LLVM API Documentation

InstCombineAddSub.cpp
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00001 //===- InstCombineAddSub.cpp ----------------------------------------------===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file is distributed under the University of Illinois Open Source
00006 // License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements the visit functions for add, fadd, sub, and fsub.
00011 //
00012 //===----------------------------------------------------------------------===//
00013 
00014 #include "InstCombineInternal.h"
00015 #include "llvm/ADT/STLExtras.h"
00016 #include "llvm/Analysis/InstructionSimplify.h"
00017 #include "llvm/IR/DataLayout.h"
00018 #include "llvm/IR/GetElementPtrTypeIterator.h"
00019 #include "llvm/IR/PatternMatch.h"
00020 using namespace llvm;
00021 using namespace PatternMatch;
00022 
00023 #define DEBUG_TYPE "instcombine"
00024 
00025 namespace {
00026 
00027   /// Class representing coefficient of floating-point addend.
00028   /// This class needs to be highly efficient, which is especially true for
00029   /// the constructor. As of I write this comment, the cost of the default
00030   /// constructor is merely 4-byte-store-zero (Assuming compiler is able to
00031   /// perform write-merging).
00032   ///
00033   class FAddendCoef {
00034   public:
00035     // The constructor has to initialize a APFloat, which is unnecessary for
00036     // most addends which have coefficient either 1 or -1. So, the constructor
00037     // is expensive. In order to avoid the cost of the constructor, we should
00038     // reuse some instances whenever possible. The pre-created instances
00039     // FAddCombine::Add[0-5] embodies this idea.
00040     //
00041     FAddendCoef() : IsFp(false), BufHasFpVal(false), IntVal(0) {}
00042     ~FAddendCoef();
00043 
00044     void set(short C) {
00045       assert(!insaneIntVal(C) && "Insane coefficient");
00046       IsFp = false; IntVal = C;
00047     }
00048 
00049     void set(const APFloat& C);
00050 
00051     void negate();
00052 
00053     bool isZero() const { return isInt() ? !IntVal : getFpVal().isZero(); }
00054     Value *getValue(Type *) const;
00055 
00056     // If possible, don't define operator+/operator- etc because these
00057     // operators inevitably call FAddendCoef's constructor which is not cheap.
00058     void operator=(const FAddendCoef &A);
00059     void operator+=(const FAddendCoef &A);
00060     void operator-=(const FAddendCoef &A);
00061     void operator*=(const FAddendCoef &S);
00062 
00063     bool isOne() const { return isInt() && IntVal == 1; }
00064     bool isTwo() const { return isInt() && IntVal == 2; }
00065     bool isMinusOne() const { return isInt() && IntVal == -1; }
00066     bool isMinusTwo() const { return isInt() && IntVal == -2; }
00067 
00068   private:
00069     bool insaneIntVal(int V) { return V > 4 || V < -4; }
00070     APFloat *getFpValPtr(void)
00071       { return reinterpret_cast<APFloat*>(&FpValBuf.buffer[0]); }
00072     const APFloat *getFpValPtr(void) const
00073       { return reinterpret_cast<const APFloat*>(&FpValBuf.buffer[0]); }
00074 
00075     const APFloat &getFpVal(void) const {
00076       assert(IsFp && BufHasFpVal && "Incorret state");
00077       return *getFpValPtr();
00078     }
00079 
00080     APFloat &getFpVal(void) {
00081       assert(IsFp && BufHasFpVal && "Incorret state");
00082       return *getFpValPtr();
00083     }
00084 
00085     bool isInt() const { return !IsFp; }
00086 
00087     // If the coefficient is represented by an integer, promote it to a
00088     // floating point.
00089     void convertToFpType(const fltSemantics &Sem);
00090 
00091     // Construct an APFloat from a signed integer.
00092     // TODO: We should get rid of this function when APFloat can be constructed
00093     //       from an *SIGNED* integer.
00094     APFloat createAPFloatFromInt(const fltSemantics &Sem, int Val);
00095   private:
00096 
00097     bool IsFp;
00098 
00099     // True iff FpValBuf contains an instance of APFloat.
00100     bool BufHasFpVal;
00101 
00102     // The integer coefficient of an individual addend is either 1 or -1,
00103     // and we try to simplify at most 4 addends from neighboring at most
00104     // two instructions. So the range of <IntVal> falls in [-4, 4]. APInt
00105     // is overkill of this end.
00106     short IntVal;
00107 
00108     AlignedCharArrayUnion<APFloat> FpValBuf;
00109   };
00110 
00111   /// FAddend is used to represent floating-point addend. An addend is
00112   /// represented as <C, V>, where the V is a symbolic value, and C is a
00113   /// constant coefficient. A constant addend is represented as <C, 0>.
00114   ///
00115   class FAddend {
00116   public:
00117     FAddend() { Val = nullptr; }
00118 
00119     Value *getSymVal (void) const { return Val; }
00120     const FAddendCoef &getCoef(void) const { return Coeff; }
00121 
00122     bool isConstant() const { return Val == nullptr; }
00123     bool isZero() const { return Coeff.isZero(); }
00124 
00125     void set(short Coefficient, Value *V) { Coeff.set(Coefficient), Val = V; }
00126     void set(const APFloat& Coefficient, Value *V)
00127       { Coeff.set(Coefficient); Val = V; }
00128     void set(const ConstantFP* Coefficient, Value *V)
00129       { Coeff.set(Coefficient->getValueAPF()); Val = V; }
00130 
00131     void negate() { Coeff.negate(); }
00132 
00133     /// Drill down the U-D chain one step to find the definition of V, and
00134     /// try to break the definition into one or two addends.
00135     static unsigned drillValueDownOneStep(Value* V, FAddend &A0, FAddend &A1);
00136 
00137     /// Similar to FAddend::drillDownOneStep() except that the value being
00138     /// splitted is the addend itself.
00139     unsigned drillAddendDownOneStep(FAddend &Addend0, FAddend &Addend1) const;
00140 
00141     void operator+=(const FAddend &T) {
00142       assert((Val == T.Val) && "Symbolic-values disagree");
00143       Coeff += T.Coeff;
00144     }
00145 
00146   private:
00147     void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; }
00148 
00149     // This addend has the value of "Coeff * Val".
00150     Value *Val;
00151     FAddendCoef Coeff;
00152   };
00153 
00154   /// FAddCombine is the class for optimizing an unsafe fadd/fsub along
00155   /// with its neighboring at most two instructions.
00156   ///
00157   class FAddCombine {
00158   public:
00159     FAddCombine(InstCombiner::BuilderTy *B) : Builder(B), Instr(nullptr) {}
00160     Value *simplify(Instruction *FAdd);
00161 
00162   private:
00163     typedef SmallVector<const FAddend*, 4> AddendVect;
00164 
00165     Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota);
00166 
00167     Value *performFactorization(Instruction *I);
00168 
00169     /// Convert given addend to a Value
00170     Value *createAddendVal(const FAddend &A, bool& NeedNeg);
00171 
00172     /// Return the number of instructions needed to emit the N-ary addition.
00173     unsigned calcInstrNumber(const AddendVect& Vect);
00174     Value *createFSub(Value *Opnd0, Value *Opnd1);
00175     Value *createFAdd(Value *Opnd0, Value *Opnd1);
00176     Value *createFMul(Value *Opnd0, Value *Opnd1);
00177     Value *createFDiv(Value *Opnd0, Value *Opnd1);
00178     Value *createFNeg(Value *V);
00179     Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota);
00180     void createInstPostProc(Instruction *NewInst, bool NoNumber = false);
00181 
00182     InstCombiner::BuilderTy *Builder;
00183     Instruction *Instr;
00184 
00185   private:
00186      // Debugging stuff are clustered here.
00187     #ifndef NDEBUG
00188       unsigned CreateInstrNum;
00189       void initCreateInstNum() { CreateInstrNum = 0; }
00190       void incCreateInstNum() { CreateInstrNum++; }
00191     #else
00192       void initCreateInstNum() {}
00193       void incCreateInstNum() {}
00194     #endif
00195   };
00196 }
00197 
00198 //===----------------------------------------------------------------------===//
00199 //
00200 // Implementation of
00201 //    {FAddendCoef, FAddend, FAddition, FAddCombine}.
00202 //
00203 //===----------------------------------------------------------------------===//
00204 FAddendCoef::~FAddendCoef() {
00205   if (BufHasFpVal)
00206     getFpValPtr()->~APFloat();
00207 }
00208 
00209 void FAddendCoef::set(const APFloat& C) {
00210   APFloat *P = getFpValPtr();
00211 
00212   if (isInt()) {
00213     // As the buffer is meanless byte stream, we cannot call
00214     // APFloat::operator=().
