xref: /freebsd/contrib/llvm-project/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp (revision 85868e8a1daeaae7a0e48effb2ea2310ae3b02c6)
1 //===- InstCombineAddSub.cpp ------------------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the visit functions for add, fadd, sub, and fsub.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "InstCombineInternal.h"
14 #include "llvm/ADT/APFloat.h"
15 #include "llvm/ADT/APInt.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/Analysis/InstructionSimplify.h"
19 #include "llvm/Analysis/ValueTracking.h"
20 #include "llvm/IR/Constant.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/InstrTypes.h"
23 #include "llvm/IR/Instruction.h"
24 #include "llvm/IR/Instructions.h"
25 #include "llvm/IR/Operator.h"
26 #include "llvm/IR/PatternMatch.h"
27 #include "llvm/IR/Type.h"
28 #include "llvm/IR/Value.h"
29 #include "llvm/Support/AlignOf.h"
30 #include "llvm/Support/Casting.h"
31 #include "llvm/Support/KnownBits.h"
32 #include <cassert>
33 #include <utility>
34 
35 using namespace llvm;
36 using namespace PatternMatch;
37 
38 #define DEBUG_TYPE "instcombine"
39 
40 namespace {
41 
42   /// Class representing coefficient of floating-point addend.
43   /// This class needs to be highly efficient, which is especially true for
44   /// the constructor. As of I write this comment, the cost of the default
45   /// constructor is merely 4-byte-store-zero (Assuming compiler is able to
46   /// perform write-merging).
47   ///
48   class FAddendCoef {
49   public:
50     // The constructor has to initialize a APFloat, which is unnecessary for
51     // most addends which have coefficient either 1 or -1. So, the constructor
52     // is expensive. In order to avoid the cost of the constructor, we should
53     // reuse some instances whenever possible. The pre-created instances
54     // FAddCombine::Add[0-5] embodies this idea.
55     FAddendCoef() = default;
56     ~FAddendCoef();
57 
58     // If possible, don't define operator+/operator- etc because these
59     // operators inevitably call FAddendCoef's constructor which is not cheap.
60     void operator=(const FAddendCoef &A);
61     void operator+=(const FAddendCoef &A);
62     void operator*=(const FAddendCoef &S);
63 
64     void set(short C) {
65       assert(!insaneIntVal(C) && "Insane coefficient");
66       IsFp = false; IntVal = C;
67     }
68 
69     void set(const APFloat& C);
70 
71     void negate();
72 
73     bool isZero() const { return isInt() ? !IntVal : getFpVal().isZero(); }
74     Value *getValue(Type *) const;
75 
76     bool isOne() const { return isInt() && IntVal == 1; }
77     bool isTwo() const { return isInt() && IntVal == 2; }
78     bool isMinusOne() const { return isInt() && IntVal == -1; }
79     bool isMinusTwo() const { return isInt() && IntVal == -2; }
80 
81   private:
82     bool insaneIntVal(int V) { return V > 4 || V < -4; }
83 
84     APFloat *getFpValPtr()
85       { return reinterpret_cast<APFloat *>(&FpValBuf.buffer[0]); }
86 
87     const APFloat *getFpValPtr() const
88       { return reinterpret_cast<const APFloat *>(&FpValBuf.buffer[0]); }
89 
90     const APFloat &getFpVal() const {
91       assert(IsFp && BufHasFpVal && "Incorret state");
92       return *getFpValPtr();
93     }
94 
95     APFloat &getFpVal() {
96       assert(IsFp && BufHasFpVal && "Incorret state");
97       return *getFpValPtr();
98     }
99 
100     bool isInt() const { return !IsFp; }
101 
102     // If the coefficient is represented by an integer, promote it to a
103     // floating point.
104     void convertToFpType(const fltSemantics &Sem);
105 
106     // Construct an APFloat from a signed integer.
107     // TODO: We should get rid of this function when APFloat can be constructed
108     //       from an *SIGNED* integer.
109     APFloat createAPFloatFromInt(const fltSemantics &Sem, int Val);
110 
111     bool IsFp = false;
112 
113     // True iff FpValBuf contains an instance of APFloat.
114     bool BufHasFpVal = false;
115 
116     // The integer coefficient of an individual addend is either 1 or -1,
117     // and we try to simplify at most 4 addends from neighboring at most
118     // two instructions. So the range of <IntVal> falls in [-4, 4]. APInt
119     // is overkill of this end.
120     short IntVal = 0;
121 
122     AlignedCharArrayUnion<APFloat> FpValBuf;
123   };
124 
125   /// FAddend is used to represent floating-point addend. An addend is
126   /// represented as <C, V>, where the V is a symbolic value, and C is a
127   /// constant coefficient. A constant addend is represented as <C, 0>.
128   class FAddend {
129   public:
130     FAddend() = default;
131 
132     void operator+=(const FAddend &T) {
133       assert((Val == T.Val) && "Symbolic-values disagree");
134       Coeff += T.Coeff;
135     }
136 
137     Value *getSymVal() const { return Val; }
138     const FAddendCoef &getCoef() const { return Coeff; }
139 
140     bool isConstant() const { return Val == nullptr; }
141     bool isZero() const { return Coeff.isZero(); }
142 
143     void set(short Coefficient, Value *V) {
144       Coeff.set(Coefficient);
145       Val = V;
146     }
147     void set(const APFloat &Coefficient, Value *V) {
148       Coeff.set(Coefficient);
149       Val = V;
150     }
151     void set(const ConstantFP *Coefficient, Value *V) {
152       Coeff.set(Coefficient->getValueAPF());
153       Val = V;
154     }
155 
156     void negate() { Coeff.negate(); }
157 
158     /// Drill down the U-D chain one step to find the definition of V, and
159     /// try to break the definition into one or two addends.
160     static unsigned drillValueDownOneStep(Value* V, FAddend &A0, FAddend &A1);
161 
162     /// Similar to FAddend::drillDownOneStep() except that the value being
163     /// splitted is the addend itself.
164     unsigned drillAddendDownOneStep(FAddend &Addend0, FAddend &Addend1) const;
165 
166   private:
167     void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; }
168 
169     // This addend has the value of "Coeff * Val".
170     Value *Val = nullptr;
171     FAddendCoef Coeff;
172   };
173 
174   /// FAddCombine is the class for optimizing an unsafe fadd/fsub along
175   /// with its neighboring at most two instructions.
176   ///
177   class FAddCombine {
178   public:
179     FAddCombine(InstCombiner::BuilderTy &B) : Builder(B) {}
180 
181     Value *simplify(Instruction *FAdd);
182 
183   private:
184     using AddendVect = SmallVector<const FAddend *, 4>;
185 
186     Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota);
187 
188     /// Convert given addend to a Value
189     Value *createAddendVal(const FAddend &A, bool& NeedNeg);
190 
191     /// Return the number of instructions needed to emit the N-ary addition.
192     unsigned calcInstrNumber(const AddendVect& Vect);
193 
194     Value *createFSub(Value *Opnd0, Value *Opnd1);
195     Value *createFAdd(Value *Opnd0, Value *Opnd1);
196     Value *createFMul(Value *Opnd0, Value *Opnd1);
197     Value *createFNeg(Value *V);
198     Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota);
199     void createInstPostProc(Instruction *NewInst, bool NoNumber = false);
200 
201      // Debugging stuff are clustered here.
202     #ifndef NDEBUG
203       unsigned CreateInstrNum;
204       void initCreateInstNum() { CreateInstrNum = 0; }
205       void incCreateInstNum() { CreateInstrNum++; }
206     #else
207       void initCreateInstNum() {}
208       void incCreateInstNum() {}
209     #endif
210 
211     InstCombiner::BuilderTy &Builder;
212     Instruction *Instr = nullptr;
213   };
214 
215 } // end anonymous namespace
216 
217 //===----------------------------------------------------------------------===//
218 //
219 // Implementation of
220 //    {FAddendCoef, FAddend, FAddition, FAddCombine}.
221 //
222 //===----------------------------------------------------------------------===//
223 FAddendCoef::~FAddendCoef() {
224   if (BufHasFpVal)
225     getFpValPtr()->~APFloat();
226 }
227 
228 void FAddendCoef::set(const APFloat& C) {
229   APFloat *P = getFpValPtr();
230 
231   if (isInt()) {
232     // As the buffer is meanless byte stream, we cannot call
233     // APFloat::operator=().
234     new(P) APFloat(C);
235   } else
236     *P = C;
237 
238   IsFp = BufHasFpVal = true;
239 }
240 
241 void FAddendCoef::convertToFpType(const fltSemantics &Sem) {
242   if (!isInt())
243     return;
244 
245   APFloat *P = getFpValPtr();
246   if (IntVal > 0)
247     new(P) APFloat(Sem, IntVal);
248   else {
249     new(P) APFloat(Sem, 0 - IntVal);
250     P->changeSign();
251   }
252   IsFp = BufHasFpVal = true;
253 }
254 
255 APFloat FAddendCoef::createAPFloatFromInt(const fltSemantics &Sem, int Val) {
256   if (Val >= 0)
257     return APFloat(Sem, Val);
258 
259   APFloat T(Sem, 0 - Val);
260   T.changeSign();
261 
262   return T;
263 }
264 
265 void FAddendCoef::operator=(const FAddendCoef &That) {
266   if (That.isInt())
267     set(That.IntVal);
268   else
269     set(That.getFpVal());
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().add(That.getFpVal(), RndMode);
279     return;
280   }
281 
282   if (isInt()) {
283     const APFloat &T = That.getFpVal();
284     convertToFpType(T.getSemantics());
285     getFpVal().add(T, RndMode);
286     return;
287   }
288 
289   APFloat &T = getFpVal();
290   T.add(createAPFloatFromInt(T.getSemantics(), That.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 
323 void FAddendCoef::negate() {
324   if (isInt())
325     IntVal = 0 - IntVal;
326   else
327     getFpVal().changeSign();
328 }
329 
330 Value *FAddendCoef::getValue(Type *Ty) const {
331   return isInt() ?
332     ConstantFP::get(Ty, float(IntVal)) :
333     ConstantFP::get(Ty->getContext(), getFpVal());
334 }
335 
336 // The definition of <Val>     Addends
337 // =========================================
338 //  A + B                     <1, A>, <1,B>
339 //  A - B                     <1, A>, <1,B>
340 //  0 - B                     <-1, B>
341 //  C * A,                    <C, A>
342 //  A + C                     <1, A> <C, NULL>
343 //  0 +/- 0                   <0, NULL> (corner case)
344 //
345 // Legend: A and B are not constant, C is constant
346 unsigned FAddend::drillValueDownOneStep
347   (Value *Val, FAddend &Addend0, FAddend &Addend1) {
348   Instruction *I = nullptr;
349   if (!Val || !(I = dyn_cast<Instruction>(Val)))
350     return 0;
351 
352   unsigned Opcode = I->getOpcode();
353 
354   if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub) {
355     ConstantFP *C0, *C1;
356     Value *Opnd0 = I->getOperand(0);
357     Value *Opnd1 = I->getOperand(1);
358     if ((C0 = dyn_cast<ConstantFP>(Opnd0)) && C0->isZero())
359       Opnd0 = nullptr;
360 
361     if ((C1 = dyn_cast<ConstantFP>(Opnd1)) && C1->isZero())
362       Opnd1 = nullptr;
363 
364     if (Opnd0) {
365       if (!C0)
366         Addend0.set(1, Opnd0);
367       else
368         Addend0.set(C0, nullptr);
369     }
370 
371     if (Opnd1) {
372       FAddend &Addend = Opnd0 ? Addend1 : Addend0;
373       if (!C1)
374         Addend.set(1, Opnd1);
375       else
376         Addend.set(C1, nullptr);
377       if (Opcode == Instruction::FSub)
378         Addend.negate();
379     }
380 
381     if (Opnd0 || Opnd1)
382       return Opnd0 && Opnd1 ? 2 : 1;
383 
384     // Both operands are zero. Weird!
