//===- InstCombineAddSub.cpp ----------------------------------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the visit functions for add, fadd, sub, and fsub. // //===----------------------------------------------------------------------===// #include "InstCombine.h" #include "llvm/ADT/STLExtras.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/GetElementPtrTypeIterator.h" #include "llvm/IR/PatternMatch.h" 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 uncessary 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() : IsFp(false), BufHasFpVal(false), IntVal(0) {} ~FAddendCoef(); 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; // 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 &A); void operator*=(const FAddendCoef &S); 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(void) { return reinterpret_cast(&FpValBuf.buffer[0]); } const APFloat *getFpValPtr(void) const { return reinterpret_cast(&FpValBuf.buffer[0]); } const APFloat &getFpVal(void) const { assert(IsFp && BufHasFpVal && "Incorret state"); return *getFpValPtr(); } APFloat &getFpVal(void) { 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); private: bool IsFp; // True iff FpValBuf contains an instance of APFloat. bool BufHasFpVal; // 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; 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() { Val = nullptr; } Value *getSymVal (void) const { return Val; } const FAddendCoef &getCoef(void) 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; void operator+=(const FAddend &T) { assert((Val == T.Val) && "Symbolic-values disagree"); Coeff += T.Coeff; } private: void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; } // This addend has the value of "Coeff * Val". Value *Val; 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), Instr(nullptr) {} Value *simplify(Instruction *FAdd); private: typedef SmallVector AddendVect; Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota); Value *performFactorization(Instruction *I); /// 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 *createFDiv(Value *Opnd0, Value *Opnd1); Value *createFNeg(Value *V); Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota); void createInstPostProc(Instruction *NewInst, bool NoNumber = false); InstCombiner::BuilderTy *Builder; Instruction *Instr; private: // Debugging stuff are clustered here. #ifndef NDEBUG unsigned CreateInstrNum; void initCreateInstNum() { CreateInstrNum = 0; } void incCreateInstNum() { CreateInstrNum++; } #else void initCreateInstNum() {} void incCreateInstNum() {} #endif }; } //===----------------------------------------------------------------------===// // // 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) { enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven; if (isInt() == That.isInt()) { if (isInt()) IntVal -= That.IntVal; else getFpVal().subtract(That.getFpVal(), RndMode); return; } if (isInt()) { const APFloat &T = That.getFpVal(); convertToFpType(T.getSemantics()); getFpVal().subtract(T, RndMode); return; } APFloat &T = getFpVal(); T.subtract(createAPFloatFromInt(T.getSemantics(), 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); return; } 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; } // Try to perform following optimization on the input instruction I. Return the // simplified expression if was successful; otherwise, return 0. // // Instruction "I" is Simplified into // ------------------------------------------------------- // (x * y) +/- (x * z) x * (y +/- z) // (y / x) +/- (z / x) (y +/- z) / x // Value *FAddCombine::performFactorization(Instruction *I) { assert((I->getOpcode() == Instruction::FAdd || I->getOpcode() == Instruction::FSub) && "Expect add/sub"); Instruction *I0 = dyn_cast(I->getOperand(0)); Instruction *I1 = dyn_cast(I->getOperand(1)); if (!I0 || !I1 || I0->getOpcode() != I1->getOpcode()) return nullptr; bool isMpy = false; if (I0->getOpcode() == Instruction::FMul) isMpy = true; else if (I0->getOpcode() != Instruction::FDiv) return nullptr; Value *Opnd0_0 = I0->getOperand(0); Value *Opnd0_1 = I0->getOperand(1); Value *Opnd1_0 = I1->getOperand(0); Value *Opnd1_1 = I1->getOperand(1); // Input Instr I Factor AddSub0 AddSub1 // ---------------------------------------------- // (x*y) +/- (x*z) x y z // (y/x) +/- (z/x) x y z // Value *Factor = nullptr; Value *AddSub0 = nullptr, *AddSub1 = nullptr; if (isMpy) { if (Opnd0_0 == Opnd1_0 || Opnd0_0 == Opnd1_1) Factor = Opnd0_0; else if (Opnd0_1 == Opnd1_0 || Opnd0_1 == Opnd1_1) Factor = Opnd0_1; if (Factor) { AddSub0 = (Factor == Opnd0_0) ? Opnd0_1 : Opnd0_0; AddSub1 = (Factor == Opnd1_0) ? Opnd1_1 : Opnd1_0; } } else if (Opnd0_1 == Opnd1_1) { Factor = Opnd0_1; AddSub0 = Opnd0_0; AddSub1 = Opnd1_0; } if (!Factor) return nullptr; FastMathFlags Flags; Flags.setUnsafeAlgebra(); if (I0) Flags &= I->getFastMathFlags(); if (I1) Flags &= I->getFastMathFlags(); // Create expression "NewAddSub = AddSub0 +/- AddsSub1" Value *NewAddSub = (I->getOpcode() == Instruction::FAdd) ? createFAdd(AddSub0, AddSub1) : createFSub(AddSub0, AddSub1); if (ConstantFP *CFP = dyn_cast(NewAddSub)) { const APFloat &F = CFP->getValueAPF(); if (!F.isNormal()) return nullptr; } else if (Instruction *II = dyn_cast(NewAddSub)) II->setFastMathFlags(Flags); if (isMpy) { Value *RI = createFMul(Factor, NewAddSub); if (Instruction *II = dyn_cast(RI)) II->setFastMathFlags(Flags); return RI; } Value *RI = createFDiv(NewAddSub, Factor); if (Instruction *II = dyn_cast(RI)) II->setFastMathFlags(Flags); return RI; } Value *FAddCombine::simplify(Instruction *I) { assert(I->hasUnsafeAlgebra() && "Should be in unsafe mode"); // 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; } // step 6: Try factorization as the last resort, return performFactorization(I); } 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 (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end(); I != E; I++) { bool NeedNeg; Value *V = createAddendVal(**I, 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 *Zero = cast(ConstantFP::get(V->getType(), 0.0)); Value *NewV = createFSub(Zero, 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; } Value *FAddCombine::createFDiv(Value *Opnd0, Value *Opnd1) { Value *V = Builder->CreateFDiv(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 (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end(); I != E; I++) { const FAddend *Opnd = *I; if (Opnd->isConstant()) 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++; } if (NegOpndNum == OpndNum) 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())); } // If one of the operands only has one non-zero bit, and if the other // operand has a known-zero bit in a more significant place than it (not // including the sign bit) the ripple may go up to and fill the zero, but // won't change the sign. For example, (X & ~4) + 1. static bool checkRippleForAdd(const APInt &Op0KnownZero, const APInt &Op1KnownZero) { APInt Op1MaybeOne = ~Op1KnownZero; // Make sure that one of the operand has at most one bit set to 1. if (Op1MaybeOne.countPopulation() != 1) return false; // Find the most significant known 0 other than the sign bit. int BitWidth = Op0KnownZero.getBitWidth(); APInt Op0KnownZeroTemp(Op0KnownZero); Op0KnownZeroTemp.clearBit(BitWidth - 1); int Op0ZeroPosition = BitWidth - Op0KnownZeroTemp.countLeadingZeros() - 1; int Op1OnePosition = BitWidth - Op1MaybeOne.countLeadingZeros() - 1; assert(Op1OnePosition >= 0); // This also covers the case of no known zero, since in that case // Op0ZeroPosition is -1. return Op0ZeroPosition >= Op1OnePosition; } /// WillNotOverflowSignedAdd - Return true if we can prove that: /// (sext (add LHS, RHS)) === (add (sext LHS), (sext RHS)) /// This basically requires proving that the add in the original type would not /// overflow to change the sign bit or have a carry out. /// TODO: Handle this for Vectors. bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) { // There are different heuristics we can use for this. Here are some simple // ones. // If LHS and RHS each have at least two sign bits, the addition will look // like // // XX..... + // YY..... // // If the carry into the most significant position is 0, X and Y can't both // be 1 and therefore the carry out of the addition