//===- InstCombineAddSub.cpp ------------------------------------*- C++ -*-===// // // 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 add, fadd, sub, and fsub. // //===----------------------------------------------------------------------===// #include "InstCombineInternal.h" #include "llvm/ADT/APFloat.h" #include "llvm/ADT/APInt.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/SmallVector.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Analysis/ValueTracking.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/Operator.h" #include "llvm/IR/PatternMatch.h" #include "llvm/IR/Type.h" #include "llvm/IR/Value.h" #include "llvm/Support/AlignOf.h" #include "llvm/Support/Casting.h" #include "llvm/Support/KnownBits.h" #include "llvm/Transforms/InstCombine/InstCombiner.h" #include #include using namespace llvm; using namespace PatternMatch; #define DEBUG_TYPE "instcombine" namespace { /// Class representing coefficient of floating-point addend. /// This class needs to be highly efficient, which is especially true for /// the constructor. As of I write this comment, the cost of the default /// constructor is merely 4-byte-store-zero (Assuming compiler is able to /// perform write-merging). /// class FAddendCoef { public: // The constructor has to initialize a APFloat, which is unnecessary for // most addends which have coefficient either 1 or -1. So, the constructor // is expensive. In order to avoid the cost of the constructor, we should // reuse some instances whenever possible. The pre-created instances // FAddCombine::Add[0-5] embodies this idea. FAddendCoef() = default; ~FAddendCoef(); // If possible, don't define operator+/operator- etc because these // operators inevitably call FAddendCoef's constructor which is not cheap. void operator=(const FAddendCoef &A); void operator+=(const FAddendCoef &A); void operator*=(const FAddendCoef &S); void set(short C) { assert(!insaneIntVal(C) && "Insane coefficient"); IsFp = false; IntVal = C; } void set(const APFloat& C); void negate(); bool isZero() const { return isInt() ? !IntVal : getFpVal().isZero(); } Value *getValue(Type *) const; bool isOne() const { return isInt() && IntVal == 1; } bool isTwo() const { return isInt() && IntVal == 2; } bool isMinusOne() const { return isInt() && IntVal == -1; } bool isMinusTwo() const { return isInt() && IntVal == -2; } private: bool insaneIntVal(int V) { return V > 4 || V < -4; } APFloat *getFpValPtr() { return reinterpret_cast(&FpValBuf); } const APFloat *getFpValPtr() const { return reinterpret_cast(&FpValBuf); } const APFloat &getFpVal() const { assert(IsFp && BufHasFpVal && "Incorret state"); return *getFpValPtr(); } APFloat &getFpVal() { assert(IsFp && BufHasFpVal && "Incorret state"); return *getFpValPtr(); } bool isInt() const { return !IsFp; } // If the coefficient is represented by an integer, promote it to a // floating point. void convertToFpType(const fltSemantics &Sem); // Construct an APFloat from a signed integer. // TODO: We should get rid of this function when APFloat can be constructed // from an *SIGNED* integer. APFloat createAPFloatFromInt(const fltSemantics &Sem, int Val); bool IsFp = false; // True iff FpValBuf contains an instance of APFloat. bool BufHasFpVal = false; // The integer coefficient of an individual addend is either 1 or -1, // and we try to simplify at most 4 addends from neighboring at most // two instructions. So the range of falls in [-4, 4]. APInt // is overkill of this end. short IntVal = 0; AlignedCharArrayUnion FpValBuf; }; /// FAddend is used to represent floating-point addend. An addend is /// represented as , where the V is a symbolic value, and C is a /// constant coefficient. A constant addend is represented as . class FAddend { public: FAddend() = default; void operator+=(const FAddend &T) { assert((Val == T.Val) && "Symbolic-values disagree"); Coeff += T.Coeff; } Value *getSymVal() const { return Val; } const FAddendCoef &getCoef() const { return Coeff; } bool isConstant() const { return Val == nullptr; } bool isZero() const { return Coeff.isZero(); } void set(short Coefficient, Value *V) { Coeff.set(Coefficient); Val = V; } void set(const APFloat &Coefficient, Value *V) { Coeff.set(Coefficient); Val = V; } void set(const ConstantFP *Coefficient, Value *V) { Coeff.set(Coefficient->getValueAPF()); Val = V; } void negate() { Coeff.negate(); } /// Drill down the U-D chain one step to find the definition of V, and /// try to break the definition into one or two addends. static unsigned drillValueDownOneStep(Value* V, FAddend &A0, FAddend &A1); /// Similar to FAddend::drillDownOneStep() except that the value being /// splitted is the addend itself. unsigned drillAddendDownOneStep(FAddend &Addend0, FAddend &Addend1) const; private: void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; } // This addend has the value of "Coeff * Val". Value *Val = nullptr; FAddendCoef Coeff; }; /// FAddCombine is the class for optimizing an unsafe fadd/fsub along /// with its neighboring at most two instructions. /// class FAddCombine { public: FAddCombine(InstCombiner::BuilderTy &B) : Builder(B) {} Value *simplify(Instruction *FAdd); private: using AddendVect = SmallVector; Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota); /// Convert given addend to a Value Value *createAddendVal(const FAddend &A, bool& NeedNeg); /// Return the number of instructions needed to emit the N-ary addition. unsigned calcInstrNumber(const AddendVect& Vect); Value *createFSub(Value *Opnd0, Value *Opnd1); Value *createFAdd(Value *Opnd0, Value *Opnd1); Value *createFMul(Value *Opnd0, Value *Opnd1); Value *createFNeg(Value *V); Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota); void createInstPostProc(Instruction *NewInst, bool NoNumber = false); // Debugging stuff are clustered here. #ifndef NDEBUG unsigned CreateInstrNum; void initCreateInstNum() { CreateInstrNum = 0; } void incCreateInstNum() { CreateInstrNum++; } #else void initCreateInstNum() {} void incCreateInstNum() {} #endif InstCombiner::BuilderTy &Builder; Instruction *Instr = nullptr; }; } // end anonymous namespace //===----------------------------------------------------------------------===// // // Implementation of // {FAddendCoef, FAddend, FAddition, FAddCombine}. // //===----------------------------------------------------------------------===// FAddendCoef::~FAddendCoef() { if (BufHasFpVal) getFpValPtr()->~APFloat(); } void FAddendCoef::set(const APFloat& C) { APFloat *P = getFpValPtr(); if (isInt()) { // As the buffer is meanless byte stream, we cannot call // APFloat::operator=(). new(P) APFloat(C); } else *P = C; IsFp = BufHasFpVal = true; } void FAddendCoef::convertToFpType(const fltSemantics &Sem) { if (!isInt()) return; APFloat *P = getFpValPtr(); if (IntVal > 0) new(P) APFloat(Sem, IntVal); else { new(P) APFloat(Sem, 0 - IntVal); P->changeSign(); } IsFp = BufHasFpVal = true; } APFloat FAddendCoef::createAPFloatFromInt(const fltSemantics &Sem, int Val) { if (Val >= 0) return APFloat(Sem, Val); APFloat T(Sem, 0 - Val); T.changeSign(); return T; } void FAddendCoef::operator=(const FAddendCoef &That) { if (That.isInt()) set(That.IntVal); else set(That.getFpVal()); } void FAddendCoef::operator+=(const FAddendCoef &That) { RoundingMode RndMode = RoundingMode::NearestTiesToEven; if (isInt() == That.isInt()) { if (isInt()) IntVal += That.IntVal; else getFpVal().add(That.getFpVal(), RndMode); return; } if (isInt()) { const APFloat &T = That.getFpVal(); convertToFpType(T.getSemantics()); getFpVal().add(T, RndMode); return; } APFloat &T = getFpVal(); T.add(createAPFloatFromInt(T.getSemantics(), That.IntVal), RndMode); } void FAddendCoef::operator*=(const FAddendCoef &That) { if (That.isOne()) return; if (That.isMinusOne()) { negate(); return; } if (isInt() && That.isInt()) { int Res = IntVal * (int)That.IntVal; assert(!insaneIntVal(Res) && "Insane int value"); IntVal = Res; return; } const fltSemantics &Semantic = isInt() ? That.getFpVal().getSemantics() : getFpVal().getSemantics(); if (isInt()) convertToFpType(Semantic); APFloat &F0 = getFpVal(); if (That.isInt()) F0.multiply(createAPFloatFromInt(Semantic, That.IntVal), APFloat::rmNearestTiesToEven); else F0.multiply(That.getFpVal(), APFloat::rmNearestTiesToEven); } void FAddendCoef::negate() { if (isInt()) IntVal = 0 - IntVal; else getFpVal().changeSign(); } Value *FAddendCoef::getValue(Type *Ty) const { return isInt() ? ConstantFP::get(Ty, float(IntVal)) : ConstantFP::get(Ty->getContext(), getFpVal()); } // The definition of Addends // ========================================= // A + B <1, A>, <1,B> // A - B <1, A>, <1,B> // 0 - B <-1, B> // C * A, // A + C <1, A> // 0 +/- 0 <0, NULL> (corner case) // // Legend: A and B are not constant, C is constant unsigned FAddend::drillValueDownOneStep (Value *Val, FAddend &Addend0, FAddend &Addend1) { Instruction *I = nullptr; if (!Val || !(I = dyn_cast(Val))) return 0; unsigned Opcode = I->getOpcode(); if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub) { ConstantFP *C0, *C1; Value *Opnd0 = I->getOperand(0); Value *Opnd1 = I->getOperand(1); if ((C0 = dyn_cast(Opnd0)) && C0->isZero()) Opnd0 = nullptr; if ((C1 = dyn_cast(Opnd1)) && C1->isZero()) Opnd1 = nullptr; if (Opnd0) { if (!C0) Addend0.set(1, Opnd0); else Addend0.set(C0, nullptr); } if (Opnd1) { FAddend &Addend = Opnd0 ? Addend1 : Addend0; if (!C1) Addend.set(1, Opnd1); else Addend.set(C1, nullptr); if (Opcode == Instruction::FSub) Addend.negate(); } if (Opnd0 || Opnd1) return Opnd0 && Opnd1 ? 2 : 1; // Both operands are zero. Weird! Addend0.set(APFloat(C0->getValueAPF().getSemantics()), nullptr); return 1; } if (I->getOpcode() == Instruction::FMul) { Value *V0 = I->getOperand(0); Value *V1 = I->getOperand(1); if (ConstantFP *C = dyn_cast(V0)) { Addend0.set(C, V1); return 1; } if (ConstantFP *C = dyn_cast(V1)) { Addend0.set(C, V0); return 1; } } return 0; } // Try to break *this* addend into two addends. e.g. Suppose this addend is // <2.3, V>, and V = X + Y, by calling this function, we obtain two addends, // i.e. <2.3, X> and <2.3, Y>. unsigned FAddend::drillAddendDownOneStep (FAddend &Addend0, FAddend &Addend1) const { if (isConstant()) return 0; unsigned BreakNum = FAddend::drillValueDownOneStep(Val, Addend0, Addend1); if (!BreakNum || Coeff.isOne()) return BreakNum; Addend0.Scale(Coeff); if (BreakNum == 2) Addend1.Scale(Coeff); return BreakNum; } Value *FAddCombine::simplify(Instruction *I) { assert(I->hasAllowReassoc() && I->hasNoSignedZeros() && "Expected 'reassoc'+'nsz' instruction"); // Currently we are not able to handle vector type. if (I->getType()->isVectorTy()) return nullptr; assert((I->getOpcode() == Instruction::FAdd || I->getOpcode() == Instruction::FSub) && "Expect add/sub"); // Save the instruction before calling other member-functions. Instr = I; FAddend Opnd0, Opnd1, Opnd0_0, Opnd0_1, Opnd1_0, Opnd1_1; unsigned OpndNum = FAddend::drillValueDownOneStep(I, Opnd0, Opnd1); // Step 1: Expand the 1st addend into Opnd0_0 and Opnd0_1. unsigned Opnd0_ExpNum = 0; unsigned Opnd1_ExpNum = 0; if (!Opnd0.isConstant()) Opnd0_ExpNum = Opnd0.drillAddendDownOneStep(Opnd0_0, Opnd0_1); // Step 2: Expand the 2nd addend into Opnd1_0 and Opnd1_1. if (OpndNum == 2 && !Opnd1.isConstant()) Opnd1_ExpNum = Opnd1.drillAddendDownOneStep(Opnd1_0, Opnd1_1); // Step 3: Try to optimize Opnd0_0 + Opnd0_1 + Opnd1_0 + Opnd1_1 if (Opnd0_ExpNum && Opnd1_ExpNum) { AddendVect AllOpnds; AllOpnds.push_back(&Opnd0_0); AllOpnds.push_back(&Opnd1_0); if (Opnd0_ExpNum == 2) AllOpnds.push_back(&Opnd0_1); if (Opnd1_ExpNum == 2) AllOpnds.push_back(&Opnd1_1); // Compute instruction quota. We should save at least one instruction. unsigned InstQuota = 0; Value *V0 = I->getOperand(0); Value *V1 = I->getOperand(1); InstQuota = ((!isa(V0) && V0->hasOneUse()) && (!isa(V1) && V1->hasOneUse())) ? 