385     Addend0.set(APFloat(C0->getValueAPF().getSemantics()), nullptr);
386     return 1;
387   }
388 
389   if (I->getOpcode() == Instruction::FMul) {
390     Value *V0 = I->getOperand(0);
391     Value *V1 = I->getOperand(1);
392     if (ConstantFP *C = dyn_cast<ConstantFP>(V0)) {
393       Addend0.set(C, V1);
394       return 1;
395     }
396 
397     if (ConstantFP *C = dyn_cast<ConstantFP>(V1)) {
398       Addend0.set(C, V0);
399       return 1;
400     }
401   }
402 
403   return 0;
404 }
405 
406 // Try to break *this* addend into two addends. e.g. Suppose this addend is
407 // <2.3, V>, and V = X + Y, by calling this function, we obtain two addends,
408 // i.e. <2.3, X> and <2.3, Y>.
409 unsigned FAddend::drillAddendDownOneStep
410   (FAddend &Addend0, FAddend &Addend1) const {
411   if (isConstant())
412     return 0;
413 
414   unsigned BreakNum = FAddend::drillValueDownOneStep(Val, Addend0, Addend1);
415   if (!BreakNum || Coeff.isOne())
416     return BreakNum;
417 
418   Addend0.Scale(Coeff);
419 
420   if (BreakNum == 2)
421     Addend1.Scale(Coeff);
422 
423   return BreakNum;
424 }
425 
426 Value *FAddCombine::simplify(Instruction *I) {
427   assert(I->hasAllowReassoc() && I->hasNoSignedZeros() &&
428          "Expected 'reassoc'+'nsz' instruction");
429 
430   // Currently we are not able to handle vector type.
431   if (I->getType()->isVectorTy())
432     return nullptr;
433 
434   assert((I->getOpcode() == Instruction::FAdd ||
435           I->getOpcode() == Instruction::FSub) && "Expect add/sub");
436 
437   // Save the instruction before calling other member-functions.
438   Instr = I;
439 
440   FAddend Opnd0, Opnd1, Opnd0_0, Opnd0_1, Opnd1_0, Opnd1_1;
441 
442   unsigned OpndNum = FAddend::drillValueDownOneStep(I, Opnd0, Opnd1);
443 
444   // Step 1: Expand the 1st addend into Opnd0_0 and Opnd0_1.
445   unsigned Opnd0_ExpNum = 0;
446   unsigned Opnd1_ExpNum = 0;
447 
448   if (!Opnd0.isConstant())
449     Opnd0_ExpNum = Opnd0.drillAddendDownOneStep(Opnd0_0, Opnd0_1);
450 
451   // Step 2: Expand the 2nd addend into Opnd1_0 and Opnd1_1.
452   if (OpndNum == 2 && !Opnd1.isConstant())
453     Opnd1_ExpNum = Opnd1.drillAddendDownOneStep(Opnd1_0, Opnd1_1);
454 
455   // Step 3: Try to optimize Opnd0_0 + Opnd0_1 + Opnd1_0 + Opnd1_1
456   if (Opnd0_ExpNum && Opnd1_ExpNum) {
457     AddendVect AllOpnds;
458     AllOpnds.push_back(&Opnd0_0);
459     AllOpnds.push_back(&Opnd1_0);
460     if (Opnd0_ExpNum == 2)
461       AllOpnds.push_back(&Opnd0_1);
462     if (Opnd1_ExpNum == 2)
463       AllOpnds.push_back(&Opnd1_1);
464 
465     // Compute instruction quota. We should save at least one instruction.
466     unsigned InstQuota = 0;
467 
468     Value *V0 = I->getOperand(0);
469     Value *V1 = I->getOperand(1);
470     InstQuota = ((!isa<Constant>(V0) && V0->hasOneUse()) &&
471                  (!isa<Constant>(V1) && V1->hasOneUse())) ? 2 : 1;
472 
473     if (Value *R = simplifyFAdd(AllOpnds, InstQuota))
474       return R;
475   }
476 
477   if (OpndNum != 2) {
478     // The input instruction is : "I=0.0 +/- V". If the "V" were able to be
479     // splitted into two addends, say "V = X - Y", the instruction would have
480     // been optimized into "I = Y - X" in the previous steps.
481     //
482     const FAddendCoef &CE = Opnd0.getCoef();
483     return CE.isOne() ? Opnd0.getSymVal() : nullptr;
484   }
485 
486   // step 4: Try to optimize Opnd0 + Opnd1_0 [+ Opnd1_1]
487   if (Opnd1_ExpNum) {
488     AddendVect AllOpnds;
489     AllOpnds.push_back(&Opnd0);
490     AllOpnds.push_back(&Opnd1_0);
491     if (Opnd1_ExpNum == 2)
492       AllOpnds.push_back(&Opnd1_1);
493 
494     if (Value *R = simplifyFAdd(AllOpnds, 1))
495       return R;
496   }
497 
498   // step 5: Try to optimize Opnd1 + Opnd0_0 [+ Opnd0_1]
499   if (Opnd0_ExpNum) {
500     AddendVect AllOpnds;
501     AllOpnds.push_back(&Opnd1);
502     AllOpnds.push_back(&Opnd0_0);
503     if (Opnd0_ExpNum == 2)
504       AllOpnds.push_back(&Opnd0_1);
505 
506     if (Value *R = simplifyFAdd(AllOpnds, 1))
507       return R;
508   }
509 
510   return nullptr;
511 }
512 
513 Value *FAddCombine::simplifyFAdd(AddendVect& Addends, unsigned InstrQuota) {
514   unsigned AddendNum = Addends.size();
515   assert(AddendNum <= 4 && "Too many addends");
516 
517   // For saving intermediate results;
518   unsigned NextTmpIdx = 0;
519   FAddend TmpResult[3];
520 
521   // Points to the constant addend of the resulting simplified expression.
522   // If the resulting expr has constant-addend, this constant-addend is
523   // desirable to reside at the top of the resulting expression tree. Placing
524   // constant close to supper-expr(s) will potentially reveal some optimization
525   // opportunities in super-expr(s).
526   const FAddend *ConstAdd = nullptr;
527 
528   // Simplified addends are placed <SimpVect>.
529   AddendVect SimpVect;
530 
531   // The outer loop works on one symbolic-value at a time. Suppose the input
532   // addends are : <a1, x>, <b1, y>, <a2, x>, <c1, z>, <b2, y>, ...
533   // The symbolic-values will be processed in this order: x, y, z.
534   for (unsigned SymIdx = 0; SymIdx < AddendNum; SymIdx++) {
535 
536     const FAddend *ThisAddend = Addends[SymIdx];
537     if (!ThisAddend) {
538       // This addend was processed before.
539       continue;
540     }
541 
542     Value *Val = ThisAddend->getSymVal();
543     unsigned StartIdx = SimpVect.size();
544     SimpVect.push_back(ThisAddend);
545 
546     // The inner loop collects addends sharing same symbolic-value, and these
547     // addends will be later on folded into a single addend. Following above
548     // example, if the symbolic value "y" is being processed, the inner loop
549     // will collect two addends "<b1,y>" and "<b2,Y>". These two addends will
550     // be later on folded into "<b1+b2, y>".
551     for (unsigned SameSymIdx = SymIdx + 1;
552          SameSymIdx < AddendNum; SameSymIdx++) {
553       const FAddend *T = Addends[SameSymIdx];
554       if (T && T->getSymVal() == Val) {
555         // Set null such that next iteration of the outer loop will not process
556         // this addend again.
557         Addends[SameSymIdx] = nullptr;
558         SimpVect.push_back(T);
559       }
560     }
561 
562     // If multiple addends share same symbolic value, fold them together.
563     if (StartIdx + 1 != SimpVect.size()) {
564       FAddend &R = TmpResult[NextTmpIdx ++];
565       R = *SimpVect[StartIdx];
566       for (unsigned Idx = StartIdx + 1; Idx < SimpVect.size(); Idx++)
567         R += *SimpVect[Idx];
568 
569       // Pop all addends being folded and push the resulting folded addend.
570       SimpVect.resize(StartIdx);
571       if (Val) {
572         if (!R.isZero()) {
573           SimpVect.push_back(&R);
574         }
575       } else {
576         // Don't push constant addend at this time. It will be the last element
577         // of <SimpVect>.
578         ConstAdd = &R;
579       }
580     }
581   }
582 
583   assert((NextTmpIdx <= array_lengthof(TmpResult) + 1) &&
584          "out-of-bound access");
585 
586   if (ConstAdd)
587     SimpVect.push_back(ConstAdd);
588 
589   Value *Result;
590   if (!SimpVect.empty())
591     Result = createNaryFAdd(SimpVect, InstrQuota);
592   else {
593     // The addition is folded to 0.0.
594     Result = ConstantFP::get(Instr->getType(), 0.0);
595   }
596 
597   return Result;
598 }
599 
600 Value *FAddCombine::createNaryFAdd
601   (const AddendVect &Opnds, unsigned InstrQuota) {
602   assert(!Opnds.empty() && "Expect at least one addend");
603 
604   // Step 1: Check if the # of instructions needed exceeds the quota.
605 
606   unsigned InstrNeeded = calcInstrNumber(Opnds);
607   if (InstrNeeded > InstrQuota)
608     return nullptr;
609 
610   initCreateInstNum();
611 
612   // step 2: Emit the N-ary addition.
613   // Note that at most three instructions are involved in Fadd-InstCombine: the
614   // addition in question, and at most two neighboring instructions.
615   // The resulting optimized addition should have at least one less instruction
616   // than the original addition expression tree. This implies that the resulting
617   // N-ary addition has at most two instructions, and we don't need to worry
618   // about tree-height when constructing the N-ary addition.
619 
620   Value *LastVal = nullptr;
621   bool LastValNeedNeg = false;
622 
623   // Iterate the addends, creating fadd/fsub using adjacent two addends.
624   for (const FAddend *Opnd : Opnds) {
625     bool NeedNeg;
626     Value *V = createAddendVal(*Opnd, NeedNeg);
627     if (!LastVal) {
628       LastVal = V;
629       LastValNeedNeg = NeedNeg;
630       continue;
631     }
632 
633     if (LastValNeedNeg == NeedNeg) {
634       LastVal = createFAdd(LastVal, V);
635       continue;
636     }
637 
638     if (LastValNeedNeg)
639       LastVal = createFSub(V, LastVal);
640     else
641       LastVal = createFSub(LastVal, V);
642 
643     LastValNeedNeg = false;
644   }
645 
646   if (LastValNeedNeg) {
647     LastVal = createFNeg(LastVal);
648   }
649 
650 #ifndef NDEBUG
651   assert(CreateInstrNum == InstrNeeded &&
652          "Inconsistent in instruction numbers");
653 #endif
654 
655   return LastVal;
656 }
657 
658 Value *FAddCombine::createFSub(Value *Opnd0, Value *Opnd1) {
659   Value *V = Builder.CreateFSub(Opnd0, Opnd1);
660   if (Instruction *I = dyn_cast<Instruction>(V))
661     createInstPostProc(I);
662   return V;
663 }
664 
665 Value *FAddCombine::createFNeg(Value *V) {
666   Value *Zero = cast<Value>(ConstantFP::getZeroValueForNegation(V->getType()));
667   Value *NewV = createFSub(Zero, V);
668   if (Instruction *I = dyn_cast<Instruction>(NewV))
669     createInstPostProc(I, true); // fneg's don't receive instruction numbers.
670   return NewV;
671 }
672 
673 Value *FAddCombine::createFAdd(Value *Opnd0, Value *Opnd1) {
674   Value *V = Builder.CreateFAdd(Opnd0, Opnd1);
675   if (Instruction *I = dyn_cast<Instruction>(V))
676     createInstPostProc(I);
677   return V;
678 }
679 
680 Value *FAddCombine::createFMul(Value *Opnd0, Value *Opnd1) {
681   Value *V = Builder.CreateFMul(Opnd0, Opnd1);
682   if (Instruction *I = dyn_cast<Instruction>(V))
683     createInstPostProc(I);
684   return V;
685 }
686 
687 void FAddCombine::createInstPostProc(Instruction *NewInstr, bool NoNumber) {
688   NewInstr->setDebugLoc(Instr->getDebugLoc());
689 
690   // Keep track of the number of instruction created.
