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      1 //===- InstCombineAddSub.cpp ----------------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements the visit functions for add, fadd, sub, and fsub.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "InstCombine.h"
     15 #include "llvm/ADT/STLExtras.h"
     16 #include "llvm/Analysis/InstructionSimplify.h"
     17 #include "llvm/IR/DataLayout.h"
     18 #include "llvm/Support/GetElementPtrTypeIterator.h"
     19 #include "llvm/Support/PatternMatch.h"
     20 using namespace llvm;
     21 using namespace PatternMatch;
     22 
     23 namespace {
     24 
     25   /// Class representing coefficient of floating-point addend.
     26   /// This class needs to be highly efficient, which is especially true for
     27   /// the constructor. As of I write this comment, the cost of the default
     28   /// constructor is merely 4-byte-store-zero (Assuming compiler is able to
     29   /// perform write-merging).
     30   ///
     31   class FAddendCoef {
     32   public:
     33     // The constructor has to initialize a APFloat, which is uncessary for
     34     // most addends which have coefficient either 1 or -1. So, the constructor
     35     // is expensive. In order to avoid the cost of the constructor, we should
     36     // reuse some instances whenever possible. The pre-created instances
     37     // FAddCombine::Add[0-5] embodies this idea.
     38     //
     39     FAddendCoef() : IsFp(false), BufHasFpVal(false), IntVal(0) {}
     40     ~FAddendCoef();
     41 
     42     void set(short C) {
     43       assert(!insaneIntVal(C) && "Insane coefficient");
     44       IsFp = false; IntVal = C;
     45     }
     46 
     47     void set(const APFloat& C);
     48 
     49     void negate();
     50 
     51     bool isZero() const { return isInt() ? !IntVal : getFpVal().isZero(); }
     52     Value *getValue(Type *) const;
     53 
     54     // If possible, don't define operator+/operator- etc because these
     55     // operators inevitably call FAddendCoef's constructor which is not cheap.
     56     void operator=(const FAddendCoef &A);
     57     void operator+=(const FAddendCoef &A);
     58     void operator-=(const FAddendCoef &A);
     59     void operator*=(const FAddendCoef &S);
     60 
     61     bool isOne() const { return isInt() && IntVal == 1; }
     62     bool isTwo() const { return isInt() && IntVal == 2; }
     63     bool isMinusOne() const { return isInt() && IntVal == -1; }
     64     bool isMinusTwo() const { return isInt() && IntVal == -2; }
     65 
     66   private:
     67     bool insaneIntVal(int V) { return V > 4 || V < -4; }
     68     APFloat *getFpValPtr(void)
     69       { return reinterpret_cast<APFloat*>(&FpValBuf.buffer[0]); }
     70     const APFloat *getFpValPtr(void) const
     71       { return reinterpret_cast<const APFloat*>(&FpValBuf.buffer[0]); }
     72 
     73     const APFloat &getFpVal(void) const {
     74       assert(IsFp && BufHasFpVal && "Incorret state");
     75       return *getFpValPtr();
     76     }
     77 
     78     APFloat &getFpVal(void) {
     79       assert(IsFp && BufHasFpVal && "Incorret state");
     80       return *getFpValPtr();
     81     }
     82 
     83     bool isInt() const { return !IsFp; }
     84 
     85     // If the coefficient is represented by an integer, promote it to a
     86     // floating point.
     87     void convertToFpType(const fltSemantics &Sem);
     88 
     89     // Construct an APFloat from a signed integer.
     90     // TODO: We should get rid of this function when APFloat can be constructed
     91     //       from an *SIGNED* integer.
     92     APFloat createAPFloatFromInt(const fltSemantics &Sem, int Val);
     93   private:
     94 
     95     bool IsFp;
     96 
     97     // True iff FpValBuf contains an instance of APFloat.
     98     bool BufHasFpVal;
     99 
    100     // The integer coefficient of an individual addend is either 1 or -1,
    101     // and we try to simplify at most 4 addends from neighboring at most
    102     // two instructions. So the range of <IntVal> falls in [-4, 4]. APInt
    103     // is overkill of this end.
    104     short IntVal;
    105 
    106     AlignedCharArrayUnion<APFloat> FpValBuf;
    107   };
    108 
    109   /// FAddend is used to represent floating-point addend. An addend is
    110   /// represented as <C, V>, where the V is a symbolic value, and C is a
    111   /// constant coefficient. A constant addend is represented as <C, 0>.
    112   ///
    113   class FAddend {
    114   public:
    115     FAddend() { Val = 0; }
    116 
    117     Value *getSymVal (void) const { return Val; }
    118     const FAddendCoef &getCoef(void) const { return Coeff; }
    119 
    120     bool isConstant() const { return Val == 0; }
    121     bool isZero() const { return Coeff.isZero(); }
    122 
    123     void set(short Coefficient, Value *V) { Coeff.set(Coefficient), Val = V; }
    124     void set(const APFloat& Coefficient, Value *V)
    125       { Coeff.set(Coefficient); Val = V; }
    126     void set(const ConstantFP* Coefficient, Value *V)
    127       { Coeff.set(Coefficient->getValueAPF()); Val = V; }
    128 
    129     void negate() { Coeff.negate(); }
    130 
    131     /// Drill down the U-D chain one step to find the definition of V, and
    132     /// try to break the definition into one or two addends.
    133     static unsigned drillValueDownOneStep(Value* V, FAddend &A0, FAddend &A1);
    134 
    135     /// Similar to FAddend::drillDownOneStep() except that the value being
    136     /// splitted is the addend itself.
    137     unsigned drillAddendDownOneStep(FAddend &Addend0, FAddend &Addend1) const;
    138 
    139     void operator+=(const FAddend &T) {
    140       assert((Val == T.Val) && "Symbolic-values disagree");
    141       Coeff += T.Coeff;
    142     }
    143 
    144   private:
    145     void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; }
    146 
    147     // This addend has the value of "Coeff * Val".
    148     Value *Val;
    149     FAddendCoef Coeff;
    150   };
    151 
    152   /// FAddCombine is the class for optimizing an unsafe fadd/fsub along
    153   /// with its neighboring at most two instructions.
    154   ///
    155   class FAddCombine {
    156   public:
    157     FAddCombine(InstCombiner::BuilderTy *B) : Builder(B), Instr(0) {}
    158     Value *simplify(Instruction *FAdd);
    159 
    160   private:
    161     typedef SmallVector<const FAddend*, 4> AddendVect;
    162 
    163     Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota);
    164 
    165     Value *performFactorization(Instruction *I);
    166 
    167     /// Convert given addend to a Value
    168     Value *createAddendVal(const FAddend &A, bool& NeedNeg);
    169 
    170     /// Return the number of instructions needed to emit the N-ary addition.
    171     unsigned calcInstrNumber(const AddendVect& Vect);
    172     Value *createFSub(Value *Opnd0, Value *Opnd1);
    173     Value *createFAdd(Value *Opnd0, Value *Opnd1);
    174     Value *createFMul(Value *Opnd0, Value *Opnd1);
    175     Value *createFDiv(Value *Opnd0, Value *Opnd1);
    176     Value *createFNeg(Value *V);
    177     Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota);
    178     void createInstPostProc(Instruction *NewInst);
    179 
    180     InstCombiner::BuilderTy *Builder;
    181     Instruction *Instr;
    182 
    183   private:
    184      // Debugging stuff are clustered here.
    185     #ifndef NDEBUG
    186       unsigned CreateInstrNum;
    187       void initCreateInstNum() { CreateInstrNum = 0; }
    188       void incCreateInstNum() { CreateInstrNum++; }
    189     #else
    190       void initCreateInstNum() {}
    191       void incCreateInstNum() {}
    192     #endif
    193   };
    194 }
    195 
    196 //===----------------------------------------------------------------------===//
    197 //
    198 // Implementation of
    199 //    {FAddendCoef, FAddend, FAddition, FAddCombine}.