2 : 1; if (Value *R = simplifyFAdd(AllOpnds, InstQuota)) return R; } if (OpndNum != 2) { // The input instruction is : "I=0.0 +/- V". If the "V" were able to be // splitted into two addends, say "V = X - Y", the instruction would have // been optimized into "I = Y - X" in the previous steps. // const FAddendCoef &CE = Opnd0.getCoef(); return CE.isOne() ? Opnd0.getSymVal() : nullptr; } // step 4: Try to optimize Opnd0 + Opnd1_0 [+ Opnd1_1] if (Opnd1_ExpNum) { AddendVect AllOpnds; AllOpnds.push_back(&Opnd0); AllOpnds.push_back(&Opnd1_0); if (Opnd1_ExpNum == 2) AllOpnds.push_back(&Opnd1_1); if (Value *R = simplifyFAdd(AllOpnds, 1)) return R; } // step 5: Try to optimize Opnd1 + Opnd0_0 [+ Opnd0_1] if (Opnd0_ExpNum) { AddendVect AllOpnds; AllOpnds.push_back(&Opnd1); AllOpnds.push_back(&Opnd0_0); if (Opnd0_ExpNum == 2) AllOpnds.push_back(&Opnd0_1); if (Value *R = simplifyFAdd(AllOpnds, 1)) return R; } return nullptr; } Value *FAddCombine::simplifyFAdd(AddendVect& Addends, unsigned InstrQuota) { unsigned AddendNum = Addends.size(); assert(AddendNum <= 4 && "Too many addends"); // For saving intermediate results; unsigned NextTmpIdx = 0; FAddend TmpResult[3]; // Simplified addends are placed . AddendVect SimpVect; // The outer loop works on one symbolic-value at a time. Suppose the input // addends are : , , , , , ... // The symbolic-values will be processed in this order: x, y, z. for (unsigned SymIdx = 0; SymIdx < AddendNum; SymIdx++) { const FAddend *ThisAddend = Addends[SymIdx]; if (!ThisAddend) { // This addend was processed before. continue; } Value *Val = ThisAddend->getSymVal(); // If the resulting expr has constant-addend, this constant-addend is // desirable to reside at the top of the resulting expression tree. Placing // constant close to super-expr(s) will potentially reveal some // optimization opportunities in super-expr(s). Here we do not implement // this logic intentionally and rely on SimplifyAssociativeOrCommutative // call later. unsigned StartIdx = SimpVect.size(); SimpVect.push_back(ThisAddend); // The inner loop collects addends sharing same symbolic-value, and these // addends will be later on folded into a single addend. Following above // example, if the symbolic value "y" is being processed, the inner loop // will collect two addends "" and "". These two addends will // be later on folded into "". for (unsigned SameSymIdx = SymIdx + 1; SameSymIdx < AddendNum; SameSymIdx++) { const FAddend *T = Addends[SameSymIdx]; if (T && T->getSymVal() == Val) { // Set null such that next iteration of the outer loop will not process // this addend again. Addends[SameSymIdx] = nullptr; SimpVect.push_back(T); } } // If multiple addends share same symbolic value, fold them together. if (StartIdx + 1 != SimpVect.size()) { FAddend &R = TmpResult[NextTmpIdx ++]; R = *SimpVect[StartIdx]; for (unsigned Idx = StartIdx + 1; Idx < SimpVect.size(); Idx++) R += *SimpVect[Idx]; // Pop all addends being folded and push the resulting folded addend. SimpVect.resize(StartIdx); if (!R.isZero()) { SimpVect.push_back(&R); } } } assert((NextTmpIdx <= std::size(TmpResult) + 1) && "out-of-bound access"); Value *Result; if (!SimpVect.empty()) Result = createNaryFAdd(SimpVect, InstrQuota); else { // The addition is folded to 0.0. Result = ConstantFP::get(Instr->getType(), 0.0); } return Result; } Value *FAddCombine::createNaryFAdd (const AddendVect &Opnds, unsigned InstrQuota) { assert(!Opnds.empty() && "Expect at least one addend"); // Step 1: Check if the # of instructions needed exceeds the quota. unsigned InstrNeeded = calcInstrNumber(Opnds); if (InstrNeeded > InstrQuota) return nullptr; initCreateInstNum(); // step 2: Emit the N-ary addition. // Note that at most three instructions are involved in Fadd-InstCombine: the // addition in question, and at most two neighboring instructions. // The resulting optimized addition should have at least one less instruction // than the original addition expression tree. This implies that the resulting // N-ary addition has at most two instructions, and we don't need to worry // about tree-height when constructing the N-ary addition. Value *LastVal = nullptr; bool LastValNeedNeg = false; // Iterate the addends, creating fadd/fsub using adjacent two addends. for (const FAddend *Opnd : Opnds) { bool NeedNeg; Value *V = createAddendVal(*Opnd, NeedNeg); if (!LastVal) { LastVal = V; LastValNeedNeg = NeedNeg; continue; } if (LastValNeedNeg == NeedNeg) { LastVal = createFAdd(LastVal, V); continue; } if (LastValNeedNeg) LastVal = createFSub(V, LastVal); else LastVal = createFSub(LastVal, V); LastValNeedNeg = false; } if (LastValNeedNeg) { LastVal = createFNeg(LastVal); } #ifndef NDEBUG assert(CreateInstrNum == InstrNeeded && "Inconsistent in instruction numbers"); #endif return LastVal; } Value *FAddCombine::createFSub(Value *Opnd0, Value *Opnd1) { Value *V = Builder.CreateFSub(Opnd0, Opnd1); if (Instruction *I = dyn_cast(V)) createInstPostProc(I); return V; } Value *FAddCombine::createFNeg(Value *V) { Value *NewV = Builder.CreateFNeg(V); if (Instruction *I = dyn_cast(NewV)) createInstPostProc(I, true); // fneg's don't receive instruction numbers. return NewV; } Value *FAddCombine::createFAdd(Value *Opnd0, Value *Opnd1) { Value *V = Builder.CreateFAdd(Opnd0, Opnd1); if (Instruction *I = dyn_cast(V)) createInstPostProc(I); return V; } Value *FAddCombine::createFMul(Value *Opnd0, Value *Opnd1) { Value *V = Builder.CreateFMul(Opnd0, Opnd1); if (Instruction *I = dyn_cast(V)) createInstPostProc(I); return V; } void FAddCombine::createInstPostProc(Instruction *NewInstr, bool NoNumber) { NewInstr->setDebugLoc(Instr->getDebugLoc()); // Keep track of the number of instruction created. if (!NoNumber) incCreateInstNum(); // Propagate fast-math flags NewInstr->setFastMathFlags(Instr->getFastMathFlags()); } // Return the number of instruction needed to emit the N-ary addition. // NOTE: Keep this function in sync with createAddendVal(). unsigned FAddCombine::calcInstrNumber(const AddendVect &Opnds) { unsigned OpndNum = Opnds.size(); unsigned InstrNeeded = OpndNum - 1; // Adjust the number of instructions needed to emit the N-ary add. for (const FAddend *Opnd : Opnds) { if (Opnd->isConstant()) continue; // The constant check above is really for a few special constant // coefficients. if (isa(Opnd->getSymVal())) continue; const FAddendCoef &CE = Opnd->getCoef(); // Let the addend be "c * x". If "c == +/-1", the value of the addend // is immediately available; otherwise, it needs exactly one instruction // to evaluate the value. if (!CE.isMinusOne() && !CE.isOne()) InstrNeeded++; } return InstrNeeded; } // Input Addend Value NeedNeg(output) // ================================================================ // Constant C C false // <+/-1, V> V coefficient is -1 // <2/-2, V> "fadd V, V" coefficient is -2 // "fmul V, C" false // // NOTE: Keep this function in sync with FAddCombine::calcInstrNumber. Value *FAddCombine::createAddendVal(const FAddend &Opnd, bool &NeedNeg) { const FAddendCoef &Coeff = Opnd.getCoef(); if (Opnd.isConstant()) { NeedNeg = false; return Coeff.getValue(Instr->getType()); } Value *OpndVal = Opnd.getSymVal(); if (Coeff.isMinusOne() || Coeff.isOne()) { NeedNeg = Coeff.isMinusOne(); return OpndVal; } if (Coeff.isTwo() || Coeff.isMinusTwo()) { NeedNeg = Coeff.isMinusTwo(); return createFAdd(OpndVal, OpndVal); } NeedNeg = false; return createFMul(OpndVal, Coeff.getValue(Instr->getType())); } // Checks if any operand is negative and we can convert add to sub. // This function checks for following negative patterns // ADD(XOR(OR(Z, NOT(C)), C)), 1) == NEG(AND(Z, C)) // ADD(XOR(AND(Z, C), C), 1) == NEG(OR(Z, ~C)) // XOR(AND(Z, C), (C + 1)) == NEG(OR(Z, ~C)) if C is even static Value *checkForNegativeOperand(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); // This function creates 2 instructions to replace ADD, we need at least one // of LHS or RHS to have one use to ensure benefit in transform. if (!LHS->hasOneUse() && !RHS->hasOneUse()) return nullptr; Value *X = nullptr, *Y = nullptr, *Z = nullptr; const APInt *C1 = nullptr, *C2 = nullptr; // if ONE is on other side, swap if (match(RHS, m_Add(m_Value(X), m_One()))) std::swap(LHS, RHS); if (match(LHS, m_Add(m_Value(X), m_One()))) { // if XOR on other side, swap if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1)))) std::swap(X, RHS); if (match(X, m_Xor(m_Value(Y), m_APInt(C1)))) { // X = XOR(Y, C1), Y = OR(Z, C2), C2 = NOT(C1) ==> X == NOT(AND(Z, C1)) // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, AND(Z, C1)) if (match(Y, m_Or(m_Value(Z), m_APInt(C2))) && (*C2 == ~(*C1))) { Value *NewAnd = Builder.CreateAnd(Z, *C1); return Builder.CreateSub(RHS, NewAnd, "sub"); } else if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && (*C1 == *C2)) { // X = XOR(Y, C1), Y = AND(Z, C2), C2 == C1 ==> X == NOT(OR(Z, ~C1)) // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, OR(Z, ~C1)) Value *NewOr = Builder.CreateOr(Z, ~(*C1)); return Builder.CreateSub(RHS, NewOr, "sub"); } } } // Restore LHS and RHS LHS = I.getOperand(0); RHS = I.getOperand(1); // if XOR is on other side, swap if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1)))) std::swap(LHS, RHS); // C2 is ODD // LHS = XOR(Y, C1), Y = AND(Z, C2), C1 == (C2 + 1) => LHS == NEG(OR(Z, ~C2)) // ADD(LHS, RHS) == SUB(RHS, OR(Z, ~C2)) if (match(LHS, m_Xor(m_Value(Y), m_APInt(C1)))) if (C1->countr_zero() == 0) if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && *C1 == (*C2 + 1)) { Value *NewOr = Builder.CreateOr(Z, ~(*C2)); return Builder.CreateSub(RHS, NewOr, "sub"); } return nullptr; } /// Wrapping flags may allow combining constants separated by an extend. static Instruction *foldNoWrapAdd(BinaryOperator &Add, InstCombiner::BuilderTy &Builder) { Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1); Type *Ty = Add.getType(); Constant *Op1C; if (!match(Op1, m_Constant(Op1C))) return nullptr; // Try this match first because it results in an add in the narrow type. // (zext (X +nuw C2)) + C1 --> zext (X + (C2 + trunc(C1))) Value *X; const APInt *C1, *C2; if (match(Op1, m_APInt(C1)) && match(Op0, m_ZExt(m_NUWAddLike(m_Value(X), m_APInt(C2)))) && C1->isNegative() && C1->sge(-C2->sext(C1->getBitWidth()))) { APInt NewC = *C2 + C1->trunc(C2->getBitWidth()); // If the smaller add will fold to zero, we don't need to check one use. if (NewC.isZero()) return new ZExtInst(X, Ty); // Otherwise only do this if the existing zero extend will be removed. if (Op0->hasOneUse()) return new ZExtInst( Builder.CreateNUWAdd(X, ConstantInt::get(X->getType(), NewC)), Ty); } // More general combining of constants in the wide type. // (sext (X +nsw NarrowC)) + C --> (sext X) + (sext(NarrowC) + C) // or (zext nneg (X +nsw NarrowC)) + C --> (sext X) + (sext(NarrowC) + C) Constant *NarrowC; if (match(Op0, m_OneUse(m_SExtLike( m_NSWAddLike(m_Value(X), m_Constant(NarrowC)))))) { Value *WideC = Builder.CreateSExt(NarrowC, Ty); Value *NewC = Builder.CreateAdd(WideC, Op1C); Value *WideX = Builder.CreateSExt(X, Ty); return BinaryOperator::CreateAdd(WideX, NewC); } // (zext (X +nuw NarrowC)) + C --> (zext X) + (zext(NarrowC) + C) if (match(Op0, m_OneUse(m_ZExt(m_NUWAddLike(m_Value(X), m_Constant(NarrowC)))))) { Value *WideC = Builder.CreateZExt(NarrowC, Ty); Value *NewC = Builder.CreateAdd(WideC, Op1C); Value *WideX = Builder.CreateZExt(X, Ty); return BinaryOperator::CreateAdd(WideX, NewC); } return nullptr; } Instruction *InstCombinerImpl::foldAddWithConstant(BinaryOperator &Add) { Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1); Type *Ty = Add.getType(); Constant *Op1C; if (!match(Op1, m_ImmConstant(Op1C))) return nullptr; if (Instruction *NV = foldBinOpIntoSelectOrPhi(Add)) return NV; Value *X; Constant *Op00C; // add (sub C1, X), C2 --> sub (add C1, C2), X if (match(Op0, m_Sub(m_Constant(Op00C), m_Value(X)))) return BinaryOperator::CreateSub(ConstantExpr::getAdd(Op00C, Op1C), X); Value *Y; // add (sub X, Y), -1 --> add (not Y), X if (match(Op0, m_OneUse(m_Sub(m_Value(X), m_Value(Y)))) && match(Op1, m_AllOnes())) return BinaryOperator::CreateAdd(Builder.CreateNot(Y), X); // zext(bool) + C -> bool ? C + 1 : C if (match(Op0, m_ZExt(m_Value(X))) && X->getType()->getScalarSizeInBits() == 1) return SelectInst::Create(X, InstCombiner::AddOne(Op1C), Op1); // sext(bool) + C -> bool ? C - 1 : C if (match(Op0, m_SExt(m_Value(X))) && X->getType()->getScalarSizeInBits() == 1) return SelectInst::Create(X, InstCombiner::SubOne(Op1C), Op1); // ~X + C --> (C-1) - X if (match(Op0, m_Not(m_Value(X)))) { // ~X + C has NSW and (C-1) won't oveflow => (C-1)-X can have NSW auto *COne = ConstantInt::get(Op1C->getType(), 1); bool WillNotSOV = willNotOverflowSignedSub(Op1C, COne, Add); BinaryOperator *Res = BinaryOperator::CreateSub(ConstantExpr::getSub(Op1C, COne), X); Res->setHasNoSignedWrap(Add.hasNoSignedWrap() && WillNotSOV); return Res; } // (iN X s>> (N - 1)) + 1 --> zext (X > -1) const APInt *C; unsigned BitWidth = Ty->getScalarSizeInBits(); if (match(Op0, m_OneUse(m_AShr(m_Value(X), m_SpecificIntAllowPoison(BitWidth - 1)))) && match(Op1, m_One())) return new ZExtInst(Builder.CreateIsNotNeg(X, "isnotneg"), Ty); if (!match(Op1, m_APInt(C))) return nullptr; // (X | Op01C) + Op1C --> X + (Op01C + Op1C) iff the `or` is actually an `add` Constant *Op01C; if (match(Op0, m_DisjointOr(m_Value(X), m_ImmConstant(Op01C)))) { BinaryOperator *NewAdd = BinaryOperator::CreateAdd(X, ConstantExpr::getAdd(Op01C, Op1C)); NewAdd->setHasNoSignedWrap(Add.hasNoSignedWrap() && willNotOverflowSignedAdd(Op01C, Op1C, Add)); NewAdd->setHasNoUnsignedWrap(Add.hasNoUnsignedWrap()); return NewAdd; } // (X | C2) + C --> (X | C2) ^ C2 iff (C2 == -C) const APInt *C2; if (match(Op0, m_Or(m_Value(), m_APInt(C2))) && *C2 == -*C) return BinaryOperator::CreateXor(Op0, ConstantInt::get(Add.getType(), *C2)); if (C->isSignMask()) { // If wrapping is not allowed, then the addition must set the sign bit: // X + (signmask) --> X | signmask if (Add.hasNoSignedWrap() || Add.hasNoUnsignedWrap()) return BinaryOperator::CreateOr(Op0, Op1); // If wrapping is allowed, then the addition flips the sign bit of LHS: // X + (signmask) --> X ^ signmask return BinaryOperator::CreateXor(Op0, Op1); } // Is this add the last step in a convoluted sext? // add(zext(xor i16 X, -32768), -32768) --> sext X if (match(Op0, m_ZExt(m_Xor(m_Value(X), m_APInt(C2)))) && C2->isMinSignedValue() && C2->sext(Ty->getScalarSizeInBits()) == *C) return CastInst::Create(Instruction::SExt, X, Ty); if (match(Op0, m_Xor(m_Value(X), m_APInt(C2)))) { // (X ^ signmask) + C --> (X + (signmask ^ C)) if (C2->isSignMask()) return BinaryOperator::CreateAdd(X, ConstantInt::get(Ty, *C2 ^ *C)); // If X has no high-bits set above an xor mask: // add (xor X, LowMaskC), C --> sub (LowMaskC + C), X if (C2->isMask()) { KnownBits LHSKnown = computeKnownBits(X, 0, &Add); if ((*C2 | LHSKnown.Zero).isAllOnes()) return BinaryOperator::CreateSub(ConstantInt::get(Ty, *C2 + *C), X); } // Look for a math+logic pattern that corresponds to sext-in-register of a // value with cleared high bits. Convert that into a pair of shifts: // add (xor X, 0x80), 0xF..F80 --> (X << ShAmtC) >>s ShAmtC // add (xor X, 0xF..F80), 0x80 --> (X << ShAmtC) >>s ShAmtC if (Op0->hasOneUse() && *C2 == -(*C)) { unsigned BitWidth = Ty->getScalarSizeInBits(); unsigned ShAmt = 0; if (C->isPowerOf2()) ShAmt = BitWidth - C->logBase2() - 1; else if (C2->isPowerOf2()) ShAmt = BitWidth - C2->logBase2() - 1; if (ShAmt && MaskedValueIsZero(X, APInt::getHighBitsSet(BitWidth, ShAmt), 0, &Add)) { Constant *ShAmtC = ConstantInt::get(Ty, ShAmt); Value *NewShl = Builder.CreateShl(X, ShAmtC, "sext"); return BinaryOperator::CreateAShr(NewShl, ShAmtC); } } } if (C->isOne() && Op0->hasOneUse()) { // add (sext i1 X), 1 --> zext (not X) // TODO: The smallest IR representation is (select X, 0, 1), and that would // not require the one-use check. But we need to remove a transform in // visitSelect and make sure that IR value tracking for select is equal or // better than for these ops. if (match(Op0, m_SExt(m_Value(X))) && X->getType()->getScalarSizeInBits() == 1) return new ZExtInst(Builder.CreateNot(X), Ty); // Shifts and add used to flip and mask off the low bit: // add (ashr (shl i32 X, 31), 31), 1 --> and (not X), 1 const APInt *C3; if (match(Op0, m_AShr(m_Shl(m_Value(X), m_APInt(C2)), m_APInt(C3))) && C2 == C3 && *C2 == Ty->getScalarSizeInBits() - 1) { Value *NotX = Builder.CreateNot(X); return BinaryOperator::CreateAnd(NotX, ConstantInt::get(Ty, 1)); } } // Fold (add (zext (add X, -1)), 1) -> (zext X) if X is non-zero. // TODO: There's a general form for any constant on the outer add. if (C->isOne()) { if (match(Op0, m_ZExt(m_Add(m_Value(X), m_AllOnes())))) { const SimplifyQuery Q = SQ.getWithInstruction(&Add); if (llvm::isKnownNonZero(X, Q)) return new ZExtInst(X, Ty); } } return nullptr; } // match variations of a^2 + 2*a*b + b^2 // // to reuse the code between the FP and Int versions, the instruction OpCodes // and constant types have been turned into template parameters. // // Mul2Rhs: The constant to perform the multiplicative equivalent of X*2 with; // should be `m_SpecificFP(2.0)` for FP and `m_SpecificInt(1)` for Int // (we're matching `X<<1` instead of `X*2` for Int) template static bool matchesSquareSum(BinaryOperator &I, Mul2Rhs M2Rhs, Value *&A, Value *&B) { constexpr unsigned MulOp = FP ? Instruction::FMul : Instruction::Mul; constexpr unsigned AddOp = FP ? Instruction::FAdd : Instruction::Add; constexpr unsigned Mul2Op = FP ? Instruction::FMul : Instruction::Shl; // (a * a) + (((a * 2) + b) * b) if (match(&I, m_c_BinOp( AddOp, m_OneUse(m_BinOp(MulOp, m_Value(A), m_Deferred(A))), m_OneUse(m_c_BinOp( MulOp, m_c_BinOp(AddOp, m_BinOp(Mul2Op, m_Deferred(A), M2Rhs), m_Value(B)), m_Deferred(B)))))) return true; // ((a * b) * 2) or ((a * 2) * b) // + // (a * a + b * b) or (b * b + a * a) return match( &I, m_c_BinOp( AddOp, m_CombineOr( m_OneUse(m_BinOp( Mul2Op, m_BinOp(MulOp, m_Value(A), m_Value(B)), M2Rhs)), m_OneUse(m_c_BinOp(MulOp, m_BinOp(Mul2Op, m_Value(A), M2Rhs), m_Value(B)))), m_OneUse( m_c_BinOp(AddOp, m_BinOp(MulOp, m_Deferred(A), m_Deferred(A)), m_BinOp(MulOp, m_Deferred(B), m_Deferred(B)))))); } // Fold integer variations of a^2 + 2*a*b + b^2 -> (a + b)^2 Instruction *InstCombinerImpl::foldSquareSumInt(BinaryOperator &I) { Value *A, *B; if (matchesSquareSum(I, m_SpecificInt(1), A, B)) { Value *AB = Builder.CreateAdd(A, B); return BinaryOperator::CreateMul(AB, AB); } return nullptr; } // Fold floating point variations of a^2 + 2*a*b + b^2 -> (a + b)^2 // Requires `nsz` and `reassoc`. Instruction *InstCombinerImpl::foldSquareSumFP(BinaryOperator &I) { assert(I.hasAllowReassoc() && I.hasNoSignedZeros() && "Assumption mismatch"); Value *A, *B; if (matchesSquareSum(I, m_SpecificFP(2.0), A, B)) { Value *AB = Builder.CreateFAddFMF(A, B, &I); return BinaryOperator::CreateFMulFMF(AB, AB, &I); } return nullptr; } // Matches multiplication expression Op * C where C is a constant. Returns the // constant value in C and the other operand in Op. Returns true if such a // match is found. static bool MatchMul(Value *E, Value *&Op, APInt &C) { const APInt *AI; if (match(E, m_Mul(m_Value(Op), m_APInt(AI)))) { C = *AI; return true; } if (match(E, m_Shl(m_Value(Op), m_APInt(AI)))) { C = APInt(AI->getBitWidth(), 1); C <<= *AI; return true; } return false; } // Matches remainder expression Op % C where C is a constant. Returns the // constant value in C and the other operand in Op. Returns the signedness of // the remainder operation in IsSigned. Returns true if such a match is // found. static bool MatchRem(Value *E, Value *&Op, APInt &C, bool &IsSigned) { const APInt *AI; IsSigned = false; if (match(E, m_SRem(m_Value(Op), m_APInt(AI)))) { IsSigned = true; C = *AI; return true; } if (match(E, m_URem(m_Value(Op), m_APInt(AI)))) { C = *AI; return true; } if (match(E, m_And(m_Value(Op), m_APInt(AI))) && (*AI + 1).isPowerOf2()) { C = *AI + 1; return true; } return false; } // Matches division expression Op / C with the given signedness as indicated // by IsSigned, where C is a constant. Returns the constant value in C and the // other operand in Op. Returns true if such a match is found. static bool MatchDiv(Value *E, Value *&Op, APInt &C, bool IsSigned) { const APInt *AI; if (IsSigned && match(E, m_SDiv(m_Value(Op), m_APInt(AI)))) { C = *AI; return true; } if (!IsSigned) { if (match(E, m_UDiv(m_Value(Op), m_APInt(AI)))) { C = *AI; return true; } if (match(E, m_LShr(m_Value(Op), m_APInt(AI)))) { C = APInt(AI->getBitWidth(), 1); C <<= *AI; return true; } } return false; } // Returns whether C0 * C1 with the given signedness overflows. static bool MulWillOverflow(APInt &C0, APInt &C1, bool IsSigned) { bool overflow; if (IsSigned) (void)C0.smul_ov(C1, overflow); else (void)C0.umul_ov(C1, overflow); return overflow; } // Simplifies X % C0 + (( X / C0 ) % C1) * C0 to X % (C0 * C1), where (C0 * C1) // does not overflow. // Simplifies (X / C0) * C1 + (X % C0) * C2 to // (X / C0) * (C1 - C2 * C0) + X * C2 Value *InstCombinerImpl::SimplifyAddWithRemainder(BinaryOperator &I) { Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); Value *X, *MulOpV; APInt C0, MulOpC; bool IsSigned; // Match I = X % C0 + MulOpV * C0 if (((MatchRem(LHS, X, C0, IsSigned) && MatchMul(RHS, MulOpV, MulOpC)) || (MatchRem(RHS, X, C0, IsSigned) && MatchMul(LHS, MulOpV, MulOpC))) && C0 == MulOpC) { Value *RemOpV; APInt C1; bool Rem2IsSigned; // Match MulOpC = RemOpV % C1 if (MatchRem(MulOpV, RemOpV, C1, Rem2IsSigned) && IsSigned == Rem2IsSigned) { Value *DivOpV; APInt DivOpC; // Match RemOpV = X / C0 if (MatchDiv(RemOpV, DivOpV, DivOpC, IsSigned) && X == DivOpV && C0 == DivOpC && !MulWillOverflow(C0, C1, IsSigned)) { Value *NewDivisor = ConstantInt::get(X->getType(), C0 * C1); return IsSigned ? Builder.CreateSRem(X, NewDivisor, "srem") : Builder.CreateURem(X, NewDivisor, "urem"); } } } // Match I = (X / C0) * C1 + (X % C0) * C2 Value *Div, *Rem; APInt C1, C2; if (!LHS->hasOneUse() || !MatchMul(LHS, Div, C1)) Div = LHS, C1 = APInt(I.getType()->getScalarSizeInBits(), 1); if (!RHS->hasOneUse() || !MatchMul(RHS, Rem, C2)) Rem = RHS, C2 = APInt(I.getType()->getScalarSizeInBits(), 1); if (match(Div, m_IRem(m_Value(), m_Value()))) { std::swap(Div, Rem); std::swap(C1, C2); } Value *DivOpV; APInt DivOpC; if (MatchRem(Rem, X, C0, IsSigned) && MatchDiv(Div, DivOpV, DivOpC, IsSigned) && X == DivOpV && C0 == DivOpC) { APInt NewC = C1 - C2 * C0; if (!NewC.isZero() && !Rem->hasOneUse()) return nullptr; if (!isGuaranteedNotToBeUndef(X, &AC, &I, &DT)) return nullptr; Value *MulXC2 = Builder.CreateMul(X, ConstantInt::get(X->getType(), C2)); if (NewC.isZero()) return MulXC2; return Builder.CreateAdd( Builder.CreateMul(Div, ConstantInt::get(X->getType(), NewC)), MulXC2); } return nullptr; } /// Fold /// (1 << NBits) - 1 /// Into: /// ~(-(1 << NBits)) /// Because a 'not' is better for bit-tracking analysis and other transforms /// than an 'add'. The new shl is always nsw, and is nuw if old `and` was. static Instruction *canonicalizeLowbitMask(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { Value *NBits; if (!match(&I, m_Add(m_OneUse(m_Shl(m_One(), m_Value(NBits))), m_AllOnes()))) return nullptr; Constant *MinusOne = Constant::getAllOnesValue(NBits->getType()); Value *NotMask = Builder.CreateShl(MinusOne, NBits, "notmask"); // Be wary of constant folding. if (auto *BOp = dyn_cast(NotMask)) { // Always NSW. But NUW propagates from `add`. BOp->setHasNoSignedWrap(); BOp->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); } return BinaryOperator::CreateNot(NotMask, I.getName()); } static Instruction *foldToUnsignedSaturatedAdd(BinaryOperator &I) { assert(I.getOpcode() == Instruction::Add && "Expecting add instruction"); Type *Ty = I.getType(); auto getUAddSat = [&]() { return Intrinsic::getDeclaration(I.getModule(), Intrinsic::uadd_sat, Ty); }; // add (umin X, ~Y), Y --> uaddsat X, Y Value *X, *Y; if (match(&I, m_c_Add(m_c_UMin(m_Value(X), m_Not(m_Value(Y))), m_Deferred(Y)))) return CallInst::Create(getUAddSat(), { X, Y }); // add (umin X, ~C), C --> uaddsat X, C const APInt *C, *NotC; if (match(&I, m_Add(m_UMin(m_Value(X), m_APInt(NotC)), m_APInt(C))) && *C == ~*NotC) return CallInst::Create(getUAddSat(), { X, ConstantInt::get(Ty, *C) }); return nullptr; } // Transform: // (add A, (shl (neg B), Y)) // -> (sub A, (shl B, Y)) static Instruction *combineAddSubWithShlAddSub(InstCombiner::BuilderTy &Builder, const BinaryOperator &I) { Value *A, *B, *Cnt; if (match(&I, m_c_Add(m_OneUse(m_Shl(m_OneUse(m_Neg(m_Value(B))), m_Value(Cnt))), m_Value(A)))) { Value *NewShl = Builder.CreateShl(B, Cnt); return BinaryOperator::CreateSub(A, NewShl); } return nullptr; } /// Try to reduce signed division by power-of-2 to an arithmetic shift right. static Instruction *foldAddToAshr(BinaryOperator &Add) { // Division must be by power-of-2, but not the minimum signed value. Value *X; const APInt *DivC; if (!match(Add.getOperand(0), m_SDiv(m_Value(X), m_Power2(DivC))) || DivC->isNegative()) return nullptr; // Rounding is done by adding -1 if the dividend (X) is negative and has any // low bits set. It recognizes two canonical patterns: // 1. For an 'ugt' cmp with the signed minimum value (SMIN), the // pattern is: sext (icmp ugt (X & (DivC - 1)), SMIN). // 2. For an 'eq' cmp, the pattern's: sext (icmp eq X & (SMIN + 1), SMIN + 1). // Note that, by the time we end up here, if possible, ugt has been // canonicalized into eq. const APInt *MaskC, *MaskCCmp; ICmpInst::Predicate Pred; if (!match(Add.getOperand(1), m_SExt(m_ICmp(Pred, m_And(m_Specific(X), m_APInt(MaskC)), m_APInt(MaskCCmp))))) return nullptr; if ((Pred != ICmpInst::ICMP_UGT || !MaskCCmp->isSignMask()) && (Pred != ICmpInst::ICMP_EQ || *MaskCCmp != *MaskC)) return nullptr; APInt SMin = APInt::getSignedMinValue(Add.getType()->getScalarSizeInBits()); bool IsMaskValid = Pred == ICmpInst::ICMP_UGT ? (*MaskC == (SMin | (*DivC - 1))) : (*DivC == 2 && *MaskC == SMin + 1); if (!IsMaskValid) return nullptr; // (X / DivC) + sext ((X & (SMin | (DivC - 1)) >u SMin) --> X >>s log2(DivC) return BinaryOperator::CreateAShr( X, ConstantInt::get(Add.getType(), DivC->exactLogBase2())); } Instruction *InstCombinerImpl:: canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract( BinaryOperator &I) { assert((I.getOpcode() == Instruction::Add || I.getOpcode() == Instruction::Or || I.getOpcode() == Instruction::Sub) && "Expecting add/or/sub instruction"); // We have a subtraction/addition between a (potentially truncated) *logical* // right-shift of X and a "select". Value *X, *Select; Instruction *LowBitsToSkip, *Extract; if (!match(&I, m_c_BinOp(m_TruncOrSelf(m_CombineAnd( m_LShr(m_Value(X), m_Instruction(LowBitsToSkip)), m_Instruction(Extract))), m_Value(Select)))) return nullptr; // `add`/`or` is commutative; but for `sub`, "select" *must* be on RHS. if (I.getOpcode() == Instruction::Sub && I.getOperand(1) != Select) return nullptr; Type *XTy = X->getType(); bool HadTrunc = I.getType() != XTy; // If there was a truncation of extracted value, then we'll need to produce // one extra instruction, so we need to ensure one instruction will go away. if (HadTrunc && !match(&I, m_c_BinOp(m_OneUse(m_Value()), m_Value()))) return nullptr; // Extraction should extract high NBits bits, with shift amount calculated as: // low bits to skip = shift bitwidth - high bits to extract // The shift amount itself may be extended, and we need to look past zero-ext // when matching NBits, that will matter for matching later. Constant *C; Value *NBits; if (!match( LowBitsToSkip, m_ZExtOrSelf(m_Sub(m_Constant(C), m_ZExtOrSelf(m_Value(NBits))))) || !match(C, m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_EQ, APInt(C->getType()->getScalarSizeInBits(), X->getType()->getScalarSizeInBits())))) return nullptr; // Sign-extending value can be zero-extended if we `sub`tract it, // or sign-extended otherwise. auto SkipExtInMagic = [&I](Value *&V) { if (I.getOpcode() == Instruction::Sub) match(V, m_ZExtOrSelf(m_Value(V))); else match(V, m_SExtOrSelf(m_Value(V))); }; // Now, finally validate the sign-extending magic. // `select` itself may be appropriately extended, look past that. SkipExtInMagic(Select); ICmpInst::Predicate Pred; const APInt *Thr; Value *SignExtendingValue, *Zero; bool ShouldSignext; // It must be a select between two values we will later establish to be a // sign-extending value and a zero constant. The condition guarding the // sign-extension must be based on a sign bit of the same X we had in `lshr`. if (!match(Select, m_Select(m_ICmp(Pred, m_Specific(X), m_APInt(Thr)), m_Value(SignExtendingValue), m_Value(Zero))) || !isSignBitCheck(Pred, *Thr, ShouldSignext)) return nullptr; // icmp-select pair is commutative. if (!ShouldSignext) std::swap(SignExtendingValue, Zero); // If we should not perform sign-extension then we must add/or/subtract zero. if (!match(Zero, m_Zero())) return nullptr; // Otherwise, it should be some constant, left-shifted by the same NBits we // had in `lshr`. Said left-shift can also be appropriately extended. // Again, we must look past zero-ext when looking for NBits. SkipExtInMagic(SignExtendingValue); Constant *SignExtendingValueBaseConstant; if (!match(SignExtendingValue, m_Shl(m_Constant(SignExtendingValueBaseConstant), m_ZExtOrSelf(m_Specific(NBits))))) return nullptr; // If we `sub`, then the constant should be one, else it should be all-ones. if (I.getOpcode() == Instruction::Sub ? !match(SignExtendingValueBaseConstant, m_One()) : !match(SignExtendingValueBaseConstant, m_AllOnes())) return nullptr; auto *NewAShr = BinaryOperator::CreateAShr(X, LowBitsToSkip, Extract->getName() + ".sext"); NewAShr->copyIRFlags(Extract); // Preserve `exact`-ness. if (!HadTrunc) return NewAShr; Builder.Insert(NewAShr); return TruncInst::CreateTruncOrBitCast(NewAShr, I.getType()); } /// This is a specialization of a more general transform from /// foldUsingDistributiveLaws. If that code can be made to work optimally /// for multi-use cases or propagating nsw/nuw, then we would not need this. static Instruction *factorizeMathWithShlOps(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { // TODO: Also handle mul by doubling the shift amount? assert((I.getOpcode() == Instruction::Add || I.getOpcode() == Instruction::Sub) && "Expected add/sub"); auto *Op0 = dyn_cast(I.getOperand(0)); auto *Op1 = dyn_cast(I.getOperand(1)); if (!Op0 || !Op1 || !(Op0->hasOneUse() || Op1->hasOneUse())) return nullptr; Value *X, *Y, *ShAmt; if (!match(Op0, m_Shl(m_Value(X), m_Value(ShAmt))) || !match(Op1, m_Shl(m_Value(Y), m_Specific(ShAmt)))) return nullptr; // No-wrap propagates only when all ops have no-wrap. bool HasNSW = I.hasNoSignedWrap() && Op0->hasNoSignedWrap() && Op1->hasNoSignedWrap(); bool HasNUW = I.hasNoUnsignedWrap() && Op0->hasNoUnsignedWrap() && Op1->hasNoUnsignedWrap(); // add/sub (X << ShAmt), (Y << ShAmt) --> (add/sub X, Y) << ShAmt Value *NewMath = Builder.CreateBinOp(I.getOpcode(), X, Y); if (auto *NewI = dyn_cast(NewMath)) { NewI->setHasNoSignedWrap(HasNSW); NewI->setHasNoUnsignedWrap(HasNUW); } auto *NewShl = BinaryOperator::CreateShl(NewMath, ShAmt); NewShl->setHasNoSignedWrap(HasNSW); NewShl->setHasNoUnsignedWrap(HasNUW); return NewShl; } /// Reduce a sequence of masked half-width multiplies to a single multiply. /// ((XLow * YHigh) + (YLow * XHigh)) << HalfBits) + (XLow * YLow) --> X * Y static Instruction *foldBoxMultiply(BinaryOperator &I) { unsigned BitWidth = I.getType()->getScalarSizeInBits(); // Skip the odd bitwidth types. if ((BitWidth & 0x1)) return nullptr; unsigned HalfBits = BitWidth >> 1; APInt HalfMask = APInt::getMaxValue(HalfBits); // ResLo = (CrossSum << HalfBits) + (YLo * XLo) Value *XLo, *YLo; Value *CrossSum; // Require one-use on the multiply to avoid increasing the number of // multiplications. if (!match(&I, m_c_Add(m_Shl(m_Value(CrossSum), m_SpecificInt(HalfBits)), m_OneUse(m_Mul(m_Value(YLo), m_Value(XLo)))))) return nullptr; // XLo = X & HalfMask // YLo = Y & HalfMask // TODO: Refactor with SimplifyDemandedBits or KnownBits known leading zeros // to enhance robustness Value *X, *Y; if (!match(XLo, m_And(m_Value(X), m_SpecificInt(HalfMask))) || !match(YLo, m_And(m_Value(Y), m_SpecificInt(HalfMask)))) return nullptr; // CrossSum = (X' * (Y >> Halfbits)) + (Y' * (X >> HalfBits)) // X' can be either X or XLo in the pattern (and the same for Y') if (match(CrossSum, m_c_Add(m_c_Mul(m_LShr(m_Specific(Y), m_SpecificInt(HalfBits)), m_CombineOr(m_Specific(X), m_Specific(XLo))), m_c_Mul(m_LShr(m_Specific(X), m_SpecificInt(HalfBits)), m_CombineOr(m_Specific(Y), m_Specific(YLo)))))) return BinaryOperator::CreateMul(X, Y); return nullptr; } Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) { if (Value *V = simplifyAddInst(I.getOperand(0), I.getOperand(1), I.hasNoSignedWrap(), I.hasNoUnsignedWrap(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (SimplifyAssociativeOrCommutative(I)) return &I; if (Instruction *X = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; // (A*B)+(A*C) -> A*(B+C) etc if (Value *V = foldUsingDistributiveLaws(I)) return replaceInstUsesWith(I, V); if (Instruction *R = foldBoxMultiply(I)) return R; if (Instruction *R = factorizeMathWithShlOps(I, Builder)) return R; if (Instruction *X = foldAddWithConstant(I)) return X; if (Instruction *X = foldNoWrapAdd(I, Builder)) return X; if (Instruction *R = foldBinOpShiftWithShift(I)) return R; if (Instruction *R = combineAddSubWithShlAddSub(Builder, I)) return R; Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); Type *Ty = I.getType(); if (Ty->isIntOrIntVectorTy(1)) return BinaryOperator::CreateXor(LHS, RHS); // X + X --> X << 1 if (LHS == RHS) { auto *Shl = BinaryOperator::CreateShl(LHS, ConstantInt::get(Ty, 1)); Shl->setHasNoSignedWrap(I.hasNoSignedWrap()); Shl->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); return Shl; } Value *A, *B; if (match(LHS, m_Neg(m_Value(A)))) { // -A + -B --> -(A + B) if (match(RHS, m_Neg(m_Value(B)))) return BinaryOperator::CreateNeg(Builder.CreateAdd(A, B)); // -A + B --> B - A auto *Sub = BinaryOperator::CreateSub(RHS, A); auto *OB0 = cast(LHS); Sub->setHasNoSignedWrap(I.hasNoSignedWrap() && OB0->hasNoSignedWrap()); return Sub; } // A + -B --> A - B if (match(RHS, m_Neg(m_Value(B)))) return BinaryOperator::CreateSub(LHS, B); if (Value *V = checkForNegativeOperand(I, Builder)) return replaceInstUsesWith(I, V); // (A + 1) + ~B --> A - B // ~B + (A + 1) --> A - B // (~B + A) + 1 --> A - B // (A + ~B) + 1 --> A - B if (match(&I, m_c_BinOp(m_Add(m_Value(A), m_One()), m_Not(m_Value(B)))) || match(&I, m_BinOp(m_c_Add(m_Not(m_Value(B)), m_Value(A)), m_One()))) return BinaryOperator::CreateSub(A, B); // (A + RHS) + RHS --> A + (RHS << 1) if (match(LHS, m_OneUse(m_c_Add(m_Value(A), m_Specific(RHS))))) return BinaryOperator::CreateAdd(A, Builder.CreateShl(RHS, 1, "reass.add")); // LHS + (A + LHS) --> A + (LHS << 1) if (match(RHS, m_OneUse(m_c_Add(m_Value(A), m_Specific(LHS))))) return BinaryOperator::CreateAdd(A, Builder.CreateShl(LHS, 1, "reass.add")); { // (A + C1) + (C2 - B) --> (A - B) + (C1 + C2) Constant *C1, *C2; if (match(&I, m_c_Add(m_Add(m_Value(A), m_ImmConstant(C1)), m_Sub(m_ImmConstant(C2), m_Value(B)))) && (LHS->hasOneUse() || RHS->hasOneUse())) { Value *Sub = Builder.CreateSub(A, B); return BinaryOperator::CreateAdd(Sub, ConstantExpr::getAdd(C1, C2)); } // Canonicalize a constant sub operand as an add operand for better folding: // (C1 - A) + B --> (B - A) + C1 if (match(&I, m_c_Add(m_OneUse(m_Sub(m_ImmConstant(C1), m_Value(A))), m_Value(B)))) { Value *Sub = Builder.CreateSub(B, A, "reass.sub"); return