00215     new(P) APFloat(C);
00216   } else
00217     *P = C;
00218 
00219   IsFp = BufHasFpVal = true;
00220 }
00221 
00222 void FAddendCoef::convertToFpType(const fltSemantics &Sem) {
00223   if (!isInt())
00224     return;
00225 
00226   APFloat *P = getFpValPtr();
00227   if (IntVal > 0)
00228     new(P) APFloat(Sem, IntVal);
00229   else {
00230     new(P) APFloat(Sem, 0 - IntVal);
00231     P->changeSign();
00232   }
00233   IsFp = BufHasFpVal = true;
00234 }
00235 
00236 APFloat FAddendCoef::createAPFloatFromInt(const fltSemantics &Sem, int Val) {
00237   if (Val >= 0)
00238     return APFloat(Sem, Val);
00239 
00240   APFloat T(Sem, 0 - Val);
00241   T.changeSign();
00242 
00243   return T;
00244 }
00245 
00246 void FAddendCoef::operator=(const FAddendCoef &That) {
00247   if (That.isInt())
00248     set(That.IntVal);
00249   else
00250     set(That.getFpVal());
00251 }
00252 
00253 void FAddendCoef::operator+=(const FAddendCoef &That) {
00254   enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven;
00255   if (isInt() == That.isInt()) {
00256     if (isInt())
00257       IntVal += That.IntVal;
00258     else
00259       getFpVal().add(That.getFpVal(), RndMode);
00260     return;
00261   }
00262 
00263   if (isInt()) {
00264     const APFloat &T = That.getFpVal();
00265     convertToFpType(T.getSemantics());
00266     getFpVal().add(T, RndMode);
00267     return;
00268   }
00269 
00270   APFloat &T = getFpVal();
00271   T.add(createAPFloatFromInt(T.getSemantics(), That.IntVal), RndMode);
00272 }
00273 
00274 void FAddendCoef::operator-=(const FAddendCoef &That) {
00275   enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven;
00276   if (isInt() == That.isInt()) {
00277     if (isInt())
00278       IntVal -= That.IntVal;
00279     else
00280       getFpVal().subtract(That.getFpVal(), RndMode);
00281     return;
00282   }
00283 
00284   if (isInt()) {
00285     const APFloat &T = That.getFpVal();
00286     convertToFpType(T.getSemantics());
00287     getFpVal().subtract(T, RndMode);
00288     return;
00289   }
00290 
00291   APFloat &T = getFpVal();
00292   T.subtract(createAPFloatFromInt(T.getSemantics(), IntVal), RndMode);
00293 }
00294 
00295 void FAddendCoef::operator*=(const FAddendCoef &That) {
00296   if (That.isOne())
00297     return;
00298 
00299   if (That.isMinusOne()) {
00300     negate();
00301     return;
00302   }
00303 
00304   if (isInt() && That.isInt()) {
00305     int Res = IntVal * (int)That.IntVal;
00306     assert(!insaneIntVal(Res) && "Insane int value");
00307     IntVal = Res;
00308     return;
00309   }
00310 
00311   const fltSemantics &Semantic =
00312     isInt() ? That.getFpVal().getSemantics() : getFpVal().getSemantics();
00313 
00314   if (isInt())
00315     convertToFpType(Semantic);
00316   APFloat &F0 = getFpVal();
00317 
00318   if (That.isInt())
00319     F0.multiply(createAPFloatFromInt(Semantic, That.IntVal),
00320                 APFloat::rmNearestTiesToEven);
00321   else
00322     F0.multiply(That.getFpVal(), APFloat::rmNearestTiesToEven);
00323 
00324   return;
00325 }
00326 
00327 void FAddendCoef::negate() {
00328   if (isInt())
00329     IntVal = 0 - IntVal;
00330   else
00331     getFpVal().changeSign();
00332 }
00333 
00334 Value *FAddendCoef::getValue(Type *Ty) const {
00335   return isInt() ?
00336     ConstantFP::get(Ty, float(IntVal)) :
00337     ConstantFP::get(Ty->getContext(), getFpVal());
00338 }
00339 
00340 // The definition of <Val>     Addends
00341 // =========================================
00342 //  A + B                     <1, A>, <1,B>
00343 //  A - B                     <1, A>, <1,B>
00344 //  0 - B                     <-1, B>
00345 //  C * A,                    <C, A>
00346 //  A + C                     <1, A> <C, NULL>
00347 //  0 +/- 0                   <0, NULL> (corner case)
00348 //
00349 // Legend: A and B are not constant, C is constant
00350 //
00351 unsigned FAddend::drillValueDownOneStep
00352   (Value *Val, FAddend &Addend0, FAddend &Addend1) {
00353   Instruction *I = nullptr;
00354   if (!Val || !(I = dyn_cast<Instruction>(Val)))
00355     return 0;
00356 
00357   unsigned Opcode = I->getOpcode();
00358 
00359   if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub) {
00360     ConstantFP *C0, *C1;
00361     Value *Opnd0 = I->getOperand(0);
00362     Value *Opnd1 = I->getOperand(1);
00363     if ((C0 = dyn_cast<ConstantFP>(Opnd0)) && C0->isZero())
00364       Opnd0 = nullptr;
00365 
00366     if ((C1 = dyn_cast<ConstantFP>(Opnd1)) && C1->isZero())
00367       Opnd1 = nullptr;
00368 
00369     if (Opnd0) {
00370       if (!C0)
00371         Addend0.set(1, Opnd0);
00372       else
00373         Addend0.set(C0, nullptr);
00374     }
00375 
00376     if (Opnd1) {
00377       FAddend &Addend = Opnd0 ? Addend1 : Addend0;
00378       if (!C1)
00379         Addend.set(1, Opnd1);
00380       else
00381         Addend.set(C1, nullptr);
00382       if (Opcode == Instruction::FSub)
00383         Addend.negate();
00384     }
00385 
00386     if (Opnd0 || Opnd1)
00387       return Opnd0 && Opnd1 ? 2 : 1;
00388 
00389     // Both operands are zero. Weird!
00390     Addend0.set(APFloat(C0->getValueAPF().getSemantics()), nullptr);
00391     return 1;
00392   }
00393 
00394   if (I->getOpcode() == Instruction::FMul) {
00395     Value *V0 = I->getOperand(0);
00396     Value *V1 = I->getOperand(1);
00397     if (ConstantFP *C = dyn_cast<ConstantFP>(V0)) {
00398       Addend0.set(C, V1);
00399       return 1;
00400     }
00401 
00402     if (ConstantFP *C = dyn_cast<ConstantFP>(V1)) {
00403       Addend0.set(C, V0);
00404       return 1;
00405     }
00406   }
00407 
00408   return 0;
00409 }
00410 
00411 // Try to break *this* addend into two addends. e.g. Suppose this addend is
00412 // <2.3, V>, and V = X + Y, by calling this function, we obtain two addends,
00413 // i.e. <2.3, X> and <2.3, Y>.
00414 //
00415 unsigned FAddend::drillAddendDownOneStep
00416   (FAddend &Addend0, FAddend &Addend1) const {
00417   if (isConstant())
00418     return 0;
00419 
00420   unsigned BreakNum = FAddend::drillValueDownOneStep(Val, Addend0, Addend1);
00421   if (!BreakNum || Coeff.isOne())
00422     return BreakNum;
00423 
00424   Addend0.Scale(Coeff);
00425 
00426   if (BreakNum == 2)
00427     Addend1.Scale(Coeff);
00428 
00429   return BreakNum;
00430 }
00431 
00432 // Try to perform following optimization on the input instruction I. Return the
00433 // simplified expression if was successful; otherwise, return 0.
00434 //
00435 //   Instruction "I" is                Simplified into
00436 // -------------------------------------------------------
00437 //   (x * y) +/- (x * z)               x * (y +/- z)
00438 //   (y / x) +/- (z / x)               (y +/- z) / x
00439 //
00440 Value *FAddCombine::performFactorization(Instruction *I) {
00441   assert((I->getOpcode() == Instruction::FAdd ||
00442           I->getOpcode() == Instruction::FSub) && "Expect add/sub");
00443 
00444   Instruction *I0 = dyn_cast<Instruction>(I->getOperand(0));
00445   Instruction *I1 = dyn_cast<Instruction>(I->getOperand(1));
00446 
00447   if (!I0 || !I1 || I0->getOpcode() != I1->getOpcode())
00448     return nullptr;
00449 
00450   bool isMpy = false;
00451   if (I0->getOpcode() == Instruction::FMul)
00452     isMpy = true;
00453   else if (I0->getOpcode() != Instruction::FDiv)
00454     return nullptr;
00455 
00456   Value *Opnd0_0 = I0->getOperand(0);
00457   Value *Opnd0_1 = I0->getOperand(1);
00458   Value *Opnd1_0 = I1->getOperand(0);
00459   Value *Opnd1_1 = I1->getOperand(1);
00460 
00461   //  Input Instr I       Factor   AddSub0  AddSub1
00462   //  ----------------------------------------------
00463   // (x*y) +/- (x*z)        x        y         z
00464   // (y/x) +/- (z/x)        x        y         z
00465   //
00466   Value *Factor = nullptr;
00467   Value *AddSub0 = nullptr, *AddSub1 = nullptr;
00468 
00469   if (isMpy) {
00470     if (Opnd0_0 == Opnd1_0 || Opnd0_0 == Opnd1_1)
00471       Factor = Opnd0_0;
00472     else if (Opnd0_1 == Opnd1_0 || Opnd0_1 == Opnd1_1)
00473       Factor = Opnd0_1;
00474 
00475     if (Factor) {
00476       AddSub0 = (Factor == Opnd0_0) ? Opnd0_1 : Opnd0_0;
00477       AddSub1 = (Factor == Opnd1_0) ? Opnd1_1 : Opnd1_0;
00478     }
00479   } else if (Opnd0_1 == Opnd1_1) {
00480     Factor = Opnd0_1;
00481     AddSub0 = Opnd0_0;
00482     AddSub1 = Opnd1_0;
00483   }
00484 
00485   if (!Factor)
00486     return nullptr;
00487 
00488   FastMathFlags Flags;
00489   Flags.setUnsafeAlgebra();
00490   if (I0) Flags &= I->getFastMathFlags();
00491   if (I1) Flags &= I->getFastMathFlags();
00492 
00493   // Create expression "NewAddSub = AddSub0 +/- AddsSub1"