    200 //
    201 //===----------------------------------------------------------------------===//
    202 FAddendCoef::~FAddendCoef() {
    203   if (BufHasFpVal)
    204     getFpValPtr()->~APFloat();
    205 }
    206 
    207 void FAddendCoef::set(const APFloat& C) {
    208   APFloat *P = getFpValPtr();
    209 
    210   if (isInt()) {
    211     // As the buffer is meanless byte stream, we cannot call
    212     // APFloat::operator=().
    213     new(P) APFloat(C);
    214   } else
    215     *P = C;
    216 
    217   IsFp = BufHasFpVal = true;
    218 }
    219 
    220 void FAddendCoef::convertToFpType(const fltSemantics &Sem) {
    221   if (!isInt())
    222     return;
    223 
    224   APFloat *P = getFpValPtr();
    225   if (IntVal > 0)
    226     new(P) APFloat(Sem, IntVal);
    227   else {
    228     new(P) APFloat(Sem, 0 - IntVal);
    229     P->changeSign();
    230   }
    231   IsFp = BufHasFpVal = true;
    232 }
    233 
    234 APFloat FAddendCoef::createAPFloatFromInt(const fltSemantics &Sem, int Val) {
    235   if (Val >= 0)
    236     return APFloat(Sem, Val);
    237 
    238   APFloat T(Sem, 0 - Val);
    239   T.changeSign();
    240 
    241   return T;
    242 }
    243 
    244 void FAddendCoef::operator=(const FAddendCoef &That) {
    245   if (That.isInt())
    246     set(That.IntVal);
    247   else
    248     set(That.getFpVal());
    249 }
    250 
    251 void FAddendCoef::operator+=(const FAddendCoef &That) {
    252   enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven;
    253   if (isInt() == That.isInt()) {
    254     if (isInt())
    255       IntVal += That.IntVal;
    256     else
    257       getFpVal().add(That.getFpVal(), RndMode);
    258     return;
    259   }
    260 
    261   if (isInt()) {
    262     const APFloat &T = That.getFpVal();
    263     convertToFpType(T.getSemantics());
    264     getFpVal().add(T, RndMode);
    265     return;
    266   }
    267 
    268   APFloat &T = getFpVal();
    269   T.add(createAPFloatFromInt(T.getSemantics(), That.IntVal), RndMode);
    270 }
    271 
    272 void FAddendCoef::operator-=(const FAddendCoef &That) {
    273   enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven;
    274   if (isInt() == That.isInt()) {
    275     if (isInt())
    276       IntVal -= That.IntVal;
    277     else
    278       getFpVal().subtract(That.getFpVal(), RndMode);
    279     return;
    280   }
    281 
    282   if (isInt()) {
    283     const APFloat &T = That.getFpVal();
    284     convertToFpType(T.getSemantics());
    285     getFpVal().subtract(T, RndMode);
    286     return;
    287   }
    288 
    289   APFloat &T = getFpVal();
    290   T.subtract(createAPFloatFromInt(T.getSemantics(), IntVal), RndMode);
    291 }
    292 
    293 void FAddendCoef::operator*=(const FAddendCoef &That) {
    294   if (That.isOne())
    295     return;
    296 
    297   if (That.isMinusOne()) {
    298     negate();
    299     return;
    300   }
    301 
    302   if (isInt() && That.isInt()) {
    303     int Res = IntVal * (int)That.IntVal;
    304     assert(!insaneIntVal(Res) && "Insane int value");
    305     IntVal = Res;
    306     return;
    307   }
    308 
    309   const fltSemantics &Semantic =
    310     isInt() ? That.getFpVal().getSemantics() : getFpVal().getSemantics();
    311 
    312   if (isInt())
    313     convertToFpType(Semantic);
    314   APFloat &F0 = getFpVal();
    315 
    316   if (That.isInt())
    317     F0.multiply(createAPFloatFromInt(Semantic, That.IntVal),
    318                 APFloat::rmNearestTiesToEven);
    319   else
    320     F0.multiply(That.getFpVal(), APFloat::rmNearestTiesToEven);
    321 
    322   return;
    323 }
    324 
    325 void FAddendCoef::negate() {
    326   if (isInt())
    327     IntVal = 0 - IntVal;
    328   else
    329     getFpVal().changeSign();
    330 }
    331 
    332 Value *FAddendCoef::getValue(Type *Ty) const {
    333   return isInt() ?
    334     ConstantFP::get(Ty, float(IntVal)) :
    335     ConstantFP::get(Ty->getContext(), getFpVal());
    336 }
    337 
    338 // The definition of <Val>     Addends
    339 // =========================================
    340 //  A + B                     <1, A>, <1,B>
    341 //  A - B                     <1, A>, <1,B>
    342 //  0 - B                     <-1, B>
    343 //  C * A,                    <C, A>
    344 //  A + C                     <1, A> <C, NULL>
    345 //  0 +/- 0                   <0, NULL> (corner case)
    346 //
    347 // Legend: A and B are not constant, C is constant
    348 //
    349 unsigned FAddend::drillValueDownOneStep
    350   (Value *Val, FAddend &Addend0, FAddend &Addend1) {
    351   Instruction *I = 0;
    352   if (Val == 0 || !(I = dyn_cast<Instruction>(Val)))
    353     return 0;
    354 
    355   unsigned Opcode = I->getOpcode();
    356 
    357   if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub) {
    358     ConstantFP *C0, *C1;
    359     Value *Opnd0 = I->getOperand(0);
    360     Value *Opnd1 = I->getOperand(1);
    361     if ((C0 = dyn_cast<ConstantFP>(Opnd0)) && C0->isZero())
    362       Opnd0 = 0;
    363 
    364     if ((C1 = dyn_cast<ConstantFP>(Opnd1)) && C1->isZero())
    365       Opnd1 = 0;
    366 
    367     if (Opnd0) {
    368       if (!C0)
    369         Addend0.set(1, Opnd0);
    370       else
    371         Addend0.set(C0, 0);
    372     }
    373 
    374     if (Opnd1) {
    375       FAddend &Addend = Opnd0 ? Addend1 : Addend0;
    376       if (!C1)
    377         Addend.set(1, Opnd1);
    378       else
    379         Addend.set(C1, 0);
    380       if (Opcode == Instruction::FSub)
    381         Addend.negate();
    382     }
    383 
    384     if (Opnd0 || Opnd1)
    385       return Opnd0 && Opnd1 ? 2 : 1;
    386 
    387     // Both operands are zero. Weird!
    388     Addend0.set(APFloat(C0->getValueAPF().getSemantics()), 0);
    389     return 1;
    390   }
    391 
    392   if (I->getOpcode() == Instruction::FMul) {
    393     Value *V0 = I->getOperand(0);
    394     Value *V1 = I->getOperand(1);
    395     if (ConstantFP *C = dyn_cast<ConstantFP>(V0)) {
    396       Addend0.set(C, V1);
    397       return 1;
    398     }
    399 
    400     if (ConstantFP *C = dyn_cast<ConstantFP>(V1)) {
    401       Addend0.set(C, V0);
    402       return 1;
    403     }
    404   }
    405 
    406   return 0;
    407 }
    408 
    409 // Try to break *this* addend into two addends. e.g. Suppose this addend is
    410 // <2.3, V>, and V = X + Y, by calling this function, we obtain two addends,
    411 // i.e. <2.3, X> and <2.3, Y>.
    412 //
    413 unsigned FAddend::drillAddendDownOneStep
    414   (FAddend &Addend0, FAddend &Addend1) const {
    415   if (isConstant())
    416     return 0;
    417 
    418   unsigned BreakNum = FAddend::drillValueDownOneStep(Val, Addend0, Addend1);
    419   if (!BreakNum || Coeff.isOne())
    420     return BreakNum;
    421 
    422   Addend0.Scale(Coeff);
    423 
    424   if (BreakNum == 2)
    425     Addend1.Scale(Coeff);
    426 
    427   return BreakNum;
    428 }
    429 
    430 // Try to perform following optimization on the input instruction I. Return the
    431 // simplified expression if was successful; otherwise, return 0.