BinaryOperator::CreateAdd(Sub, C1); } } // X % C0 + (( X / C0 ) % C1) * C0 => X % (C0 * C1) if (Value *V = SimplifyAddWithRemainder(I)) return replaceInstUsesWith(I, V); // ((X s/ C1) << C2) + X => X s% -C1 where -C1 is 1 << C2 const APInt *C1, *C2; if (match(LHS, m_Shl(m_SDiv(m_Specific(RHS), m_APInt(C1)), m_APInt(C2)))) { APInt one(C2->getBitWidth(), 1); APInt minusC1 = -(*C1); if (minusC1 == (one << *C2)) { Constant *NewRHS = ConstantInt::get(RHS->getType(), minusC1); return BinaryOperator::CreateSRem(RHS, NewRHS); } } // (A & 2^C1) + A => A & (2^C1 - 1) iff bit C1 in A is a sign bit if (match(&I, m_c_Add(m_And(m_Value(A), m_APInt(C1)), m_Deferred(A))) && C1->isPowerOf2() && (ComputeNumSignBits(A) > C1->countl_zero())) { Constant *NewMask = ConstantInt::get(RHS->getType(), *C1 - 1); return BinaryOperator::CreateAnd(A, NewMask); } // ZExt (B - A) + ZExt(A) --> ZExt(B) if ((match(RHS, m_ZExt(m_Value(A))) && match(LHS, m_ZExt(m_NUWSub(m_Value(B), m_Specific(A))))) || (match(LHS, m_ZExt(m_Value(A))) && match(RHS, m_ZExt(m_NUWSub(m_Value(B), m_Specific(A)))))) return new ZExtInst(B, LHS->getType()); // zext(A) + sext(A) --> 0 if A is i1 if (match(&I, m_c_BinOp(m_ZExt(m_Value(A)), m_SExt(m_Deferred(A)))) && A->getType()->isIntOrIntVectorTy(1)) return replaceInstUsesWith(I, Constant::getNullValue(I.getType())); // A+B --> A|B iff A and B have no bits set in common. WithCache LHSCache(LHS), RHSCache(RHS); if (haveNoCommonBitsSet(LHSCache, RHSCache, SQ.getWithInstruction(&I))) return BinaryOperator::CreateDisjointOr(LHS, RHS); if (Instruction *Ext = narrowMathIfNoOverflow(I)) return Ext; // (add (xor A, B) (and A, B)) --> (or A, B) // (add (and A, B) (xor A, B)) --> (or A, B) if (match(&I, m_c_BinOp(m_Xor(m_Value(A), m_Value(B)), m_c_And(m_Deferred(A), m_Deferred(B))))) return BinaryOperator::CreateOr(A, B); // (add (or A, B) (and A, B)) --> (add A, B) // (add (and A, B) (or A, B)) --> (add A, B) if (match(&I, m_c_BinOp(m_Or(m_Value(A), m_Value(B)), m_c_And(m_Deferred(A), m_Deferred(B))))) { // Replacing operands in-place to preserve nuw/nsw flags. replaceOperand(I, 0, A); replaceOperand(I, 1, B); return &I; } // (add A (or A, -A)) --> (and (add A, -1) A) // (add A (or -A, A)) --> (and (add A, -1) A) // (add (or A, -A) A) --> (and (add A, -1) A) // (add (or -A, A) A) --> (and (add A, -1) A) if (match(&I, m_c_BinOp(m_Value(A), m_OneUse(m_c_Or(m_Neg(m_Deferred(A)), m_Deferred(A)))))) { Value *Add = Builder.CreateAdd(A, Constant::getAllOnesValue(A->getType()), "", I.hasNoUnsignedWrap(), I.hasNoSignedWrap()); return BinaryOperator::CreateAnd(Add, A); } // Canonicalize ((A & -A) - 1) --> ((A - 1) & ~A) // Forms all commutable operations, and simplifies ctpop -> cttz folds. if (match(&I, m_Add(m_OneUse(m_c_And(m_Value(A), m_OneUse(m_Neg(m_Deferred(A))))), m_AllOnes()))) { Constant *AllOnes = ConstantInt::getAllOnesValue(RHS->getType()); Value *Dec = Builder.CreateAdd(A, AllOnes); Value *Not = Builder.CreateXor(A, AllOnes); return BinaryOperator::CreateAnd(Dec, Not); } // Disguised reassociation/factorization: // ~(A * C1) + A // ((A * -C1) - 1) + A // ((A * -C1) + A) - 1 // (A * (1 - C1)) - 1 if (match(&I, m_c_Add(m_OneUse(m_Not(m_OneUse(m_Mul(m_Value(A), m_APInt(C1))))), m_Deferred(A)))) { Type *Ty = I.getType(); Constant *NewMulC = ConstantInt::get(Ty, 1 - *C1); Value *NewMul = Builder.CreateMul(A, NewMulC); return BinaryOperator::CreateAdd(NewMul, ConstantInt::getAllOnesValue(Ty)); } // (A * -2**C) + B --> B - (A << C) const APInt *NegPow2C; if (match(&I, m_c_Add(m_OneUse(m_Mul(m_Value(A), m_NegatedPower2(NegPow2C))), m_Value(B)))) { Constant *ShiftAmtC = ConstantInt::get(Ty, NegPow2C->countr_zero()); Value *Shl = Builder.CreateShl(A, ShiftAmtC); return BinaryOperator::CreateSub(B, Shl); } // Canonicalize signum variant that ends in add: // (A s>> (BW - 1)) + (zext (A s> 0)) --> (A s>> (BW - 1)) | (zext (A != 0)) ICmpInst::Predicate Pred; uint64_t BitWidth = Ty->getScalarSizeInBits(); if (match(LHS, m_AShr(m_Value(A), m_SpecificIntAllowPoison(BitWidth - 1))) && match(RHS, m_OneUse(m_ZExt( m_OneUse(m_ICmp(Pred, m_Specific(A), m_ZeroInt()))))) && Pred == CmpInst::ICMP_SGT) { Value *NotZero = Builder.CreateIsNotNull(A, "isnotnull"); Value *Zext = Builder.CreateZExt(NotZero, Ty, "isnotnull.zext"); return BinaryOperator::CreateOr(LHS, Zext); } { Value *Cond, *Ext; Constant *C; // (add X, (sext/zext (icmp eq X, C))) // -> (select (icmp eq X, C), (add C, (sext/zext 1)), X) auto CondMatcher = m_CombineAnd( m_Value(Cond), m_ICmp(Pred, m_Deferred(A), m_ImmConstant(C))); if (match(&I, m_c_Add(m_Value(A), m_CombineAnd(m_Value(Ext), m_ZExtOrSExt(CondMatcher)))) && Pred == ICmpInst::ICMP_EQ && Ext->hasOneUse()) { Value *Add = isa(Ext) ? InstCombiner::AddOne(C) : InstCombiner::SubOne(C); return replaceInstUsesWith(I, Builder.CreateSelect(Cond, Add, A)); } } if (Instruction *Ashr = foldAddToAshr(I)) return Ashr; // (~X) + (~Y) --> -2 - (X + Y) { // To ensure we can save instructions we need to ensure that we consume both // LHS/RHS (i.e they have a `not`). bool ConsumesLHS, ConsumesRHS; if (isFreeToInvert(LHS, LHS->hasOneUse(), ConsumesLHS) && ConsumesLHS && isFreeToInvert(RHS, RHS->hasOneUse(), ConsumesRHS) && ConsumesRHS) { Value *NotLHS = getFreelyInverted(LHS, LHS->hasOneUse(), &Builder); Value *NotRHS = getFreelyInverted(RHS, RHS->hasOneUse(), &Builder); assert(NotLHS != nullptr && NotRHS != nullptr && "isFreeToInvert desynced with getFreelyInverted"); Value *LHSPlusRHS = Builder.CreateAdd(NotLHS, NotRHS); return BinaryOperator::CreateSub( ConstantInt::getSigned(RHS->getType(), -2), LHSPlusRHS); } } if (Instruction *R = tryFoldInstWithCtpopWithNot(&I)) return R; // TODO(jingyue): Consider willNotOverflowSignedAdd and // willNotOverflowUnsignedAdd to reduce the number of invocations of // computeKnownBits. bool Changed = false; if (!I.hasNoSignedWrap() && willNotOverflowSignedAdd(LHSCache, RHSCache, I)) { Changed = true; I.setHasNoSignedWrap(true); } if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedAdd(LHSCache, RHSCache, I)) { Changed = true; I.setHasNoUnsignedWrap(true); } if (Instruction *V = canonicalizeLowbitMask(I, Builder)) return V; if (Instruction *V = canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(I)) return V; if (Instruction *SatAdd = foldToUnsignedSaturatedAdd(I)) return SatAdd; // usub.sat(A, B) + B => umax(A, B) if (match(&I, m_c_BinOp( m_OneUse(m_Intrinsic(m_Value(A), m_Value(B))), m_Deferred(B)))) { return replaceInstUsesWith(I, Builder.CreateIntrinsic(Intrinsic::umax, {I.getType()}, {A, B})); } // ctpop(A) + ctpop(B) => ctpop(A | B) if A and B have no bits set in common. if (match(LHS, m_OneUse(m_Intrinsic(m_Value(A)))) && match(RHS, m_OneUse(m_Intrinsic(m_Value(B)))) && haveNoCommonBitsSet(A, B, SQ.getWithInstruction(&I))) return replaceInstUsesWith( I, Builder.CreateIntrinsic(Intrinsic::ctpop, {I.getType()}, {Builder.CreateOr(A, B)})); // Fold the log2_ceil idiom: // zext(ctpop(A) >u/!= 1) + (ctlz(A, true) ^ (BW - 1)) // --> // BW - ctlz(A - 1, false) const APInt *XorC; if (match(&I, m_c_Add( m_ZExt(m_ICmp(Pred, m_Intrinsic(m_Value(A)), m_One())), m_OneUse(m_ZExtOrSelf(m_OneUse(m_Xor( m_OneUse(m_TruncOrSelf(m_OneUse( m_Intrinsic(m_Deferred(A), m_One())))), m_APInt(XorC))))))) && (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_NE) && *XorC == A->getType()->getScalarSizeInBits() - 1) { Value *Sub = Builder.CreateAdd(A, Constant::getAllOnesValue(A->getType())); Value *Ctlz = Builder.CreateIntrinsic(Intrinsic::ctlz, {A->getType()}, {Sub, Builder.getFalse()}); Value *Ret = Builder.CreateSub( ConstantInt::get(A->getType(), A->getType()->getScalarSizeInBits()), Ctlz, "", /*HasNUW*/ true, /*HasNSW*/ true); return replaceInstUsesWith(I, Builder.CreateZExtOrTrunc(Ret, I.getType())); } if (Instruction *Res = foldSquareSumInt(I)) return Res; if (Instruction *Res = foldBinOpOfDisplacedShifts(I)) return Res; if (Instruction *Res = foldBinOpOfSelectAndCastOfSelectCondition(I)) return Res; return Changed ? &I : nullptr; } /// Eliminate an op from a linear interpolation (lerp) pattern. static Instruction *factorizeLerp(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { Value *X, *Y, *Z; if (!match(&I, m_c_FAdd(m_OneUse(m_c_FMul(m_Value(Y), m_OneUse(m_FSub(m_FPOne(), m_Value(Z))))), m_OneUse(m_c_FMul(m_Value(X), m_Deferred(Z)))))) return nullptr; // (Y * (1.0 - Z)) + (X * Z) --> Y + Z * (X - Y) [8 commuted variants] Value *XY = Builder.CreateFSubFMF(X, Y, &I); Value *MulZ = Builder.CreateFMulFMF(Z, XY, &I); return BinaryOperator::CreateFAddFMF(Y, MulZ, &I); } /// Factor a common operand out of fadd/fsub of fmul/fdiv. static Instruction *factorizeFAddFSub(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { assert((I.getOpcode() == Instruction::FAdd || I.getOpcode() == Instruction::FSub) && "Expecting fadd/fsub"); assert(I.hasAllowReassoc() && I.hasNoSignedZeros() && "FP factorization requires FMF"); if (Instruction *Lerp = factorizeLerp(I, Builder)) return Lerp; Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (!Op0->hasOneUse() || !Op1->hasOneUse()) return nullptr; Value *X, *Y, *Z; bool IsFMul; if ((match(Op0, m_FMul(m_Value(X), m_Value(Z))) && match(Op1, m_c_FMul(m_Value(Y), m_Specific(Z)))) || (match(Op0, m_FMul(m_Value(Z), m_Value(X))) && match(Op1, m_c_FMul(m_Value(Y), m_Specific(Z))))) IsFMul = true; else if (match(Op0, m_FDiv(m_Value(X), m_Value(Z))) && match(Op1, m_FDiv(m_Value(Y), m_Specific(Z)))) IsFMul = false; else return nullptr; // (X * Z) + (Y * Z) --> (X + Y) * Z // (X * Z) - (Y * Z) --> (X - Y) * Z // (X / Z) + (Y / Z) --> (X + Y) / Z // (X / Z) - (Y / Z) --> (X - Y) / Z bool IsFAdd = I.getOpcode() == Instruction::FAdd; Value *XY = IsFAdd ? Builder.CreateFAddFMF(X, Y, &I) : Builder.CreateFSubFMF(X, Y, &I); // Bail out if we just created a denormal constant. // TODO: This is copied from a previous implementation. Is it necessary? const APFloat *C; if (match(XY, m_APFloat(C)) && !C->isNormal()) return nullptr; return IsFMul ? BinaryOperator::CreateFMulFMF(XY, Z, &I) : BinaryOperator::CreateFDivFMF(XY, Z, &I); } Instruction *InstCombinerImpl::visitFAdd(BinaryOperator &I) { if (Value *V = simplifyFAddInst(I.getOperand(0), I.getOperand(1), I.getFastMathFlags(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (SimplifyAssociativeOrCommutative(I)) return &I; if (Instruction *X = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; if (Instruction *FoldedFAdd = foldBinOpIntoSelectOrPhi(I)) return FoldedFAdd; // (-X) + Y --> Y - X Value *X, *Y; if (match(&I, m_c_FAdd(m_FNeg(m_Value(X)), m_Value(Y)))) return BinaryOperator::CreateFSubFMF(Y, X, &I); // Similar to above, but look through fmul/fdiv for the negated term. // (-X * Y) + Z --> Z - (X * Y) [4 commuted variants] Value *Z; if (match(&I, m_c_FAdd(m_OneUse(m_c_FMul(m_FNeg(m_Value(X)), m_Value(Y))), m_Value(Z)))) { Value *XY = Builder.CreateFMulFMF(X, Y, &I); return BinaryOperator::CreateFSubFMF(Z, XY, &I); } // (-X / Y) + Z --> Z - (X / Y) [2 commuted variants] // (X / -Y) + Z --> Z - (X / Y) [2 commuted variants] if (match(&I, m_c_FAdd(m_OneUse(m_FDiv(m_FNeg(m_Value(X)), m_Value(Y))), m_Value(Z))) || match(&I, m_c_FAdd(m_OneUse(m_FDiv(m_Value(X), m_FNeg(m_Value(Y)))), m_Value(Z)))) { Value *XY = Builder.CreateFDivFMF(X, Y, &I); return BinaryOperator::CreateFSubFMF(Z, XY, &I); } // Check for (fadd double (sitofp x), y), see if we can merge this into an // integer add followed by a promotion. if (Instruction *R = foldFBinOpOfIntCasts(I)) return R; Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); // Handle specials cases for FAdd with selects feeding the operation if (Value *V = SimplifySelectsFeedingBinaryOp(I, LHS, RHS)) return replaceInstUsesWith(I, V); if (I.hasAllowReassoc() && I.hasNoSignedZeros()) { if (Instruction *F = factorizeFAddFSub(I, Builder)) return F; if (Instruction *F = foldSquareSumFP(I)) return F; // Try to fold