00494   Value *NewAddSub = (I->getOpcode() == Instruction::FAdd) ?
00495                       createFAdd(AddSub0, AddSub1) :
00496                       createFSub(AddSub0, AddSub1);
00497   if (ConstantFP *CFP = dyn_cast<ConstantFP>(NewAddSub)) {
00498     const APFloat &F = CFP->getValueAPF();
00499     if (!F.isNormal())
00500       return nullptr;
00501   } else if (Instruction *II = dyn_cast<Instruction>(NewAddSub))
00502     II->setFastMathFlags(Flags);
00503 
00504   if (isMpy) {
00505     Value *RI = createFMul(Factor, NewAddSub);
00506     if (Instruction *II = dyn_cast<Instruction>(RI))
00507       II->setFastMathFlags(Flags);
00508     return RI;
00509   }
00510 
00511   Value *RI = createFDiv(NewAddSub, Factor);
00512   if (Instruction *II = dyn_cast<Instruction>(RI))
00513     II->setFastMathFlags(Flags);
00514   return RI;
00515 }
00516 
00517 Value *FAddCombine::simplify(Instruction *I) {
00518   assert(I->hasUnsafeAlgebra() && "Should be in unsafe mode");
00519 
00520   // Currently we are not able to handle vector type.
00521   if (I->getType()->isVectorTy())
00522     return nullptr;
00523 
00524   assert((I->getOpcode() == Instruction::FAdd ||
00525           I->getOpcode() == Instruction::FSub) && "Expect add/sub");
00526 
00527   // Save the instruction before calling other member-functions.
00528   Instr = I;
00529 
00530   FAddend Opnd0, Opnd1, Opnd0_0, Opnd0_1, Opnd1_0, Opnd1_1;
00531 
00532   unsigned OpndNum = FAddend::drillValueDownOneStep(I, Opnd0, Opnd1);
00533 
00534   // Step 1: Expand the 1st addend into Opnd0_0 and Opnd0_1.
00535   unsigned Opnd0_ExpNum = 0;
00536   unsigned Opnd1_ExpNum = 0;
00537 
00538   if (!Opnd0.isConstant())
00539     Opnd0_ExpNum = Opnd0.drillAddendDownOneStep(Opnd0_0, Opnd0_1);
00540 
00541   // Step 2: Expand the 2nd addend into Opnd1_0 and Opnd1_1.
00542   if (OpndNum == 2 && !Opnd1.isConstant())
00543     Opnd1_ExpNum = Opnd1.drillAddendDownOneStep(Opnd1_0, Opnd1_1);
00544 
00545   // Step 3: Try to optimize Opnd0_0 + Opnd0_1 + Opnd1_0 + Opnd1_1
00546   if (Opnd0_ExpNum && Opnd1_ExpNum) {
00547     AddendVect AllOpnds;
00548     AllOpnds.push_back(&Opnd0_0);
00549     AllOpnds.push_back(&Opnd1_0);
00550     if (Opnd0_ExpNum == 2)
00551       AllOpnds.push_back(&Opnd0_1);
00552     if (Opnd1_ExpNum == 2)
00553       AllOpnds.push_back(&Opnd1_1);
00554 
00555     // Compute instruction quota. We should save at least one instruction.
00556     unsigned InstQuota = 0;
00557 
00558     Value *V0 = I->getOperand(0);
00559     Value *V1 = I->getOperand(1);
00560     InstQuota = ((!isa<Constant>(V0) && V0->hasOneUse()) &&
00561                  (!isa<Constant>(V1) && V1->hasOneUse())) ? 2 : 1;
00562 
00563     if (Value *R = simplifyFAdd(AllOpnds, InstQuota))
00564       return R;
00565   }
00566 
00567   if (OpndNum != 2) {
00568     // The input instruction is : "I=0.0 +/- V". If the "V" were able to be
00569     // splitted into two addends, say "V = X - Y", the instruction would have
00570     // been optimized into "I = Y - X" in the previous steps.
00571     //
00572     const FAddendCoef &CE = Opnd0.getCoef();
00573     return CE.isOne() ? Opnd0.getSymVal() : nullptr;
00574   }
00575 
00576   // step 4: Try to optimize Opnd0 + Opnd1_0 [+ Opnd1_1]
00577   if (Opnd1_ExpNum) {
00578     AddendVect AllOpnds;
00579     AllOpnds.push_back(&Opnd0);
00580     AllOpnds.push_back(&Opnd1_0);
00581     if (Opnd1_ExpNum == 2)
00582       AllOpnds.push_back(&Opnd1_1);
00583 
00584     if (Value *R = simplifyFAdd(AllOpnds, 1))
00585       return R;
00586   }
00587 
00588   // step 5: Try to optimize Opnd1 + Opnd0_0 [+ Opnd0_1]
00589   if (Opnd0_ExpNum) {
00590     AddendVect AllOpnds;
00591     AllOpnds.push_back(&Opnd1);
00592     AllOpnds.push_back(&Opnd0_0);
00593     if (Opnd0_ExpNum == 2)
00594       AllOpnds.push_back(&Opnd0_1);
00595 
00596     if (Value *R = simplifyFAdd(AllOpnds, 1))
00597       return R;
00598   }
00599 
00600   // step 6: Try factorization as the last resort,
00601   return performFactorization(I);
00602 }
00603 
00604 Value *FAddCombine::simplifyFAdd(AddendVect& Addends, unsigned InstrQuota) {
00605 
00606   unsigned AddendNum = Addends.size();
00607   assert(AddendNum <= 4 && "Too many addends");
00608 
00609   // For saving intermediate results;
00610   unsigned NextTmpIdx = 0;
00611   FAddend TmpResult[3];
00612 
00613   // Points to the constant addend of the resulting simplified expression.
00614   // If the resulting expr has constant-addend, this constant-addend is
00615   // desirable to reside at the top of the resulting expression tree. Placing
00616   // constant close to supper-expr(s) will potentially reveal some optimization
00617   // opportunities in super-expr(s).
00618   //
00619   const FAddend *ConstAdd = nullptr;
00620 
00621   // Simplified addends are placed <SimpVect>.
00622   AddendVect SimpVect;
00623 
00624   // The outer loop works on one symbolic-value at a time. Suppose the input
00625   // addends are : <a1, x>, <b1, y>, <a2, x>, <c1, z>, <b2, y>, ...
00626   // The symbolic-values will be processed in this order: x, y, z.
00627   //
00628   for (unsigned SymIdx = 0; SymIdx < AddendNum; SymIdx++) {
00629 
00630     const FAddend *ThisAddend = Addends[SymIdx];
00631     if (!ThisAddend) {
00632       // This addend was processed before.
00633       continue;
00634     }
00635 
00636     Value *Val = ThisAddend->getSymVal();
00637     unsigned StartIdx = SimpVect.size();
00638     SimpVect.push_back(ThisAddend);
00639 
00640     // The inner loop collects addends sharing same symbolic-value, and these
00641     // addends will be later on folded into a single addend. Following above
00642     // example, if the symbolic value "y" is being processed, the inner loop
00643     // will collect two addends "<b1,y>" and "<b2,Y>". These two addends will
00644     // be later on folded into "<b1+b2, y>".
00645     //
00646     for (unsigned SameSymIdx = SymIdx + 1;
00647          SameSymIdx < AddendNum; SameSymIdx++) {
00648       const FAddend *T = Addends[SameSymIdx];
00649       if (T && T->getSymVal() == Val) {
00650         // Set null such that next iteration of the outer loop will not process
00651         // this addend again.
00652         Addends[SameSymIdx] = nullptr;
00653         SimpVect.push_back(T);
00654       }
00655     }
00656 
00657     // If multiple addends share same symbolic value, fold them together.
00658     if (StartIdx + 1 != SimpVect.size()) {
00659       FAddend &R = TmpResult[NextTmpIdx ++];
00660       R = *SimpVect[StartIdx];
00661       for (unsigned Idx = StartIdx + 1; Idx < SimpVect.size(); Idx++)
00662         R += *SimpVect[Idx];
00663 
00664       // Pop all addends being folded and push the resulting folded addend.
00665       SimpVect.resize(StartIdx);
00666       if (Val) {
00667         if (!R.isZero()) {
00668           SimpVect.push_back(&R);
00669         }
00670       } else {
00671         // Don't push constant addend at this time. It will be the last element
00672         // of <SimpVect>.