    432 //
    433 //   Instruction "I" is                Simplified into
    434 // -------------------------------------------------------
    435 //   (x * y) +/- (x * z)               x * (y +/- z)
    436 //   (y / x) +/- (z / x)               (y +/- z) / x
    437 //
    438 Value *FAddCombine::performFactorization(Instruction *I) {
    439   assert((I->getOpcode() == Instruction::FAdd ||
    440           I->getOpcode() == Instruction::FSub) && "Expect add/sub");
    441 
    442   Instruction *I0 = dyn_cast<Instruction>(I->getOperand(0));
    443   Instruction *I1 = dyn_cast<Instruction>(I->getOperand(1));
    444 
    445   if (!I0 || !I1 || I0->getOpcode() != I1->getOpcode())
    446     return 0;
    447 
    448   bool isMpy = false;
    449   if (I0->getOpcode() == Instruction::FMul)
    450     isMpy = true;
    451   else if (I0->getOpcode() != Instruction::FDiv)
    452     return 0;
    453 
    454   Value *Opnd0_0 = I0->getOperand(0);
    455   Value *Opnd0_1 = I0->getOperand(1);
    456   Value *Opnd1_0 = I1->getOperand(0);
    457   Value *Opnd1_1 = I1->getOperand(1);
    458 
    459   //  Input Instr I       Factor   AddSub0  AddSub1
    460   //  ----------------------------------------------
    461   // (x*y) +/- (x*z)        x        y         z
    462   // (y/x) +/- (z/x)        x        y         z
    463   //
    464   Value *Factor = 0;
    465   Value *AddSub0 = 0, *AddSub1 = 0;
    466 
    467   if (isMpy) {
    468     if (Opnd0_0 == Opnd1_0 || Opnd0_0 == Opnd1_1)
    469       Factor = Opnd0_0;
    470     else if (Opnd0_1 == Opnd1_0 || Opnd0_1 == Opnd1_1)
    471       Factor = Opnd0_1;
    472 
    473     if (Factor) {
    474       AddSub0 = (Factor == Opnd0_0) ? Opnd0_1 : Opnd0_0;
    475       AddSub1 = (Factor == Opnd1_0) ? Opnd1_1 : Opnd1_0;
    476     }
    477   } else if (Opnd0_1 == Opnd1_1) {
    478     Factor = Opnd0_1;
    479     AddSub0 = Opnd0_0;
    480     AddSub1 = Opnd1_0;
    481   }
    482 
    483   if (!Factor)
    484     return 0;
    485 
    486   // Create expression "NewAddSub = AddSub0 +/- AddsSub1"
    487   Value *NewAddSub = (I->getOpcode() == Instruction::FAdd) ?
    488                       createFAdd(AddSub0, AddSub1) :
    489                       createFSub(AddSub0, AddSub1);
    490   if (ConstantFP *CFP = dyn_cast<ConstantFP>(NewAddSub)) {
    491     const APFloat &F = CFP->getValueAPF();
    492     if (!F.isNormal())
    493       return 0;
    494   }
    495 
    496   if (isMpy)
    497     return createFMul(Factor, NewAddSub);
    498 
    499   return createFDiv(NewAddSub, Factor);
    500 }
    501 
    502 Value *FAddCombine::simplify(Instruction *I) {
    503   assert(I->hasUnsafeAlgebra() && "Should be in unsafe mode");
    504 
    505   // Currently we are not able to handle vector type.
    506   if (I->getType()->isVectorTy())
    507     return 0;
    508 
    509   assert((I->getOpcode() == Instruction::FAdd ||
    510           I->getOpcode() == Instruction::FSub) && "Expect add/sub");
    511 
    512   // Save the instruction before calling other member-functions.
    513   Instr = I;
    514 
    515   FAddend Opnd0, Opnd1, Opnd0_0, Opnd0_1, Opnd1_0, Opnd1_1;
    516 
    517   unsigned OpndNum = FAddend::drillValueDownOneStep(I, Opnd0, Opnd1);
    518 
    519   // Step 1: Expand the 1st addend into Opnd0_0 and Opnd0_1.
    520   unsigned Opnd0_ExpNum = 0;
    521   unsigned Opnd1_ExpNum = 0;
    522 
    523   if (!Opnd0.isConstant())
    524     Opnd0_ExpNum = Opnd0.drillAddendDownOneStep(Opnd0_0, Opnd0_1);
    525 
    526   // Step 2: Expand the 2nd addend into Opnd1_0 and Opnd1_1.
    527   if (OpndNum == 2 && !Opnd1.isConstant())
    528     Opnd1_ExpNum = Opnd1.drillAddendDownOneStep(Opnd1_0, Opnd1_1);
    529 
    530   // Step 3: Try to optimize Opnd0_0 + Opnd0_1 + Opnd1_0 + Opnd1_1
    531   if (Opnd0_ExpNum && Opnd1_ExpNum) {
    532     AddendVect AllOpnds;
    533     AllOpnds.push_back(&Opnd0_0);
    534     AllOpnds.push_back(&Opnd1_0);
    535     if (Opnd0_ExpNum == 2)
    536       AllOpnds.push_back(&Opnd0_1);
    537     if (Opnd1_ExpNum == 2)
    538       AllOpnds.push_back(&Opnd1_1);
    539 
    540     // Compute instruction quota. We should save at least one instruction.
    541     unsigned InstQuota = 0;
    542 
    543     Value *V0 = I->getOperand(0);
    544     Value *V1 = I->getOperand(1);
    545     InstQuota = ((!isa<Constant>(V0) && V0->hasOneUse()) &&
    546                  (!isa<Constant>(V1) && V1->hasOneUse())) ? 2 : 1;
    547 
    548     if (Value *R = simplifyFAdd(AllOpnds, InstQuota))
    549       return R;
    550   }
    551 
    552   if (OpndNum != 2) {
    553     // The input instruction is : "I=0.0 +/- V". If the "V" were able to be
    554     // splitted into two addends, say "V = X - Y", the instruction would have
    555     // been optimized into "I = Y - X" in the previous steps.
    556     //
    557     const FAddendCoef &CE = Opnd0.getCoef();
    558     return CE.isOne() ? Opnd0.getSymVal() : 0;
    559   }
    560 
    561   // step 4: Try to optimize Opnd0 + Opnd1_0 [+ Opnd1_1]
    562   if (Opnd1_ExpNum) {
    563     AddendVect AllOpnds;
    564     AllOpnds.push_back(&Opnd0);
    565     AllOpnds.push_back(&Opnd1_0);
    566     if (Opnd1_ExpNum == 2)
    567       AllOpnds.push_back(&Opnd1_1);
    568 
    569     if (Value *R = simplifyFAdd(AllOpnds, 1))
    570       return R;
    571   }
    572 
    573   // step 5: Try to optimize Opnd1 + Opnd0_0 [+ Opnd0_1]
    574   if (Opnd0_ExpNum) {
    575     AddendVect AllOpnds;
    576     AllOpnds.push_back(&Opnd1);
    577     AllOpnds.push_back(&Opnd0_0);
    578     if (Opnd0_ExpNum == 2)
    579       AllOpnds.push_back(&Opnd0_1);
    580 
    581     if (Value *R = simplifyFAdd(AllOpnds, 1))
    582       return R;
    583   }
    584 
    585   // step 6: Try factorization as the last resort,
    586   return performFactorization(I);
    587 }
    588 
    589 Value *FAddCombine::simplifyFAdd(AddendVect& Addends, unsigned InstrQuota) {
    590 
    591   unsigned AddendNum = Addends.size();
    592   assert(AddendNum <= 4 && "Too many addends");
    593 
    594   // For saving intermediate results;
    595   unsigned NextTmpIdx = 0;
    596   FAddend TmpResult[3];
    597 
    598   // Points to the constant addend of the resulting simplified expression.
    599   // If the resulting expr has constant-addend, this constant-addend is
    600   // desirable to reside at the top of the resulting expression tree. Placing
    601   // constant close to supper-expr(s) will potentially reveal some optimization
    602   // opportunities in super-expr(s).
    603   //
    604   const FAddend *ConstAdd = 0;
    605 
    606   // Simplified addends are placed <SimpVect>.
