//===- 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 #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.buffer[0]); } const APFloat *getFpValPtr() const { return reinterpret_cast(&FpValBuf.buffer[0]); } 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) { enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven; 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]; // Points to the constant addend of the resulting simplified expression. // 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 supper-expr(s) will potentially reveal some optimization // opportunities in super-expr(s). const FAddend *ConstAdd = nullptr; // 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(); 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 (Val) { if (!R.isZero()) { SimpVect.push_back(&R); } } else { // Don't push constant addend at this time. It will be the last element // of . ConstAdd = &R; } } } assert((NextTmpIdx <= array_lengthof(TmpResult) + 1) && "out-of-bound access"); if (ConstAdd) SimpVect.push_back(ConstAdd); 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; // The number of addends in the form of "(-1)*x". unsigned NegOpndNum = 0; // 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(); if (CE.isMinusOne() || CE.isMinusTwo()) NegOpndNum++; // 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->countTrailingZeros() == 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_OneUse(m_ZExt(m_NUWAdd(m_Value(X), m_APInt(C2))))) && C1->isNegative() && C1->sge(-C2->sext(C1->getBitWidth()))) { Constant *NewC = ConstantInt::get(X->getType(), *C2 + C1->trunc(C2->getBitWidth())); return new ZExtInst(Builder.CreateNUWAdd(X, NewC), Ty); } // More general combining of constants in the wide type. // (sext (X +nsw NarrowC)) + C --> (sext X) + (sext(NarrowC) + C) Constant *NarrowC; if (match(Op0, m_OneUse(m_SExt(m_NSWAdd(m_Value(X), m_Constant(NarrowC)))))) { Constant *WideC = ConstantExpr::getSExt(NarrowC, Ty); Constant *NewC = ConstantExpr::getAdd(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_NUWAdd(m_Value(X), m_Constant(NarrowC)))))) { Constant *WideC = ConstantExpr::getZExt(NarrowC, Ty); Constant *NewC = ConstantExpr::getAdd(WideC, Op1C); Value *WideX = Builder.CreateZExt(X, Ty); return BinaryOperator::CreateAdd(WideX, NewC); } return nullptr; } Instruction *InstCombiner::foldAddWithConstant(BinaryOperator &Add) { Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1); Constant *Op1C; if (!match(Op1, m_Constant(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, 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, SubOne(Op1C), Op1); // ~X + C --> (C-1) - X if (match(Op0, m_Not(m_Value(X)))) return BinaryOperator::CreateSub(SubOne(Op1C), X); const APInt *C; if (!match(Op1, m_APInt(C))) return nullptr; // (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 Type *Ty = Add.getType(); 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 (C->isOneValue() && 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)); } } 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. Value *InstCombiner::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"); } } } 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; } Instruction * InstCombiner::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()); } Instruction *InstCombiner::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; // (A*B)+(A*C) -> A*(B+C) etc if (Value *V = SimplifyUsingDistributiveLaws(I)) return replaceInstUsesWith(I, V); if (Instruction *X = foldAddWithConstant(I)) return X; if (Instruction *X = foldNoWrapAdd(I, Builder)) return X; // FIXME: This should be moved into the above helper function to allow these // transforms for general constant or constant splat vectors. Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); Type *Ty = I.getType(); if (ConstantInt *CI = dyn_cast(RHS)) { Value *XorLHS = nullptr; ConstantInt *XorRHS = nullptr; if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) { unsigned TySizeBits = Ty->getScalarSizeInBits(); const APInt &RHSVal = CI->getValue(); unsigned ExtendAmt = 0; // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext. // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext. if (XorRHS->getValue() == -RHSVal) { if (RHSVal.isPowerOf2()) ExtendAmt = TySizeBits - RHSVal.logBase2() - 1; else if (XorRHS->getValue().isPowerOf2()) ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1; } if (ExtendAmt) { APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt); if (!MaskedValueIsZero(XorLHS, Mask, 0, &I)) ExtendAmt = 0; } if (ExtendAmt) { Constant *ShAmt = ConstantInt::get(Ty, ExtendAmt); Value *NewShl = Builder.CreateShl(XorLHS, ShAmt, "sext"); return BinaryOperator::CreateAShr(NewShl, ShAmt); } // If this is a xor that was canonicalized from a sub, turn it back into // a sub and fuse this add with it. if (LHS->hasOneUse() && (XorRHS->getValue()+1).isPowerOf2()) { KnownBits LHSKnown = computeKnownBits(XorLHS, 0, &I); if ((XorRHS->getValue() | LHSKnown.Zero).isAllOnesValue()) return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI), XorLHS); } // (X + signmask) + C could have gotten canonicalized to (X^signmask) + C, // transform them into (X + (signmask ^ C)) if (XorRHS->getValue().isSignMask()) return BinaryOperator::CreateAdd(XorLHS, ConstantExpr::getXor(XorRHS, CI)); } } 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 return BinaryOperator::CreateSub(RHS, A); } // 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); // X % C0 + (( X / C0 ) % C1) * C0 => X % (C0 * C1) if (Value *V = SimplifyAddWithRemainder(I)) return replaceInstUsesWith(I, V); // A+B --> A|B iff A and B have no bits set in common. if (haveNoCommonBitsSet(LHS, RHS, DL, &AC, &I, &DT)) return BinaryOperator::CreateOr(LHS, RHS); // FIXME: We already did a check for ConstantInt RHS above this. // FIXME: Is this pattern covered by another fold? No regression tests fail on // removal. if (ConstantInt *CRHS = dyn_cast(RHS)) { // (X & FF00) + xx00 -> (X+xx00) & FF00 Value *X; ConstantInt *C2; if (LHS->hasOneUse() && match(LHS, m_And(m_Value(X), m_ConstantInt(C2))) && CRHS->getValue() == (CRHS->getValue() & C2->getValue())) { // See if all bits from the first bit set in the Add RHS up are included // in the mask. First, get the rightmost bit. const APInt &AddRHSV = CRHS->getValue(); // Form a mask of all bits from the lowest bit added through the top. APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1)); // See if the and mask includes all of these bits. APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue()); if (AddRHSHighBits == AddRHSHighBitsAnd) { // Okay, the xform is safe. Insert the new add pronto. Value *NewAdd = Builder.CreateAdd(X, CRHS, LHS->getName()); return BinaryOperator::CreateAnd(NewAdd, C2); } } } // add (select X 0 (sub n A)) A --> select X A n { SelectInst *SI = dyn_cast(LHS); Value *A = RHS; if (!SI) { SI = dyn_cast(RHS); A = LHS; } if (SI && SI->hasOneUse()) { Value *TV = SI->getTrueValue(); Value *FV = SI->getFalseValue(); Value *N; // Can we fold the add into the argument of the select? // We check both true and false select arguments for a matching subtract. if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A)))) // Fold the add into the true select value. return SelectInst::Create(SI->getCondition(), N, A); if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A)))) // Fold the add into the false select value. return SelectInst::Create(SI->getCondition(), A, N); } } 