00673         ConstAdd = &R;
00674       }
00675     }
00676   }
00677 
00678   assert((NextTmpIdx <= array_lengthof(TmpResult) + 1) &&
00679          "out-of-bound access");
00680 
00681   if (ConstAdd)
00682     SimpVect.push_back(ConstAdd);
00683 
00684   Value *Result;
00685   if (!SimpVect.empty())
00686     Result = createNaryFAdd(SimpVect, InstrQuota);
00687   else {
00688     // The addition is folded to 0.0.
00689     Result = ConstantFP::get(Instr->getType(), 0.0);
00690   }
00691 
00692   return Result;
00693 }
00694 
00695 Value *FAddCombine::createNaryFAdd
00696   (const AddendVect &Opnds, unsigned InstrQuota) {
00697   assert(!Opnds.empty() && "Expect at least one addend");
00698 
00699   // Step 1: Check if the # of instructions needed exceeds the quota.
00700   //
00701   unsigned InstrNeeded = calcInstrNumber(Opnds);
00702   if (InstrNeeded > InstrQuota)
00703     return nullptr;
00704 
00705   initCreateInstNum();
00706 
00707   // step 2: Emit the N-ary addition.
00708   // Note that at most three instructions are involved in Fadd-InstCombine: the
00709   // addition in question, and at most two neighboring instructions.
00710   // The resulting optimized addition should have at least one less instruction
00711   // than the original addition expression tree. This implies that the resulting
00712   // N-ary addition has at most two instructions, and we don't need to worry
00713   // about tree-height when constructing the N-ary addition.
00714 
00715   Value *LastVal = nullptr;
00716   bool LastValNeedNeg = false;
00717 
00718   // Iterate the addends, creating fadd/fsub using adjacent two addends.
00719   for (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end();
00720        I != E; I++) {
00721     bool NeedNeg;
00722     Value *V = createAddendVal(**I, NeedNeg);
00723     if (!LastVal) {
00724       LastVal = V;
00725       LastValNeedNeg = NeedNeg;
00726       continue;
00727     }
00728 
00729     if (LastValNeedNeg == NeedNeg) {
00730       LastVal = createFAdd(LastVal, V);
00731       continue;
00732     }
00733 
00734     if (LastValNeedNeg)
00735       LastVal = createFSub(V, LastVal);
00736     else
00737       LastVal = createFSub(LastVal, V);
00738 
00739     LastValNeedNeg = false;
00740   }
00741 
00742   if (LastValNeedNeg) {
00743     LastVal = createFNeg(LastVal);
00744   }
00745 
00746   #ifndef NDEBUG
00747     assert(CreateInstrNum == InstrNeeded &&
00748            "Inconsistent in instruction numbers");
00749   #endif
00750 
00751   return LastVal;
00752 }
00753 
00754 Value *FAddCombine::createFSub(Value *Opnd0, Value *Opnd1) {
00755   Value *V = Builder->CreateFSub(Opnd0, Opnd1);
00756   if (Instruction *I = dyn_cast<Instruction>(V))
00757     createInstPostProc(I);
00758   return V;
00759 }
00760 
00761 Value *FAddCombine::createFNeg(Value *V) {
00762   Value *Zero = cast<Value>(ConstantFP::getZeroValueForNegation(V->getType()));
00763   Value *NewV = createFSub(Zero, V);
00764   if (Instruction *I = dyn_cast<Instruction>(NewV))
00765     createInstPostProc(I, true); // fneg's don't receive instruction numbers.
00766   return NewV;
00767 }
00768 
00769 Value *FAddCombine::createFAdd(Value *Opnd0, Value *Opnd1) {
00770   Value *V = Builder->CreateFAdd(Opnd0, Opnd1);
00771   if (Instruction *I = dyn_cast<Instruction>(V))
00772     createInstPostProc(I);
00773   return V;
00774 }
00775 
00776 Value *FAddCombine::createFMul(Value *Opnd0, Value *Opnd1) {
00777   Value *V = Builder->CreateFMul(Opnd0, Opnd1);
00778   if (Instruction *I = dyn_cast<Instruction>(V))
00779     createInstPostProc(I);
00780   return V;
00781 }
00782 
00783 Value *FAddCombine::createFDiv(Value *Opnd0, Value *Opnd1) {
00784   Value *V = Builder->CreateFDiv(Opnd0, Opnd1);
00785   if (Instruction *I = dyn_cast<Instruction>(V))
00786     createInstPostProc(I);
00787   return V;
00788 }
00789 
00790 void FAddCombine::createInstPostProc(Instruction *NewInstr, bool NoNumber) {
00791   NewInstr->setDebugLoc(Instr->getDebugLoc());
00792 
00793   // Keep track of the number of instruction created.
00794   if (!NoNumber)
00795     incCreateInstNum();
00796 
00797   // Propagate fast-math flags
00798   NewInstr->setFastMathFlags(Instr->getFastMathFlags());
00799 }
00800 
00801 // Return the number of instruction needed to emit the N-ary addition.
00802 // NOTE: Keep this function in sync with createAddendVal().
00803 unsigned FAddCombine::calcInstrNumber(const AddendVect &Opnds) {
00804   unsigned OpndNum = Opnds.size();
00805   unsigned InstrNeeded = OpndNum - 1;
00806 
00807   // The number of addends in the form of "(-1)*x".
00808   unsigned NegOpndNum = 0;
00809 
00810   // Adjust the number of instructions needed to emit the N-ary add.
00811   for (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end();
00812        I != E; I++) {
00813     const FAddend *Opnd = *I;
00814     if (Opnd->isConstant())
00815       continue;
00816 
00817     const FAddendCoef &CE = Opnd->getCoef();
00818     if (CE.isMinusOne() || CE.isMinusTwo())
00819       NegOpndNum++;
00820 
00821     // Let the addend be "c * x". If "c == +/-1", the value of the addend
00822     // is immediately available; otherwise, it needs exactly one instruction
00823     // to evaluate the value.
00824     if (!CE.isMinusOne() && !CE.isOne())
00825       InstrNeeded++;
00826   }
00827   if (NegOpndNum == OpndNum)
00828     InstrNeeded++;
00829   return InstrNeeded;
00830 }
00831 
00832 // Input Addend        Value           NeedNeg(output)
00833 // ================================================================
00834 // Constant C          C               false
00835 // <+/-1, V>           V               coefficient is -1
00836 // <2/-2, V>          "fadd V, V"      coefficient is -2
00837 // <C, V>             "fmul V, C"      false
00838 //
00839 // NOTE: Keep this function in sync with FAddCombine::calcInstrNumber.
00840 Value *FAddCombine::createAddendVal(const FAddend &Opnd, bool &NeedNeg) {
00841   const FAddendCoef &Coeff = Opnd.getCoef();
00842 
00843   if (Opnd.isConstant()) {
00844     NeedNeg = false;
00845     return Coeff.getValue(Instr->getType());
00846   }
00847 
00848   Value *OpndVal = Opnd.getSymVal();
00849 
00850   if (Coeff.isMinusOne() || Coeff.isOne()) {
00851     NeedNeg = Coeff.isMinusOne();
00852     return OpndVal;
00853   }
00854 
00855   if (Coeff.isTwo() || Coeff.isMinusTwo()) {
00856     NeedNeg = Coeff.isMinusTwo();
00857     return createFAdd(OpndVal, OpndVal);
00858   }
00859 
00860   NeedNeg = false;
00861   return createFMul(OpndVal, Coeff.getValue(Instr->getType()));
00862 }
00863 
00864 // If one of the operands only has one non-zero bit, and if the other
00865 // operand has a known-zero bit in a more significant place than it (not
00866 // including the sign bit) the ripple may go up to and fill the zero, but
00867 // won't change the sign. For example, (X & ~4) + 1.
00868 static bool checkRippleForAdd(const APInt &Op0KnownZero,
00869                               const APInt &Op1KnownZero) {
00870   APInt Op1MaybeOne = ~Op1KnownZero;
00871   // Make sure that one of the operand has at most one bit set to 1.
00872   if (Op1MaybeOne.countPopulation() != 1)
00873     return false;
00874 
00875   // Find the most significant known 0 other than the sign bit.
00876   int BitWidth = Op0KnownZero.getBitWidth();
00877   APInt Op0KnownZeroTemp(Op0KnownZero);
00878   Op0KnownZeroTemp.clearBit(BitWidth - 1);
00879   int Op0ZeroPosition = BitWidth - Op0KnownZeroTemp.countLeadingZeros() - 1;
00880 
00881   int Op1OnePosition = BitWidth - Op1MaybeOne.countLeadingZeros() - 1;
00882   assert(Op1OnePosition >= 0);
00883 
00884   // This also covers the case of no known zero, since in that case
00885   // Op0ZeroPosition is -1.
00886   return Op0ZeroPosition >= Op1OnePosition;
00887 }
00888 
00889 /// WillNotOverflowSignedAdd - Return true if we can prove that:
00890 ///    (sext (add LHS, RHS))  === (add (sext LHS), (sext RHS))
00891 /// This basically requires proving that the add in the original type would not
00892 /// overflow to change the sign bit or have a carry out.
00893 bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS,
00894                                             Instruction *CxtI) {
00895   // There are different heuristics we can use for this.  Here are some simple
00896   // ones.