is also 0. // // If the carry into the most significant position is 1, X and Y can't both // be 0 and therefore the carry out of the addition is also 1. // // Since the carry into the most significant position is always equal to // the carry out of the addition, there is no signed overflow. if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1) return true; if (IntegerType *IT = dyn_cast(LHS->getType())) { int BitWidth = IT->getBitWidth(); APInt LHSKnownZero(BitWidth, 0); APInt LHSKnownOne(BitWidth, 0); computeKnownBits(LHS, LHSKnownZero, LHSKnownOne); APInt RHSKnownZero(BitWidth, 0); APInt RHSKnownOne(BitWidth, 0); computeKnownBits(RHS, RHSKnownZero, RHSKnownOne); // Addition of two 2's compliment numbers having opposite signs will never // overflow. if ((LHSKnownOne[BitWidth - 1] && RHSKnownZero[BitWidth - 1]) || (LHSKnownZero[BitWidth - 1] && RHSKnownOne[BitWidth - 1])) return true; // Check if carry bit of addition will not cause overflow. if (checkRippleForAdd(LHSKnownZero, RHSKnownZero)) return true; if (checkRippleForAdd(RHSKnownZero, LHSKnownZero)) return true; } return false; } /// WillNotOverflowUnsignedAdd - Return true if we can prove that: /// (zext (add LHS, RHS)) === (add (zext LHS), (zext RHS)) bool InstCombiner::WillNotOverflowUnsignedAdd(Value *LHS, Value *RHS) { // There are different heuristics we can use for this. Here is a simple one. // If the sign bit of LHS and that of RHS are both zero, no unsigned wrap. bool LHSKnownNonNegative, LHSKnownNegative; bool RHSKnownNonNegative, RHSKnownNegative; ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, DL, 0); ComputeSignBit(RHS, RHSKnownNonNegative, RHSKnownNegative, DL, 0); if (LHSKnownNonNegative && RHSKnownNonNegative) return true; return false; } // 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)) if C is odd // TODO: XOR(AND(Z, C), (C + 1)) == NEG(OR(Z, ~C)) if C is even 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 (C1->countTrailingZeros() == 0) { // if C1 is ODD and // 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)) if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && (*C1 == *C2)) { Value *NewOr = Builder->CreateOr(Z, ~(*C1)); return Builder->CreateSub(RHS, NewOr, "sub"); } } } } return nullptr; } Instruction *InstCombiner::visitAdd(BinaryOperator &I) { bool Changed = SimplifyAssociativeOrCommutative(I); Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); if (Value *V = SimplifyVectorOp(I)) return ReplaceInstUsesWith(I, V); if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(), I.hasNoUnsignedWrap(), DL)) return ReplaceInstUsesWith(I, V); // (A*B)+(A*C) -> A*(B+C) etc if (Value *V = SimplifyUsingDistributiveLaws(I)) return ReplaceInstUsesWith(I, V); if (ConstantInt *CI = dyn_cast(RHS)) { // X + (signbit) --> X ^ signbit const APInt &Val = CI->getValue(); if (Val.isSignBit()) return BinaryOperator::CreateXor(LHS, RHS); // See if SimplifyDemandedBits can simplify this. This handles stuff like // (X & 254)+1 -> (X&254)|1 if (SimplifyDemandedInstructionBits(I)) return &I; // zext(bool) + C -> bool ? C + 1 : C if (ZExtInst *ZI = dyn_cast(LHS)) if (ZI->getSrcTy()->isIntegerTy(1)) return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI); Value *XorLHS = nullptr; ConstantInt *XorRHS = nullptr; if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) { uint32_t TySizeBits = I.getType()->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)) ExtendAmt = 0; } if (ExtendAmt) { Constant *ShAmt = ConstantInt::get(I.getType(), 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()) { IntegerType *IT = cast(I.getType()); APInt LHSKnownOne(IT->getBitWidth(), 0); APInt LHSKnownZero(IT->getBitWidth(), 0); computeKnownBits(XorLHS, LHSKnownZero, LHSKnownOne); if ((XorRHS->getValue() | LHSKnownZero).isAllOnesValue()) return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI), XorLHS); } // (X + signbit) + C could have gotten canonicalized to (X ^ signbit) + C, // transform them into (X + (signbit ^ C)) if (XorRHS->getValue().isSignBit()) return BinaryOperator::CreateAdd(XorLHS, ConstantExpr::getXor(XorRHS, CI)); } } if (isa(RHS) && isa(LHS)) if (Instruction *NV = FoldOpIntoPhi(I)) return NV; if (I.getType()->getScalarType()->isIntegerTy(1)) return BinaryOperator::CreateXor(LHS, RHS); // X + X --> X << 1 if (LHS == RHS) { BinaryOperator *New = BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1)); New->setHasNoSignedWrap(I.hasNoSignedWrap()); New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); return New; } // -A + B --> B - A // -A + -B --> -(A + B) if (Value *LHSV = dyn_castNegVal(LHS)) { if (!isa(RHS)) if (Value *RHSV = dyn_castNegVal(RHS)) { Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum"); return BinaryOperator::CreateNeg(NewAdd); } return BinaryOperator::CreateSub(RHS, LHSV); } // A + -B --> A - B if (!isa(RHS)) if (Value *V = dyn_castNegVal(RHS)) return BinaryOperator::CreateSub(LHS, V); if (Value *V = checkForNegativeOperand(I, Builder)) return ReplaceInstUsesWith(I, V); // A+B --> A|B iff A and B have no bits set in common. if (IntegerType *IT = dyn_cast(I.getType())) { APInt LHSKnownOne(IT->getBitWidth(), 0); APInt LHSKnownZero(IT->getBitWidth(), 0); computeKnownBits(LHS, LHSKnownZero, LHSKnownOne); if (LHSKnownZero != 0) { APInt RHSKnownOne(IT->getBitWidth(), 0); APInt RHSKnownZero(IT->getBitWidth(), 0); computeKnownBits(RHS, RHSKnownZero, RHSKnownOne); // No bits in common -> bitwise or. if ((LHSKnownZero|RHSKnownZero).isAllOnesValue()) return BinaryOperator::CreateOr(LHS, RHS); } } if (Constant *CRHS = dyn_cast(RHS)) { Value *X; if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X return BinaryOperator::CreateSub(SubOne(CRHS), X); } 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); } } // Try to fold constant add into select arguments. if (SelectInst *SI = dyn_cast(LHS)) if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; } // 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); } } // Check for (add (sext x), y), see if we can merge this into an // integer add followed by a sext. if (SExtInst *LHSConv = dyn_cast(LHS)) { // (add (sext x), cst) --> (sext (add x, cst')) if (ConstantInt *RHSC = dyn_cast(RHS)) { Constant *CI = ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType()); if (LHSConv->hasOneUse() && ConstantExpr::getSExt(CI, I.getType()) == RHSC && WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) { // Insert the new, smaller add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), CI, "addconv"); return new SExtInst(NewAdd, I.getType()); } } // (add (sext x), (sext y)) --> (sext (add int x, y)) if (SExtInst *RHSConv = dyn_cast(RHS)) { // Only do this if x/y have the same type, if at last one of them has a // single use (so we don't increase the number of sexts), and if the // integer add will not overflow. if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&& (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && WillNotOverflowSignedAdd(LHSConv->getOperand(0), RHSConv->getOperand(0))) { // Insert the new integer add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), RHSConv->getOperand(0), "addconv"); return new SExtInst(NewAdd, I.getType()); } } } // Check for (x & y) + (x ^ y) { Value *A = nullptr, *B = nullptr; if (match(RHS, m_Xor(m_Value(A), m_Value(B))) && (match(LHS, m_And(m_Specific(A), m_Specific(B))) || match(LHS, m_And(m_Specific(B), m_Specific(A))))) return BinaryOperator::CreateOr(A, B); if (match(LHS, m_Xor(m_Value(A), m_Value(B))) && (match(RHS, m_And(m_Specific(A), m_Specific(B))) || match(RHS, m_And(m_Specific(B), m_Specific(A))))) return BinaryOperator::CreateOr(A, B); } // TODO(jingyue): Consider WillNotOverflowSignedAdd and // WillNotOverflowUnsignedAdd to reduce the number of invocations of // computeKnownBits. if (!I.hasNoSignedWrap() && WillNotOverflowSignedAdd(LHS, RHS)) { Changed = true; I.setHasNoSignedWrap(true); } if (!I.hasNoUnsignedWrap() && WillNotOverflowUnsignedAdd(LHS, RHS)) { Changed = true; I.setHasNoUnsignedWrap(true); } return Changed ? &I : nullptr; } Instruction *InstCombiner::visitFAdd(BinaryOperator &I) { bool Changed = SimplifyAssociativeOrCommutative(I); Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); if (Value *V = SimplifyVectorOp(I)) return