    607   AddendVect SimpVect;
    608 
    609   // The outer loop works on one symbolic-value at a time. Suppose the input
    610   // addends are : <a1, x>, <b1, y>, <a2, x>, <c1, z>, <b2, y>, ...
    611   // The symbolic-values will be processed in this order: x, y, z.
    612   //
    613   for (unsigned SymIdx = 0; SymIdx < AddendNum; SymIdx++) {
    614 
    615     const FAddend *ThisAddend = Addends[SymIdx];
    616     if (!ThisAddend) {
    617       // This addend was processed before.
    618       continue;
    619     }
    620 
    621     Value *Val = ThisAddend->getSymVal();
    622     unsigned StartIdx = SimpVect.size();
    623     SimpVect.push_back(ThisAddend);
    624 
    625     // The inner loop collects addends sharing same symbolic-value, and these
    626     // addends will be later on folded into a single addend. Following above
    627     // example, if the symbolic value "y" is being processed, the inner loop
    628     // will collect two addends "<b1,y>" and "<b2,Y>". These two addends will
    629     // be later on folded into "<b1+b2, y>".
    630     //
    631     for (unsigned SameSymIdx = SymIdx + 1;
    632          SameSymIdx < AddendNum; SameSymIdx++) {
    633       const FAddend *T = Addends[SameSymIdx];
    634       if (T && T->getSymVal() == Val) {
    635         // Set null such that next iteration of the outer loop will not process
    636         // this addend again.
    637         Addends[SameSymIdx] = 0;
    638         SimpVect.push_back(T);
    639       }
    640     }
    641 
    642     // If multiple addends share same symbolic value, fold them together.
    643     if (StartIdx + 1 != SimpVect.size()) {
    644       FAddend &R = TmpResult[NextTmpIdx ++];
    645       R = *SimpVect[StartIdx];
    646       for (unsigned Idx = StartIdx + 1; Idx < SimpVect.size(); Idx++)
    647         R += *SimpVect[Idx];
    648 
    649       // Pop all addends being folded and push the resulting folded addend.
    650       SimpVect.resize(StartIdx);
    651       if (Val != 0) {
    652         if (!R.isZero()) {
    653           SimpVect.push_back(&R);
    654         }
    655       } else {
    656         // Don't push constant addend at this time. It will be the last element
    657         // of <SimpVect>.
    658         ConstAdd = &R;
    659       }
    660     }
    661   }
    662 
    663   assert((NextTmpIdx <= array_lengthof(TmpResult) + 1) &&
    664          "out-of-bound access");
    665 
    666   if (ConstAdd)
    667     SimpVect.push_back(ConstAdd);
    668 
    669   Value *Result;
    670   if (!SimpVect.empty())
    671     Result = createNaryFAdd(SimpVect, InstrQuota);
    672   else {
    673     // The addition is folded to 0.0.
    674     Result = ConstantFP::get(Instr->getType(), 0.0);
    675   }
    676 
    677   return Result;
    678 }
    679 
    680 Value *FAddCombine::createNaryFAdd
    681   (const AddendVect &Opnds, unsigned InstrQuota) {
    682   assert(!Opnds.empty() && "Expect at least one addend");
    683 
    684   // Step 1: Check if the # of instructions needed exceeds the quota.
    685   //
    686   unsigned InstrNeeded = calcInstrNumber(Opnds);
    687   if (InstrNeeded > InstrQuota)
    688     return 0;
    689 
    690   initCreateInstNum();
    691 
    692   // step 2: Emit the N-ary addition.
    693   // Note that at most three instructions are involved in Fadd-InstCombine: the
    694   // addition in question, and at most two neighboring instructions.
    695   // The resulting optimized addition should have at least one less instruction
    696   // than the original addition expression tree. This implies that the resulting
    697   // N-ary addition has at most two instructions, and we don't need to worry
    698   // about tree-height when constructing the N-ary addition.
    699 
    700   Value *LastVal = 0;
    701   bool LastValNeedNeg = false;
    702 
    703   // Iterate the addends, creating fadd/fsub using adjacent two addends.
    704   for (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end();
    705        I != E; I++) {
    706     bool NeedNeg;
    707     Value *V = createAddendVal(**I, NeedNeg);
    708     if (!LastVal) {
    709       LastVal = V;
    710       LastValNeedNeg = NeedNeg;
    711       continue;
    712     }
    713 
    714     if (LastValNeedNeg == NeedNeg) {
    715       LastVal = createFAdd(LastVal, V);
    716       continue;
    717     }
    718 
    719     if (LastValNeedNeg)
    720       LastVal = createFSub(V, LastVal);
    721     else
    722       LastVal = createFSub(LastVal, V);
    723 
    724     LastValNeedNeg = false;
    725   }
    726 
    727   if (LastValNeedNeg) {
    728     LastVal = createFNeg(LastVal);
    729   }
    730 
    731   #ifndef NDEBUG
    732     assert(CreateInstrNum == InstrNeeded &&
    733            "Inconsistent in instruction numbers");
    734   #endif
    735 
    736   return LastVal;
    737 }
    738 
    739 Value *FAddCombine::createFSub
    740   (Value *Opnd0, Value *Opnd1) {
    741   Value *V = Builder->CreateFSub(Opnd0, Opnd1);
    742   if (Instruction *I = dyn_cast<Instruction>(V))
    743     createInstPostProc(I);
    744   return V;
    745 }
    746 
    747 Value *FAddCombine::createFNeg(Value *V) {
    748   Value *Zero = cast<Value>(ConstantFP::get(V->getType(), 0.0));
    749   return createFSub(Zero, V);
    750 }
    751 
    752 Value *FAddCombine::createFAdd
    753   (Value *Opnd0, Value *Opnd1) {
    754   Value *V = Builder->CreateFAdd(Opnd0, Opnd1);
    755   if (Instruction *I = dyn_cast<Instruction>(V))
    756     createInstPostProc(I);
    757   return V;
    758 }
    759 
    760 Value *FAddCombine::createFMul(Value *Opnd0, Value *Opnd1) {
    761   Value *V = Builder->CreateFMul(Opnd0, Opnd1);
    762   if (Instruction *I = dyn_cast<Instruction>(V))
    763     createInstPostProc(I);
    764   return V;
    765 }
    766 
    767 Value *FAddCombine::createFDiv(Value *Opnd0, Value *Opnd1) {
    768   Value *V = Builder->CreateFDiv(Opnd0, Opnd1);
    769   if (Instruction *I = dyn_cast<Instruction>(V))
    770     createInstPostProc(I);
    771   return V;
    772 }
    773 
    774 void FAddCombine::createInstPostProc(Instruction *NewInstr) {
    775   NewInstr->setDebugLoc(Instr->getDebugLoc());
    776 
    777   // Keep track of the number of instruction created.
    778   incCreateInstNum();
    779 
    780   // Propagate fast-math flags
    781   NewInstr->setFastMathFlags(Instr->getFastMathFlags());
    782 }
    783 
    784 // Return the number of instruction needed to emit the N-ary addition.
    785 // NOTE: Keep this function in sync with createAddendVal().
    786 unsigned FAddCombine::calcInstrNumber(const AddendVect &Opnds) {
    787   unsigned OpndNum = Opnds.size();
    788   unsigned InstrNeeded = OpndNum - 1;
    789 
    790   // The number of addends in the form of "(-1)*x".
    791   unsigned NegOpndNum = 0;
    792 
    793   // Adjust the number of instructions needed to emit the N-ary add.
    794   for (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end();
    795        I != E; I++) {
    796     const FAddend *Opnd = *I;
    797     if (Opnd->isConstant())
    798       continue;
    799 
    800     const FAddendCoef &CE = Opnd->getCoef();
    801     if (CE.isMinusOne() || CE.isMinusTwo())
    802       NegOpndNum++;
    803 
    804     // Let the addend be "c * x". If "c == +/-1", the value of the addend
    805     // is immediately available; otherwise, it needs exactly one instruction
    806     // to evaluate the value.