00897 
00898   // If LHS and RHS each have at least two sign bits, the addition will look
00899   // like
00900   //
00901   // XX..... +
00902   // YY.....
00903   //
00904   // If the carry into the most significant position is 0, X and Y can't both
00905   // be 1 and therefore the carry out of the addition is also 0.
00906   //
00907   // If the carry into the most significant position is 1, X and Y can't both
00908   // be 0 and therefore the carry out of the addition is also 1.
00909   //
00910   // Since the carry into the most significant position is always equal to
00911   // the carry out of the addition, there is no signed overflow.
00912   if (ComputeNumSignBits(LHS, 0, CxtI) > 1 &&
00913       ComputeNumSignBits(RHS, 0, CxtI) > 1)
00914     return true;
00915 
00916   unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
00917   APInt LHSKnownZero(BitWidth, 0);
00918   APInt LHSKnownOne(BitWidth, 0);
00919   computeKnownBits(LHS, LHSKnownZero, LHSKnownOne, 0, CxtI);
00920 
00921   APInt RHSKnownZero(BitWidth, 0);
00922   APInt RHSKnownOne(BitWidth, 0);
00923   computeKnownBits(RHS, RHSKnownZero, RHSKnownOne, 0, CxtI);
00924 
00925   // Addition of two 2's compliment numbers having opposite signs will never
00926   // overflow.
00927   if ((LHSKnownOne[BitWidth - 1] && RHSKnownZero[BitWidth - 1]) ||
00928       (LHSKnownZero[BitWidth - 1] && RHSKnownOne[BitWidth - 1]))
00929     return true;
00930 
00931   // Check if carry bit of addition will not cause overflow.
00932   if (checkRippleForAdd(LHSKnownZero, RHSKnownZero))
00933     return true;
00934   if (checkRippleForAdd(RHSKnownZero, LHSKnownZero))
00935     return true;
00936 
00937   return false;
00938 }
00939 
00940 /// \brief Return true if we can prove that:
00941 ///    (sub LHS, RHS)  === (sub nsw LHS, RHS)
00942 /// This basically requires proving that the add in the original type would not
00943 /// overflow to change the sign bit or have a carry out.
00944 /// TODO: Handle this for Vectors.
00945 bool InstCombiner::WillNotOverflowSignedSub(Value *LHS, Value *RHS,
00946                                             Instruction *CxtI) {
00947   // If LHS and RHS each have at least two sign bits, the subtraction
00948   // cannot overflow.
00949   if (ComputeNumSignBits(LHS, 0, CxtI) > 1 &&
00950       ComputeNumSignBits(RHS, 0, CxtI) > 1)
00951     return true;
00952 
00953   unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
00954   APInt LHSKnownZero(BitWidth, 0);
00955   APInt LHSKnownOne(BitWidth, 0);
00956   computeKnownBits(LHS, LHSKnownZero, LHSKnownOne, 0, CxtI);
00957 
00958   APInt RHSKnownZero(BitWidth, 0);
00959   APInt RHSKnownOne(BitWidth, 0);
00960   computeKnownBits(RHS, RHSKnownZero, RHSKnownOne, 0, CxtI);
00961 
00962   // Subtraction of two 2's compliment numbers having identical signs will
00963   // never overflow.
00964   if ((LHSKnownOne[BitWidth - 1] && RHSKnownOne[BitWidth - 1]) ||
00965       (LHSKnownZero[BitWidth - 1] && RHSKnownZero[BitWidth - 1]))
00966     return true;
00967 
00968   // TODO: implement logic similar to checkRippleForAdd
00969   return false;
00970 }
00971 
00972 /// \brief Return true if we can prove that:
00973 ///    (sub LHS, RHS)  === (sub nuw LHS, RHS)
00974 bool InstCombiner::WillNotOverflowUnsignedSub(Value *LHS, Value *RHS,
00975                                               Instruction *CxtI) {
00976   // If the LHS is negative and the RHS is non-negative, no unsigned wrap.
00977   bool LHSKnownNonNegative, LHSKnownNegative;
00978   bool RHSKnownNonNegative, RHSKnownNegative;
00979   ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, /*Depth=*/0, CxtI);
00980   ComputeSignBit(RHS, RHSKnownNonNegative, RHSKnownNegative, /*Depth=*/0, CxtI);
00981   if (LHSKnownNegative && RHSKnownNonNegative)
00982     return true;
00983 
00984   return false;
00985 }
00986 
00987 // Checks if any operand is negative and we can convert add to sub.
00988 // This function checks for following negative patterns
00989 //   ADD(XOR(OR(Z, NOT(C)), C)), 1) == NEG(AND(Z, C))
00990 //   ADD(XOR(AND(Z, C), C), 1) == NEG(OR(Z, ~C))
00991 //   XOR(AND(Z, C), (C + 1)) == NEG(OR(Z, ~C)) if C is even
00992 static Value *checkForNegativeOperand(BinaryOperator &I,
00993                                       InstCombiner::BuilderTy *Builder) {
00994   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
00995 
00996   // This function creates 2 instructions to replace ADD, we need at least one
00997   // of LHS or RHS to have one use to ensure benefit in transform.
00998   if (!LHS->hasOneUse() && !RHS->hasOneUse())
00999     return nullptr;
01000 
01001   Value *X = nullptr, *Y = nullptr, *Z = nullptr;
01002   const APInt *C1 = nullptr, *C2 = nullptr;
01003 
01004   // if ONE is on other side, swap
01005   if (match(RHS, m_Add(m_Value(X), m_One())))
01006     std::swap(LHS, RHS);
01007 
01008   if (match(LHS, m_Add(m_Value(X), m_One()))) {
01009     // if XOR on other side, swap
01010     if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1))))
01011       std::swap(X, RHS);
01012 
01013     if (match(X, m_Xor(m_Value(Y), m_APInt(C1)))) {
01014       // X = XOR(Y, C1), Y = OR(Z, C2), C2 = NOT(C1) ==> X == NOT(AND(Z, C1))
01015       // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, AND(Z, C1))
01016       if (match(Y, m_Or(m_Value(Z), m_APInt(C2))) && (*C2 == ~(*C1))) {
01017         Value *NewAnd = Builder->CreateAnd(Z, *C1);
01018         return Builder->CreateSub(RHS, NewAnd, "sub");
01019       } else if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && (*C1 == *C2)) {
01020         // X = XOR(Y, C1), Y = AND(Z, C2), C2 == C1 ==> X == NOT(OR(Z, ~C1))
01021         // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, OR(Z, ~C1))
01022         Value *NewOr = Builder->CreateOr(Z, ~(*C1));
01023         return Builder->CreateSub(RHS, NewOr, "sub");
01024       }
01025     }
01026   }
01027 
01028   // Restore LHS and RHS
01029   LHS = I.getOperand(0);
01030   RHS = I.getOperand(1);
01031 
01032   // if XOR is on other side, swap
01033   if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1))))
01034     std::swap(LHS, RHS);
01035 
01036   // C2 is ODD
01037   // LHS = XOR(Y, C1), Y = AND(Z, C2), C1 == (C2 + 1) => LHS == NEG(OR(Z, ~C2))
01038   // ADD(LHS, RHS) == SUB(RHS, OR(Z, ~C2))
01039   if (match(LHS, m_Xor(m_Value(Y), m_APInt(C1))))
01040     if (C1->countTrailingZeros() == 0)
01041       if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && *C1 == (*C2 + 1)) {
01042         Value *NewOr = Builder->CreateOr(Z, ~(*C2));
01043         return Builder->CreateSub(RHS, NewOr, "sub");
01044       }
01045   return nullptr;
01046 }
01047 
01048 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
01049    bool Changed = SimplifyAssociativeOrCommutative(I);
01050    Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
01051 
01052    if (Value *V = SimplifyVectorOp(I))
01053      return ReplaceInstUsesWith(I, V);
01054 
01055    if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(),
01056                                   I.hasNoUnsignedWrap(), DL, TLI, DT, AC))
01057      return ReplaceInstUsesWith(I, V);
01058 
01059    // (A*B)+(A*C) -> A*(B+C) etc
01060   if (Value *V = SimplifyUsingDistributiveLaws(I))
01061     return ReplaceInstUsesWith(I, V);
01062 
01063   if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
01064     // X + (signbit) --> X ^ signbit
01065     const APInt &Val = CI->getValue();
01066     if (Val.isSignBit())
01067       return BinaryOperator::CreateXor(LHS, RHS);
01068 
01069     // See if SimplifyDemandedBits can simplify this.  This handles stuff like
01070     // (X & 254)+1 -> (X&254)|1
01071     if (SimplifyDemandedInstructionBits(I))
01072       return &I;
01073 
01074     // zext(bool) + C -> bool ? C + 1 : C
01075     if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
01076       if (ZI->getSrcTy()->isIntegerTy(1))
01077         return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
01078 
01079     Value *XorLHS = nullptr; ConstantInt *XorRHS = nullptr;
01080     if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
01081       uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
01082       const APInt &RHSVal = CI->getValue();
01083       unsigned ExtendAmt = 0;
01084       // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
01085       // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
01086       if (XorRHS->getValue() == -RHSVal) {
01087         if (RHSVal.isPowerOf2())
01088           ExtendAmt = TySizeBits - RHSVal.logBase2() - 1;
01089         else if (XorRHS->getValue().isPowerOf2())
01090           ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1;
01091       }
01092 
01093       if (ExtendAmt) {
01094         APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt);
01095         if (!MaskedValueIsZero(XorLHS, Mask, 0, &I))
01096           ExtendAmt = 0;
01097       }
01098 
01099       if (ExtendAmt) {
01100         Constant *ShAmt = ConstantInt::get(I.getType(), ExtendAmt);
01101         Value *NewShl = Builder->CreateShl(XorLHS, ShAmt, "sext");
01102         return BinaryOperator::CreateAShr(NewShl, ShAmt);
01103       }
01104 
01105       // If this is a xor that was canonicalized from a sub, turn it back into
01106       // a sub and fuse this add with it.