691   if (!NoNumber)
692     incCreateInstNum();
693 
694   // Propagate fast-math flags
695   NewInstr->setFastMathFlags(Instr->getFastMathFlags());
696 }
697 
698 // Return the number of instruction needed to emit the N-ary addition.
699 // NOTE: Keep this function in sync with createAddendVal().
700 unsigned FAddCombine::calcInstrNumber(const AddendVect &Opnds) {
701   unsigned OpndNum = Opnds.size();
702   unsigned InstrNeeded = OpndNum - 1;
703 
704   // The number of addends in the form of "(-1)*x".
705   unsigned NegOpndNum = 0;
706 
707   // Adjust the number of instructions needed to emit the N-ary add.
708   for (const FAddend *Opnd : Opnds) {
709     if (Opnd->isConstant())
710       continue;
711 
712     // The constant check above is really for a few special constant
713     // coefficients.
714     if (isa<UndefValue>(Opnd->getSymVal()))
715       continue;
716 
717     const FAddendCoef &CE = Opnd->getCoef();
718     if (CE.isMinusOne() || CE.isMinusTwo())
719       NegOpndNum++;
720 
721     // Let the addend be "c * x". If "c == +/-1", the value of the addend
722     // is immediately available; otherwise, it needs exactly one instruction
723     // to evaluate the value.
724     if (!CE.isMinusOne() && !CE.isOne())
725       InstrNeeded++;
726   }
727   if (NegOpndNum == OpndNum)
728     InstrNeeded++;
729   return InstrNeeded;
730 }
731 
732 // Input Addend        Value           NeedNeg(output)
733 // ================================================================
734 // Constant C          C               false
735 // <+/-1, V>           V               coefficient is -1
736 // <2/-2, V>          "fadd V, V"      coefficient is -2
737 // <C, V>             "fmul V, C"      false
738 //
739 // NOTE: Keep this function in sync with FAddCombine::calcInstrNumber.
740 Value *FAddCombine::createAddendVal(const FAddend &Opnd, bool &NeedNeg) {
741   const FAddendCoef &Coeff = Opnd.getCoef();
742 
743   if (Opnd.isConstant()) {
744     NeedNeg = false;
745     return Coeff.getValue(Instr->getType());
746   }
747 
748   Value *OpndVal = Opnd.getSymVal();
749 
750   if (Coeff.isMinusOne() || Coeff.isOne()) {
751     NeedNeg = Coeff.isMinusOne();
752     return OpndVal;
753   }
754 
755   if (Coeff.isTwo() || Coeff.isMinusTwo()) {
756     NeedNeg = Coeff.isMinusTwo();
757     return createFAdd(OpndVal, OpndVal);
758   }
759 
760   NeedNeg = false;
761   return createFMul(OpndVal, Coeff.getValue(Instr->getType()));
762 }
763 
764 // Checks if any operand is negative and we can convert add to sub.
765 // This function checks for following negative patterns
766 //   ADD(XOR(OR(Z, NOT(C)), C)), 1) == NEG(AND(Z, C))
767 //   ADD(XOR(AND(Z, C), C), 1) == NEG(OR(Z, ~C))
768 //   XOR(AND(Z, C), (C + 1)) == NEG(OR(Z, ~C)) if C is even
769 static Value *checkForNegativeOperand(BinaryOperator &I,
770                                       InstCombiner::BuilderTy &Builder) {
771   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
772 
773   // This function creates 2 instructions to replace ADD, we need at least one
774   // of LHS or RHS to have one use to ensure benefit in transform.
775   if (!LHS->hasOneUse() && !RHS->hasOneUse())
776     return nullptr;
777 
778   Value *X = nullptr, *Y = nullptr, *Z = nullptr;
779   const APInt *C1 = nullptr, *C2 = nullptr;
780 
781   // if ONE is on other side, swap
782   if (match(RHS, m_Add(m_Value(X), m_One())))
783     std::swap(LHS, RHS);
784 
785   if (match(LHS, m_Add(m_Value(X), m_One()))) {
786     // if XOR on other side, swap
787     if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1))))
788       std::swap(X, RHS);
789 
790     if (match(X, m_Xor(m_Value(Y), m_APInt(C1)))) {
791       // X = XOR(Y, C1), Y = OR(Z, C2), C2 = NOT(C1) ==> X == NOT(AND(Z, C1))
792       // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, AND(Z, C1))
793       if (match(Y, m_Or(m_Value(Z), m_APInt(C2))) && (*C2 == ~(*C1))) {
794         Value *NewAnd = Builder.CreateAnd(Z, *C1);
795         return Builder.CreateSub(RHS, NewAnd, "sub");
796       } else if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && (*C1 == *C2)) {
797         // X = XOR(Y, C1), Y = AND(Z, C2), C2 == C1 ==> X == NOT(OR(Z, ~C1))
798         // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, OR(Z, ~C1))
799         Value *NewOr = Builder.CreateOr(Z, ~(*C1));
800         return Builder.CreateSub(RHS, NewOr, "sub");
801       }
802     }
803   }
804 
805   // Restore LHS and RHS
806   LHS = I.getOperand(0);
807   RHS = I.getOperand(1);
808 
809   // if XOR is on other side, swap
810   if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1))))
811     std::swap(LHS, RHS);
812 
813   // C2 is ODD
814   // LHS = XOR(Y, C1), Y = AND(Z, C2), C1 == (C2 + 1) => LHS == NEG(OR(Z, ~C2))
815   // ADD(LHS, RHS) == SUB(RHS, OR(Z, ~C2))
816   if (match(LHS, m_Xor(m_Value(Y), m_APInt(C1))))
817     if (C1->countTrailingZeros() == 0)
818       if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && *C1 == (*C2 + 1)) {
819         Value *NewOr = Builder.CreateOr(Z, ~(*C2));
820         return Builder.CreateSub(RHS, NewOr, "sub");
821       }
822   return nullptr;
823 }
824 
825 /// Wrapping flags may allow combining constants separated by an extend.
826 static Instruction *foldNoWrapAdd(BinaryOperator &Add,
827                                   InstCombiner::BuilderTy &Builder) {
828   Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1);
829   Type *Ty = Add.getType();
830   Constant *Op1C;
831   if (!match(Op1, m_Constant(Op1C)))
832     return nullptr;
833 
834   // Try this match first because it results in an add in the narrow type.
835   // (zext (X +nuw C2)) + C1 --> zext (X + (C2 + trunc(C1)))
836   Value *X;
837   const APInt *C1, *C2;
838   if (match(Op1, m_APInt(C1)) &&
839       match(Op0, m_OneUse(m_ZExt(m_NUWAdd(m_Value(X), m_APInt(C2))))) &&
840       C1->isNegative() && C1->sge(-C2->sext(C1->getBitWidth()))) {
841     Constant *NewC =
842         ConstantInt::get(X->getType(), *C2 + C1->trunc(C2->getBitWidth()));
843     return new ZExtInst(Builder.CreateNUWAdd(X, NewC), Ty);
844   }
845 
846   // More general combining of constants in the wide type.
847   // (sext (X +nsw NarrowC)) + C --> (sext X) + (sext(NarrowC) + C)
848   Constant *NarrowC;
849   if (match(Op0, m_OneUse(m_SExt(m_NSWAdd(m_Value(X), m_Constant(NarrowC)))))) {
850     Constant *WideC = ConstantExpr::getSExt(NarrowC, Ty);
851     Constant *NewC = ConstantExpr::getAdd(WideC, Op1C);
852     Value *WideX = Builder.CreateSExt(X, Ty);
853     return BinaryOperator::CreateAdd(WideX, NewC);
854   }
855   // (zext (X +nuw NarrowC)) + C --> (zext X) + (zext(NarrowC) + C)
856   if (match(Op0, m_OneUse(m_ZExt(m_NUWAdd(m_Value(X), m_Constant(NarrowC)))))) {
857     Constant *WideC = ConstantExpr::getZExt(NarrowC, Ty);
858     Constant *NewC = ConstantExpr::getAdd(WideC, Op1C);
859     Value *WideX = Builder.CreateZExt(X, Ty);
860     return BinaryOperator::CreateAdd(WideX, NewC);
861   }
862 
863   return nullptr;
864 }
865 
866 Instruction *InstCombiner::foldAddWithConstant(BinaryOperator &Add) {
867   Value *Op0 = Add.getOperand(0), *Op1 = Add.getOperand(1);
868   Constant *Op1C;
869   if (!match(Op1, m_Constant(Op1C)))
870     return nullptr;
871 
872   if (Instruction *NV = foldBinOpIntoSelectOrPhi(Add))
873     return NV;
874 
875   Value *X;
876   Constant *Op00C;
877 
878   // add (sub C1, X), C2 --> sub (add C1, C2), X
879   if (match(Op0, m_Sub(m_Constant(Op00C), m_Value(X))))
880     return BinaryOperator::CreateSub(ConstantExpr::getAdd(Op00C, Op1C), X);
881 
882   Value *Y;
883 
884   // add (sub X, Y), -1 --> add (not Y), X
885   if (match(Op0, m_OneUse(m_Sub(m_Value(X), m_Value(Y)))) &&
886       match(Op1, m_AllOnes()))
887     return BinaryOperator::CreateAdd(Builder.CreateNot(Y), X);
888 
889   // zext(bool) + C -> bool ? C + 1 : C
890   if (match(Op0, m_ZExt(m_Value(X))) &&
891       X->getType()->getScalarSizeInBits() == 1)
892     return SelectInst::Create(X, AddOne(Op1C), Op1);
893 
894   // ~X + C --> (C-1) - X
895   if (match(Op0, m_Not(m_Value(X))))
896     return BinaryOperator::CreateSub(SubOne(Op1C), X);
897 
898   const APInt *C;
899   if (!match(Op1, m_APInt(C)))
900     return nullptr;
901 
902   // (X | C2) + C --> (X | C2) ^ C2 iff (C2 == -C)
903   const APInt *C2;
904   if (match(Op0, m_Or(m_Value(), m_APInt(C2))) && *C2 == -*C)
905     return BinaryOperator::CreateXor(Op0, ConstantInt::get(Add.getType(), *C2));
906 
907   if (C->isSignMask()) {
908     // If wrapping is not allowed, then the addition must set the sign bit:
909     // X + (signmask) --> X | signmask
910     if (Add.hasNoSignedWrap() || Add.hasNoUnsignedWrap())
911       return BinaryOperator::CreateOr(Op0, Op1);
912 
913     // If wrapping is allowed, then the addition flips the sign bit of LHS:
914     // X + (signmask) --> X ^ signmask
915     return BinaryOperator::CreateXor(Op0, Op1);
916   }
917 
918   // Is this add the last step in a convoluted sext?
919   // add(zext(xor i16 X, -32768), -32768) --> sext X
920   Type *Ty = Add.getType();
921   if (match(Op0, m_ZExt(m_Xor(m_Value(X), m_APInt(C2)))) &&
922       C2->isMinSignedValue() && C2->sext(Ty->getScalarSizeInBits()) == *C)
923     return CastInst::Create(Instruction::SExt, X, Ty);
924 
925   if (C->isOneValue() && Op0->hasOneUse()) {
926     // add (sext i1 X), 1 --> zext (not X)
927     // TODO: The smallest IR representation is (select X, 0, 1), and that would
928     // not require the one-use check. But we need to remove a transform in
929     // visitSelect and make sure that IR value tracking for select is equal or
930     // better than for these ops.
931     if (match(Op0, m_SExt(m_Value(X))) &&
932         X->getType()->getScalarSizeInBits() == 1)
933       return new ZExtInst(Builder.CreateNot(X), Ty);
934 
935     // Shifts and add used to flip and mask off the low bit:
936     // add (ashr (shl i32 X, 31), 31), 1 --> and (not X), 1
937     const APInt *C3;
938     if (match(Op0, m_AShr(m_Shl(m_Value(X), m_APInt(C2)), m_APInt(C3))) &&
939         C2 == C3 && *C2 == Ty->getScalarSizeInBits() - 1) {
940       Value *NotX = Builder.CreateNot(X);
941       return BinaryOperator::CreateAnd(NotX, ConstantInt::get(Ty, 1));
942     }
943   }
944 
945   return nullptr;
946 }
947 
948 // Matches multiplication expression Op * C where C is a constant. Returns the
949 // constant value in C and the other operand in Op. Returns true if such a
950 // match is found.