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; } // TODO(jingyue): Consider willNotOverflowSignedAdd and // willNotOverflowUnsignedAdd to reduce the number of invocations of // computeKnownBits. bool Changed = false; if (!I.hasNoSignedWrap() && willNotOverflowSignedAdd(LHS, RHS, I)) { Changed = true; I.setHasNoSignedWrap(true); } if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedAdd(LHS, RHS, 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; 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); Value *X, *Y, *Z; bool IsFMul; if ((match(Op0, m_OneUse(m_FMul(m_Value(X), m_Value(Z)))) && match(Op1, m_OneUse(m_c_FMul(m_Value(Y), m_Specific(Z))))) || (match(Op0, m_OneUse(m_FMul(m_Value(Z), m_Value(X)))) && match(Op1, m_OneUse(m_c_FMul(m_Value(Y), m_Specific(Z)))))) IsFMul = true; else if (match(Op0, m_OneUse(m_FDiv(m_Value(X), m_Value(Z)))) && match(Op1, m_OneUse(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 *InstCombiner::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 *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. Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); if (SIToFPInst *LHSConv = dyn_cast(LHS)) { Value *LHSIntVal = LHSConv->getOperand(0); Type *FPType = LHSConv->getType(); // TODO: This check is overly conservative. In many cases known bits // analysis can tell us that the result of the addition has less significant // bits than the integer type can hold. auto IsValidPromotion = [](Type *FTy, Type *ITy) { Type *FScalarTy = FTy->getScalarType(); Type *IScalarTy = ITy->getScalarType(); // Do we have enough bits in the significand to represent the result of // the integer addition? unsigned MaxRepresentableBits = APFloat::semanticsPrecision(FScalarTy->getFltSemantics()); return IScalarTy->getIntegerBitWidth() <= MaxRepresentableBits; }; // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst)) // ... if the constant fits in the integer value. This is useful for things // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer // requires a constant pool load, and generally allows the add to be better // instcombined. if (ConstantFP *CFP = dyn_cast(RHS)) if (IsValidPromotion(FPType, LHSIntVal->getType())) { Constant *CI = ConstantExpr::getFPToSI(CFP, LHSIntVal->getType()); if (LHSConv->hasOneUse() && ConstantExpr::getSIToFP(CI, I.getType()) == CFP && willNotOverflowSignedAdd(LHSIntVal, CI, I)) { // Insert the new integer add. Value *NewAdd = Builder.CreateNSWAdd(LHSIntVal, CI, "addconv"); return new SIToFPInst(NewAdd, I.getType()); } } // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y)) if (SIToFPInst *RHSConv = dyn_cast(RHS)) { Value *RHSIntVal = RHSConv->getOperand(0); // It's enough to check LHS types only because we require int types to // be the same for this transform. if (IsValidPromotion(FPType, LHSIntVal->getType())) { // Only do this if x/y have the same type, if at least one of them has a // single use (so we don't increase the number of int->fp conversions), // and if the integer add will not overflow. if (LHSIntVal->getType() == RHSIntVal->getType() && (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && willNotOverflowSignedAdd(LHSIntVal, RHSIntVal, I)) { // Insert the new integer add. Value *NewAdd = Builder.CreateNSWAdd(LHSIntVal, RHSIntVal, "addconv"); return new SIToFPInst(NewAdd, I.getType()); } } } } // 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 (Value *V = FAddCombine(Builder).simplify(&I)) return replaceInstUsesWith(I, V); } 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 *InstCombiner::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; // For now we require one side to be the base pointer "A" or a constant // GEP derived from it. if (GEPOperator *LHSGEP = dyn_cast(LHS)) { // (gep