    807     if (!CE.isMinusOne() && !CE.isOne())
    808       InstrNeeded++;
    809   }
    810   if (NegOpndNum == OpndNum)
    811     InstrNeeded++;
    812   return InstrNeeded;
    813 }
    814 
    815 // Input Addend        Value           NeedNeg(output)
    816 // ================================================================
    817 // Constant C          C               false
    818 // <+/-1, V>           V               coefficient is -1
    819 // <2/-2, V>          "fadd V, V"      coefficient is -2
    820 // <C, V>             "fmul V, C"      false
    821 //
    822 // NOTE: Keep this function in sync with FAddCombine::calcInstrNumber.
    823 Value *FAddCombine::createAddendVal
    824   (const FAddend &Opnd, bool &NeedNeg) {
    825   const FAddendCoef &Coeff = Opnd.getCoef();
    826 
    827   if (Opnd.isConstant()) {
    828     NeedNeg = false;
    829     return Coeff.getValue(Instr->getType());
    830   }
    831 
    832   Value *OpndVal = Opnd.getSymVal();
    833 
    834   if (Coeff.isMinusOne() || Coeff.isOne()) {
    835     NeedNeg = Coeff.isMinusOne();
    836     return OpndVal;
    837   }
    838 
    839   if (Coeff.isTwo() || Coeff.isMinusTwo()) {
    840     NeedNeg = Coeff.isMinusTwo();
    841     return createFAdd(OpndVal, OpndVal);
    842   }
    843 
    844   NeedNeg = false;
    845   return createFMul(OpndVal, Coeff.getValue(Instr->getType()));
    846 }
    847 
    848 /// AddOne - Add one to a ConstantInt.
    849 static Constant *AddOne(Constant *C) {
    850   return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
    851 }
    852 
    853 /// SubOne - Subtract one from a ConstantInt.
    854 static Constant *SubOne(ConstantInt *C) {
    855   return ConstantInt::get(C->getContext(), C->getValue()-1);
    856 }
    857 
    858 
    859 // dyn_castFoldableMul - If this value is a multiply that can be folded into
    860 // other computations (because it has a constant operand), return the
    861 // non-constant operand of the multiply, and set CST to point to the multiplier.
    862 // Otherwise, return null.
    863 //
    864 static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
    865   if (!V->hasOneUse() || !V->getType()->isIntegerTy())
    866     return 0;
    867 
    868   Instruction *I = dyn_cast<Instruction>(V);
    869   if (I == 0) return 0;
    870 
    871   if (I->getOpcode() == Instruction::Mul)
    872     if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
    873       return I->getOperand(0);
    874   if (I->getOpcode() == Instruction::Shl)
    875     if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
    876       // The multiplier is really 1 << CST.
    877       uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
    878       uint32_t CSTVal = CST->getLimitedValue(BitWidth);
    879       CST = ConstantInt::get(V->getType()->getContext(),
    880                              APInt::getOneBitSet(BitWidth, CSTVal));
    881       return I->getOperand(0);
    882     }
    883   return 0;
    884 }
    885 
    886 
    887 /// WillNotOverflowSignedAdd - Return true if we can prove that:
    888 ///    (sext (add LHS, RHS))  === (add (sext LHS), (sext RHS))
    889 /// This basically requires proving that the add in the original type would not
    890 /// overflow to change the sign bit or have a carry out.
    891 bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) {
    892   // There are different heuristics we can use for this.  Here are some simple
    893   // ones.
    894 
    895   // Add has the property that adding any two 2's complement numbers can only
    896   // have one carry bit which can change a sign.  As such, if LHS and RHS each
    897   // have at least two sign bits, we know that the addition of the two values
    898   // will sign extend fine.
    899   if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1)
    900     return true;
    901 
    902 
    903   // If one of the operands only has one non-zero bit, and if the other operand
    904   // has a known-zero bit in a more significant place than it (not including the
    905   // sign bit) the ripple may go up to and fill the zero, but won't change the
    906   // sign.  For example, (X & ~4) + 1.
    907 
    908   // TODO: Implement.
    909 
    910   return false;
    911 }
    912 
    913 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
    914   bool Changed = SimplifyAssociativeOrCommutative(I);
    915   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
    916 
    917   if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(),
    918                                  I.hasNoUnsignedWrap(), TD))
    919     return ReplaceInstUsesWith(I, V);
    920 
    921   // (A*B)+(A*C) -> A*(B+C) etc
    922   if (Value *V = SimplifyUsingDistributiveLaws(I))
    923     return ReplaceInstUsesWith(I, V);
    924 
    925   if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
    926     // X + (signbit) --> X ^ signbit
    927     const APInt &Val = CI->getValue();
    928     if (Val.isSignBit())
    929       return BinaryOperator::CreateXor(LHS, RHS);
    930 
    931     // See if SimplifyDemandedBits can simplify this.  This handles stuff like
    932     // (X & 254)+1 -> (X&254)|1
    933     if (SimplifyDemandedInstructionBits(I))
    934       return &I;
    935 
    936     // zext(bool) + C -> bool ? C + 1 : C
    937     if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
    938       if (ZI->getSrcTy()->isIntegerTy(1))
    939         return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI);
    940 
    941     Value *XorLHS = 0; ConstantInt *XorRHS = 0;
    942     if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
    943       uint32_t TySizeBits = I.getType()->getScalarSizeInBits();
    944       const APInt &RHSVal = CI->getValue();
    945       unsigned ExtendAmt = 0;
    946       // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
    947       // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
    948       if (XorRHS->getValue() == -RHSVal) {
    949         if (RHSVal.isPowerOf2())
    950           ExtendAmt = TySizeBits - RHSVal.logBase2() - 1;
    951         else if (XorRHS->getValue().isPowerOf2())
    952           ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1;
    953       }
    954 
    955       if (ExtendAmt) {
    956         APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt);
    957         if (!MaskedValueIsZero(XorLHS, Mask))
    958           ExtendAmt = 0;
    959       }
    960 
    961       if (ExtendAmt) {
    962         Constant *ShAmt = ConstantInt::get(I.getType(), ExtendAmt);
    963         Value *NewShl = Builder->CreateShl(XorLHS, ShAmt, "sext");
    964         return BinaryOperator::CreateAShr(NewShl, ShAmt);
    965       }
    966 
    967       // If this is a xor that was canonicalized from a sub, turn it back into
    968       // a sub and fuse this add with it.
    969       if (LHS->hasOneUse() && (XorRHS->getValue()+1).isPowerOf2()) {
    970         IntegerType *IT = cast<IntegerType>(I.getType());
    971         APInt LHSKnownOne(IT->getBitWidth(), 0);
    972         APInt LHSKnownZero(IT->getBitWidth(), 0);
    973         ComputeMaskedBits(XorLHS, LHSKnownZero, LHSKnownOne);
    974         if ((XorRHS->getValue() | LHSKnownZero).isAllOnesValue())
    975           return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI),
    976                                            XorLHS);
    977       }
    978       // (X + signbit) + C could have gotten canonicalized to (X ^ signbit) + C,
    979       // transform them into (X + (signbit ^ C))
    980       if (XorRHS->getValue().isSignBit())
    981           return BinaryOperator::CreateAdd(XorLHS,
    982                                            ConstantExpr::getXor(XorRHS, CI));
    983     }
    984   }
    985 
    986   if (isa<Constant>(RHS) && isa<PHINode>(LHS))
    987     if (Instruction *NV = FoldOpIntoPhi(I))
    988       return NV;
    989 
    990   if (I.getType()->isIntegerTy(1))
    991     return BinaryOperator::CreateXor(LHS, RHS);
    992 
    993   // X + X --> X << 1
    994   if (LHS == RHS) {
    995     BinaryOperator *New =
    996       BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1));
    997     New->setHasNoSignedWrap(I.hasNoSignedWrap());
    998     New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
    999     return New;
   1000   }
   1001 
   1002   // -A + B  -->  B - A
   1003   // -A + -B  -->  -(A + B)
   1004   if (Value *LHSV = dyn_castNegVal(LHS)) {
   1005     if (!isa<Constant>(RHS))
   1006       if (Value *RHSV = dyn_castNegVal(RHS)) {
   1007         Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
   1008         return BinaryOperator::CreateNeg(NewAdd);
   1009       }
   1010 
   1011     return BinaryOperator::CreateSub(RHS, LHSV);
   1012   }
   1013 
   1014   // A + -B  -->  A - B
   1015   if (!isa<Constant>(RHS))
   1016     if (Value *V = dyn_castNegVal(RHS))
   1017       return BinaryOperator::CreateSub(LHS, V);
   1018 
   1019 
   1020   ConstantInt *C2;
   1021   if (Value *X = dyn_castFoldableMul(LHS, C2)) {
   1022     if (X == RHS)   // X*C + X --> X * (C+1)
   1023       return BinaryOperator::CreateMul(RHS, AddOne(C2));
   1024 
   1025     // X*C1 + X*C2 --> X * (C1+C2)
   1026     ConstantInt *C1;
   1027     if (X == dyn_castFoldableMul(RHS, C1))
   1028       return BinaryOperator::CreateMul(X, ConstantExpr::getAdd(C1, C2));
   1029   }
   1030 
   1031   // X + X*C --> X * (C+1)
   1032   if (dyn_castFoldableMul(RHS, C2) == LHS)
   1033     return BinaryOperator::CreateMul(LHS, AddOne(C2));
   1034 
   1035   // A+B --> A|B iff A and B have no bits set in common.