951 static bool MatchMul(Value *E, Value *&Op, APInt &C) {
952   const APInt *AI;
953   if (match(E, m_Mul(m_Value(Op), m_APInt(AI)))) {
954     C = *AI;
955     return true;
956   }
957   if (match(E, m_Shl(m_Value(Op), m_APInt(AI)))) {
958     C = APInt(AI->getBitWidth(), 1);
959     C <<= *AI;
960     return true;
961   }
962   return false;
963 }
964 
965 // Matches remainder expression Op % C where C is a constant. Returns the
966 // constant value in C and the other operand in Op. Returns the signedness of
967 // the remainder operation in IsSigned. Returns true if such a match is
968 // found.
969 static bool MatchRem(Value *E, Value *&Op, APInt &C, bool &IsSigned) {
970   const APInt *AI;
971   IsSigned = false;
972   if (match(E, m_SRem(m_Value(Op), m_APInt(AI)))) {
973     IsSigned = true;
974     C = *AI;
975     return true;
976   }
977   if (match(E, m_URem(m_Value(Op), m_APInt(AI)))) {
978     C = *AI;
979     return true;
980   }
981   if (match(E, m_And(m_Value(Op), m_APInt(AI))) && (*AI + 1).isPowerOf2()) {
982     C = *AI + 1;
983     return true;
984   }
985   return false;
986 }
987 
988 // Matches division expression Op / C with the given signedness as indicated
989 // by IsSigned, where C is a constant. Returns the constant value in C and the
990 // other operand in Op. Returns true if such a match is found.
991 static bool MatchDiv(Value *E, Value *&Op, APInt &C, bool IsSigned) {
992   const APInt *AI;
993   if (IsSigned && match(E, m_SDiv(m_Value(Op), m_APInt(AI)))) {
994     C = *AI;
995     return true;
996   }
997   if (!IsSigned) {
998     if (match(E, m_UDiv(m_Value(Op), m_APInt(AI)))) {
999       C = *AI;
1000       return true;
1001     }
1002     if (match(E, m_LShr(m_Value(Op), m_APInt(AI)))) {
1003       C = APInt(AI->getBitWidth(), 1);
1004       C <<= *AI;
1005       return true;
1006     }
1007   }
1008   return false;
1009 }
1010 
1011 // Returns whether C0 * C1 with the given signedness overflows.
1012 static bool MulWillOverflow(APInt &C0, APInt &C1, bool IsSigned) {
1013   bool overflow;
1014   if (IsSigned)
1015     (void)C0.smul_ov(C1, overflow);
1016   else
1017     (void)C0.umul_ov(C1, overflow);
1018   return overflow;
1019 }
1020 
1021 // Simplifies X % C0 + (( X / C0 ) % C1) * C0 to X % (C0 * C1), where (C0 * C1)
1022 // does not overflow.
1023 Value *InstCombiner::SimplifyAddWithRemainder(BinaryOperator &I) {
1024   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
1025   Value *X, *MulOpV;
1026   APInt C0, MulOpC;
1027   bool IsSigned;
1028   // Match I = X % C0 + MulOpV * C0
1029   if (((MatchRem(LHS, X, C0, IsSigned) && MatchMul(RHS, MulOpV, MulOpC)) ||
1030        (MatchRem(RHS, X, C0, IsSigned) && MatchMul(LHS, MulOpV, MulOpC))) &&
1031       C0 == MulOpC) {
1032     Value *RemOpV;
1033     APInt C1;
1034     bool Rem2IsSigned;
1035     // Match MulOpC = RemOpV % C1
1036     if (MatchRem(MulOpV, RemOpV, C1, Rem2IsSigned) &&
1037         IsSigned == Rem2IsSigned) {
1038       Value *DivOpV;
1039       APInt DivOpC;
1040       // Match RemOpV = X / C0
1041       if (MatchDiv(RemOpV, DivOpV, DivOpC, IsSigned) && X == DivOpV &&
1042           C0 == DivOpC && !MulWillOverflow(C0, C1, IsSigned)) {
1043         Value *NewDivisor =
1044             ConstantInt::get(X->getType()->getContext(), C0 * C1);
1045         return IsSigned ? Builder.CreateSRem(X, NewDivisor, "srem")
1046                         : Builder.CreateURem(X, NewDivisor, "urem");
1047       }
1048     }
1049   }
1050 
1051   return nullptr;
1052 }
1053 
1054 /// Fold
1055 ///   (1 << NBits) - 1
1056 /// Into:
1057 ///   ~(-(1 << NBits))
1058 /// Because a 'not' is better for bit-tracking analysis and other transforms
1059 /// than an 'add'. The new shl is always nsw, and is nuw if old `and` was.
1060 static Instruction *canonicalizeLowbitMask(BinaryOperator &I,
1061                                            InstCombiner::BuilderTy &Builder) {
1062   Value *NBits;
1063   if (!match(&I, m_Add(m_OneUse(m_Shl(m_One(), m_Value(NBits))), m_AllOnes())))
1064     return nullptr;
1065 
1066   Constant *MinusOne = Constant::getAllOnesValue(NBits->getType());
1067   Value *NotMask = Builder.CreateShl(MinusOne, NBits, "notmask");
1068   // Be wary of constant folding.
1069   if (auto *BOp = dyn_cast<BinaryOperator>(NotMask)) {
1070     // Always NSW. But NUW propagates from `add`.
1071     BOp->setHasNoSignedWrap();
1072     BOp->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
1073   }
1074 
1075   return BinaryOperator::CreateNot(NotMask, I.getName());
1076 }
1077 
1078 static Instruction *foldToUnsignedSaturatedAdd(BinaryOperator &I) {
1079   assert(I.getOpcode() == Instruction::Add && "Expecting add instruction");
1080   Type *Ty = I.getType();
1081   auto getUAddSat = [&]() {
1082     return Intrinsic::getDeclaration(I.getModule(), Intrinsic::uadd_sat, Ty);
1083   };
1084 
1085   // add (umin X, ~Y), Y --> uaddsat X, Y
1086   Value *X, *Y;
1087   if (match(&I, m_c_Add(m_c_UMin(m_Value(X), m_Not(m_Value(Y))),
1088                         m_Deferred(Y))))
1089     return CallInst::Create(getUAddSat(), { X, Y });
1090 
1091   // add (umin X, ~C), C --> uaddsat X, C
1092   const APInt *C, *NotC;
1093   if (match(&I, m_Add(m_UMin(m_Value(X), m_APInt(NotC)), m_APInt(C))) &&
1094       *C == ~*NotC)
1095     return CallInst::Create(getUAddSat(), { X, ConstantInt::get(Ty, *C) });
1096 
1097   return nullptr;
1098 }
1099 
1100 Instruction *
1101 InstCombiner::canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(
1102     BinaryOperator &I) {
1103   assert((I.getOpcode() == Instruction::Add ||
1104           I.getOpcode() == Instruction::Or ||
1105           I.getOpcode() == Instruction::Sub) &&
1106          "Expecting add/or/sub instruction");
1107 
1108   // We have a subtraction/addition between a (potentially truncated) *logical*
1109   // right-shift of X and a "select".
1110   Value *X, *Select;
1111   Instruction *LowBitsToSkip, *Extract;
1112   if (!match(&I, m_c_BinOp(m_TruncOrSelf(m_CombineAnd(
1113                                m_LShr(m_Value(X), m_Instruction(LowBitsToSkip)),
1114                                m_Instruction(Extract))),
1115                            m_Value(Select))))
1116     return nullptr;
1117 
1118   // `add`/`or` is commutative; but for `sub`, "select" *must* be on RHS.
1119   if (I.getOpcode() == Instruction::Sub && I.getOperand(1) != Select)
1120     return nullptr;
1121 
1122   Type *XTy = X->getType();
1123   bool HadTrunc = I.getType() != XTy;
1124 
1125   // If there was a truncation of extracted value, then we'll need to produce
1126   // one extra instruction, so we need to ensure one instruction will go away.
1127   if (HadTrunc && !match(&I, m_c_BinOp(m_OneUse(m_Value()), m_Value())))
1128     return nullptr;
1129 
1130   // Extraction should extract high NBits bits, with shift amount calculated as:
1131   //   low bits to skip = shift bitwidth - high bits to extract
1132   // The shift amount itself may be extended, and we need to look past zero-ext
1133   // when matching NBits, that will matter for matching later.
1134   Constant *C;
1135   Value *NBits;
1136   if (!match(
1137           LowBitsToSkip,
1138           m_ZExtOrSelf(m_Sub(m_Constant(C), m_ZExtOrSelf(m_Value(NBits))))) ||
1139       !match(C, m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_EQ,
1140                                    APInt(C->getType()->getScalarSizeInBits(),
1141                                          X->getType()->getScalarSizeInBits()))))
1142     return nullptr;
1143 
1144   // Sign-extending value can be zero-extended if we `sub`tract it,
1145   // or sign-extended otherwise.
1146   auto SkipExtInMagic = [&I](Value *&V) {
1147     if (I.getOpcode() == Instruction::Sub)
1148       match(V, m_ZExtOrSelf(m_Value(V)));
1149     else
1150       match(V, m_SExtOrSelf(m_Value(V)));
1151   };
1152 
1153   // Now, finally validate the sign-extending magic.
1154   // `select` itself may be appropriately extended, look past that.
1155   SkipExtInMagic(Select);
1156 
1157   ICmpInst::Predicate Pred;
1158   const APInt *Thr;
1159   Value *SignExtendingValue, *Zero;
1160   bool ShouldSignext;
1161   // It must be a select between two values we will later establish to be a
1162   // sign-extending value and a zero constant. The condition guarding the
1163   // sign-extension must be based on a sign bit of the same X we had in `lshr`.
1164   if (!match(Select, m_Select(m_ICmp(Pred, m_Specific(X), m_APInt(Thr)),
1165                               m_Value(SignExtendingValue), m_Value(Zero))) ||
1166       !isSignBitCheck(Pred, *Thr, ShouldSignext))
1167     return nullptr;
1168 
1169   // icmp-select pair is commutative.
1170   if (!ShouldSignext)
1171     std::swap(SignExtendingValue, Zero);
1172 
1173   // If we should not perform sign-extension then we must add/or/subtract zero.
1174   if (!match(Zero, m_Zero()))
1175     return nullptr;
1176   // Otherwise, it should be some constant, left-shifted by the same NBits we
1177   // had in `lshr`. Said left-shift can also be appropriately extended.
1178   // Again, we must look past zero-ext when looking for NBits.
1179   SkipExtInMagic(SignExtendingValue);
1180   Constant *SignExtendingValueBaseConstant;
1181   if (!match(SignExtendingValue,
1182              m_Shl(m_Constant(SignExtendingValueBaseConstant),
1183                    m_ZExtOrSelf(m_Specific(NBits)))))
1184     return nullptr;
1185   // If we `sub`, then the constant should be one, else it should be all-ones.
1186   if (I.getOpcode() == Instruction::Sub
1187           ? !match(SignExtendingValueBaseConstant, m_One())
1188           : !match(SignExtendingValueBaseConstant, m_AllOnes()))
1189     return nullptr;
1190 
1191   auto *NewAShr = BinaryOperator::CreateAShr(X, LowBitsToSkip,
1192                                              Extract->getName() + ".sext");
1193   NewAShr->copyIRFlags(Extract); // Preserve `exact`-ness.
1194   if (!HadTrunc)
1195     return NewAShr;
1196 
1197   Builder.Insert(NewAShr);
1198   return TruncInst::CreateTruncOrBitCast(NewAShr, I.getType());
1199 }
1200 
1201 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
1202   if (Value *V = SimplifyAddInst(I.getOperand(0), I.getOperand(1),
1203                                  I.hasNoSignedWrap(), I.hasNoUnsignedWrap(),
1204                                  SQ.getWithInstruction(&I)))
1205     return replaceInstUsesWith(I, V);
1206 
1207   if (SimplifyAssociativeOrCommutative(I))
1208     return &I;
1209 
1210   if (Instruction *X = foldVectorBinop(I))
1211     return X;
1212 
1213   // (A*B)+(A*C) -> A*(B+C) etc
1214   if (Value *V = SimplifyUsingDistributiveLaws(I))
1215     return replaceInstUsesWith(I, V);
1216 
1217   if (Instruction *X = foldAddWithConstant(I))
1218     return X;
1219 
1220   if (Instruction *X = foldNoWrapAdd(I, Builder))
1221     return X;
1222 
1223   // FIXME: This should be moved into the above helper function to allow these
1224   // transforms for general constant or constant splat vectors.