X, ...) - X if (LHSGEP->getOperand(0) == RHS) { GEP1 = LHSGEP; Swapped = false; } else if (GEPOperator *RHSGEP = dyn_cast(RHS)) { // (gep X, ...) - (gep X, ...) if (LHSGEP->getOperand(0)->stripPointerCasts() == RHSGEP->getOperand(0)->stripPointerCasts()) { GEP2 = RHSGEP; GEP1 = LHSGEP; Swapped = false; } } } if (GEPOperator *RHSGEP = dyn_cast(RHS)) { // X - (gep X, ...) if (RHSGEP->getOperand(0) == LHS) { GEP1 = RHSGEP; Swapped = true; } else if (GEPOperator *LHSGEP = dyn_cast(LHS)) { // (gep X, ...) - (gep X, ...) if (RHSGEP->getOperand(0)->stripPointerCasts() == LHSGEP->getOperand(0)->stripPointerCasts()) { GEP2 = LHSGEP; GEP1 = RHSGEP; Swapped = true; } } } if (!GEP1) // No GEP found. return nullptr; if (GEP2) { // (gep X, ...) - (gep X, ...) // // Avoid duplicating the arithmetic if there are more than one non-constant // indices between the two GEPs and either GEP has a non-constant index and // multiple users. If zero non-constant index, the result is a constant and // there is no duplication. If one non-constant index, the result is an add // or sub with a constant, which is no larger than the original code, and // there's no duplicated arithmetic, even if either GEP has multiple // users. If more than one non-constant indices combined, as long as the GEP // with at least one non-constant index doesn't have multiple users, there // is no duplication. unsigned NumNonConstantIndices1 = GEP1->countNonConstantIndices(); unsigned NumNonConstantIndices2 = GEP2->countNonConstantIndices(); if (NumNonConstantIndices1 + NumNonConstantIndices2 > 1 && ((NumNonConstantIndices1 > 0 && !GEP1->hasOneUse()) || (NumNonConstantIndices2 > 0 && !GEP2->hasOneUse()))) { return nullptr; } } // Emit the offset of the GEP and an intptr_t. Value *Result = EmitGEPOffset(GEP1); // If this is a single inbounds GEP and the original sub was nuw, // then the final multiplication is also nuw. We match an extra add zero // here, because that's what EmitGEPOffset() generates. Instruction *I; if (IsNUW && !GEP2 && !Swapped && GEP1->isInBounds() && match(Result, m_Add(m_Instruction(I), m_Zero())) && I->getOpcode() == Instruction::Mul) I->setHasNoUnsignedWrap(); // If we had a constant expression GEP on the other side offsetting the // pointer, subtract it from the offset we have. if (GEP2) { Value *Offset = EmitGEPOffset(GEP2); Result = Builder.CreateSub(Result, Offset); } // 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); } Instruction *InstCombiner::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; // (A*B)-(A*C) -> A*(B-C) etc if (Value *V = SimplifyUsingDistributiveLaws(I)) return replaceInstUsesWith(I, V); // If this is a 'B = x-(-A)', change to B = x+A. Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 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; } 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) - (~Y) --> Y - X Value *X, *Y; if (match(Op0, m_Not(m_Value(X))) && match(Op1, m_Not(m_Value(Y)))) return BinaryOperator::CreateSub(Y, X); // (X + -1) - Y --> ~Y + X if (match(Op0, m_OneUse(m_Add(m_Value(X), m_AllOnes())))) return BinaryOperator::CreateAdd(Builder.CreateNot(Op1), X); // Y - (X + 1) --> ~X + Y if (match(Op1, m_OneUse(m_Add(m_Value(X), m_One())))) return BinaryOperator::CreateAdd(Builder.CreateNot(X), Op0); // Y - ~X --> (X + 1) + Y if (match(Op1, m_OneUse(m_Not(m_Value(X))))) { return BinaryOperator::CreateAdd( Builder.CreateAdd(Op0, ConstantInt::get(I.getType(), 1)), X); } if (Constant *C = dyn_cast(Op0)) { // -f(x) -> f(-x) if possible. if (match(C, m_Zero())) if (Value *Neg = freelyNegateValue(Op1)) return replaceInstUsesWith(I, Neg); 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, 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, AddOne(C), C); // C - ~X == X + (1+C) if (match(Op1, m_Not(m_Value(X)))) return BinaryOperator::CreateAdd(X, 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_Constant(C2), m_Value(X)))) return BinaryOperator::CreateAdd(X, ConstantExpr::getSub(C, C2)); // C-(X+C2) --> (C-C2)-X if (match(Op1, m_Add(m_Value(X), m_Constant(C2)))) return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X); } const APInt *Op0C; if (match(Op0, m_APInt(Op0C))) { if (Op0C->isNullValue() && Op1->hasOneUse()) { Value *LHS, *RHS; SelectPatternFlavor SPF = matchSelectPattern(Op1, LHS, RHS).Flavor; if (SPF == SPF_ABS || SPF == SPF_NABS) { // This is a negate of an ABS/NABS pattern. Just swap the operands // of the select. cast(Op1)->swapValues(); // Don't swap prof metadata, we didn't change the branch behavior. return replaceInstUsesWith(I, Op1); } } // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known // zero. if (Op0C->isMask()) { KnownBits RHSKnown = computeKnownBits(Op1, 0, &I); if ((*Op0C | RHSKnown.Zero).isAllOnesValue()) return BinaryOperator::CreateXor(Op1, Op0); } } { 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 (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))); } } { // 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")); if (Op1->hasOneUse()) { Value *Y = nullptr, *Z = nullptr; Constant *C = nullptr; // (X - (Y - Z)) --> (X + (Z - Y)). if (match(Op1, m_Sub(m_Value(Y), m_Value(Z)))) return BinaryOperator::CreateAdd(Op0, Builder.CreateSub(Z, Y, Op1->getName())); // Subtracting -1/0 is the same as adding 1/0: // sub [nsw] Op0, sext(bool Y) -> add [nsw] Op0, zext(bool Y) // 'nuw' is dropped in favor of the canonical form. if (match(Op1, m_SExt(m_Value(Y))) && Y->getType()->getScalarSizeInBits() == 1) { Value *Zext = Builder.CreateZExt(Y, I.getType()); BinaryOperator *Add = BinaryOperator::CreateAdd(Op0, Zext); Add->setHasNoSignedWrap(I.hasNoSignedWrap()); return Add; } // sub [nsw] X, zext(bool Y) -> add [nsw] X, sext(bool Y) // 'nuw' is dropped in favor of the canonical form. if (match(Op1, m_ZExt(m_Value(Y))) && Y->getType()->isIntOrIntVectorTy(1)) { Value *Sext = Builder.CreateSExt(Y, I.getType()); BinaryOperator *Add = BinaryOperator::CreateAdd(Op0, Sext); Add->setHasNoSignedWrap(I.hasNoSignedWrap()); return Add; } // X - A*-B -> X + A*B // X - -A*B -> X + A*B Value *A, *B; if (match(Op1, m_c_Mul(m_Value(A), m_Neg(m_Value(B))))) return BinaryOperator::CreateAdd(Op0, Builder.CreateMul(A, B)); // X - A*C -> X + A*-C // No need to handle commuted multiply because multiply handling will // ensure constant will be move to the right hand side. if (match(Op1, m_Mul(m_Value(A), m_Constant(C))) && !isa(C)) { Value *NewMul = Builder.CreateMul(A, ConstantExpr::getNeg(C)); return BinaryOperator::CreateAdd(Op0, NewMul); } } { // ~A - Min/Max(~A, O) -> Max/Min(A, ~O) - A // ~A - Min/Max(O, ~A) -> Max/Min(A, ~O) - A // Min/Max(~A, O) - ~A -> A - Max/Min(A, ~O) // Min/Max(O, ~A) - ~A -> A - Max/Min(A, ~O) // So long as O here is freely invertible, this will be neutral or a win. Value *LHS, *RHS, *A; Value *NotA = Op0, *MinMax = Op1; SelectPatternFlavor SPF = matchSelectPattern(MinMax, LHS, RHS).Flavor; if (!SelectPatternResult::isMinOrMax(SPF)) { NotA = Op1; MinMax = Op0; SPF = matchSelectPattern(MinMax, LHS, RHS).Flavor; } if (SelectPatternResult::isMinOrMax(SPF) && match(NotA, m_Not(m_Value(A))) && (NotA == LHS || NotA == RHS)) { if (NotA == LHS) std::swap(LHS, RHS); // LHS is now O above and expected to have at least 2 uses (the min/max) // NotA is epected to have 2 uses from the min/max and 1 from the sub. if (isFreeToInvert(LHS, !LHS->hasNUsesOrMore(3)) && !NotA->hasNUsesOrMore(4)) { // Note: We don't generate the inverse max/min, just create the not of // it and let other folds do