   1036   if (IntegerType *IT = dyn_cast<IntegerType>(I.getType())) {
   1037     APInt LHSKnownOne(IT->getBitWidth(), 0);
   1038     APInt LHSKnownZero(IT->getBitWidth(), 0);
   1039     ComputeMaskedBits(LHS, LHSKnownZero, LHSKnownOne);
   1040     if (LHSKnownZero != 0) {
   1041       APInt RHSKnownOne(IT->getBitWidth(), 0);
   1042       APInt RHSKnownZero(IT->getBitWidth(), 0);
   1043       ComputeMaskedBits(RHS, RHSKnownZero, RHSKnownOne);
   1044 
   1045       // No bits in common -> bitwise or.
   1046       if ((LHSKnownZero|RHSKnownZero).isAllOnesValue())
   1047         return BinaryOperator::CreateOr(LHS, RHS);
   1048     }
   1049   }
   1050 
   1051   // W*X + Y*Z --> W * (X+Z)  iff W == Y
   1052   {
   1053     Value *W, *X, *Y, *Z;
   1054     if (match(LHS, m_Mul(m_Value(W), m_Value(X))) &&
   1055         match(RHS, m_Mul(m_Value(Y), m_Value(Z)))) {
   1056       if (W != Y) {
   1057         if (W == Z) {
   1058           std::swap(Y, Z);
   1059         } else if (Y == X) {
   1060           std::swap(W, X);
   1061         } else if (X == Z) {
   1062           std::swap(Y, Z);
   1063           std::swap(W, X);
   1064         }
   1065       }
   1066 
   1067       if (W == Y) {
   1068         Value *NewAdd = Builder->CreateAdd(X, Z, LHS->getName());
   1069         return BinaryOperator::CreateMul(W, NewAdd);
   1070       }
   1071     }
   1072   }
   1073 
   1074   if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
   1075     Value *X = 0;
   1076     if (match(LHS, m_Not(m_Value(X))))    // ~X + C --> (C-1) - X
   1077       return BinaryOperator::CreateSub(SubOne(CRHS), X);
   1078 
   1079     // (X & FF00) + xx00  -> (X+xx00) & FF00
   1080     if (LHS->hasOneUse() &&
   1081         match(LHS, m_And(m_Value(X), m_ConstantInt(C2))) &&
   1082         CRHS->getValue() == (CRHS->getValue() & C2->getValue())) {
   1083       // See if all bits from the first bit set in the Add RHS up are included
   1084       // in the mask.  First, get the rightmost bit.
   1085       const APInt &AddRHSV = CRHS->getValue();
   1086 
   1087       // Form a mask of all bits from the lowest bit added through the top.
   1088       APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
   1089 
   1090       // See if the and mask includes all of these bits.
   1091       APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
   1092 
   1093       if (AddRHSHighBits == AddRHSHighBitsAnd) {
   1094         // Okay, the xform is safe.  Insert the new add pronto.
   1095         Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName());
   1096         return BinaryOperator::CreateAnd(NewAdd, C2);
   1097       }
   1098     }
   1099 
   1100     // Try to fold constant add into select arguments.
   1101     if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
   1102       if (Instruction *R = FoldOpIntoSelect(I, SI))
   1103         return R;
   1104   }
   1105 
   1106   // add (select X 0 (sub n A)) A  -->  select X A n
   1107   {
   1108     SelectInst *SI = dyn_cast<SelectInst>(LHS);
   1109     Value *A = RHS;
   1110     if (!SI) {
   1111       SI = dyn_cast<SelectInst>(RHS);
   1112       A = LHS;
   1113     }
   1114     if (SI && SI->hasOneUse()) {
   1115       Value *TV = SI->getTrueValue();
   1116       Value *FV = SI->getFalseValue();
   1117       Value *N;
   1118 
   1119       // Can we fold the add into the argument of the select?
   1120       // We check both true and false select arguments for a matching subtract.
   1121       if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A))))
   1122         // Fold the add into the true select value.
   1123         return SelectInst::Create(SI->getCondition(), N, A);
   1124 
   1125       if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A))))
   1126         // Fold the add into the false select value.
   1127         return SelectInst::Create(SI->getCondition(), A, N);
   1128     }
   1129   }
   1130 
   1131   // Check for (add (sext x), y), see if we can merge this into an
   1132   // integer add followed by a sext.
   1133   if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
   1134     // (add (sext x), cst) --> (sext (add x, cst'))
   1135     if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
   1136       Constant *CI =
   1137         ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
   1138       if (LHSConv->hasOneUse() &&
   1139           ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
   1140           WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
   1141         // Insert the new, smaller add.
   1142         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
   1143                                               CI, "addconv");
   1144         return new SExtInst(NewAdd, I.getType());
   1145       }
   1146     }
   1147 
   1148     // (add (sext x), (sext y)) --> (sext (add int x, y))
   1149     if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) {
   1150       // Only do this if x/y have the same type, if at last one of them has a
   1151       // single use (so we don't increase the number of sexts), and if the
   1152       // integer add will not overflow.
   1153       if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
   1154           (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
   1155           WillNotOverflowSignedAdd(LHSConv->getOperand(0),
   1156                                    RHSConv->getOperand(0))) {
   1157         // Insert the new integer add.
   1158         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
   1159                                              RHSConv->getOperand(0), "addconv");
   1160         return new SExtInst(NewAdd, I.getType());
   1161       }
   1162     }
   1163   }
   1164 
   1165   // Check for (x & y) + (x ^ y)
   1166   {
   1167     Value *A = 0, *B = 0;
   1168     if (match(RHS, m_Xor(m_Value(A), m_Value(B))) &&
   1169         (match(LHS, m_And(m_Specific(A), m_Specific(B))) ||
   1170          match(LHS, m_And(m_Specific(B), m_Specific(A)))))
   1171       return BinaryOperator::CreateOr(A, B);
   1172 
   1173     if (match(LHS, m_Xor(m_Value(A), m_Value(B))) &&
   1174         (match(RHS, m_And(m_Specific(A), m_Specific(B))) ||
   1175          match(RHS, m_And(m_Specific(B), m_Specific(A)))))
   1176       return BinaryOperator::CreateOr(A, B);
   1177   }
   1178 
   1179   return Changed ? &I : 0;
   1180 }
   1181 
   1182 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
   1183   bool Changed = SimplifyAssociativeOrCommutative(I);
   1184   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
   1185 
   1186   if (Value *V = SimplifyFAddInst(LHS, RHS, I.getFastMathFlags(), TD))
   1187     return ReplaceInstUsesWith(I, V);
   1188 
   1189   if (isa<Constant>(RHS)) {
   1190     if (isa<PHINode>(LHS))
   1191       if (Instruction *NV = FoldOpIntoPhi(I))
   1192         return NV;
   1193 
   1194     if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
   1195       if (Instruction *NV = FoldOpIntoSelect(I, SI))
   1196         return NV;
   1197   }
   1198 
   1199   // -A + B  -->  B - A
   1200   // -A + -B  -->  -(A + B)
   1201   if (Value *LHSV = dyn_castFNegVal(LHS))
   1202     return BinaryOperator::CreateFSub(RHS, LHSV);
   1203 
   1204   // A + -B  -->  A - B
   1205   if (!isa<Constant>(RHS))
   1206     if (Value *V = dyn_castFNegVal(RHS))
   1207       return BinaryOperator::CreateFSub(LHS, V);
   1208 
   1209   // Check for (fadd double (sitofp x), y), see if we can merge this into an
   1210   // integer add followed by a promotion.