1225   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
1226   Type *Ty = I.getType();
1227   if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
1228     Value *XorLHS = nullptr; ConstantInt *XorRHS = nullptr;
1229     if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
1230       unsigned TySizeBits = Ty->getScalarSizeInBits();
1231       const APInt &RHSVal = CI->getValue();
1232       unsigned ExtendAmt = 0;
1233       // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
1234       // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
1235       if (XorRHS->getValue() == -RHSVal) {
1236         if (RHSVal.isPowerOf2())
1237           ExtendAmt = TySizeBits - RHSVal.logBase2() - 1;
1238         else if (XorRHS->getValue().isPowerOf2())
1239           ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1;
1240       }
1241 
1242       if (ExtendAmt) {
1243         APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt);
1244         if (!MaskedValueIsZero(XorLHS, Mask, 0, &I))
1245           ExtendAmt = 0;
1246       }
1247 
1248       if (ExtendAmt) {
1249         Constant *ShAmt = ConstantInt::get(Ty, ExtendAmt);
1250         Value *NewShl = Builder.CreateShl(XorLHS, ShAmt, "sext");
1251         return BinaryOperator::CreateAShr(NewShl, ShAmt);
1252       }
1253 
1254       // If this is a xor that was canonicalized from a sub, turn it back into
1255       // a sub and fuse this add with it.
1256       if (LHS->hasOneUse() && (XorRHS->getValue()+1).isPowerOf2()) {
1257         KnownBits LHSKnown = computeKnownBits(XorLHS, 0, &I);
1258         if ((XorRHS->getValue() | LHSKnown.Zero).isAllOnesValue())
1259           return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI),
1260                                            XorLHS);
1261       }
1262       // (X + signmask) + C could have gotten canonicalized to (X^signmask) + C,
1263       // transform them into (X + (signmask ^ C))
1264       if (XorRHS->getValue().isSignMask())
1265         return BinaryOperator::CreateAdd(XorLHS,
1266                                          ConstantExpr::getXor(XorRHS, CI));
1267     }
1268   }
1269 
1270   if (Ty->isIntOrIntVectorTy(1))
1271     return BinaryOperator::CreateXor(LHS, RHS);
1272 
1273   // X + X --> X << 1
1274   if (LHS == RHS) {
1275     auto *Shl = BinaryOperator::CreateShl(LHS, ConstantInt::get(Ty, 1));
1276     Shl->setHasNoSignedWrap(I.hasNoSignedWrap());
1277     Shl->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
1278     return Shl;
1279   }
1280 
1281   Value *A, *B;
1282   if (match(LHS, m_Neg(m_Value(A)))) {
1283     // -A + -B --> -(A + B)
1284     if (match(RHS, m_Neg(m_Value(B))))
1285       return BinaryOperator::CreateNeg(Builder.CreateAdd(A, B));
1286 
1287     // -A + B --> B - A
1288     return BinaryOperator::CreateSub(RHS, A);
1289   }
1290 
1291   // Canonicalize sext to zext for better value tracking potential.
1292   // add A, sext(B) --> sub A, zext(B)
1293   if (match(&I, m_c_Add(m_Value(A), m_OneUse(m_SExt(m_Value(B))))) &&
1294       B->getType()->isIntOrIntVectorTy(1))
1295     return BinaryOperator::CreateSub(A, Builder.CreateZExt(B, Ty));
1296 
1297   // A + -B  -->  A - B
1298   if (match(RHS, m_Neg(m_Value(B))))
1299     return BinaryOperator::CreateSub(LHS, B);
1300 
1301   if (Value *V = checkForNegativeOperand(I, Builder))
1302     return replaceInstUsesWith(I, V);
1303 
1304   // (A + 1) + ~B --> A - B
1305   // ~B + (A + 1) --> A - B
1306   // (~B + A) + 1 --> A - B
1307   // (A + ~B) + 1 --> A - B
1308   if (match(&I, m_c_BinOp(m_Add(m_Value(A), m_One()), m_Not(m_Value(B)))) ||
1309       match(&I, m_BinOp(m_c_Add(m_Not(m_Value(B)), m_Value(A)), m_One())))
1310     return BinaryOperator::CreateSub(A, B);
1311 
1312   // X % C0 + (( X / C0 ) % C1) * C0 => X % (C0 * C1)
1313   if (Value *V = SimplifyAddWithRemainder(I)) return replaceInstUsesWith(I, V);
1314 
1315   // A+B --> A|B iff A and B have no bits set in common.
1316   if (haveNoCommonBitsSet(LHS, RHS, DL, &AC, &I, &DT))
1317     return BinaryOperator::CreateOr(LHS, RHS);
1318 
1319   // FIXME: We already did a check for ConstantInt RHS above this.
1320   // FIXME: Is this pattern covered by another fold? No regression tests fail on
1321   // removal.
1322   if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
1323     // (X & FF00) + xx00  -> (X+xx00) & FF00
1324     Value *X;
1325     ConstantInt *C2;
1326     if (LHS->hasOneUse() &&
1327         match(LHS, m_And(m_Value(X), m_ConstantInt(C2))) &&
1328         CRHS->getValue() == (CRHS->getValue() & C2->getValue())) {
1329       // See if all bits from the first bit set in the Add RHS up are included
1330       // in the mask.  First, get the rightmost bit.
1331       const APInt &AddRHSV = CRHS->getValue();
1332 
1333       // Form a mask of all bits from the lowest bit added through the top.
1334       APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
1335 
1336       // See if the and mask includes all of these bits.
1337       APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
1338 
1339       if (AddRHSHighBits == AddRHSHighBitsAnd) {
1340         // Okay, the xform is safe.  Insert the new add pronto.
1341         Value *NewAdd = Builder.CreateAdd(X, CRHS, LHS->getName());
1342         return BinaryOperator::CreateAnd(NewAdd, C2);
1343       }
1344     }
1345   }
1346 
1347   // add (select X 0 (sub n A)) A  -->  select X A n
1348   {
1349     SelectInst *SI = dyn_cast<SelectInst>(LHS);
1350     Value *A = RHS;
1351     if (!SI) {
1352       SI = dyn_cast<SelectInst>(RHS);
1353       A = LHS;
1354     }
1355     if (SI && SI->hasOneUse()) {
1356       Value *TV = SI->getTrueValue();
1357       Value *FV = SI->getFalseValue();
1358       Value *N;
1359 
1360       // Can we fold the add into the argument of the select?
1361       // We check both true and false select arguments for a matching subtract.
1362       if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A))))
1363         // Fold the add into the true select value.
1364         return SelectInst::Create(SI->getCondition(), N, A);
1365 
1366       if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A))))
1367         // Fold the add into the false select value.
1368         return SelectInst::Create(SI->getCondition(), A, N);
1369     }
1370   }
1371 
1372   if (Instruction *Ext = narrowMathIfNoOverflow(I))
1373     return Ext;
1374 
1375   // (add (xor A, B) (and A, B)) --> (or A, B)
1376   // (add (and A, B) (xor A, B)) --> (or A, B)
1377   if (match(&I, m_c_BinOp(m_Xor(m_Value(A), m_Value(B)),
1378                           m_c_And(m_Deferred(A), m_Deferred(B)))))
1379     return BinaryOperator::CreateOr(A, B);
1380 
1381   // (add (or A, B) (and A, B)) --> (add A, B)
1382   // (add (and A, B) (or A, B)) --> (add A, B)
1383   if (match(&I, m_c_BinOp(m_Or(m_Value(A), m_Value(B)),
1384                           m_c_And(m_Deferred(A), m_Deferred(B))))) {
1385     I.setOperand(0, A);
1386     I.setOperand(1, B);
1387     return &I;
1388   }
1389 
1390   // TODO(jingyue): Consider willNotOverflowSignedAdd and
1391   // willNotOverflowUnsignedAdd to reduce the number of invocations of
1392   // computeKnownBits.
1393   bool Changed = false;
1394   if (!I.hasNoSignedWrap() && willNotOverflowSignedAdd(LHS, RHS, I)) {
1395     Changed = true;
1396     I.setHasNoSignedWrap(true);
1397   }
1398   if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedAdd(LHS, RHS, I)) {
1399     Changed = true;
1400     I.setHasNoUnsignedWrap(true);
1401   }
1402 
1403   if (Instruction *V = canonicalizeLowbitMask(I, Builder))
1404     return V;
1405 
1406   if (Instruction *V =
1407           canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(I))
1408     return V;
1409 
1410   if (Instruction *SatAdd = foldToUnsignedSaturatedAdd(I))
1411     return SatAdd;
1412 
1413   return Changed ? &I : nullptr;
1414 }
1415 
1416 /// Eliminate an op from a linear interpolation (lerp) pattern.
1417 static Instruction *factorizeLerp(BinaryOperator &I,
1418                                   InstCombiner::BuilderTy &Builder) {
1419   Value *X, *Y, *Z;
1420   if (!match(&I, m_c_FAdd(m_OneUse(m_c_FMul(m_Value(Y),
1421                                             m_OneUse(m_FSub(m_FPOne(),
1422                                                             m_Value(Z))))),
1423                           m_OneUse(m_c_FMul(m_Value(X), m_Deferred(Z))))))
1424     return nullptr;
1425 
1426   // (Y * (1.0 - Z)) + (X * Z) --> Y + Z * (X - Y) [8 commuted variants]
1427   Value *XY = Builder.CreateFSubFMF(X, Y, &I);
1428   Value *MulZ = Builder.CreateFMulFMF(Z, XY, &I);
1429   return BinaryOperator::CreateFAddFMF(Y, MulZ, &I);
1430 }
1431 
1432 /// Factor a common operand out of fadd/fsub of fmul/fdiv.
1433 static Instruction *factorizeFAddFSub(BinaryOperator &I,
1434                                       InstCombiner::BuilderTy &Builder) {
1435   assert((I.getOpcode() == Instruction::FAdd ||
1436           I.getOpcode() == Instruction::FSub) && "Expecting fadd/fsub");
1437   assert(I.hasAllowReassoc() && I.hasNoSignedZeros() &&
1438          "FP factorization requires FMF");
1439 
1440   if (Instruction *Lerp = factorizeLerp(I, Builder))
1441     return Lerp;
1442 
1443   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1444   Value *X, *Y, *Z;
1445   bool IsFMul;
1446   if ((match(Op0, m_OneUse(m_FMul(m_Value(X), m_Value(Z)))) &&
1447        match(Op1, m_OneUse(m_c_FMul(m_Value(Y), m_Specific(Z))))) ||
1448       (match(Op0, m_OneUse(m_FMul(m_Value(Z), m_Value(X)))) &&
1449        match(Op1, m_OneUse(m_c_FMul(m_Value(Y), m_Specific(Z))))))
1450     IsFMul = true;
1451   else if (match(Op0, m_OneUse(m_FDiv(m_Value(X), m_Value(Z)))) &&
1452            match(Op1, m_OneUse(m_FDiv(m_Value(Y), m_Specific(Z)))))
1453     IsFMul = false;
1454   else
1455     return nullptr;
1456 
1457   // (X * Z) + (Y * Z) --> (X + Y) * Z
1458   // (X * Z) - (Y * Z) --> (X - Y) * Z
1459   // (X / Z) + (Y / Z) --> (X + Y) / Z
1460   // (X / Z) - (Y / Z) --> (X - Y) / Z
1461   bool IsFAdd = I.getOpcode() == Instruction::FAdd;
1462   Value *XY = IsFAdd ? Builder.CreateFAddFMF(X, Y, &I)
1463                      : Builder.CreateFSubFMF(X, Y, &I);
1464 
1465   // Bail out if we just created a denormal constant.
