(m_Value(X), m_ConstantInt(C1)))) { Value *Add = Builder->CreateMul(X, CI); return BinaryOperator::CreateAdd(Add, Builder->CreateMul(C1, CI)); } } // (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 = 0, *Y = 0; if (Op0->hasOneUse()) { ConstantInt *C1; Value *Sub = 0; 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(Op1)) { // Try to fold constant mul into select arguments. if (SelectInst *SI = dyn_cast(Op0)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; if (isa(Op0)) if (Instruction *NV = FoldOpIntoPhi(I)) return NV; } if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y if (Value *Op1v = dyn_castNegVal(Op1)) return BinaryOperator::CreateMul(Op0v, Op1v); // (X / Y) * Y = X - (X % Y) // (X / Y) * -Y = (X % Y) - X { Value *Op1C = Op1; BinaryOperator *BO = dyn_cast(Op0); if (!BO || (BO->getOpcode() != Instruction::UDiv && BO->getOpcode() != Instruction::SDiv)) { Op1C = Op0; BO = dyn_cast(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(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()->isIntegerTy(1)) return BinaryOperator::CreateAnd(Op0, Op1); // X*(1 << Y) --> X << Y // (1 << Y)*X --> X << Y { Value *Y; if (match(Op0, m_Shl(m_One(), m_Value(Y)))) return BinaryOperator::CreateShl(Op1, Y); if (match(Op1, m_Shl(m_One(), m_Value(Y)))) return BinaryOperator::CreateShl(Op0, Y); } // 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 = 0, *OtherOp = 0; if (MaskedValueIsZero(Op0, Negative2)) BoolCast = Op0, OtherOp = Op1; else if (MaskedValueIsZero(Op1, Negative2)) BoolCast = Op1, OtherOp = Op0; if (BoolCast) { Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()), BoolCast); return BinaryOperator::CreateAnd(V, OtherOp); } } return Changed ? &I : 0; } Instruction *InstCombiner::visitFMul(BinaryOperator &I) { bool Changed = SimplifyAssociativeOrCommutative(I); Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); // Simplify mul instructions with a constant RHS. if (Constant *Op1C = dyn_cast(Op1)) { if (ConstantFP *Op1F = dyn_cast(Op1C)) { // "In IEEE floating point, x*1 is not equivalent to x for nans. However, // ANSI says we can drop signals, so we can do this anyway." (from GCC) if (Op1F->isExactlyValue(1.0)) return ReplaceInstUsesWith(I, Op0); // Eliminate 'fmul double %X, 1.0' } else if (ConstantDataVector *Op1V = dyn_cast(Op1C)) { // As above, vector X*splat(1.0) -> X in all defined cases. if (ConstantFP *F = dyn_cast_or_null(Op1V->getSplatValue())) if (F->isExactlyValue(1.0)) return ReplaceInstUsesWith(I, Op0); } // Try to fold constant mul into select arguments. if (SelectInst *SI = dyn_cast(Op0)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; if (isa(Op0)) if (Instruction *NV = FoldOpIntoPhi(I)) return NV; } if (Value *Op0v = dyn_castFNegVal(Op0)) // -X * -Y = X*Y if (Value *Op1v = dyn_castFNegVal(Op1)) return BinaryOperator::CreateFMul(Op0v, Op1v); return Changed ? &I : 0; } /// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select /// instruction. bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) { SelectInst *SI = cast(I.getOperand(1)); // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y int NonNullOperand = -1; if (Constant *ST = dyn_cast(SI->getOperand(1))) if (ST->isNullValue()) NonNullOperand = 2; // div/rem X, (Cond ? Y : 0) -> div/rem X, Y if (Constant *ST = dyn_cast(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(BBI) && !isa(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(BBI->getContext()) : ConstantInt::getFalse(BBI->getContext()); Worklist.Add(BBI); } } // If we past the instruction, quit looking for it. if (&*BBI == SI) SI = 0; if (&*BBI == SelectCond) SelectCond = 0; // If we ran out of things to eliminate, break out of the loop. if (SelectCond == 0 && SI == 0) 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.setOperand(1, V); return &I; } // Handle cases involving: [su]div X, (select Cond, Y, Z) // This does not apply for fdiv. if (isa(Op1) && SimplifyDivRemOfSelect(I)) return &I; if (ConstantInt *RHS = dyn_cast(Op1)) { // (X / C1) / C2 -> X / (C1*C2) if (Instruction *LHS = dyn_cast(Op0)) if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode()) if (ConstantInt *LHSRHS = dyn_cast(LHS->getOperand(1))) { if (MultiplyOverflows(RHS, LHSRHS, I.getOpcode()==Instruction::SDiv)) return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0), ConstantExpr::getMul(RHS, LHSRHS)); } if (!RHS->isZero()) { // avoid X udiv 0 if (SelectInst *SI = dyn_cast(Op0)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; if (isa(Op0)) if (Instruction *NV = FoldOpIntoPhi(I)) return NV; } } // 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 = 0, *Z = 0; 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 0; } /// 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(V)) { if (Z->getSrcTy() == Ty) return Z->getOperand(0); } else if (ConstantInt *C = dyn_cast(V)) { if (C->getValue().getActiveBits() <= cast(Ty)->getBitWidth()) return ConstantExpr::getTrunc(C, Ty); } return 0; } Instruction *InstCombiner::visitUDiv(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifyUDivInst(Op0, Op1, TD)) return ReplaceInstUsesWith(I, V); // Handle the integer div common cases if (Instruction *Common = commonIDivTransforms(I)) return Common; { // X udiv 2^C -> X >> C // Check to see if this is an unsigned division with an exact power of 2, // if so, convert to a right shift. const APInt *C; if (match(Op1, m_Power2(C))) { BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, ConstantInt::get(Op0->getType(), C->logBase2())); if (I.isExact()) LShr->setIsExact(); return LShr; } } if (ConstantInt *C = dyn_cast(Op1)) { // X udiv C, where C >= signbit if (C->getValue().isNegative()) { Value *IC = Builder->CreateICmpULT(Op0, C); return SelectInst::Create(IC, Constant::getNullValue(I.getType()), ConstantInt::get(I.getType(), 1)); } } // X udiv (C1 << N), where C1 is "1< X >> (N+C2) { const APInt *CI; Value *N; if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) || match(Op1, m_ZExt(m_Shl(m_Power2(CI), m_Value(N))))) { if (*CI != 1) N = Builder->CreateAdd(N, ConstantInt::get(I.getType(),CI->logBase2())); if (ZExtInst *Z = dyn_cast(Op1)) N = Builder->CreateZExt(N, Z->getDestTy()); if (I.isExact()) return BinaryOperator::CreateExactLShr(Op0, N); return BinaryOperator::CreateLShr(Op0, N); } } // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2) // where C1&C2 are powers of two. { Value *Cond; const APInt *C1, *C2; if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) { // Construct the "on true" case of the select Value *TSI = Builder->CreateLShr(Op0, C1->logBase2(), Op1->getName()+".t", I.isExact()); // Construct the "on false" case of the select Value *FSI = Builder->CreateLShr(Op0, C2->logBase2(), Op1->getName()+".f", I.isExact()); // construct the select instruction and return it. return SelectInst::Create(Cond, TSI, FSI); } } // (zext A) udiv (zext B) --> zext (A udiv B) if (ZExtInst *ZOp0 = dyn_cast(Op0)) if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy())) return new ZExtInst(Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div", I.isExact()), I.getType()); return 0; } Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifySDivInst(Op0, Op1, TD)) return ReplaceInstUsesWith(I, V); // Handle the integer div common cases if (Instruction *Common = commonIDivTransforms(I)) return Common; if (ConstantInt *RHS = dyn_cast(Op1)) { // sdiv X, -1 == -X if (RHS->isAllOnesValue()) return BinaryOperator::CreateNeg(Op0); // 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()); } // -X/C --> X/-C provided the negation doesn't