01107       if (LHS->hasOneUse() && (XorRHS->getValue()+1).isPowerOf2()) {
01108         IntegerType *IT = cast<IntegerType>(I.getType());
01109         APInt LHSKnownOne(IT->getBitWidth(), 0);
01110         APInt LHSKnownZero(IT->getBitWidth(), 0);
01111         computeKnownBits(XorLHS, LHSKnownZero, LHSKnownOne, 0, &I);
01112         if ((XorRHS->getValue() | LHSKnownZero).isAllOnesValue())
01113           return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI),
01114                                            XorLHS);
01115       }
01116       // (X + signbit) + C could have gotten canonicalized to (X ^ signbit) + C,
01117       // transform them into (X + (signbit ^ C))
01118       if (XorRHS->getValue().isSignBit())
01119           return BinaryOperator::CreateAdd(XorLHS,
01120                                            ConstantExpr::getXor(XorRHS, CI));
01121     }
01122   }
01123 
01124   if (isa<Constant>(RHS) && isa<PHINode>(LHS))
01125     if (Instruction *NV = FoldOpIntoPhi(I))
01126       return NV;
01127 
01128   if (I.getType()->getScalarType()->isIntegerTy(1))
01129     return BinaryOperator::CreateXor(LHS, RHS);
01130 
01131   // X + X --> X << 1
01132   if (LHS == RHS) {
01133     BinaryOperator *New =
01134       BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
01135     New->setHasNoSignedWrap(I.hasNoSignedWrap());
01136     New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
01137     return New;
01138   }
01139 
01140   // -A + B  -->  B - A
01141   // -A + -B  -->  -(A + B)
01142   if (Value *LHSV = dyn_castNegVal(LHS)) {
01143     if (!isa<Constant>(RHS))
01144       if (Value *RHSV = dyn_castNegVal(RHS)) {
01145         Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
01146         return BinaryOperator::CreateNeg(NewAdd);
01147       }
01148 
01149     return BinaryOperator::CreateSub(RHS, LHSV);
01150   }
01151 
01152   // A + -B  -->  A - B
01153   if (!isa<Constant>(RHS))
01154     if (Value *V = dyn_castNegVal(RHS))
01155       return BinaryOperator::CreateSub(LHS, V);
01156 
01157   if (Value *V = checkForNegativeOperand(I, Builder))
01158     return ReplaceInstUsesWith(I, V);
01159 
01160   // A+B --> A|B iff A and B have no bits set in common.
01161   if (IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
01162     APInt LHSKnownOne(IT->getBitWidth(), 0);
01163     APInt LHSKnownZero(IT->getBitWidth(), 0);
01164     computeKnownBits(LHS, LHSKnownZero, LHSKnownOne, 0, &I);
01165     if (LHSKnownZero != 0) {
01166       APInt RHSKnownOne(IT->getBitWidth(), 0);
01167       APInt RHSKnownZero(IT->getBitWidth(), 0);
01168       computeKnownBits(RHS, RHSKnownZero, RHSKnownOne, 0, &I);
01169 
01170       // No bits in common -> bitwise or.
01171       if ((LHSKnownZero|RHSKnownZero).isAllOnesValue())
01172         return BinaryOperator::CreateOr(LHS, RHS);
01173     }
01174   }
01175 
01176   if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
01177     Value *X;
01178     if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X
01179       return BinaryOperator::CreateSub(SubOne(CRHS), X);
01180   }
01181 
01182   if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
01183     // (X & FF00) + xx00  -> (X+xx00) & FF00
01184     Value *X;
01185     ConstantInt *C2;
01186     if (LHS->hasOneUse() &&
01187         match(LHS, m_And(m_Value(X), m_ConstantInt(C2))) &&
01188         CRHS->getValue() == (CRHS->getValue() & C2->getValue())) {
01189       // See if all bits from the first bit set in the Add RHS up are included
01190       // in the mask.  First, get the rightmost bit.
01191       const APInt &AddRHSV = CRHS->getValue();
01192 
01193       // Form a mask of all bits from the lowest bit added through the top.
01194       APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
01195 
01196       // See if the and mask includes all of these bits.
01197       APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
01198 
01199       if (AddRHSHighBits == AddRHSHighBitsAnd) {
01200         // Okay, the xform is safe.  Insert the new add pronto.
01201         Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName());
01202         return BinaryOperator::CreateAnd(NewAdd, C2);
01203       }
01204     }
01205 
01206     // Try to fold constant add into select arguments.
01207     if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
01208       if (Instruction *R = FoldOpIntoSelect(I, SI))
01209         return R;
01210   }
01211 
01212   // add (select X 0 (sub n A)) A  -->  select X A n
01213   {
01214     SelectInst *SI = dyn_cast<SelectInst>(LHS);
01215     Value *A = RHS;
01216     if (!SI) {
01217       SI = dyn_cast<SelectInst>(RHS);
01218       A = LHS;
01219     }
01220     if (SI && SI->hasOneUse()) {
01221       Value *TV = SI->getTrueValue();
01222       Value *FV = SI->getFalseValue();
01223       Value *N;
01224 
01225       // Can we fold the add into the argument of the select?
01226       // We check both true and false select arguments for a matching subtract.
01227       if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A))))
01228         // Fold the add into the true select value.
01229         return SelectInst::Create(SI->getCondition(), N, A);
01230 
01231       if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A))))
01232         // Fold the add into the false select value.
01233         return SelectInst::Create(SI->getCondition(), A, N);
01234     }
01235   }
01236 
01237   // Check for (add (sext x), y), see if we can merge this into an
01238   // integer add followed by a sext.
01239   if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
01240     // (add (sext x), cst) --> (sext (add x, cst'))
01241     if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
01242       Constant *CI =
01243         ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
01244       if (LHSConv->hasOneUse() &&
01245           ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
01246           WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI, &I)) {
01247         // Insert the new, smaller add.
01248         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
01249                                               CI, "addconv");
01250         return new SExtInst(NewAdd, I.getType());
01251       }
01252     }
01253 
01254     // (add (sext x), (sext y)) --> (sext (add int x, y))
01255     if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) {
01256       // Only do this if x/y have the same type, if at last one of them has a
01257       // single use (so we don't increase the number of sexts), and if the
01258       // integer add will not overflow.
01259       if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
01260           (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
01261           WillNotOverflowSignedAdd(LHSConv->getOperand(0),
01262                                    RHSConv->getOperand(0), &I)) {
01263         // Insert the new integer add.
01264         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
01265                                              RHSConv->getOperand(0), "addconv");
01266         return new SExtInst(NewAdd, I.getType());
01267       }
01268     }
01269   }
01270 
01271   // (add (xor A, B) (and A, B)) --> (or A, B)
01272   {
01273     Value *A = nullptr, *B = nullptr;
01274     if (match(RHS, m_Xor(m_Value(A), m_Value(B))) &&
01275         (match(LHS, m_And(m_Specific(A), m_Specific(B))) ||
01276          match(LHS, m_And(m_Specific(B), m_Specific(A)))))
01277       return BinaryOperator::CreateOr(A, B);
01278 
01279     if (match(LHS, m_Xor(m_Value(A), m_Value(B))) &&
01280         (match(RHS, m_And(m_Specific(A), m_Specific(B))) ||
01281          match(RHS, m_And(m_Specific(B), m_Specific(A)))))
01282       return BinaryOperator::CreateOr(A, B);
01283   }
01284 
01285   // (add (or A, B) (and A, B)) --> (add A, B)
01286   {
01287     Value *A = nullptr, *B = nullptr;
01288     if (match(RHS, m_Or(m_Value(A), m_Value(B))) &&
01289         (match(LHS, m_And(m_Specific(A), m_Specific(B))) ||
01290          match(LHS, m_And(m_Specific(B), m_Specific(A))))) {
01291       auto *New = BinaryOperator::CreateAdd(A, B);
01292       New->setHasNoSignedWrap(I.hasNoSignedWrap());
01293       New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
01294       return New;
01295     }
01296 
01297     if (match(LHS, m_Or(m_Value(A), m_Value(B))) &&
01298         (match(RHS, m_And(m_Specific(A), m_Specific(B))) ||
01299          match(RHS, m_And(m_Specific(B), m_Specific(A))))) {
01300       auto *New = BinaryOperator::CreateAdd(A, B);
01301       New->setHasNoSignedWrap(I.hasNoSignedWrap());
01302       New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
01303       return New;
01304     }
01305   }
01306 
01307   // TODO(jingyue): Consider WillNotOverflowSignedAdd and
01308   // WillNotOverflowUnsignedAdd to reduce the number of invocations of
01309   // computeKnownBits.