1466   // TODO: This is copied from a previous implementation. Is it necessary?
1467   const APFloat *C;
1468   if (match(XY, m_APFloat(C)) && !C->isNormal())
1469     return nullptr;
1470 
1471   return IsFMul ? BinaryOperator::CreateFMulFMF(XY, Z, &I)
1472                 : BinaryOperator::CreateFDivFMF(XY, Z, &I);
1473 }
1474 
1475 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
1476   if (Value *V = SimplifyFAddInst(I.getOperand(0), I.getOperand(1),
1477                                   I.getFastMathFlags(),
1478                                   SQ.getWithInstruction(&I)))
1479     return replaceInstUsesWith(I, V);
1480 
1481   if (SimplifyAssociativeOrCommutative(I))
1482     return &I;
1483 
1484   if (Instruction *X = foldVectorBinop(I))
1485     return X;
1486 
1487   if (Instruction *FoldedFAdd = foldBinOpIntoSelectOrPhi(I))
1488     return FoldedFAdd;
1489 
1490   // (-X) + Y --> Y - X
1491   Value *X, *Y;
1492   if (match(&I, m_c_FAdd(m_FNeg(m_Value(X)), m_Value(Y))))
1493     return BinaryOperator::CreateFSubFMF(Y, X, &I);
1494 
1495   // Similar to above, but look through fmul/fdiv for the negated term.
1496   // (-X * Y) + Z --> Z - (X * Y) [4 commuted variants]
1497   Value *Z;
1498   if (match(&I, m_c_FAdd(m_OneUse(m_c_FMul(m_FNeg(m_Value(X)), m_Value(Y))),
1499                          m_Value(Z)))) {
1500     Value *XY = Builder.CreateFMulFMF(X, Y, &I);
1501     return BinaryOperator::CreateFSubFMF(Z, XY, &I);
1502   }
1503   // (-X / Y) + Z --> Z - (X / Y) [2 commuted variants]
1504   // (X / -Y) + Z --> Z - (X / Y) [2 commuted variants]
1505   if (match(&I, m_c_FAdd(m_OneUse(m_FDiv(m_FNeg(m_Value(X)), m_Value(Y))),
1506                          m_Value(Z))) ||
1507       match(&I, m_c_FAdd(m_OneUse(m_FDiv(m_Value(X), m_FNeg(m_Value(Y)))),
1508                          m_Value(Z)))) {
1509     Value *XY = Builder.CreateFDivFMF(X, Y, &I);
1510     return BinaryOperator::CreateFSubFMF(Z, XY, &I);
1511   }
1512 
1513   // Check for (fadd double (sitofp x), y), see if we can merge this into an
1514   // integer add followed by a promotion.
1515   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
1516   if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) {
1517     Value *LHSIntVal = LHSConv->getOperand(0);
1518     Type *FPType = LHSConv->getType();
1519 
1520     // TODO: This check is overly conservative. In many cases known bits
1521     // analysis can tell us that the result of the addition has less significant
1522     // bits than the integer type can hold.
1523     auto IsValidPromotion = [](Type *FTy, Type *ITy) {
1524       Type *FScalarTy = FTy->getScalarType();
1525       Type *IScalarTy = ITy->getScalarType();
1526 
1527       // Do we have enough bits in the significand to represent the result of
1528       // the integer addition?
1529       unsigned MaxRepresentableBits =
1530           APFloat::semanticsPrecision(FScalarTy->getFltSemantics());
1531       return IScalarTy->getIntegerBitWidth() <= MaxRepresentableBits;
1532     };
1533 
1534     // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst))
1535     // ... if the constant fits in the integer value.  This is useful for things
1536     // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer
1537     // requires a constant pool load, and generally allows the add to be better
1538     // instcombined.
1539     if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS))
1540       if (IsValidPromotion(FPType, LHSIntVal->getType())) {
1541         Constant *CI =
1542           ConstantExpr::getFPToSI(CFP, LHSIntVal->getType());
1543         if (LHSConv->hasOneUse() &&
1544             ConstantExpr::getSIToFP(CI, I.getType()) == CFP &&
1545             willNotOverflowSignedAdd(LHSIntVal, CI, I)) {
1546           // Insert the new integer add.
1547           Value *NewAdd = Builder.CreateNSWAdd(LHSIntVal, CI, "addconv");
1548           return new SIToFPInst(NewAdd, I.getType());
1549         }
1550       }
1551 
1552     // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y))
1553     if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) {
1554       Value *RHSIntVal = RHSConv->getOperand(0);
1555       // It's enough to check LHS types only because we require int types to
1556       // be the same for this transform.
1557       if (IsValidPromotion(FPType, LHSIntVal->getType())) {
1558         // Only do this if x/y have the same type, if at least one of them has a
1559         // single use (so we don't increase the number of int->fp conversions),
1560         // and if the integer add will not overflow.
1561         if (LHSIntVal->getType() == RHSIntVal->getType() &&
1562             (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
1563             willNotOverflowSignedAdd(LHSIntVal, RHSIntVal, I)) {
1564           // Insert the new integer add.
1565           Value *NewAdd = Builder.CreateNSWAdd(LHSIntVal, RHSIntVal, "addconv");
1566           return new SIToFPInst(NewAdd, I.getType());
1567         }
1568       }
1569     }
1570   }
1571 
1572   // Handle specials cases for FAdd with selects feeding the operation
1573   if (Value *V = SimplifySelectsFeedingBinaryOp(I, LHS, RHS))
1574     return replaceInstUsesWith(I, V);
1575 
1576   if (I.hasAllowReassoc() && I.hasNoSignedZeros()) {
1577     if (Instruction *F = factorizeFAddFSub(I, Builder))
1578       return F;
1579     if (Value *V = FAddCombine(Builder).simplify(&I))
1580       return replaceInstUsesWith(I, V);
1581   }
1582 
1583   return nullptr;
1584 }
1585 
1586 /// Optimize pointer differences into the same array into a size.  Consider:
1587 ///  &A[10] - &A[0]: we should compile this to "10".  LHS/RHS are the pointer
1588 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract.
1589 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS,
1590                                                Type *Ty) {
1591   // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize
1592   // this.
1593   bool Swapped = false;
1594   GEPOperator *GEP1 = nullptr, *GEP2 = nullptr;
1595 
1596   // For now we require one side to be the base pointer "A" or a constant
1597   // GEP derived from it.
1598   if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
1599     // (gep X, ...) - X
1600     if (LHSGEP->getOperand(0) == RHS) {
1601       GEP1 = LHSGEP;
1602       Swapped = false;
1603     } else if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
1604       // (gep X, ...) - (gep X, ...)
1605       if (LHSGEP->getOperand(0)->stripPointerCasts() ==
1606             RHSGEP->getOperand(0)->stripPointerCasts()) {
1607         GEP2 = RHSGEP;
1608         GEP1 = LHSGEP;
1609         Swapped = false;
1610       }
1611     }
1612   }
1613 
1614   if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) {
1615     // X - (gep X, ...)
1616     if (RHSGEP->getOperand(0) == LHS) {
1617       GEP1 = RHSGEP;
1618       Swapped = true;
1619     } else if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) {
1620       // (gep X, ...) - (gep X, ...)
1621       if (RHSGEP->getOperand(0)->stripPointerCasts() ==
1622             LHSGEP->getOperand(0)->stripPointerCasts()) {
1623         GEP2 = LHSGEP;
1624         GEP1 = RHSGEP;
1625         Swapped = true;
1626       }
1627     }
1628   }
1629 
1630   if (!GEP1)
1631     // No GEP found.
1632     return nullptr;
1633 
1634   if (GEP2) {
1635     // (gep X, ...) - (gep X, ...)
1636     //
1637     // Avoid duplicating the arithmetic if there are more than one non-constant
1638     // indices between the two GEPs and either GEP has a non-constant index and
1639     // multiple users. If zero non-constant index, the result is a constant and
1640     // there is no duplication. If one non-constant index, the result is an add
1641     // or sub with a constant, which is no larger than the original code, and
1642     // there's no duplicated arithmetic, even if either GEP has multiple
1643     // users. If more than one non-constant indices combined, as long as the GEP
1644     // with at least one non-constant index doesn't have multiple users, there
1645     // is no duplication.
1646     unsigned NumNonConstantIndices1 = GEP1->countNonConstantIndices();
1647     unsigned NumNonConstantIndices2 = GEP2->countNonConstantIndices();
1648     if (NumNonConstantIndices1 + NumNonConstantIndices2 > 1 &&
1649         ((NumNonConstantIndices1 > 0 && !GEP1->hasOneUse()) ||
1650          (NumNonConstantIndices2 > 0 && !GEP2->hasOneUse()))) {
1651       return nullptr;
1652     }
1653   }
1654 
1655   // Emit the offset of the GEP and an intptr_t.
1656   Value *Result = EmitGEPOffset(GEP1);
1657 
1658   // If we had a constant expression GEP on the other side offsetting the
1659   // pointer, subtract it from the offset we have.
1660   if (GEP2) {
1661     Value *Offset = EmitGEPOffset(GEP2);
1662     Result = Builder.CreateSub(Result, Offset);
1663   }
1664 
1665   // If we have p - gep(p, ...)  then we have to negate the result.
1666   if (Swapped)
1667     Result = Builder.CreateNeg(Result, "diff.neg");
1668 
1669   return Builder.CreateIntCast(Result, Ty, true);
1670 }
1671 
1672 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
1673   if (Value *V = SimplifySubInst(I.getOperand(0), I.getOperand(1),
1674                                  I.hasNoSignedWrap(), I.hasNoUnsignedWrap(),
1675                                  SQ.getWithInstruction(&I)))
1676     return replaceInstUsesWith(I, V);
1677 
1678   if (Instruction *X = foldVectorBinop(I))
1679     return X;
1680 
1681   // (A*B)-(A*C) -> A*(B-C) etc
1682   if (Value *V = SimplifyUsingDistributiveLaws(I))
1683     return replaceInstUsesWith(I, V);
1684 
1685   // If this is a 'B = x-(-A)', change to B = x+A.
1686   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1687   if (Value *V = dyn_castNegVal(Op1)) {
1688     BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
1689 
1690     if (const auto *BO = dyn_cast<BinaryOperator>(Op1)) {
1691       assert(BO->getOpcode() == Instruction::Sub &&
1692              "Expected a subtraction operator!");
1693       if (BO->hasNoSignedWrap() && I.hasNoSignedWrap())
1694         Res->setHasNoSignedWrap(true);
1695     } else {
1696       if (cast<Constant>(Op1)->isNotMinSignedValue() && I.hasNoSignedWrap())
1697         Res->setHasNoSignedWrap(true);
1698     }
1699 
1700     return Res;
1701   }
1702 
1703   if (I.getType()->isIntOrIntVectorTy(1))
1704     return BinaryOperator::CreateXor(Op0, Op1);
1705 
1706   // Replace (-1 - A) with (~A).