the rest. Value *Not = Builder.CreateNot(MinMax); if (NotA == Op0) return BinaryOperator::CreateSub(Not, A); else return BinaryOperator::CreateSub(A, 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(); if (match(Op1, m_AShr(m_Value(A), m_APInt(ShAmt))) && Op1->hasNUses(2) && *ShAmt == Ty->getScalarSizeInBits() - 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 *Cmp = Builder.CreateICmpSLT(A, ConstantInt::getNullValue(Ty)); // Copy the nuw/nsw flags from the sub to the negate. Value *Neg = Builder.CreateNeg(A, "", I.hasNoUnsignedWrap(), I.hasNoSignedWrap()); return SelectInst::Create(Cmp, Neg, A); } if (Instruction *V = canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(I)) return V; 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; } /// 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) { Value *X; Constant *C; // Fold negation into constant operand. This is limited with one-use because // fneg is assumed better for analysis and cheaper in codegen than fmul/fdiv. // -(X * C) --> X * (-C) // FIXME: It's arguable whether these should be m_OneUse or not. The current // belief is that the FNeg allows for better reassociation opportunities. if (match(&I, m_FNeg(m_OneUse(m_FMul(m_Value(X), m_Constant(C)))))) return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I); // -(X / C) --> X / (-C) if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Value(X), m_Constant(C)))))) return BinaryOperator::CreateFDivFMF(X, ConstantExpr::getFNeg(C), &I); // -(C / X) --> (-C) / X if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Constant(C), m_Value(X)))))) return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I); // 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(&I, m_FNeg(m_OneUse(m_FAdd(m_Value(X), m_Constant(C)))))) return BinaryOperator::CreateFSubFMF(ConstantExpr::getFNeg(C), X, &I); return nullptr; } static Instruction *hoistFNegAboveFMulFDiv(Instruction &I, InstCombiner::BuilderTy &Builder) { Value *FNeg; if (!match(&I, m_FNeg(m_Value(FNeg)))) return nullptr; Value *X, *Y; if (match(FNeg, m_OneUse(m_FMul(m_Value(X), m_Value(Y))))) return BinaryOperator::CreateFMulFMF(Builder.CreateFNegFMF(X, &I), Y, &I); if (match(FNeg, m_OneUse(m_FDiv(m_Value(X), m_Value(Y))))) return BinaryOperator::CreateFDivFMF(Builder.CreateFNegFMF(X, &I), Y, &I); return nullptr; } Instruction *InstCombiner::visitFNeg(UnaryOperator &I) { Value *Op = I.getOperand(0); if (Value *V = SimplifyFNegInst(Op, I.getFastMathFlags(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldFNegIntoConstant(I)) 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); if (Instruction *R = hoistFNegAboveFMulFDiv(I, Builder)) return R; return nullptr; } Instruction *InstCombiner::visitFSub(BinaryOperator &I) { if (Value *V = SimplifyFSubInst(I.getOperand(0), I.getOperand(1), I.getFastMathFlags(), SQ.getWithInstruction(&I))) return replaceInstUsesWith(I, V); if (Instruction *X = foldVectorBinop(I)) return X; // 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)) return X; if (Instruction *R = hoistFNegAboveFMulFDiv(I, Builder)) 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, SQ.TLI)) { 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_Constant(C)) && !isa(Op1)) return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &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)))) { Constant *CSubOne = ConstantExpr::getFSub(C, ConstantFP::get(Ty, 1.0)); return BinaryOperator::CreateFMulFMF(Op1, CSubOne, &I); } // X - (X * C) --> X * (1.0 - C) if (match(Op1, m_FMul(m_Specific(Op0), m_Constant(C)))) { Constant *OneSubC = ConstantExpr::getFSub(ConstantFP::get(Ty, 1.0), C); return BinaryOperator::CreateFMulFMF(Op0, OneSubC, &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; }