01310   if (!I.hasNoSignedWrap() && WillNotOverflowSignedAdd(LHS, RHS, &I)) {
01311     Changed = true;
01312     I.setHasNoSignedWrap(true);
01313   }
01314   if (!I.hasNoUnsignedWrap() &&
01315       computeOverflowForUnsignedAdd(LHS, RHS, &I) ==
01316           OverflowResult::NeverOverflows) {
01317     Changed = true;
01318     I.setHasNoUnsignedWrap(true);
01319   }
01320 
01321   return Changed ? &I : nullptr;
01322 }
01323 
01324 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
01325   bool Changed = SimplifyAssociativeOrCommutative(I);
01326   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
01327 
01328   if (Value *V = SimplifyVectorOp(I))
01329     return ReplaceInstUsesWith(I, V);
01330 
01331   if (Value *V =
01332           SimplifyFAddInst(LHS, RHS, I.getFastMathFlags(), DL, TLI, DT, AC))
01333     return ReplaceInstUsesWith(I, V);
01334 
01335   if (isa<Constant>(RHS)) {
01336     if (isa<PHINode>(LHS))
01337       if (Instruction *NV = FoldOpIntoPhi(I))
01338         return NV;
01339 
01340     if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
01341       if (Instruction *NV = FoldOpIntoSelect(I, SI))
01342         return NV;
01343   }
01344 
01345   // -A + B  -->  B - A
01346   // -A + -B  -->  -(A + B)
01347   if (Value *LHSV = dyn_castFNegVal(LHS)) {
01348     Instruction *RI = BinaryOperator::CreateFSub(RHS, LHSV);
01349     RI->copyFastMathFlags(&I);
01350     return RI;
01351   }
01352 
01353   // A + -B  -->  A - B
01354   if (!isa<Constant>(RHS))
01355     if (Value *V = dyn_castFNegVal(RHS)) {
01356       Instruction *RI = BinaryOperator::CreateFSub(LHS, V);
01357       RI->copyFastMathFlags(&I);
01358       return RI;
01359     }
01360 
01361   // Check for (fadd double (sitofp x), y), see if we can merge this into an
01362   // integer add followed by a promotion.
01363   if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
01364     // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
01365     // ... if the constant fits in the integer value.  This is useful for things
01366     // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
01367     // requires a constant pool load, and generally allows the add to be better
01368     // instcombined.
01369     if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) {
01370       Constant *CI =
01371       ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType());
01372       if (LHSConv->hasOneUse() &&
01373           ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
01374           WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI, &I)) {
01375         // Insert the new integer add.
01376         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
01377                                               CI, "addconv");
01378         return new SIToFPInst(NewAdd, I.getType());
01379       }
01380     }
01381 
01382     // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
01383     if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
01384       // Only do this if x/y have the same type, if at last one of them has a
01385       // single use (so we don't increase the number of int->fp conversions),
01386       // and if the integer add will not overflow.
01387       if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
01388           (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
01389           WillNotOverflowSignedAdd(LHSConv->getOperand(0),
01390                                    RHSConv->getOperand(0), &I)) {
01391         // Insert the new integer add.
01392         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
01393                                               RHSConv->getOperand(0),"addconv");
01394         return new SIToFPInst(NewAdd, I.getType());
01395       }
01396     }
01397   }
01398 
01399   // select C, 0, B + select C, A, 0 -> select C, A, B
01400   {
01401     Value *A1, *B1, *C1, *A2, *B2, *C2;
01402     if (match(LHS, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) &&
01403         match(RHS, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) {
01404       if (C1 == C2) {
01405         Constant *Z1=nullptr, *Z2=nullptr;
01406         Value *A, *B, *C=C1;
01407         if (match(A1, m_AnyZero()) && match(B2, m_AnyZero())) {
01408             Z1 = dyn_cast<Constant>(A1); A = A2;
01409             Z2 = dyn_cast<Constant>(B2); B = B1;
01410         } else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) {
01411             Z1 = dyn_cast<Constant>(B1); B = B2;
01412             Z2 = dyn_cast<Constant>(A2); A = A1;
01413         }
01414 
01415         if (Z1 && Z2 &&
01416             (I.hasNoSignedZeros() ||
01417              (Z1->isNegativeZeroValue() && Z2->isNegativeZeroValue()))) {
01418           return SelectInst::Create(C, A, B);
01419         }
01420       }
01421     }
01422   }
01423 
01424   if (I.hasUnsafeAlgebra()) {
01425     if (Value *V = FAddCombine(Builder).simplify(&I))
01426       return ReplaceInstUsesWith(I, V);
01427   }
01428 
01429   return Changed ? &I : nullptr;
01430 }
01431 
01432 
01433 /// Optimize pointer differences into the same array into a size.  Consider:
01434 ///  &A[10] - &A[0]: we should compile this to "10".  LHS/RHS are the pointer
01435 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract.
01436 ///
01437 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
01438                                                Type *Ty) {
01439   assert(DL && "Must have target data info for this");
01440 
01441   // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize
01442   // this.
01443   bool Swapped = false;
01444   GEPOperator *GEP1 = nullptr, *GEP2 = nullptr;
01445 
01446   // For now we require one side to be the base pointer "A" or a constant
01447   // GEP derived from it.
01448   if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
01449     // (gep X, ...) - X
01450     if (LHSGEP->getOperand(0) == RHS) {
01451       GEP1 = LHSGEP;
01452       Swapped = false;
01453     } else if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
01454       // (gep X, ...) - (gep X, ...)
01455       if (LHSGEP->getOperand(0)->stripPointerCasts() ==
01456             RHSGEP->getOperand(0)->stripPointerCasts()) {
01457         GEP2 = RHSGEP;
01458         GEP1 = LHSGEP;
01459         Swapped = false;
01460       }
01461     }
01462   }
01463 
01464   if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
01465     // X - (gep X, ...)
01466     if (RHSGEP->getOperand(0) == LHS) {
01467       GEP1 = RHSGEP;
01468       Swapped = true;
01469     } else if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
01470       // (gep X, ...) - (gep X, ...)
01471       if (RHSGEP->getOperand(0)->stripPointerCasts() ==
01472             LHSGEP->getOperand(0)->stripPointerCasts()) {
01473         GEP2 = LHSGEP;
01474         GEP1 = RHSGEP;
01475         Swapped = true;
01476       }
01477     }
01478   }
01479 
01480   // Avoid duplicating the arithmetic if GEP2 has non-constant indices and
01481   // multiple users.
01482   if (!GEP1 ||
01483       (GEP2 && !GEP2->hasAllConstantIndices() && !GEP2->hasOneUse()))
01484     return nullptr;
01485 
01486   // Emit the offset of the GEP and an intptr_t.
01487   Value *Result = EmitGEPOffset(GEP1);
01488 
01489   // If we had a constant expression GEP on the other side offsetting the
01490   // pointer, subtract it from the offset we have.
01491   if (GEP2) {
01492     Value *Offset = EmitGEPOffset(GEP2);
01493     Result = Builder->CreateSub(Result, Offset);
01494   }
01495 
01496   // If we have p - gep(p, ...)  then we have to negate the result.
01497   if (Swapped)
01498     Result = Builder->CreateNeg(Result, "diff.neg");
01499 
01500   return Builder->CreateIntCast(Result, Ty, true);
01501 }
01502 
01503 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
01504   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
01505 
01506   if (Value *V = SimplifyVectorOp(I))
01507     return ReplaceInstUsesWith(I, V);
01508 
01509   if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(),
01510                                  I.hasNoUnsignedWrap(), DL, TLI, DT, AC))
01511     return ReplaceInstUsesWith(I, V);
01512 
01513   // (A*B)-(A*C) -> A*(B-C) etc
01514   if (Value *V = SimplifyUsingDistributiveLaws(I))
01515     return ReplaceInstUsesWith(I, V);
01516 
01517   // If this is a 'B = x-(-A)', change to B = x+A.
01518   if (Value *V = dyn_castNegVal(Op1)) {
01519     BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
01520 
01521     if (const auto *BO = dyn_cast<BinaryOperator>(Op1)) {
01522       assert(BO->getOpcode() == Instruction::Sub &&
01523              "Expected a subtraction operator!");
01524       if (BO->hasNoSignedWrap() && I.hasNoSignedWrap())
01525         Res->setHasNoSignedWrap(true);
01526     } else {
01527       if (cast<Constant>(Op1)->isNotMinSignedValue() && I.hasNoSignedWrap())
01528         Res->setHasNoSignedWrap(true);
01529     }
01530 
01531     return Res;
01532   }
01533 
01534   if (I.getType()->isIntegerTy(1))
01535     return BinaryOperator::CreateXor(Op0, Op1);
01536 
01537   // Replace (-1 - A) with (~A).