1707   if (match(Op0, m_AllOnes()))
1708     return BinaryOperator::CreateNot(Op1);
1709 
1710   // (~X) - (~Y) --> Y - X
1711   Value *X, *Y;
1712   if (match(Op0, m_Not(m_Value(X))) && match(Op1, m_Not(m_Value(Y))))
1713     return BinaryOperator::CreateSub(Y, X);
1714 
1715   // (X + -1) - Y --> ~Y + X
1716   if (match(Op0, m_OneUse(m_Add(m_Value(X), m_AllOnes()))))
1717     return BinaryOperator::CreateAdd(Builder.CreateNot(Op1), X);
1718 
1719   // Y - (X + 1) --> ~X + Y
1720   if (match(Op1, m_OneUse(m_Add(m_Value(X), m_One()))))
1721     return BinaryOperator::CreateAdd(Builder.CreateNot(X), Op0);
1722 
1723   // Y - ~X --> (X + 1) + Y
1724   if (match(Op1, m_OneUse(m_Not(m_Value(X))))) {
1725     return BinaryOperator::CreateAdd(
1726         Builder.CreateAdd(Op0, ConstantInt::get(I.getType(), 1)), X);
1727   }
1728 
1729   if (Constant *C = dyn_cast<Constant>(Op0)) {
1730     bool IsNegate = match(C, m_ZeroInt());
1731     Value *X;
1732     if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
1733       // 0 - (zext bool) --> sext bool
1734       // C - (zext bool) --> bool ? C - 1 : C
1735       if (IsNegate)
1736         return CastInst::CreateSExtOrBitCast(X, I.getType());
1737       return SelectInst::Create(X, SubOne(C), C);
1738     }
1739     if (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)) {
1740       // 0 - (sext bool) --> zext bool
1741       // C - (sext bool) --> bool ? C + 1 : C
1742       if (IsNegate)
1743         return CastInst::CreateZExtOrBitCast(X, I.getType());
1744       return SelectInst::Create(X, AddOne(C), C);
1745     }
1746 
1747     // C - ~X == X + (1+C)
1748     if (match(Op1, m_Not(m_Value(X))))
1749       return BinaryOperator::CreateAdd(X, AddOne(C));
1750 
1751     // Try to fold constant sub into select arguments.
1752     if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1753       if (Instruction *R = FoldOpIntoSelect(I, SI))
1754         return R;
1755 
1756     // Try to fold constant sub into PHI values.
1757     if (PHINode *PN = dyn_cast<PHINode>(Op1))
1758       if (Instruction *R = foldOpIntoPhi(I, PN))
1759         return R;
1760 
1761     Constant *C2;
1762 
1763     // C-(C2-X) --> X+(C-C2)
1764     if (match(Op1, m_Sub(m_Constant(C2), m_Value(X))))
1765       return BinaryOperator::CreateAdd(X, ConstantExpr::getSub(C, C2));
1766 
1767     // C-(X+C2) --> (C-C2)-X
1768     if (match(Op1, m_Add(m_Value(X), m_Constant(C2))))
1769       return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X);
1770   }
1771 
1772   const APInt *Op0C;
1773   if (match(Op0, m_APInt(Op0C))) {
1774 
1775     if (Op0C->isNullValue()) {
1776       Value *Op1Wide;
1777       match(Op1, m_TruncOrSelf(m_Value(Op1Wide)));
1778       bool HadTrunc = Op1Wide != Op1;
1779       bool NoTruncOrTruncIsOneUse = !HadTrunc || Op1->hasOneUse();
1780       unsigned BitWidth = Op1Wide->getType()->getScalarSizeInBits();
1781 
1782       Value *X;
1783       const APInt *ShAmt;
1784       // -(X >>u 31) -> (X >>s 31)
1785       if (NoTruncOrTruncIsOneUse &&
1786           match(Op1Wide, m_LShr(m_Value(X), m_APInt(ShAmt))) &&
1787           *ShAmt == BitWidth - 1) {
1788         Value *ShAmtOp = cast<Instruction>(Op1Wide)->getOperand(1);
1789         Instruction *NewShift = BinaryOperator::CreateAShr(X, ShAmtOp);
1790         NewShift->copyIRFlags(Op1Wide);
1791         if (!HadTrunc)
1792           return NewShift;
1793         Builder.Insert(NewShift);
1794         return TruncInst::CreateTruncOrBitCast(NewShift, Op1->getType());
1795       }
1796       // -(X >>s 31) -> (X >>u 31)
1797       if (NoTruncOrTruncIsOneUse &&
1798           match(Op1Wide, m_AShr(m_Value(X), m_APInt(ShAmt))) &&
1799           *ShAmt == BitWidth - 1) {
1800         Value *ShAmtOp = cast<Instruction>(Op1Wide)->getOperand(1);
1801         Instruction *NewShift = BinaryOperator::CreateLShr(X, ShAmtOp);
1802         NewShift->copyIRFlags(Op1Wide);
1803         if (!HadTrunc)
1804           return NewShift;
1805         Builder.Insert(NewShift);
1806         return TruncInst::CreateTruncOrBitCast(NewShift, Op1->getType());
1807       }
1808 
1809       if (!HadTrunc && Op1->hasOneUse()) {
1810         Value *LHS, *RHS;
1811         SelectPatternFlavor SPF = matchSelectPattern(Op1, LHS, RHS).Flavor;
1812         if (SPF == SPF_ABS || SPF == SPF_NABS) {
1813           // This is a negate of an ABS/NABS pattern. Just swap the operands
1814           // of the select.
1815           cast<SelectInst>(Op1)->swapValues();
1816           // Don't swap prof metadata, we didn't change the branch behavior.
1817           return replaceInstUsesWith(I, Op1);
1818         }
1819       }
1820     }
1821 
1822     // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known
1823     // zero.
1824     if (Op0C->isMask()) {
1825       KnownBits RHSKnown = computeKnownBits(Op1, 0, &I);
1826       if ((*Op0C | RHSKnown.Zero).isAllOnesValue())
1827         return BinaryOperator::CreateXor(Op1, Op0);
1828     }
1829   }
1830 
1831   {
1832     Value *Y;
1833     // X-(X+Y) == -Y    X-(Y+X) == -Y
1834     if (match(Op1, m_c_Add(m_Specific(Op0), m_Value(Y))))
1835       return BinaryOperator::CreateNeg(Y);
1836 
1837     // (X-Y)-X == -Y
1838     if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y))))
1839       return BinaryOperator::CreateNeg(Y);
1840   }
1841 
1842   // (sub (or A, B) (and A, B)) --> (xor A, B)
1843   {
1844     Value *A, *B;
1845     if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
1846         match(Op0, m_c_Or(m_Specific(A), m_Specific(B))))
1847       return BinaryOperator::CreateXor(A, B);
1848   }
1849 
1850   // (sub (and A, B) (or A, B)) --> neg (xor A, B)
1851   {
1852     Value *A, *B;
1853     if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
1854         match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) &&
1855         (Op0->hasOneUse() || Op1->hasOneUse()))
1856       return BinaryOperator::CreateNeg(Builder.CreateXor(A, B));
1857   }
1858 
1859   // (sub (or A, B), (xor A, B)) --> (and A, B)
1860   {
1861     Value *A, *B;
1862     if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
1863         match(Op0, m_c_Or(m_Specific(A), m_Specific(B))))
1864       return BinaryOperator::CreateAnd(A, B);
1865   }
1866 
1867   // (sub (xor A, B) (or A, B)) --> neg (and A, B)
1868   {
1869     Value *A, *B;
1870     if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
1871         match(Op1, m_c_Or(m_Specific(A), m_Specific(B))) &&
1872         (Op0->hasOneUse() || Op1->hasOneUse()))
1873       return BinaryOperator::CreateNeg(Builder.CreateAnd(A, B));
1874   }
1875 
1876   {
1877     Value *Y;
1878     // ((X | Y) - X) --> (~X & Y)
1879     if (match(Op0, m_OneUse(m_c_Or(m_Value(Y), m_Specific(Op1)))))
1880       return BinaryOperator::CreateAnd(
1881           Y, Builder.CreateNot(Op1, Op1->getName() + ".not"));
1882   }
1883 
1884   if (Op1->hasOneUse()) {
1885     Value *X = nullptr, *Y = nullptr, *Z = nullptr;
1886     Constant *C = nullptr;
1887 
1888     // (X - (Y - Z))  -->  (X + (Z - Y)).
1889     if (match(Op1, m_Sub(m_Value(Y), m_Value(Z))))
1890       return BinaryOperator::CreateAdd(Op0,
1891                                       Builder.CreateSub(Z, Y, Op1->getName()));
1892 
1893     // (X - (X & Y))   -->   (X & ~Y)
1894     if (match(Op1, m_c_And(m_Value(Y), m_Specific(Op0))))
1895       return BinaryOperator::CreateAnd(Op0,
1896                                   Builder.CreateNot(Y, Y->getName() + ".not"));
1897 
1898     // 0 - (X sdiv C)  -> (X sdiv -C)  provided the negation doesn't overflow.
1899     // TODO: This could be extended to match arbitrary vector constants.
1900     const APInt *DivC;
1901     if (match(Op0, m_Zero()) && match(Op1, m_SDiv(m_Value(X), m_APInt(DivC))) &&
1902         !DivC->isMinSignedValue() && *DivC != 1) {
1903       Constant *NegDivC = ConstantInt::get(I.getType(), -(*DivC));
1904       Instruction *BO = BinaryOperator::CreateSDiv(X, NegDivC);
1905       BO->setIsExact(cast<BinaryOperator>(Op1)->isExact());
1906       return BO;
1907     }
1908 
1909     // 0 - (X << Y)  -> (-X << Y)   when X is freely negatable.
1910     if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero()))
1911       if (Value *XNeg = dyn_castNegVal(X))
1912         return BinaryOperator::CreateShl(XNeg, Y);
1913 
1914     // Subtracting -1/0 is the same as adding 1/0:
1915     // sub [nsw] Op0, sext(bool Y) -> add [nsw] Op0, zext(bool Y)
1916     // 'nuw' is dropped in favor of the canonical form.
1917     if (match(Op1, m_SExt(m_Value(Y))) &&
1918         Y->getType()->getScalarSizeInBits() == 1) {
1919       Value *Zext = Builder.CreateZExt(Y, I.getType());
1920       BinaryOperator *Add = BinaryOperator::CreateAdd(Op0, Zext);
1921       Add->setHasNoSignedWrap(I.hasNoSignedWrap());
1922       return Add;
1923     }
1924 
1925     // X - A*-B -> X + A*B
1926     // X - -A*B -> X + A*B
1927     Value *A, *B;
1928     if (match(Op1, m_c_Mul(m_Value(A), m_Neg(m_Value(B)))))
1929       return BinaryOperator::CreateAdd(Op0, Builder.CreateMul(A, B));
1930 
1931     // X - A*C -> X + A*-C
1932     // No need to handle commuted multiply because multiply handling will
1933     // ensure constant will be move to the right hand side.
1934     if (match(Op1, m_Mul(m_Value(A), m_Constant(C))) && !isa<ConstantExpr>(C)) {
1935       Value *NewMul = Builder.CreateMul(A, ConstantExpr::getNeg(C));
1936       return BinaryOperator::CreateAdd(Op0, NewMul);
1937     }
1938   }
1939 
1940   {
1941     // ~A - Min/Max(~A, O) -> Max/Min(A, ~O) - A
1942     // ~A - Min/Max(O, ~A) -> Max/Min(A, ~O) - A
1943     // Min/Max(~A, O) - ~A -> A - Max/Min(A, ~O)
1944     // Min/Max(O, ~A) - ~A -> A - Max/Min(A, ~O)
1945     // So long as O here is freely invertible, this will be neutral or a win.
1946     Value *LHS, *RHS, *A;
1947     Value *NotA = Op0, *MinMax = Op1;
1948     SelectPatternFlavor SPF = matchSelectPattern(MinMax, LHS, RHS).Flavor;
1949     if (!SelectPatternResult::isMinOrMax(SPF)) {
1950       NotA = Op1;
1951       MinMax = Op0;
1952       SPF = matchSelectPattern(MinMax, LHS, RHS).Flavor;
1953     }
1954     if (SelectPatternResult::isMinOrMax(SPF) &&
1955         match(NotA, m_Not(m_Value(A))) && (NotA == LHS || NotA == RHS)) {
1956       if (NotA == LHS)
1957         std::swap(LHS, RHS);
1958       // LHS is now O above and expected to have at least 2 uses (the min/max)
1959       // NotA is epected to have 2 uses from the min/max and 1 from the sub.
1960       if (isFreeToInvert(LHS, !LHS->hasNUsesOrMore(3)) &&
1961           !NotA->hasNUsesOrMore(4)) {
1962         // Note: We don't generate the inverse max/min, just create the not of
1963         // it and let other folds do the rest.