ReplaceInstUsesWith(I, V); if (Value *V = SimplifyFAddInst(LHS, RHS, I.getFastMathFlags(), DL)) return ReplaceInstUsesWith(I, V); if (isa(RHS)) { if (isa(LHS)) if (Instruction *NV = FoldOpIntoPhi(I)) return NV; if (SelectInst *SI = dyn_cast(LHS)) if (Instruction *NV = FoldOpIntoSelect(I, SI)) return NV; } // -A + B --> B - A // -A + -B --> -(A + B) if (Value *LHSV = dyn_castFNegVal(LHS)) { Instruction *RI = BinaryOperator::CreateFSub(RHS, LHSV); RI->copyFastMathFlags(&I); return RI; } // A + -B --> A - B if (!isa(RHS)) if (Value *V = dyn_castFNegVal(RHS)) { Instruction *RI = BinaryOperator::CreateFSub(LHS, V); RI->copyFastMathFlags(&I); return RI; } // Check for (fadd double (sitofp x), y), see if we can merge this into an // integer add followed by a promotion. if (SIToFPInst *LHSConv = dyn_cast(LHS)) { // (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)) { Constant *CI = ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType()); if (LHSConv->hasOneUse() && ConstantExpr::getSIToFP(CI, I.getType()) == CFP && WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) { // Insert the new integer add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 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)) { // Only do this if x/y have the same type, if at last 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 (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&& (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && WillNotOverflowSignedAdd(LHSConv->getOperand(0), RHSConv->getOperand(0))) { // Insert the new integer add. Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), RHSConv->getOperand(0),"addconv"); return new SIToFPInst(NewAdd, I.getType()); } } } // select C, 0, B + select C, A, 0 -> select C, A, B { Value *A1, *B1, *C1, *A2, *B2, *C2; if (match(LHS, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) && match(RHS, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) { if (C1 == C2) { Constant *Z1=nullptr, *Z2=nullptr; Value *A, *B, *C=C1; if (match(A1, m_AnyZero()) && match(B2, m_AnyZero())) { Z1 = dyn_cast(A1); A = A2; Z2 = dyn_cast(B2); B = B1; } else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) { Z1 = dyn_cast(B1); B = B2; Z2 = dyn_cast(A2); A = A1; } if (Z1 && Z2 && (I.hasNoSignedZeros() || (Z1->isNegativeZeroValue() && Z2->isNegativeZeroValue()))) { return SelectInst::Create(C, A, B); } } } } if (I.hasUnsafeAlgebra()) { if (Value *V = FAddCombine(Builder).simplify(&I)) return ReplaceInstUsesWith(I, V); } return Changed ? &I : 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) { assert(DL && "Must have target data info for this"); // 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; } } } // Avoid duplicating the arithmetic if GEP2 has non-constant indices and // multiple users. if (!GEP1 || (GEP2 && !GEP2->hasAllConstantIndices() && !GEP2->hasOneUse())) return nullptr; // Emit the offset of the GEP and an intptr_t. Value *Result = EmitGEPOffset(GEP1); // 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) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifyVectorOp(I)) return ReplaceInstUsesWith(I, V); if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(), I.hasNoUnsignedWrap(), DL)) return ReplaceInstUsesWith(I, V); // (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. This preserves NSW/NUW. if (Value *V = dyn_castNegVal(Op1)) { BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V); Res->setHasNoSignedWrap(I.hasNoSignedWrap()); Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); return Res; } if (I.getType()->isIntegerTy(1)) return BinaryOperator::CreateXor(Op0, Op1); // Replace (-1 - A) with (~A). if (match(Op0, m_AllOnes())) return BinaryOperator::CreateNot(Op1); if (Constant *C = dyn_cast(Op0)) { // C - ~X == X + (1+C) Value *X = nullptr; 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; // C-(X+C2) --> (C-C2)-X Constant *C2; if (match(Op1, m_Add(m_Value(X), m_Constant(C2)))) return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X); if (SimplifyDemandedInstructionBits(I)) return &I; // Fold (sub 0, (zext bool to B)) --> (sext bool to B) if (C->isNullValue() && match(Op1, m_ZExt(m_Value(X)))) if (X->getType()->getScalarType()->isIntegerTy(1)) return CastInst::CreateSExtOrBitCast(X, Op1->getType()); // Fold (sub 0, (sext bool to B)) --> (zext bool to B) if (C->isNullValue() && match(Op1, m_SExt(m_Value(X)))) if (X->getType()->getScalarType()->isIntegerTy(1)) return CastInst::CreateZExtOrBitCast(X, Op1->getType()); } if (ConstantInt *C = dyn_cast(Op0)) { // -(X >>u 31) -> (X >>s 31) // -(X >>s 31) -> (X >>u 31) if (C->isZero()) { Value *X; ConstantInt *CI; if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) && // Verify we are shifting out everything but the sign bit. CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1) return BinaryOperator::CreateAShr(X, CI); if (match(Op1, m_AShr(m_Value(X), m_ConstantInt(CI))) && // Verify we are shifting out everything but the sign bit. CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1) return BinaryOperator::CreateLShr(X, CI); } } { Value *Y; // X-(X+Y) == -Y X-(Y+X) == -Y if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) || match(Op1, m_Add(m_Value(Y), m_Specific(Op0)))) return BinaryOperator::CreateNeg(Y); // (X-Y)-X == -Y if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y)))) return BinaryOperator::CreateNeg(Y); } if (Op1->hasOneUse()) { Value *X = nullptr, *Y = nullptr, *Z = nullptr; Constant *C = nullptr; Constant *CI = 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())); // (X - (X & Y)) --> (X & ~Y) // if (match(Op1, m_And(m_Value(Y), m_Specific(Op0))) || match(Op1, m_And(m_Specific(Op0), m_Value(Y)))) return BinaryOperator::CreateAnd(Op0, Builder->CreateNot(Y, Y->getName() + ".not")); // 0 - (X sdiv C) -> (X sdiv -C) if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) && match(Op0, m_Zero())) return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C)); // 0 - (X << Y) -> (-X << Y) when X is freely negatable. if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero())) if (Value *XNeg = dyn_castNegVal(X)) return BinaryOperator::CreateShl(XNeg, Y); // X - A*-B -> X + A*B // X - -A*B -> X + A*B Value *A, *B; if (match(Op1, m_Mul(m_Value(A), m_Neg(m_Value(B)))) || match(Op1, m_Mul(m_Neg(m_Value(A)), m_Value(B)))) return BinaryOperator::CreateAdd(Op0, Builder->CreateMul(A, B)); // X - A*CI -> X + A*-CI // X - CI*A -> X + A*-CI if (match(Op1, m_Mul(m_Value(A), m_Constant(CI))) || match(Op1, m_Mul(m_Constant(CI), m_Value(A)))) { Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(CI)); return BinaryOperator::CreateAdd(Op0, NewMul); } } // Optimize pointer differences into the same array into a size. Consider: // &A[10] - &A[0]: we should compile this to "10". if (DL) { 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())) 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())) return ReplaceInstUsesWith(I, Res); } return nullptr; } Instruction *InstCombiner::visitFSub(BinaryOperator &I) { Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); if (Value *V = SimplifyVectorOp(I)) return ReplaceInstUsesWith(I, V); if (Value *V = SimplifyFSubInst(Op0, Op1, I.getFastMathFlags(), DL)) return ReplaceInstUsesWith(I, V); if (isa(Op0)) if (SelectInst *SI = dyn_cast(Op1)) if (Instruction *NV = FoldOpIntoSelect(I, SI)) return NV; // If this is a 'B = x-(-A)', change to B = x+A, potentially looking // through FP extensions/truncations along the way. if (Value *V = dyn_castFNegVal(Op1)) { Instruction *NewI = BinaryOperator::CreateFAdd(Op0, V); NewI->copyFastMathFlags(&I); return NewI; } if (FPTruncInst *FPTI = dyn_cast(Op1)) { if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) { Value *NewTrunc = Builder->CreateFPTrunc(V, I.getType()); Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewTrunc); NewI->copyFastMathFlags(&I); return NewI; } } else if (FPExtInst *FPEI = dyn_cast(Op1)) { if (Value *V = dyn_castFNegVal(FPEI->getOperand(0))) { Value *NewExt = Builder->CreateFPExt(V, I.getType()); Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewExt); NewI->copyFastMathFlags(&I); return NewI; } } if (I.hasUnsafeAlgebra()) { if (Value *V = FAddCombine(Builder).simplify(&I)) return ReplaceInstUsesWith(I, V); } return nullptr; }