01538   if (match(Op0, m_AllOnes()))
01539     return BinaryOperator::CreateNot(Op1);
01540 
01541   if (Constant *C = dyn_cast<Constant>(Op0)) {
01542     // C - ~X == X + (1+C)
01543     Value *X = nullptr;
01544     if (match(Op1, m_Not(m_Value(X))))
01545       return BinaryOperator::CreateAdd(X, AddOne(C));
01546 
01547     // Try to fold constant sub into select arguments.
01548     if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
01549       if (Instruction *R = FoldOpIntoSelect(I, SI))
01550         return R;
01551 
01552     // C-(X+C2) --> (C-C2)-X
01553     Constant *C2;
01554     if (match(Op1, m_Add(m_Value(X), m_Constant(C2))))
01555       return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
01556 
01557     if (SimplifyDemandedInstructionBits(I))
01558       return &I;
01559 
01560     // Fold (sub 0, (zext bool to B)) --> (sext bool to B)
01561     if (C->isNullValue() && match(Op1, m_ZExt(m_Value(X))))
01562       if (X->getType()->getScalarType()->isIntegerTy(1))
01563         return CastInst::CreateSExtOrBitCast(X, Op1->getType());
01564 
01565     // Fold (sub 0, (sext bool to B)) --> (zext bool to B)
01566     if (C->isNullValue() && match(Op1, m_SExt(m_Value(X))))
01567       if (X->getType()->getScalarType()->isIntegerTy(1))
01568         return CastInst::CreateZExtOrBitCast(X, Op1->getType());
01569   }
01570 
01571   if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
01572     // -(X >>u 31) -> (X >>s 31)
01573     // -(X >>s 31) -> (X >>u 31)
01574     if (C->isZero()) {
01575       Value *X;
01576       ConstantInt *CI;
01577       if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) &&
01578           // Verify we are shifting out everything but the sign bit.
01579           CI->getValue() == I.getType()->getPrimitiveSizeInBits() - 1)
01580         return BinaryOperator::CreateAShr(X, CI);
01581 
01582       if (match(Op1, m_AShr(m_Value(X), m_ConstantInt(CI))) &&
01583           // Verify we are shifting out everything but the sign bit.
01584           CI->getValue() == I.getType()->getPrimitiveSizeInBits() - 1)
01585         return BinaryOperator::CreateLShr(X, CI);
01586     }
01587   }
01588 
01589 
01590   {
01591     Value *Y;
01592     // X-(X+Y) == -Y    X-(Y+X) == -Y
01593     if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) ||
01594         match(Op1, m_Add(m_Value(Y), m_Specific(Op0))))
01595       return BinaryOperator::CreateNeg(Y);
01596 
01597     // (X-Y)-X == -Y
01598     if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y))))
01599       return BinaryOperator::CreateNeg(Y);
01600   }
01601 
01602   // (sub (or A, B) (xor A, B)) --> (and A, B)
01603   {
01604     Value *A = nullptr, *B = nullptr;
01605     if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
01606         (match(Op0, m_Or(m_Specific(A), m_Specific(B))) ||
01607          match(Op0, m_Or(m_Specific(B), m_Specific(A)))))
01608       return BinaryOperator::CreateAnd(A, B);
01609   }
01610 
01611   if (Op0->hasOneUse()) {
01612     Value *Y = nullptr;
01613     // ((X | Y) - X) --> (~X & Y)
01614     if (match(Op0, m_Or(m_Value(Y), m_Specific(Op1))) ||
01615         match(Op0, m_Or(m_Specific(Op1), m_Value(Y))))
01616       return BinaryOperator::CreateAnd(
01617           Y, Builder->CreateNot(Op1, Op1->getName() + ".not"));
01618   }
01619 
01620   if (Op1->hasOneUse()) {
01621     Value *X = nullptr, *Y = nullptr, *Z = nullptr;
01622     Constant *C = nullptr;
01623     Constant *CI = nullptr;
01624 
01625     // (X - (Y - Z))  -->  (X + (Z - Y)).
01626     if (match(Op1, m_Sub(m_Value(Y), m_Value(Z))))
01627       return BinaryOperator::CreateAdd(Op0,
01628                                       Builder->CreateSub(Z, Y, Op1->getName()));
01629 
01630     // (X - (X & Y))   -->   (X & ~Y)
01631     //
01632     if (match(Op1, m_And(m_Value(Y), m_Specific(Op0))) ||
01633         match(Op1, m_And(m_Specific(Op0), m_Value(Y))))
01634       return BinaryOperator::CreateAnd(Op0,
01635                                   Builder->CreateNot(Y, Y->getName() + ".not"));
01636 
01637     // 0 - (X sdiv C)  -> (X sdiv -C)  provided the negation doesn't overflow.
01638     if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) && match(Op0, m_Zero()) &&
01639         C->isNotMinSignedValue() && !C->isOneValue())
01640       return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C));
01641 
01642     // 0 - (X << Y)  -> (-X << Y)   when X is freely negatable.
01643     if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero()))
01644       if (Value *XNeg = dyn_castNegVal(X))
01645         return BinaryOperator::CreateShl(XNeg, Y);
01646 
01647     // X - A*-B -> X + A*B
01648     // X - -A*B -> X + A*B
01649     Value *A, *B;
01650     if (match(Op1, m_Mul(m_Value(A), m_Neg(m_Value(B)))) ||
01651         match(Op1, m_Mul(m_Neg(m_Value(A)), m_Value(B))))
01652       return BinaryOperator::CreateAdd(Op0, Builder->CreateMul(A, B));
01653 
01654     // X - A*CI -> X + A*-CI
01655     // X - CI*A -> X + A*-CI
01656     if (match(Op1, m_Mul(m_Value(A), m_Constant(CI))) ||
01657         match(Op1, m_Mul(m_Constant(CI), m_Value(A)))) {
01658       Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(CI));
01659       return BinaryOperator::CreateAdd(Op0, NewMul);
01660     }
01661   }
01662 
01663   // Optimize pointer differences into the same array into a size.  Consider:
01664   //  &A[10] - &A[0]: we should compile this to "10".
01665   if (DL) {
01666     Value *LHSOp, *RHSOp;
01667     if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
01668         match(Op1, m_PtrToInt(m_Value(RHSOp))))
01669       if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
01670         return ReplaceInstUsesWith(I, Res);
01671 
01672     // trunc(p)-trunc(q) -> trunc(p-q)
01673     if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
01674         match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
01675       if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
01676         return ReplaceInstUsesWith(I, Res);
01677       }
01678 
01679   bool Changed = false;
01680   if (!I.hasNoSignedWrap() && WillNotOverflowSignedSub(Op0, Op1, &I)) {
01681     Changed = true;
01682     I.setHasNoSignedWrap(true);
01683   }
01684   if (!I.hasNoUnsignedWrap() && WillNotOverflowUnsignedSub(Op0, Op1, &I)) {
01685     Changed = true;
01686     I.setHasNoUnsignedWrap(true);
01687   }
01688 
01689   return Changed ? &I : nullptr;
01690 }
01691 
01692 Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
01693   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
01694 
01695   if (Value *V = SimplifyVectorOp(I))
01696     return ReplaceInstUsesWith(I, V);
01697 
01698   if (Value *V =
01699           SimplifyFSubInst(Op0, Op1, I.getFastMathFlags(), DL, TLI, DT, AC))
01700     return ReplaceInstUsesWith(I, V);
01701 
01702   // fsub nsz 0, X ==> fsub nsz -0.0, X
01703   if (I.getFastMathFlags().noSignedZeros() && match(Op0, m_Zero())) {
01704     // Subtraction from -0.0 is the canonical form of fneg.
01705     Instruction *NewI = BinaryOperator::CreateFNeg(Op1);
01706     NewI->copyFastMathFlags(&I);
01707     return NewI;
01708   }
01709 
01710   if (isa<Constant>(Op0))
01711     if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
01712       if (Instruction *NV = FoldOpIntoSelect(I, SI))
01713         return NV;
01714 
01715   // If this is a 'B = x-(-A)', change to B = x+A, potentially looking
01716   // through FP extensions/truncations along the way.
01717   if (Value *V = dyn_castFNegVal(Op1)) {
01718     Instruction *NewI = BinaryOperator::CreateFAdd(Op0, V);
01719     NewI->copyFastMathFlags(&I);
01720     return NewI;
01721   }
01722   if (FPTruncInst *FPTI = dyn_cast<FPTruncInst>(Op1)) {
01723     if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) {
01724       Value *NewTrunc = Builder->CreateFPTrunc(V, I.getType());
01725       Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewTrunc);
01726       NewI->copyFastMathFlags(&I);
01727       return NewI;
01728     }
01729   } else if (FPExtInst *FPEI = dyn_cast<FPExtInst>(Op1)) {
01730     if (Value *V = dyn_castFNegVal(FPEI->getOperand(0))) {
01731       Value *NewExt = Builder->CreateFPExt(V, I.getType());
01732       Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewExt);
01733       NewI->copyFastMathFlags(&I);
01734       return NewI;
01735     }
01736   }
01737 
01738   if (I.hasUnsafeAlgebra()) {
01739     if (Value *V = FAddCombine(Builder).simplify(&I))
01740       return ReplaceInstUsesWith(I, V);
01741   }
01742 
01743   return nullptr;
01744 }