   1211   if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
   1212     // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
   1213     // ... if the constant fits in the integer value.  This is useful for things
   1214     // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
   1215     // requires a constant pool load, and generally allows the add to be better
   1216     // instcombined.
   1217     if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) {
   1218       Constant *CI =
   1219       ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType());
   1220       if (LHSConv->hasOneUse() &&
   1221           ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
   1222           WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) {
   1223         // Insert the new integer add.
   1224         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
   1225                                               CI, "addconv");
   1226         return new SIToFPInst(NewAdd, I.getType());
   1227       }
   1228     }
   1229 
   1230     // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
   1231     if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
   1232       // Only do this if x/y have the same type, if at last one of them has a
   1233       // single use (so we don't increase the number of int->fp conversions),
   1234       // and if the integer add will not overflow.
   1235       if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&&
   1236           (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
   1237           WillNotOverflowSignedAdd(LHSConv->getOperand(0),
   1238                                    RHSConv->getOperand(0))) {
   1239         // Insert the new integer add.
   1240         Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
   1241                                               RHSConv->getOperand(0),"addconv");
   1242         return new SIToFPInst(NewAdd, I.getType());
   1243       }
   1244     }
   1245   }
   1246 
   1247   // select C, 0, B + select C, A, 0 -> select C, A, B
   1248   {
   1249     Value *A1, *B1, *C1, *A2, *B2, *C2;
   1250     if (match(LHS, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) &&
   1251         match(RHS, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) {
   1252       if (C1 == C2) {
   1253         Constant *Z1=0, *Z2=0;
   1254         Value *A, *B, *C=C1;
   1255         if (match(A1, m_AnyZero()) && match(B2, m_AnyZero())) {
   1256             Z1 = dyn_cast<Constant>(A1); A = A2;
   1257             Z2 = dyn_cast<Constant>(B2); B = B1;
   1258         } else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) {
   1259             Z1 = dyn_cast<Constant>(B1); B = B2;
   1260             Z2 = dyn_cast<Constant>(A2); A = A1;
   1261         }
   1262 
   1263         if (Z1 && Z2 &&
   1264             (I.hasNoSignedZeros() ||
   1265              (Z1->isNegativeZeroValue() && Z2->isNegativeZeroValue()))) {
   1266           return SelectInst::Create(C, A, B);
   1267         }
   1268       }
   1269     }
   1270   }
   1271 
   1272   if (I.hasUnsafeAlgebra()) {
   1273     if (Value *V = FAddCombine(Builder).simplify(&I))
   1274       return ReplaceInstUsesWith(I, V);
   1275   }
   1276 
   1277   return Changed ? &I : 0;
   1278 }
   1279 
   1280 
   1281 /// Optimize pointer differences into the same array into a size.  Consider:
   1282 ///  &A[10] - &A[0]: we should compile this to "10".  LHS/RHS are the pointer
   1283 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract.
   1284 ///
   1285 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
   1286                                                Type *Ty) {
   1287   assert(TD && "Must have target data info for this");
   1288 
   1289   // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize
   1290   // this.
   1291   bool Swapped = false;
   1292   GEPOperator *GEP1 = 0, *GEP2 = 0;
   1293 
   1294   // For now we require one side to be the base pointer "A" or a constant
   1295   // GEP derived from it.
   1296   if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
   1297     // (gep X, ...) - X
   1298     if (LHSGEP->getOperand(0) == RHS) {
   1299       GEP1 = LHSGEP;
   1300       Swapped = false;
   1301     } else if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
   1302       // (gep X, ...) - (gep X, ...)
   1303       if (LHSGEP->getOperand(0)->stripPointerCasts() ==
   1304             RHSGEP->getOperand(0)->stripPointerCasts()) {
   1305         GEP2 = RHSGEP;
   1306         GEP1 = LHSGEP;
   1307         Swapped = false;
   1308       }
   1309     }
   1310   }
   1311 
   1312   if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
   1313     // X - (gep X, ...)
   1314     if (RHSGEP->getOperand(0) == LHS) {
   1315       GEP1 = RHSGEP;
   1316       Swapped = true;
   1317     } else if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
   1318       // (gep X, ...) - (gep X, ...)
   1319       if (RHSGEP->getOperand(0)->stripPointerCasts() ==
   1320             LHSGEP->getOperand(0)->stripPointerCasts()) {
   1321         GEP2 = LHSGEP;
   1322         GEP1 = RHSGEP;
   1323         Swapped = true;
   1324       }
   1325     }
   1326   }
   1327 
   1328   // Avoid duplicating the arithmetic if GEP2 has non-constant indices and
   1329   // multiple users.
   1330   if (GEP1 == 0 ||
   1331       (GEP2 != 0 && !GEP2->hasAllConstantIndices() && !GEP2->hasOneUse()))
   1332     return 0;
   1333 
   1334   // Emit the offset of the GEP and an intptr_t.
   1335   Value *Result = EmitGEPOffset(GEP1);
   1336 
   1337   // If we had a constant expression GEP on the other side offsetting the
   1338   // pointer, subtract it from the offset we have.
   1339   if (GEP2) {
   1340     Value *Offset = EmitGEPOffset(GEP2);
   1341     Result = Builder->CreateSub(Result, Offset);
   1342   }
   1343 
   1344   // If we have p - gep(p, ...)  then we have to negate the result.
   1345   if (Swapped)
   1346     Result = Builder->CreateNeg(Result, "diff.neg");
   1347 
   1348   return Builder->CreateIntCast(Result, Ty, true);
   1349 }
   1350 
   1351 
   1352 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
   1353   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
   1354 
   1355   if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(),
   1356                                  I.hasNoUnsignedWrap(), TD))
   1357     return ReplaceInstUsesWith(I, V);
   1358 
   1359   // (A*B)-(A*C) -> A*(B-C) etc
   1360   if (Value *V = SimplifyUsingDistributiveLaws(I))
   1361     return ReplaceInstUsesWith(I, V);
   1362 
   1363   // If this is a 'B = x-(-A)', change to B = x+A.  This preserves NSW/NUW.
   1364   if (Value *V = dyn_castNegVal(Op1)) {
   1365     BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
   1366     Res->setHasNoSignedWrap(I.hasNoSignedWrap());
   1367     Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
   1368     return Res;
   1369   }
   1370 
   1371   if (I.getType()->isIntegerTy(1))
   1372     return BinaryOperator::CreateXor(Op0, Op1);
   1373 
   1374   // Replace (-1 - A) with (~A).
   1375   if (match(Op0, m_AllOnes()))
   1376     return BinaryOperator::CreateNot(Op1);
   1377 
   1378   if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
   1379     // C - ~X == X + (1+C)
   1380     Value *X = 0;
   1381     if (match(Op1, m_Not(m_Value(X))))
   1382       return BinaryOperator::CreateAdd(X, AddOne(C));
   1383 
   1384     // -(X >>u 31) -> (X >>s 31)
   1385     // -(X >>s 31) -> (X >>u 31)
   1386     if (C->isZero()) {
   1387       Value *X; ConstantInt *CI;
   1388       if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) &&
   1389           // Verify we are shifting out everything but the sign bit.