fadd into start value of reduction intrinsic. if (match(&I, m_c_FAdd(m_OneUse(m_Intrinsic( m_AnyZeroFP(), m_Value(X))), m_Value(Y)))) { // fadd (rdx 0.0, X), Y --> rdx Y, X return replaceInstUsesWith( I, Builder.CreateIntrinsic(Intrinsic::vector_reduce_fadd, {X->getType()}, {Y, X}, &I)); } const APFloat *StartC, *C; if (match(LHS, m_OneUse(m_Intrinsic( m_APFloat(StartC), m_Value(X)))) && match(RHS, m_APFloat(C))) { // fadd (rdx StartC, X), C --> rdx (C + StartC), X Constant *NewStartC = ConstantFP::get(I.getType(), *C + *StartC); return replaceInstUsesWith( I, Builder.CreateIntrinsic(Intrinsic::vector_reduce_fadd, {X->getType()}, {NewStartC, X}, &I)); } // (X * MulC) + X --> X * (MulC + 1.0) Constant *MulC; if (match(&I, m_c_FAdd(m_FMul(m_Value(X), m_ImmConstant(MulC)), m_Deferred(X)))) { if (Constant *NewMulC = ConstantFoldBinaryOpOperands( Instruction::FAdd, MulC, ConstantFP::get(I.getType(), 1.0), DL)) return BinaryOperator::CreateFMulFMF(X, NewMulC, &I); } // (-X - Y) + (X + Z) --> Z - Y if (match(&I, m_c_FAdd(m_FSub(m_FNeg(m_Value(X)), m_Value(Y)), m_c_FAdd(m_Deferred(X), m_Value(Z))))) return BinaryOperator::CreateFSubFMF(Z, Y, &I); if (Value *V = FAddCombine(Builder).simplify(&I)) return replaceInstUsesWith(I, V); } // minumum(X, Y) + maximum(X, Y) => X + Y. if (match(&I, m_c_FAdd(m_Intrinsic(m_Value(X), m_Value(Y)), m_c_Intrinsic(m_Deferred(X), m_Deferred(Y))))) { BinaryOperator *Result = BinaryOperator::CreateFAddFMF(X, Y, &I); // We cannot preserve ninf if nnan flag is not set. // If X is NaN and Y is Inf then in original program we had NaN + NaN, // while in optimized version NaN + Inf and this is a poison with ninf flag. if (!Result->hasNoNaNs()) Result->setHasNoInfs(false); return Result; } return nullptr; } /// Optimize pointer differences into the same array into a size. Consider: /// &A[10] - &A[0]: we should compile this to "10". LHS/RHS are the pointer /// operands to the ptrtoint instructions for the LHS/RHS of the subtract. Value *InstCombinerImpl::OptimizePointerDifference(Value *LHS, Value *RHS, Type *Ty, bool IsNUW) { // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize // this. bool Swapped = false; GEPOperator *GEP1 = nullptr, *GEP2 = nullptr; if (!isa(LHS) && isa(RHS)) { std::swap(LHS, RHS); Swapped = true; } // Require at least one GEP with a common base pointer on both sides. if (auto *LHSGEP = dyn_cast(LHS)) { // (gep X, ...) - X if (LHSGEP->getOperand(0)->stripPointerCasts() == RHS->stripPointerCasts()) { GEP1 = LHSGEP; } else if (auto *RHSGEP = dyn_cast(RHS)) { // (gep X, ...) - (gep X, ...) if (LHSGEP->getOperand(0)->stripPointerCasts() == RHSGEP->getOperand(0)->stripPointerCasts()) { GEP1 = LHSGEP; GEP2 = RHSGEP; } } } if (!GEP1) return nullptr; // To avoid duplicating the offset arithmetic, rewrite the GEP to use the // computed offset. This may erase the original GEP, so be sure to cache the // inbounds flag before emitting the offset. // TODO: We should probably do this even if there is only one GEP. bool RewriteGEPs = GEP2 != nullptr; // Emit the offset of the GEP and an intptr_t. bool GEP1IsInBounds = GEP1->isInBounds(); Value *Result = EmitGEPOffset(GEP1, RewriteGEPs); // If this is a single inbounds GEP and the original sub was nuw, // then the final multiplication is also nuw. if (auto *I = dyn_cast(Result)) if (IsNUW && !GEP2 && !Swapped && GEP1IsInBounds && I->getOpcode() == Instruction::Mul) I->setHasNoUnsignedWrap(); // If we have a 2nd GEP of the same base pointer, subtract the offsets. // If both GEPs are inbounds, then the subtract does not have signed overflow. if (GEP2) { bool GEP2IsInBounds = GEP2->isInBounds(); Value *Offset = EmitGEPOffset(GEP2, RewriteGEPs); Result = Builder.CreateSub(Result, Offset, "gepdiff", /* NUW */ false, GEP1IsInBounds && GEP2IsInBounds); } // If we have p - gep(p, ...) then we have to negate the result. if (Swapped) Result = Builder.CreateNeg(Result, "diff.neg"); return Builder.CreateIntCast(Result, Ty, true); } static Instruction *foldSubOfMinMax(BinaryOperator &I, InstCombiner::BuilderTy &Builder) { Value *Op0 = I.getOperand(0); Value *Op1 = I.getOperand(1); Type *Ty = I.getType(); auto *MinMax = dyn_cast(Op1); if (!MinMax) return nullptr; // sub(add(X,Y), s/umin(X,Y)) --> s/umax(X,Y) // sub(add(X,Y), s/umax(X,Y)) --> s/umin(X,Y) Value *X = MinMax->getLHS(); Value *Y = MinMax->getRHS(); if (match(Op0, m_c_Add(m_Specific(X), m_Specific(Y))) && (Op0->hasOneUse() || Op1->hasOneUse())) { Intrinsic::ID InvID = getInverseMinMaxIntrinsic(MinMax->getIntrinsicID()); Function *F = Intrinsic::getDeclaration(I.getModule(), InvID, Ty); return CallInst::Create(F, {X, Y}); } // sub(add(X,Y),umin(Y,Z)) --> add(X,usub.sat(Y,Z)) // sub(add(X,Z),umin(Y,Z)) --> add(X,usub.sat(Z,Y)) Value *Z; if (match(Op1, m_OneUse(m_UMin(m_Value(Y), m_Value(Z))))) { if (match(Op0, m_OneUse(m_c_Add(m_Specific(Y), m_Value(X))))) { Value *USub = Builder.CreateIntrinsic(Intrinsic::usub_sat, Ty, {Y, Z}); return BinaryOperator::CreateAdd(X, USub); } if (match(Op0, m_OneUse(m_c_Add(m_Specific(Z), m_Value(X))))) { Value *USub = Builder.CreateIntrinsic(Intrinsic::usub_sat, Ty, {Z, Y}); return BinaryOperator::CreateAdd(X, USub); } } // sub Op0, smin((sub nsw Op0, Z), 0) --> smax Op0, Z // sub Op0, smax((sub nsw Op0, Z), 0) --> smin Op0, Z if (MinMax->isSigned() && match(Y, m_ZeroInt()) && match(X, m_NSWSub(m_Specific(Op0), m_Value(Z)))) { Intrinsic::ID InvID = getInverseMinMaxIntrinsic(MinMax->getIntrinsicID()); Function *F = Intrinsic::getDeclaration(I.getModule(), InvID, Ty); return CallInst::Create(F, {Op0, Z}); } return nullptr; } Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) { if (Value *V = simplifySubInst(I.getOperand(0), I.getOperand(1), I.hasNoSignedWrap(), I.hasNoUnsignedWrap(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); // If this is a 'B = x-(-A)', change to B = x+A. // We deal with this without involving Negator to preserve NSW flag. if (Value *V = dyn_castNegVal(Op1)) { BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V); if (const auto *BO = dyn_cast(Op1)) { assert(BO->getOpcode() == Instruction::Sub && "Expected a subtraction operator!"); if (BO->hasNoSignedWrap() && I.hasNoSignedWrap()) Res->setHasNoSignedWrap(true); } else { if (cast(Op1)->isNotMinSignedValue() && I.hasNoSignedWrap()) Res->setHasNoSignedWrap(true); } return Res; } // Try this before Negator to preserve NSW flag. if (Instruction *R = factorizeMathWithShlOps(I, Builder)) return R; Constant *C; if (match(Op0, m_ImmConstant(C))) { Value *X; Constant *C2; // C-(X+C2) --> (C-C2)-X if (match(Op1, m_Add(m_Value(X), m_ImmConstant(C2)))) { // C-C2 never overflow, and C-(X+C2), (X+C2) has NSW/NUW // => (C-C2)-X can have NSW/NUW bool WillNotSOV = willNotOverflowSignedSub(C, C2, I); BinaryOperator *Res = BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X); auto *OBO1 = cast(Op1); Res->setHasNoSignedWrap(I.hasNoSignedWrap() && OBO1->hasNoSignedWrap() && WillNotSOV); Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap() && OBO1->hasNoUnsignedWrap()); return Res; } } auto TryToNarrowDeduceFlags = [this, &I, &Op0, &Op1]() -> Instruction * { if (Instruction *Ext = narrowMathIfNoOverflow(I)) return Ext; bool Changed = false; if (!I.hasNoSignedWrap() && willNotOverflowSignedSub(Op0, Op1, I)) { Changed = true; I.setHasNoSignedWrap(true); } if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedSub(Op0, Op1, I)) { Changed = true; I.setHasNoUnsignedWrap(true); } return Changed ? &I : nullptr; }; // First, let's try to interpret `sub a, b` as `add a, (sub 0, b)`, // and let's try to sink `(sub 0, b)` into `b` itself. But only if this isn't // a pure negation used by a select that looks like abs/nabs. bool IsNegation = match(Op0, m_ZeroInt()); if (!IsNegation || none_of(I.users(), [&I, Op1](const User *U) { const Instruction *UI = dyn_cast(U); if (!UI) return false; return match(UI, m_Select(m_Value(), m_Specific(Op1), m_Specific(&I))) || match(UI, m_Select(m_Value(), m_Specific(&I), m_Specific(Op1))); })) { if (Value *NegOp1 = Negator::Negate(IsNegation, /* IsNSW */ IsNegation && I.hasNoSignedWrap(), Op1, *this)) return BinaryOperator::CreateAdd(NegOp1, Op0); } if (IsNegation) return TryToNarrowDeduceFlags(); // Should have been handled in Negator! // (A*B)-(A*C) -> A*(B-C) etc if (Value *V = foldUsingDistributiveLaws(I)) return replaceInstUsesWith(I, V); if (I.getType()->isIntOrIntVectorTy(1)) return BinaryOperator::CreateXor(Op0, Op1); // Replace (-1 - A) with (~A). if (match(Op0, m_AllOnes())) return BinaryOperator::CreateNot(Op1); // (X + -1) - Y --> ~Y + X Value *X, *Y; if (match(Op0, m_OneUse(m_Add(m_Value(X), m_AllOnes())))) return BinaryOperator::CreateAdd(Builder.CreateNot(Op1), X); // Reassociate sub/add sequences to create more add instructions and // reduce dependency chains: // ((X - Y) + Z) - Op1 --> (X + Z) - (Y + Op1) Value *Z; if (match(Op0, m_OneUse(m_c_Add(m_OneUse(m_Sub(m_Value(X), m_Value(Y))), m_Value(Z))))) { Value *XZ = Builder.CreateAdd(X, Z); Value *YW = Builder.CreateAdd(Y, Op1); return BinaryOperator::CreateSub(XZ, YW); } // ((X - Y) - Op1) --> X - (Y + Op1) if (match(Op0, m_OneUse(m_Sub(m_Value(X), m_Value(Y))))) { OverflowingBinaryOperator *LHSSub = cast(Op0); bool HasNUW = I.hasNoUnsignedWrap() && LHSSub->hasNoUnsignedWrap(); bool HasNSW = HasNUW && I.hasNoSignedWrap() && LHSSub->hasNoSignedWrap(); Value *Add = Builder.CreateAdd(Y, Op1, "", /* HasNUW */ HasNUW, /* HasNSW */ HasNSW); BinaryOperator *Sub = BinaryOperator::CreateSub(X, Add); Sub->setHasNoUnsignedWrap(HasNUW); Sub->setHasNoSignedWrap(HasNSW); return Sub; } { // (X + Z) - (Y + Z) --> (X - Y) // This is done in other passes, but we want to be able to consume this // pattern in InstCombine so we can generate it without creating infinite // loops. if (match(Op0, m_Add(m_Value(X), m_Value(Z))) && match(Op1, m_c_Add(m_Value(Y), m_Specific(Z)))) return BinaryOperator::CreateSub(X, Y); // (X + C0) - (Y + C1) --> (X - Y) + (C0 - C1) Constant *CX, *CY; if (match(Op0, m_OneUse(m_Add(m_Value(X), m_ImmConstant(CX)))) && match(Op1, m_OneUse(m_Add(m_Value(Y), m_ImmConstant(CY))))) { Value *OpsSub = Builder.CreateSub(X, Y); Constant *ConstsSub = ConstantExpr::getSub(CX, CY); return BinaryOperator::CreateAdd(OpsSub, ConstsSub); } } // (~X) - (~Y) --> Y - X { // Need to ensure we can consume at least one of the `not` instructions, // otherwise this can inf loop. bool ConsumesOp0, ConsumesOp1; if (isFreeToInvert(Op0, Op0->hasOneUse(), ConsumesOp0) && isFreeToInvert(Op1, Op1->hasOneUse(), ConsumesOp1) && (ConsumesOp0 || ConsumesOp1)) { Value *NotOp0 = getFreelyInverted(Op0, Op0->hasOneUse(), &Builder); Value *NotOp1 = getFreelyInverted(Op1, Op1->hasOneUse(), &Builder); assert(NotOp0 != nullptr && NotOp1 != nullptr && "isFreeToInvert desynced with getFreelyInverted"); return BinaryOperator::CreateSub(NotOp1, NotOp0); } } auto m_AddRdx = [](Value *&Vec) { return m_OneUse(m_Intrinsic(m_Value(Vec))); }; Value *V0, *V1; if (match(Op0, m_AddRdx(V0)) && match(Op1, m_AddRdx(V1)) && V0->getType() == V1->getType()) { // Difference of sums is sum of differences: // add_rdx(V0) - add_rdx(V1) --> add_rdx(V0 - V1) Value *Sub = Builder.CreateSub(V0, V1); Value *Rdx = Builder.CreateIntrinsic(Intrinsic::vector_reduce_add, {Sub->getType()}, {Sub}); return replaceInstUsesWith(I, Rdx); } if (Constant *C = dyn_cast(Op0)) { Value *X; if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) // C - (zext bool) --> bool ? C - 1 : C return SelectInst::Create(X, InstCombiner::SubOne(C), C); if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) // C - (sext bool) --> bool ? C + 1 : C return SelectInst::Create(X, InstCombiner::AddOne(C), C); // C - ~X == X + (1+C) if (match(Op1, m_Not(m_Value(X)))) return BinaryOperator::CreateAdd(X, InstCombiner::AddOne(C)); // Try to fold constant sub into select arguments. if (SelectInst *SI = dyn_cast(Op1)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; // Try to fold constant sub into PHI values. if (PHINode *PN = dyn_cast(Op1)) if (Instruction *R = foldOpIntoPhi(I, PN)) return R; Constant *C2; // C-(C2-X) --> X+(C-C2) if (match(Op1, m_Sub(m_ImmConstant(C2), m_Value(X)))) return BinaryOperator::CreateAdd(X, ConstantExpr::getSub(C, C2)); } const APInt *Op0C; if (match(Op0, m_APInt(Op0C))) { if (Op0C->isMask()) { // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known // zero. We don't use information from dominating conditions so this // transform is easier to reverse if necessary. KnownBits RHSKnown = llvm::computeKnownBits( Op1, 0, SQ.getWithInstruction(&I).getWithoutDomCondCache()); if ((*Op0C | RHSKnown.Zero).isAllOnes()) return BinaryOperator::CreateXor(Op1, Op0); } // C - ((C3 -nuw X) & C2) --> (C - (C2 & C3)) + (X & C2) when: // (C3 - ((C2 & C3) - 1)) is pow2 // ((C2 + C3) & ((C2 & C3) - 1)) == ((C2 & C3) - 1) // C2 is negative pow2 || sub nuw const APInt *C2, *C3; BinaryOperator *InnerSub; if (match(Op1, m_OneUse(m_And(m_BinOp(InnerSub), m_APInt(C2)))) && match(InnerSub, m_Sub(m_APInt(C3), m_Value(X))) && (InnerSub->hasNoUnsignedWrap() || C2->isNegatedPowerOf2())) { APInt C2AndC3 = *C2 & *C3; APInt C2AndC3Minus1 = C2AndC3 - 1; APInt C2AddC3 = *C2 + *C3; if ((*C3 - C2AndC3Minus1).isPowerOf2() && C2AndC3Minus1.isSubsetOf(C2AddC3)) { Value *And = Builder.CreateAnd(X, ConstantInt::get(I.getType(), *C2)); return BinaryOperator::CreateAdd( And, ConstantInt::get(I.getType(), *Op0C - C2AndC3)); } } } { Value *Y; // X-(X+Y) == -Y X-(Y+X) == -Y if (match(Op1, m_c_Add(m_Specific(Op0), m_Value(Y)))) return BinaryOperator::CreateNeg(Y); // (X-Y)-X == -Y if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y)))) return BinaryOperator::CreateNeg(Y); } // (sub (or A, B) (and A, B)) --> (xor A, B) { Value *A, *B; if (match(Op1, m_And(m_Value(A), m_Value(B))) && match(Op0, m_c_Or(m_Specific(A), m_Specific(B)))) return BinaryOperator::CreateXor(A, B); } // (sub (add A, B) (or A, B)) --> (and A, B) { Value *A, *B; if (match(Op0, m_Add(m_Value(A), m_Value(B))) && match(Op1, m_c_Or(m_Specific(A), m_Specific(B)))) return BinaryOperator::CreateAnd(A, B); } // (sub (add A, B) (and A, B)) --> (or A, B) { Value *A, *B; if (match(Op0, m_Add(m_Value(A), m_Value(B))) && match(Op1, m_c_And(m_Specific(A), m_Specific(B)))) return BinaryOperator::CreateOr(A, B); } // (sub (and A, B) (or A, B)) --> neg (xor A, B) { Value *A, *B; if (match(Op0, m_And(m_Value(A), m_Value(B))) && match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) && (Op0->hasOneUse() || Op1->hasOneUse())) return BinaryOperator::CreateNeg(Builder.CreateXor(A, B)); } // (sub (or A, B), (xor A, B)) --> (and A, B) { Value *A, *B; if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && match(Op0, m_c_Or(m_Specific(A), m_Specific(B)))) return BinaryOperator::CreateAnd(A, B); } // (sub (xor A, B) (or A, B)) --> neg (and A, B) { Value *A, *B; if (match(Op0, m_Xor(m_Value(A), m_Value(B))) && match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) && (Op0->hasOneUse() || Op1->hasOneUse())) return BinaryOperator::CreateNeg(Builder.CreateAnd(A, B)); } { Value *Y; // ((X | Y) - X) --> (~X & Y) if (match(Op0, m_OneUse(m_c_Or(m_Value(Y), m_Specific(Op1))))) return BinaryOperator::CreateAnd( Y, Builder.CreateNot(Op1, Op1->getName() + ".not")); } { // (sub (and Op1, (neg X)), Op1) --> neg (and Op1, (add X, -1)) Value *X; if (match(Op0, m_OneUse(m_c_And(m_Specific(Op1), m_OneUse(m_Neg(m_Value(X))))))) { return BinaryOperator::CreateNeg(Builder.CreateAnd( Op1, Builder.CreateAdd(X, Constant::getAllOnesValue(I.getType())))); } } { // (sub (and Op1, C), Op1) --> neg (and Op1, ~C) Constant *C; if (match(Op0, m_OneUse(m_And(m_Specific(Op1), m_Constant(C))))) { return BinaryOperator::CreateNeg( Builder.CreateAnd(Op1, Builder.CreateNot(C))); } } { // (sub (xor X, (sext C)), (sext C)) => (select C, (neg X), X) // (sub (sext C), (xor X, (sext C))) => (select C, X, (neg X)) Value *C, *X; auto m_SubXorCmp = [&C, &X](Value *LHS, Value *RHS) { return match(LHS, m_OneUse(m_c_Xor(m_Value(X), m_Specific(RHS)))) && match(RHS, m_SExt(m_Value(C))) && (C->getType()->getScalarSizeInBits() == 1); }; if (m_SubXorCmp(Op0, Op1)) return SelectInst::Create(C, Builder.CreateNeg(X), X); if (m_SubXorCmp(Op1, Op0)) return SelectInst::Create(C, X, Builder.CreateNeg(X)); } if (Instruction *R = tryFoldInstWithCtpopWithNot(&I)) return R; if (Instruction *R = foldSubOfMinMax(I, Builder)) return R; { // If we have a subtraction between some value and a select between // said value and something else, sink subtraction into select hands, i.e.: // sub (select %Cond, %TrueVal, %FalseVal), %Op1 // -> // select %Cond, (sub %TrueVal, %Op1), (sub %FalseVal, %Op1) // or // sub %Op0, (select %Cond, %TrueVal, %FalseVal) // -> // select %Cond, (sub %Op0, %TrueVal), (sub %Op0, %FalseVal) // This will result in select between new subtraction and 0. auto SinkSubIntoSelect = [Ty = I.getType()](Value *Select, Value *OtherHandOfSub, auto SubBuilder) -> Instruction * { Value *Cond, *TrueVal, *FalseVal; if (!match(Select, m_OneUse(m_Select(m_Value(Cond), m_Value(TrueVal), m_Value(FalseVal))))) return nullptr; if (OtherHandOfSub != TrueVal && OtherHandOfSub != FalseVal) return nullptr; // While it is really tempting to just create two subtractions and let // InstCombine fold one of those to 0, it isn't possible to do so // because of worklist visitation order. So ugly it is. bool OtherHandOfSubIsTrueVal = OtherHandOfSub == TrueVal; Value *NewSub = SubBuilder(OtherHandOfSubIsTrueVal ? FalseVal : TrueVal); Constant *Zero = Constant::getNullValue(Ty); SelectInst *NewSel = SelectInst::Create(Cond, OtherHandOfSubIsTrueVal ? Zero : NewSub, OtherHandOfSubIsTrueVal ? NewSub : Zero); // Preserve prof metadata if any. NewSel->copyMetadata(cast(*Select)); return NewSel; }; if (Instruction *NewSel = SinkSubIntoSelect( /*Select=*/Op0, /*OtherHandOfSub=*/Op1, [Builder = &Builder, Op1](Value *OtherHandOfSelect) { return Builder->CreateSub(OtherHandOfSelect, /*OtherHandOfSub=*/Op1); })) return NewSel; if (Instruction *NewSel = SinkSubIntoSelect( /*Select=*/Op1, /*OtherHandOfSub=*/Op0, [Builder = &Builder, Op0](Value *OtherHandOfSelect) { return Builder->CreateSub(/*OtherHandOfSub=*/Op0, OtherHandOfSelect); })) return NewSel; } // (X - (X & Y)) --> (X & ~Y) if (match(Op1, m_c_And(m_Specific(Op0), m_Value(Y))) && (Op1->hasOneUse() || isa(Y))) return BinaryOperator::CreateAnd( Op0, Builder.CreateNot(Y, Y->getName() + ".not")); // ~X - Min/Max(~X, Y) -> ~Min/Max(X, ~Y) - X // ~X - Min/Max(Y, ~X) -> ~Min/Max(X, ~Y) - X // Min/Max(~X, Y) - ~X -> X - ~Min/Max(X, ~Y) // Min/Max(Y, ~X) - ~X -> X - ~Min/Max(X, ~Y) // As long as Y is freely invertible, this will be neutral or a win. // Note: We don't generate the inverse max/min, just create the 'not' of // it and let other folds do the rest. if (match(Op0, m_Not(m_Value(X))) && match(Op1, m_c_MaxOrMin(m_Specific(Op0), m_Value(Y))) && !Op0->hasNUsesOrMore(3) && isFreeToInvert(Y, Y->hasOneUse())) { Value *Not = Builder.CreateNot(Op1); return BinaryOperator::CreateSub(Not, X); } if (match(Op1, m_Not(m_Value(X))) && match(Op0, m_c_MaxOrMin(m_Specific(Op1), m_Value(Y))) && !Op1->hasNUsesOrMore(3) && isFreeToInvert(Y, Y->hasOneUse())) { Value *Not = Builder.CreateNot(Op0); return BinaryOperator::CreateSub(X, Not); } // Optimize pointer differences into the same array into a size. Consider: // &A[10] - &A[0]: we should compile this to "10". Value *LHSOp, *RHSOp; if (match(Op0, m_PtrToInt(m_Value(LHSOp))) && match(Op1, m_PtrToInt(m_Value(RHSOp)))) if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType(), I.hasNoUnsignedWrap())) return replaceInstUsesWith(I, Res); // trunc(p)-trunc(q) -> trunc(p-q) if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) && match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp))))) if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType(), /* IsNUW */ false)) return replaceInstUsesWith(I, Res); // Canonicalize a shifty way to code absolute value to the common pattern. // There are 2 potential commuted variants. // We're relying on the fact that we only do this transform when the shift has // exactly 2 uses and the xor has exactly 1 use (otherwise, we might increase // instructions). Value *A; const APInt *ShAmt; Type *Ty = I.getType(); unsigned BitWidth = Ty->getScalarSizeInBits(); if (match(Op1, m_AShr(m_Value(A), m_APInt(ShAmt))) && Op1->hasNUses(2) && *ShAmt == BitWidth - 1 && match(Op0, m_OneUse(m_c_Xor(m_Specific(A), m_Specific(Op1))))) { // B = ashr i32 A, 31 ; smear the sign bit // sub (xor A, B), B ; flip bits if negative and subtract -1 (add 1) // --> (A < 0) ? -A : A Value *IsNeg = Builder.CreateIsNeg(A); // Copy the nsw flags from the sub to the negate. Value *NegA = I.hasNoUnsignedWrap() ? Constant::getNullValue(A->getType()) : Builder.CreateNeg(A, "", I.hasNoSignedWrap()); return SelectInst::Create(IsNeg, NegA, A); } // If we are subtracting a low-bit masked subset of some value from an add // of that same value with no low bits changed, that is clearing some low bits // of the sum: // sub (X + AddC), (X & AndC) --> and (X + AddC), ~AndC const APInt *AddC, *AndC; if (match(Op0, m_Add(m_Value(X), m_APInt(AddC))) && match(Op1, m_And(m_Specific(X), m_APInt(AndC)))) { unsigned Cttz = AddC->countr_zero(); APInt HighMask(APInt::getHighBitsSet(BitWidth, BitWidth - Cttz)); if ((HighMask & *AndC).isZero()) return BinaryOperator::CreateAnd(Op0, ConstantInt::get(Ty, ~(*AndC))); } if (Instruction *V = canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(I)) return V; // X - usub.sat(X, Y) => umin(X, Y) if (match(Op1, m_OneUse(m_Intrinsic(m_Specific(Op0), m_Value(Y))))) return replaceInstUsesWith( I, Builder.CreateIntrinsic(Intrinsic::umin, {I.getType()}, {Op0, Y})); // umax(X, Op1) - Op1 --> usub.sat(X, Op1) // TODO: The one-use restriction is not strictly necessary, but it may // require improving other pattern matching and/or codegen. if (match(Op0, m_OneUse(m_c_UMax(m_Value(X), m_Specific(Op1))))) return replaceInstUsesWith( I, Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {X, Op1})); // Op0 - umin(X, Op0) --> usub.sat(Op0, X) if (match(Op1, m_OneUse(m_c_UMin(m_Value(X), m_Specific(Op0))))) return replaceInstUsesWith( I, Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {Op0, X})); // Op0 - umax(X, Op0) --> 0 - usub.sat(X, Op0) if (match(Op1, m_OneUse(m_c_UMax(m_Value(X), m_Specific(Op0))))) { Value *USub = Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {X, Op0}); return BinaryOperator::CreateNeg(USub); } // umin(X, Op1) - Op1 --> 0 - usub.sat(Op1, X) if (match(Op0, m_OneUse(m_c_UMin(m_Value(X), m_Specific(Op1))))) { Value *USub = Builder.CreateIntrinsic(Intrinsic::usub_sat, {Ty}, {Op1, X}); return BinaryOperator::CreateNeg(USub); } // C - ctpop(X) => ctpop(~X) if C is bitwidth if (match(Op0, m_SpecificInt(BitWidth)) && match(Op1, m_OneUse(m_Intrinsic(m_Value(X))))) return replaceInstUsesWith( I, Builder.CreateIntrinsic(Intrinsic::ctpop, {I.getType()}, {Builder.CreateNot(X)})); // Reduce multiplies for difference-of-squares by factoring: // (X * X) - (Y * Y) --> (X + Y) * (X - Y) if (match(Op0, m_OneUse(m_Mul(m_Value(X), m_Deferred(X)))) && match(Op1, m_OneUse(m_Mul(m_Value(Y), m_Deferred(Y))))) { auto *OBO0 = cast(Op0); auto *OBO1 = cast(Op1); bool PropagateNSW = I.hasNoSignedWrap() && OBO0->hasNoSignedWrap() && OBO1->hasNoSignedWrap() && BitWidth > 2; bool PropagateNUW = I.hasNoUnsignedWrap() && OBO0->hasNoUnsignedWrap() && OBO1->hasNoUnsignedWrap() && BitWidth > 1; Value *Add = Builder.CreateAdd(X, Y, "add", PropagateNUW, PropagateNSW); Value *Sub = Builder.CreateSub(X, Y, "sub", PropagateNUW, PropagateNSW); Value *Mul = Builder.CreateMul(Add, Sub, "", PropagateNUW, PropagateNSW); return replaceInstUsesWith(I, Mul); } // max(X,Y) nsw/nuw - min(X,Y) --> abs(X nsw - Y) if (match(Op0, m_OneUse(m_c_SMax(m_Value(X), m_Value(Y)))) && match(Op1, m_OneUse(m_c_SMin(m_Specific(X), m_Specific(Y))))) { if (I.hasNoUnsignedWrap() || I.hasNoSignedWrap()) { Value *Sub = Builder.CreateSub(X, Y, "sub", /*HasNUW=*/false, /*HasNSW=*/true); Value *Call = Builder.CreateBinaryIntrinsic(Intrinsic::abs, Sub, Builder.getTrue()); return replaceInstUsesWith(I, Call); } } if (Instruction *Res = foldBinOpOfSelectAndCastOfSelectCondition(I)) return Res; return TryToNarrowDeduceFlags(); } /// This eliminates floating-point negation in either 'fneg(X)' or /// 'fsub(-0.0, X)' form by combining into a constant operand. static Instruction *foldFNegIntoConstant(Instruction &I, const DataLayout &DL) { // This is limited with one-use because fneg is assumed better for // reassociation and cheaper in codegen than fmul/fdiv. // TODO: Should the m_OneUse restriction be removed? Instruction *FNegOp; if (!match(&I, m_FNeg(m_OneUse(m_Instruction(FNegOp))))) return nullptr; Value *X; Constant *C; // Fold negation into constant operand. // -(X * C) --> X * (-C) if (match(FNegOp, m_FMul(m_Value(X), m_Constant(C)))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) return BinaryOperator::CreateFMulFMF(X, NegC, &I); // -(X / C) --> X / (-C) if (match(FNegOp, m_FDiv(m_Value(X), m_Constant(C)))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) return BinaryOperator::CreateFDivFMF(X, NegC, &I); // -(C / X) --> (-C) / X if (match(FNegOp, m_FDiv(m_Constant(C), m_Value(X)))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) { Instruction *FDiv = BinaryOperator::CreateFDivFMF(NegC, X, &I); // Intersect 'nsz' and 'ninf' because those special value exceptions may // not apply to the fdiv. Everything else propagates from the fneg. // TODO: We could propagate nsz/ninf from fdiv alone? FastMathFlags FMF = I.getFastMathFlags(); FastMathFlags OpFMF = FNegOp->getFastMathFlags(); FDiv->setHasNoSignedZeros(FMF.noSignedZeros() && OpFMF.noSignedZeros()); FDiv->setHasNoInfs(FMF.noInfs() && OpFMF.noInfs()); return FDiv; } // With NSZ [ counter-example with -0.0: -(-0.0 + 0.0) != 0.0 + -0.0 ]: // -(X + C) --> -X + -C --> -C - X if (I.hasNoSignedZeros() && match(FNegOp, m_FAdd(m_Value(X), m_Constant(C)))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) return BinaryOperator::CreateFSubFMF(NegC, X, &I); return nullptr; } Instruction *InstCombinerImpl::hoistFNegAboveFMulFDiv(Value *FNegOp, Instruction &FMFSource) { Value *X, *Y; if (match(FNegOp, m_FMul(m_Value(X), m_Value(Y)))) { return cast(Builder.CreateFMulFMF( Builder.CreateFNegFMF(X, &FMFSource), Y, &FMFSource)); } if (match(FNegOp, m_FDiv(m_Value(X), m_Value(Y)))) { return cast(Builder.CreateFDivFMF( Builder.CreateFNegFMF(X, &FMFSource), Y, &FMFSource)); } if (IntrinsicInst *II = dyn_cast(FNegOp)) { // Make sure to preserve flags and metadata on the call. if (II->getIntrinsicID() == Intrinsic::ldexp) { FastMathFlags FMF = FMFSource.getFastMathFlags() | II->getFastMathFlags(); IRBuilder<>::FastMathFlagGuard FMFGuard(Builder); Builder.setFastMathFlags(FMF); CallInst *New = Builder.CreateCall( II->getCalledFunction(), {Builder.CreateFNeg(II->getArgOperand(0)), II->getArgOperand(1)}); New->copyMetadata(*II); return New; } } return nullptr; } Instruction *InstCombinerImpl::visitFNeg(UnaryOperator &I) { Value *Op = I.getOperand(0); if (Value *V = simplifyFNegInst(Op, I.getFastMathFlags(), getSimplifyQuery().getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldFNegIntoConstant(I, DL)) return X; Value *X, *Y; // If we can ignore the sign of zeros: -(X - Y) --> (Y - X) if (I.hasNoSignedZeros() && match(Op, m_OneUse(m_FSub(m_Value(X), m_Value(Y))))) return BinaryOperator::CreateFSubFMF(Y, X, &I); Value *OneUse; if (!match(Op, m_OneUse(m_Value(OneUse)))) return nullptr; if (Instruction *R = hoistFNegAboveFMulFDiv(OneUse, I)) return replaceInstUsesWith(I, R); // Try to eliminate fneg if at least 1 arm of the select is negated. Value *Cond; if (match(OneUse, m_Select(m_Value(Cond), m_Value(X), m_Value(Y)))) { // Unlike most transforms, this one is not safe to propagate nsz unless // it is present on the original select. We union the flags from the select // and fneg and then remove nsz if needed. auto propagateSelectFMF = [&](SelectInst *S, bool CommonOperand) { S->copyFastMathFlags(&I); if (auto *OldSel = dyn_cast(Op)) { FastMathFlags FMF = I.getFastMathFlags() | OldSel->getFastMathFlags(); S->setFastMathFlags(FMF); if (!OldSel->hasNoSignedZeros() && !CommonOperand && !isGuaranteedNotToBeUndefOrPoison(OldSel->getCondition())) S->setHasNoSignedZeros(false); } }; // -(Cond ? -P : Y) --> Cond ? P : -Y Value *P; if (match(X, m_FNeg(m_Value(P)))) { Value *NegY = Builder.CreateFNegFMF(Y, &I, Y->getName() + ".neg"); SelectInst *NewSel = SelectInst::Create(Cond, P, NegY); propagateSelectFMF(NewSel, P == Y); return NewSel; } // -(Cond ? X : -P) --> Cond ? -X : P if (match(Y, m_FNeg(m_Value(P)))) { Value *NegX = Builder.CreateFNegFMF(X, &I, X->getName() + ".neg"); SelectInst *NewSel = SelectInst::Create(Cond, NegX, P); propagateSelectFMF(NewSel, P == X); return NewSel; } // -(Cond ? X : C) --> Cond ? -X : -C // -(Cond ? C : Y) --> Cond ? -C : -Y if (match(X, m_ImmConstant()) || match(Y, m_ImmConstant())) { Value *NegX = Builder.CreateFNegFMF(X, &I, X->getName() + ".neg"); Value *NegY = Builder.CreateFNegFMF(Y, &I, Y->getName() + ".neg"); SelectInst *NewSel = SelectInst::Create(Cond, NegX, NegY); propagateSelectFMF(NewSel, /*CommonOperand=*/true); return NewSel; } } // fneg (copysign x, y) -> copysign x, (fneg y) if (match(OneUse, m_CopySign(m_Value(X), m_Value(Y)))) { // The source copysign has an additional value input, so we can't propagate // flags the copysign doesn't also have. FastMathFlags FMF = I.getFastMathFlags(); FMF &= cast(OneUse)->getFastMathFlags(); IRBuilder<>::FastMathFlagGuard FMFGuard(Builder); Builder.setFastMathFlags(FMF); Value *NegY = Builder.CreateFNeg(Y); Value *NewCopySign = Builder.CreateCopySign(X, NegY); return replaceInstUsesWith(I, NewCopySign); } return nullptr; } Instruction *InstCombinerImpl::visitFSub(BinaryOperator &I) { if (Value *V = simplifyFSubInst(I.getOperand(0), I.getOperand(1), I.getFastMathFlags(), getSimplifyQuery().getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(I)) return X; if (Instruction *Phi = foldBinopWithPhiOperands(I)) return Phi; // Subtraction from -0.0 is the canonical form of fneg. // fsub -0.0, X ==> fneg X // fsub nsz 0.0, X ==> fneg nsz X // // FIXME This matcher does not respect FTZ or DAZ yet: // fsub -0.0, Denorm ==> +-0 // fneg Denorm ==> -Denorm Value *Op; if (match(&I, m_FNeg(m_Value(Op)))) return UnaryOperator::CreateFNegFMF(Op, &I); if (Instruction *X = foldFNegIntoConstant(I, DL)) return X; if (Instruction *R = foldFBinOpOfIntCasts(I)) return R; Value *X, *Y; Constant *C; Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); // If Op0 is not -0.0 or we can ignore -0.0: Z - (X - Y) --> Z + (Y - X) // Canonicalize to fadd to make analysis easier. // This can also help codegen because fadd is commutative. // Note that if this fsub was really an fneg, the fadd with -0.0 will get // killed later. We still limit that particular transform with 'hasOneUse' // because an fneg is assumed better/cheaper than a generic fsub. if (I.hasNoSignedZeros() || cannotBeNegativeZero(Op0, 0, getSimplifyQuery().getWithInstruction(&I))) { if (match(Op1, m_OneUse(m_FSub(m_Value(X), m_Value(Y))))) { Value *NewSub = Builder.CreateFSubFMF(Y, X, &I); return BinaryOperator::CreateFAddFMF(Op0, NewSub, &I); } } // (-X) - Op1 --> -(X + Op1) if (I.hasNoSignedZeros() && !isa(Op0) && match(Op0, m_OneUse(m_FNeg(m_Value(X))))) { Value *FAdd = Builder.CreateFAddFMF(X, Op1, &I); return UnaryOperator::CreateFNegFMF(FAdd, &I); } if (isa(Op0)) if (SelectInst *SI = dyn_cast(Op1)) if (Instruction *NV = FoldOpIntoSelect(I, SI)) return NV; // X - C --> X + (-C) // But don't transform constant expressions because there's an inverse fold // for X + (-Y) --> X - Y. if (match(Op1, m_ImmConstant(C))) if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) return BinaryOperator::CreateFAddFMF(Op0, NegC, &I); // X - (-Y) --> X + Y if (match(Op1, m_FNeg(m_Value(Y)))) return BinaryOperator::CreateFAddFMF(Op0, Y, &I); // Similar to above, but look through a cast of the negated value: // X - (fptrunc(-Y)) --> X + fptrunc(Y) Type *Ty = I.getType(); if (match(Op1, m_OneUse(m_FPTrunc(m_FNeg(m_Value(Y)))))) return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPTrunc(Y, Ty), &I); // X - (fpext(-Y)) --> X + fpext(Y) if (match(Op1, m_OneUse(m_FPExt(m_FNeg(m_Value(Y)))))) return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPExt(Y, Ty), &I); // Similar to above, but look through fmul/fdiv of the negated value: // Op0 - (-X * Y) --> Op0 + (X * Y) // Op0 - (Y * -X) --> Op0 + (X * Y) if (match(Op1, m_OneUse(m_c_FMul(m_FNeg(m_Value(X)), m_Value(Y))))) { Value *FMul = Builder.CreateFMulFMF(X, Y, &I); return BinaryOperator::CreateFAddFMF(Op0, FMul, &I); } // Op0 - (-X / Y) --> Op0 + (X / Y) // Op0 - (X / -Y) --> Op0 + (X / Y) if (match(Op1, m_OneUse(m_FDiv(m_FNeg(m_Value(X)), m_Value(Y)))) || match(Op1, m_OneUse(m_FDiv(m_Value(X), m_FNeg(m_Value(Y)))))) { Value *FDiv = Builder.CreateFDivFMF(X, Y, &I); return BinaryOperator::CreateFAddFMF(Op0, FDiv, &I); } // Handle special cases for FSub with selects feeding the operation if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1)) return replaceInstUsesWith(I, V); if (I.hasAllowReassoc() && I.hasNoSignedZeros()) { // (Y - X) - Y --> -X if (match(Op0, m_FSub(m_Specific(Op1), m_Value(X)))) return UnaryOperator::CreateFNegFMF(X, &I); // Y - (X + Y) --> -X // Y - (Y + X) --> -X if (match(Op1, m_c_FAdd(m_Specific(Op0), m_Value(X)))) return UnaryOperator::CreateFNegFMF(X, &I); // (X * C) - X --> X * (C - 1.0) if (match(Op0, m_FMul(m_Specific(Op1), m_Constant(C)))) { if (Constant *CSubOne = ConstantFoldBinaryOpOperands( Instruction::FSub, C, ConstantFP::get(Ty, 1.0), DL)) return BinaryOperator::CreateFMulFMF(Op1, CSubOne, &I); } // X - (X * C) --> X * (1.0 - C) if (match(Op1, m_FMul(m_Specific(Op0), m_Constant(C)))) { if (Constant *OneSubC = ConstantFoldBinaryOpOperands( Instruction::FSub, ConstantFP::get(Ty, 1.0), C, DL)) return BinaryOperator::CreateFMulFMF(Op0, OneSubC, &I); } // Reassociate fsub/fadd sequences to create more fadd instructions and // reduce dependency chains: // ((X - Y) + Z) - Op1 --> (X + Z) - (Y + Op1) Value *Z; if (match(Op0, m_OneUse(m_c_FAdd(m_OneUse(m_FSub(m_Value(X), m_Value(Y))), m_Value(Z))))) { Value *XZ = Builder.CreateFAddFMF(X, Z, &I); Value *YW = Builder.CreateFAddFMF(Y, Op1, &I); return BinaryOperator::CreateFSubFMF(XZ, YW, &I); } auto m_FaddRdx = [](Value *&Sum, Value *&Vec) { return m_OneUse(m_Intrinsic(m_Value(Sum), m_Value(Vec))); }; Value *A0, *A1, *V0, *V1; if (match(Op0, m_FaddRdx(A0, V0)) && match(Op1, m_FaddRdx(A1, V1)) && V0->getType() == V1->getType()) { // Difference of sums is sum of differences: // add_rdx(A0, V0) - add_rdx(A1, V1) --> add_rdx(A0, V0 - V1) - A1 Value *Sub = Builder.CreateFSubFMF(V0, V1, &I); Value *Rdx = Builder.CreateIntrinsic(Intrinsic::vector_reduce_fadd, {Sub->getType()}, {A0, Sub}, &I); return BinaryOperator::CreateFSubFMF(Rdx, A1, &I); } if (Instruction *F = factorizeFAddFSub(I, Builder)) return F; // TODO: This performs reassociative folds for FP ops. Some fraction of the // functionality has been subsumed by simple pattern matching here and in // InstSimplify. We should let a dedicated reassociation pass handle more // complex pattern matching and remove this from InstCombine. if (Value *V = FAddCombine(Builder).simplify(&I)) return replaceInstUsesWith(I, V); // (X - Y) - Op1 --> X - (Y + Op1) if (match(Op0, m_OneUse(m_FSub(m_Value(X), m_Value(Y))))) { Value *FAdd = Builder.CreateFAddFMF(Y, Op1, &I); return BinaryOperator::CreateFSubFMF(X, FAdd, &I); } } return nullptr; }