overflow. if (SubOperator *Sub = dyn_cast(Op0)) if (match(Sub->getOperand(0), m_Zero()) && Sub->hasNoSignedWrap()) return BinaryOperator::CreateSDiv(Sub->getOperand(1), ConstantExpr::getNeg(RHS)); } // 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)) { if (MaskedValueIsZero(Op1, Mask)) { // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set return BinaryOperator::CreateUDiv(Op0, Op1, I.getName()); } if (match(Op1, m_Shl(m_Power2(), m_Value()))) { // 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. return BinaryOperator::CreateUDiv(Op0, Op1, I.getName()); } } } return 0; } Instruction *InstCombiner::visitFDiv(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifyFDivInst(Op0, Op1, TD)) return ReplaceInstUsesWith(I, V); if (ConstantFP *Op1C = dyn_cast(Op1)) { const APFloat &Op1F = Op1C->getValueAPF(); // If the divisor has an exact multiplicative inverse we can turn the fdiv // into a cheaper fmul. APFloat Reciprocal(Op1F.getSemantics()); if (Op1F.getExactInverse(&Reciprocal)) { ConstantFP *RFP = ConstantFP::get(Builder->getContext(), Reciprocal); return BinaryOperator::CreateFMul(Op0, RFP); } } return 0; } /// 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.setOperand(1, V); return &I; } // Handle cases involving: rem X, (select Cond, Y, Z) if (isa(Op1) && SimplifyDivRemOfSelect(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 (isa(Op0I)) { if (Instruction *NV = FoldOpIntoPhi(I)) return NV; } // See if we can fold away this rem instruction. if (SimplifyDemandedInstructionBits(I)) return &I; } } return 0; } Instruction *InstCombiner::visitURem(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifyURemInst(Op0, Op1, TD)) return ReplaceInstUsesWith(I, V); if (Instruction *common = commonIRemTransforms(I)) return common; // X urem C^2 -> X and C-1 { const APInt *C; if (match(Op1, m_Power2(C))) return BinaryOperator::CreateAnd(Op0, ConstantInt::get(I.getType(), *C-1)); } // Turn A % (C << N), where C is 2^k, into A & ((C << N)-1) if (match(Op1, m_Shl(m_Power2(), m_Value()))) { Constant *N1 = Constant::getAllOnesValue(I.getType()); Value *Add = Builder->CreateAdd(Op1, N1); return BinaryOperator::CreateAnd(Op0, Add); } // urem X, (select Cond, 2^C1, 2^C2) --> // select Cond, (and X, C1-1), (and X, C2-1) // when C1&C2 are powers of two. { Value *Cond; const APInt *C1, *C2; if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) { Value *TrueAnd = Builder->CreateAnd(Op0, *C1-1, Op1->getName()+".t"); Value *FalseAnd = Builder->CreateAnd(Op0, *C2-1, Op1->getName()+".f"); return SelectInst::Create(Cond, TrueAnd, FalseAnd); } } // (zext A) urem (zext B) --> zext (A urem B) if (ZExtInst *ZOp0 = dyn_cast(Op0)) if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy())) return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1), I.getType()); return 0; } Instruction *InstCombiner::visitSRem(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifySRemInst(Op0, Op1, TD)) return ReplaceInstUsesWith(I, V); // Handle the integer rem common cases if (Instruction *Common = commonIRemTransforms(I)) return Common; if (Value *RHSNeg = dyn_castNegVal(Op1)) if (!isa(RHSNeg) || (isa(RHSNeg) && cast(RHSNeg)->getValue().isStrictlyPositive())) { // X % -Y -> X % Y Worklist.AddValue(I.getOperand(1)); I.setOperand(1, RHSNeg); 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) && MaskedValueIsZero(Op0, Mask)) { // 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 == 0) { 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 0; } Instruction *InstCombiner::visitFRem(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifyFRemInst(Op0, Op1, TD)) return ReplaceInstUsesWith(I, V); // Handle cases involving: rem X, (select Cond, Y, Z) if (isa(Op1) && SimplifyDivRemOfSelect(I)) return &I; return 0; }