1964         Value *Not = Builder.CreateNot(MinMax);
1965         if (NotA == Op0)
1966           return BinaryOperator::CreateSub(Not, A);
1967         else
1968           return BinaryOperator::CreateSub(A, Not);
1969       }
1970     }
1971   }
1972 
1973   // Optimize pointer differences into the same array into a size.  Consider:
1974   //  &A[10] - &A[0]: we should compile this to "10".
1975   Value *LHSOp, *RHSOp;
1976   if (match(Op0, m_PtrToInt(m_Value(LHSOp))) &&
1977       match(Op1, m_PtrToInt(m_Value(RHSOp))))
1978     if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
1979       return replaceInstUsesWith(I, Res);
1980 
1981   // trunc(p)-trunc(q) -> trunc(p-q)
1982   if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) &&
1983       match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp)))))
1984     if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType()))
1985       return replaceInstUsesWith(I, Res);
1986 
1987   // Canonicalize a shifty way to code absolute value to the common pattern.
1988   // There are 2 potential commuted variants.
1989   // We're relying on the fact that we only do this transform when the shift has
1990   // exactly 2 uses and the xor has exactly 1 use (otherwise, we might increase
1991   // instructions).
1992   Value *A;
1993   const APInt *ShAmt;
1994   Type *Ty = I.getType();
1995   if (match(Op1, m_AShr(m_Value(A), m_APInt(ShAmt))) &&
1996       Op1->hasNUses(2) && *ShAmt == Ty->getScalarSizeInBits() - 1 &&
1997       match(Op0, m_OneUse(m_c_Xor(m_Specific(A), m_Specific(Op1))))) {
1998     // B = ashr i32 A, 31 ; smear the sign bit
1999     // sub (xor A, B), B  ; flip bits if negative and subtract -1 (add 1)
2000     // --> (A < 0) ? -A : A
2001     Value *Cmp = Builder.CreateICmpSLT(A, ConstantInt::getNullValue(Ty));
2002     // Copy the nuw/nsw flags from the sub to the negate.
2003     Value *Neg = Builder.CreateNeg(A, "", I.hasNoUnsignedWrap(),
2004                                    I.hasNoSignedWrap());
2005     return SelectInst::Create(Cmp, Neg, A);
2006   }
2007 
2008   if (Instruction *V =
2009           canonicalizeCondSignextOfHighBitExtractToSignextHighBitExtract(I))
2010     return V;
2011 
2012   if (Instruction *Ext = narrowMathIfNoOverflow(I))
2013     return Ext;
2014 
2015   bool Changed = false;
2016   if (!I.hasNoSignedWrap() && willNotOverflowSignedSub(Op0, Op1, I)) {
2017     Changed = true;
2018     I.setHasNoSignedWrap(true);
2019   }
2020   if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedSub(Op0, Op1, I)) {
2021     Changed = true;
2022     I.setHasNoUnsignedWrap(true);
2023   }
2024 
2025   return Changed ? &I : nullptr;
2026 }
2027 
2028 /// This eliminates floating-point negation in either 'fneg(X)' or
2029 /// 'fsub(-0.0, X)' form by combining into a constant operand.
2030 static Instruction *foldFNegIntoConstant(Instruction &I) {
2031   Value *X;
2032   Constant *C;
2033 
2034   // Fold negation into constant operand. This is limited with one-use because
2035   // fneg is assumed better for analysis and cheaper in codegen than fmul/fdiv.
2036   // -(X * C) --> X * (-C)
2037   // FIXME: It's arguable whether these should be m_OneUse or not. The current
2038   // belief is that the FNeg allows for better reassociation opportunities.
2039   if (match(&I, m_FNeg(m_OneUse(m_FMul(m_Value(X), m_Constant(C))))))
2040     return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I);
2041   // -(X / C) --> X / (-C)
2042   if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Value(X), m_Constant(C))))))
2043     return BinaryOperator::CreateFDivFMF(X, ConstantExpr::getFNeg(C), &I);
2044   // -(C / X) --> (-C) / X
2045   if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Constant(C), m_Value(X))))))
2046     return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I);
2047 
2048   return nullptr;
2049 }
2050 
2051 static Instruction *hoistFNegAboveFMulFDiv(Instruction &I,
2052                                            InstCombiner::BuilderTy &Builder) {
2053   Value *FNeg;
2054   if (!match(&I, m_FNeg(m_Value(FNeg))))
2055     return nullptr;
2056 
2057   Value *X, *Y;
2058   if (match(FNeg, m_OneUse(m_FMul(m_Value(X), m_Value(Y)))))
2059     return BinaryOperator::CreateFMulFMF(Builder.CreateFNegFMF(X, &I), Y, &I);
2060 
2061   if (match(FNeg, m_OneUse(m_FDiv(m_Value(X), m_Value(Y)))))
2062     return BinaryOperator::CreateFDivFMF(Builder.CreateFNegFMF(X, &I), Y, &I);
2063 
2064   return nullptr;
2065 }
2066 
2067 Instruction *InstCombiner::visitFNeg(UnaryOperator &I) {
2068   Value *Op = I.getOperand(0);
2069 
2070   if (Value *V = SimplifyFNegInst(Op, I.getFastMathFlags(),
2071                                   SQ.getWithInstruction(&I)))
2072     return replaceInstUsesWith(I, V);
2073 
2074   if (Instruction *X = foldFNegIntoConstant(I))
2075     return X;
2076 
2077   Value *X, *Y;
2078 
2079   // If we can ignore the sign of zeros: -(X - Y) --> (Y - X)
2080   if (I.hasNoSignedZeros() &&
2081       match(Op, m_OneUse(m_FSub(m_Value(X), m_Value(Y)))))
2082     return BinaryOperator::CreateFSubFMF(Y, X, &I);
2083 
2084   if (Instruction *R = hoistFNegAboveFMulFDiv(I, Builder))
2085     return R;
2086 
2087   return nullptr;
2088 }
2089 
2090 Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
2091   if (Value *V = SimplifyFSubInst(I.getOperand(0), I.getOperand(1),
2092                                   I.getFastMathFlags(),
2093                                   SQ.getWithInstruction(&I)))
2094     return replaceInstUsesWith(I, V);
2095 
2096   if (Instruction *X = foldVectorBinop(I))
2097     return X;
2098 
2099   // Subtraction from -0.0 is the canonical form of fneg.
2100   // fsub nsz 0, X ==> fsub nsz -0.0, X
2101   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2102   if (I.hasNoSignedZeros() && match(Op0, m_PosZeroFP()))
2103     return BinaryOperator::CreateFNegFMF(Op1, &I);
2104 
2105   if (Instruction *X = foldFNegIntoConstant(I))
2106     return X;
2107 
2108   if (Instruction *R = hoistFNegAboveFMulFDiv(I, Builder))
2109     return R;
2110 
2111   Value *X, *Y;
2112   Constant *C;
2113 
2114   // If Op0 is not -0.0 or we can ignore -0.0: Z - (X - Y) --> Z + (Y - X)
2115   // Canonicalize to fadd to make analysis easier.
2116   // This can also help codegen because fadd is commutative.
2117   // Note that if this fsub was really an fneg, the fadd with -0.0 will get
2118   // killed later. We still limit that particular transform with 'hasOneUse'
2119   // because an fneg is assumed better/cheaper than a generic fsub.
2120   if (I.hasNoSignedZeros() || CannotBeNegativeZero(Op0, SQ.TLI)) {
2121     if (match(Op1, m_OneUse(m_FSub(m_Value(X), m_Value(Y))))) {
2122       Value *NewSub = Builder.CreateFSubFMF(Y, X, &I);
2123       return BinaryOperator::CreateFAddFMF(Op0, NewSub, &I);
2124     }
2125   }
2126 
2127   if (isa<Constant>(Op0))
2128     if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
2129       if (Instruction *NV = FoldOpIntoSelect(I, SI))
2130         return NV;
2131 
2132   // X - C --> X + (-C)
2133   // But don't transform constant expressions because there's an inverse fold
2134   // for X + (-Y) --> X - Y.
2135   if (match(Op1, m_Constant(C)) && !isa<ConstantExpr>(Op1))
2136     return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &I);
2137 
2138   // X - (-Y) --> X + Y
2139   if (match(Op1, m_FNeg(m_Value(Y))))
2140     return BinaryOperator::CreateFAddFMF(Op0, Y, &I);
2141 
2142   // Similar to above, but look through a cast of the negated value:
2143   // X - (fptrunc(-Y)) --> X + fptrunc(Y)
2144   Type *Ty = I.getType();
2145   if (match(Op1, m_OneUse(m_FPTrunc(m_FNeg(m_Value(Y))))))
2146     return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPTrunc(Y, Ty), &I);
2147 
2148   // X - (fpext(-Y)) --> X + fpext(Y)
2149   if (match(Op1, m_OneUse(m_FPExt(m_FNeg(m_Value(Y))))))
2150     return BinaryOperator::CreateFAddFMF(Op0, Builder.CreateFPExt(Y, Ty), &I);
2151 
2152   // Similar to above, but look through fmul/fdiv of the negated value:
2153   // Op0 - (-X * Y) --> Op0 + (X * Y)
2154   // Op0 - (Y * -X) --> Op0 + (X * Y)
2155   if (match(Op1, m_OneUse(m_c_FMul(m_FNeg(m_Value(X)), m_Value(Y))))) {
2156     Value *FMul = Builder.CreateFMulFMF(X, Y, &I);
2157     return BinaryOperator::CreateFAddFMF(Op0, FMul, &I);
2158   }
2159   // Op0 - (-X / Y) --> Op0 + (X / Y)
2160   // Op0 - (X / -Y) --> Op0 + (X / Y)
2161   if (match(Op1, m_OneUse(m_FDiv(m_FNeg(m_Value(X)), m_Value(Y)))) ||
2162       match(Op1, m_OneUse(m_FDiv(m_Value(X), m_FNeg(m_Value(Y)))))) {
2163     Value *FDiv = Builder.CreateFDivFMF(X, Y, &I);
2164     return BinaryOperator::CreateFAddFMF(Op0, FDiv, &I);
2165   }
2166 
2167   // Handle special cases for FSub with selects feeding the operation
2168   if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1))
2169     return replaceInstUsesWith(I, V);
2170 
2171   if (I.hasAllowReassoc() && I.hasNoSignedZeros()) {
2172     // (Y - X) - Y --> -X
2173     if (match(Op0, m_FSub(m_Specific(Op1), m_Value(X))))
2174       return BinaryOperator::CreateFNegFMF(X, &I);
2175 
2176     // Y - (X + Y) --> -X
2177     // Y - (Y + X) --> -X
2178     if (match(Op1, m_c_FAdd(m_Specific(Op0), m_Value(X))))
2179       return BinaryOperator::CreateFNegFMF(X, &I);
2180 
2181     // (X * C) - X --> X * (C - 1.0)
2182     if (match(Op0, m_FMul(m_Specific(Op1), m_Constant(C)))) {
2183       Constant *CSubOne = ConstantExpr::getFSub(C, ConstantFP::get(Ty, 1.0));
2184       return BinaryOperator::CreateFMulFMF(Op1, CSubOne, &I);
2185     }
2186     // X - (X * C) --> X * (1.0 - C)
2187     if (match(Op1, m_FMul(m_Specific(Op0), m_Constant(C)))) {
2188       Constant *OneSubC = ConstantExpr::getFSub(ConstantFP::get(Ty, 1.0), C);
2189       return BinaryOperator::CreateFMulFMF(Op0, OneSubC, &I);
2190     }
2191 
2192     if (Instruction *F = factorizeFAddFSub(I, Builder))
2193       return F;
2194 
2195     // TODO: This performs reassociative folds for FP ops. Some fraction of the
2196     // functionality has been subsumed by simple pattern matching here and in
2197     // InstSimplify. We should let a dedicated reassociation pass handle more
2198     // complex pattern matching and remove this from InstCombine.
2199     if (Value *V = FAddCombine(Builder).simplify(&I))
2200       return replaceInstUsesWith(I, V);
2201   }
2202 
2203   return nullptr;
2204 }
2205