   1390           CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1)
   1391         return BinaryOperator::CreateAShr(X, CI);
   1392 
   1393       if (match(Op1, m_AShr(m_Value(X), m_ConstantInt(CI))) &&
   1394           // Verify we are shifting out everything but the sign bit.
   1395           CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1)
   1396         return BinaryOperator::CreateLShr(X, CI);
   1397     }
   1398 
   1399     // Try to fold constant sub into select arguments.
   1400     if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
   1401       if (Instruction *R = FoldOpIntoSelect(I, SI))
   1402         return R;
   1403 
   1404     // C-(X+C2) --> (C-C2)-X
   1405     ConstantInt *C2;
   1406     if (match(Op1, m_Add(m_Value(X), m_ConstantInt(C2))))
   1407       return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
   1408 
   1409     if (SimplifyDemandedInstructionBits(I))
   1410       return &I;
   1411 
   1412     // Fold (sub 0, (zext bool to B)) --> (sext bool to B)
   1413     if (C->isZero() && match(Op1, m_ZExt(m_Value(X))))
   1414       if (X->getType()->isIntegerTy(1))
   1415         return CastInst::CreateSExtOrBitCast(X, Op1->getType());
   1416 
   1417     // Fold (sub 0, (sext bool to B)) --> (zext bool to B)
   1418     if (C->isZero() && match(Op1, m_SExt(m_Value(X))))
   1419       if (X->getType()->isIntegerTy(1))
   1420         return CastInst::CreateZExtOrBitCast(X, Op1->getType());
   1421   }
   1422 
   1423 
   1424   { Value *Y;
   1425     // X-(X+Y) == -Y    X-(Y+X) == -Y
   1426     if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) ||
   1427         match(Op1, m_Add(m_Value(Y), m_Specific(Op0))))
   1428       return BinaryOperator::CreateNeg(Y);
   1429 
   1430     // (X-Y)-X == -Y
   1431     if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y))))
   1432       return BinaryOperator::CreateNeg(Y);
   1433   }
   1434 
   1435   if (Op1->hasOneUse()) {
   1436     Value *X = 0, *Y = 0, *Z = 0;
   1437     Constant *C = 0;
   1438     ConstantInt *CI = 0;
   1439 
   1440     // (X - (Y - Z))  -->  (X + (Z - Y)).
   1441     if (match(Op1, m_Sub(m_Value(Y), m_Value(Z))))
   1442       return BinaryOperator::CreateAdd(Op0,
   1443                                       Builder->CreateSub(Z, Y, Op1->getName()));
   1444 
   1445     // (X - (X & Y))   -->   (X & ~Y)
   1446     //
   1447     if (match(Op1, m_And(m_Value(Y), m_Specific(Op0))) ||
   1448         match(Op1, m_And(m_Specific(Op0), m_Value(Y))))
   1449       return BinaryOperator::CreateAnd(Op0,
   1450                                   Builder->CreateNot(Y, Y->getName() + ".not"));
   1451 
   1452     // 0 - (X sdiv C)  -> (X sdiv -C)
   1453     if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) &&
   1454         match(Op0, m_Zero()))
   1455       return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C));
   1456 
   1457     // 0 - (X << Y)  -> (-X << Y)   when X is freely negatable.
   1458     if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero()))
   1459       if (Value *XNeg = dyn_castNegVal(X))
   1460         return BinaryOperator::CreateShl(XNeg, Y);
   1461 
   1462     // X - X*C --> X * (1-C)
   1463     if (match(Op1, m_Mul(m_Specific(Op0), m_ConstantInt(CI)))) {
   1464       Constant *CP1 = ConstantExpr::getSub(ConstantInt::get(I.getType(),1), CI);
   1465       return BinaryOperator::CreateMul(Op0, CP1);
   1466     }
   1467 
   1468     // X - X<<C --> X * (1-(1<<C))
   1469     if (match(Op1, m_Shl(m_Specific(Op0), m_ConstantInt(CI)))) {
   1470       Constant *One = ConstantInt::get(I.getType(), 1);
   1471       C = ConstantExpr::getSub(One, ConstantExpr::getShl(One, CI));
   1472       return BinaryOperator::CreateMul(Op0, C);
   1473     }
   1474 
   1475     // X - A*-B -> X + A*B
   1476     // X - -A*B -> X + A*B
   1477     Value *A, *B;
   1478     if (match(Op1, m_Mul(m_Value(A), m_Neg(m_Value(B)))) ||
   1479         match(Op1, m_Mul(m_Neg(m_Value(A)), m_Value(B))))
   1480       return BinaryOperator::CreateAdd(Op0, Builder->CreateMul(A, B));
   1481 
   1482     // X - A*CI -> X + A*-CI
   1483     // X - CI*A -> X + A*-CI
   1484     if (match(Op1, m_Mul(m_Value(A), m_ConstantInt(CI))) ||
   1485         match(Op1, m_Mul(m_ConstantInt(CI), m_Value(A)))) {
   1486       Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(CI));
   1487       return BinaryOperator::CreateAdd(Op0, NewMul);
   1488     }
   1489   }
   1490 
   1491   ConstantInt *C1;
   1492   if (Value *X = dyn_castFoldableMul(Op0, C1)) {
   1493     if (X == Op1)  // X*C - X --> X * (C-1)
   1494       return BinaryOperator::CreateMul(Op1, SubOne(C1));
   1495 
   1496     ConstantInt *C2;   // X*C1 - X*C2 -> X * (C1-C2)
   1497     if (X == dyn_castFoldableMul(Op1, C2))
   1498       return BinaryOperator::CreateMul(X, ConstantExpr::getSub(C1, C2));
   1499   }
   1500 
   1501   // Optimize pointer differences into the same array into a size.  Consider:
   1502   //  &A[10] - &A[0]: we should compile this to "10".
   1503   if (TD) {
   1504     Value *LHSOp, *RHSOp;
   1505     if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
   1506         match(Op1, m_PtrToInt(m_Value(RHSOp))))
   1507       if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
   1508         return ReplaceInstUsesWith(I, Res);
   1509 
   1510     // trunc(p)-trunc(q) -> trunc(p-q)
   1511     if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
   1512         match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
   1513       if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
   1514         return ReplaceInstUsesWith(I, Res);
   1515   }
   1516 
   1517   return 0;
   1518 }
   1519 
   1520 Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
   1521   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
   1522 
   1523   if (Value *V = SimplifyFSubInst(Op0, Op1, I.getFastMathFlags(), TD))
   1524     return ReplaceInstUsesWith(I, V);
   1525 
   1526   if (isa<Constant>(Op0))
   1527     if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
   1528       if (Instruction *NV = FoldOpIntoSelect(I, SI))
   1529         return NV;
   1530 
   1531   // If this is a 'B = x-(-A)', change to B = x+A, potentially looking
   1532   // through FP extensions/truncations along the way.
   1533   if (Value *V = dyn_castFNegVal(Op1)) {
   1534     Instruction *NewI = BinaryOperator::CreateFAdd(Op0, V);
   1535     NewI->copyFastMathFlags(&I);
   1536     return NewI;
   1537   }
   1538   if (FPTruncInst *FPTI = dyn_cast<FPTruncInst>(Op1)) {
   1539     if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) {
   1540       Value *NewTrunc = Builder->CreateFPTrunc(V, I.getType());
   1541       Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewTrunc);
   1542       NewI->copyFastMathFlags(&I);
   1543       return NewI;
   1544     }
   1545   } else if (FPExtInst *FPEI = dyn_cast<FPExtInst>(Op1)) {
   1546     if (Value *V = dyn_castFNegVal(FPEI->getOperand(0))) {
   1547       Value *NewExt = Builder->CreateFPExt(V, I.getType());
   1548       Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewExt);
   1549       NewI->copyFastMathFlags(&I);
   1550       return NewI;
   1551     }
   1552   }
   1553 
   1554   if (I.hasUnsafeAlgebra()) {
   1555     if (Value *V = FAddCombine(Builder).simplify(&I))
   1556       return ReplaceInstUsesWith(I, V);
   1557   }
   1558 
   1559   return 0;
   1560 }
   1561