1 //===- InstCombineAddSub.cpp ------------------------------------*- C++ -*-===// 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 "InstCombineInternal.h" 15 #include "llvm/ADT/STLExtras.h" 16 #include "llvm/Analysis/InstructionSimplify.h" 17 #include "llvm/IR/DataLayout.h" 18 #include "llvm/IR/GetElementPtrTypeIterator.h" 19 #include "llvm/IR/PatternMatch.h" 20 21 using namespace llvm; 22 using namespace PatternMatch; 23 24 #define DEBUG_TYPE "instcombine" 25 26 namespace { 27 28 /// Class representing coefficient of floating-point addend. 29 /// This class needs to be highly efficient, which is especially true for 30 /// the constructor. As of I write this comment, the cost of the default 31 /// constructor is merely 4-byte-store-zero (Assuming compiler is able to 32 /// perform write-merging). 33 /// 34 class FAddendCoef { 35 public: 36 // The constructor has to initialize a APFloat, which is unnecessary for 37 // most addends which have coefficient either 1 or -1. So, the constructor 38 // is expensive. In order to avoid the cost of the constructor, we should 39 // reuse some instances whenever possible. The pre-created instances 40 // FAddCombine::Add[0-5] embodies this idea. 41 // 42 FAddendCoef() : IsFp(false), BufHasFpVal(false), IntVal(0) {} 43 ~FAddendCoef(); 44 45 void set(short C) { 46 assert(!insaneIntVal(C) && "Insane coefficient"); 47 IsFp = false; IntVal = C; 48 } 49 50 void set(const APFloat& C); 51 52 void negate(); 53 54 bool isZero() const { return isInt() ? !IntVal : getFpVal().isZero(); } 55 Value *getValue(Type *) const; 56 57 // If possible, don't define operator+/operator- etc because these 58 // operators inevitably call FAddendCoef's constructor which is not cheap. 59 void operator=(const FAddendCoef &A); 60 void operator+=(const FAddendCoef &A); 61 void operator-=(const FAddendCoef &A); 62 void operator*=(const FAddendCoef &S); 63 64 bool isOne() const { return isInt() && IntVal == 1; } 65 bool isTwo() const { return isInt() && IntVal == 2; } 66 bool isMinusOne() const { return isInt() && IntVal == -1; } 67 bool isMinusTwo() const { return isInt() && IntVal == -2; } 68 69 private: 70 bool insaneIntVal(int V) { return V > 4 || V < -4; } 71 APFloat *getFpValPtr() 72 { return reinterpret_cast<APFloat*>(&FpValBuf.buffer[0]); } 73 const APFloat *getFpValPtr() const 74 { return reinterpret_cast<const APFloat*>(&FpValBuf.buffer[0]); } 75 76 const APFloat &getFpVal() const { 77 assert(IsFp && BufHasFpVal && "Incorret state"); 78 return *getFpValPtr(); 79 } 80 81 APFloat &getFpVal() { 82 assert(IsFp && BufHasFpVal && "Incorret state"); 83 return *getFpValPtr(); 84 } 85 86 bool isInt() const { return !IsFp; } 87 88 // If the coefficient is represented by an integer, promote it to a 89 // floating point. 90 void convertToFpType(const fltSemantics &Sem); 91 92 // Construct an APFloat from a signed integer. 93 // TODO: We should get rid of this function when APFloat can be constructed 94 // from an *SIGNED* integer. 95 APFloat createAPFloatFromInt(const fltSemantics &Sem, int Val); 96 97 private: 98 bool IsFp; 99 100 // True iff FpValBuf contains an instance of APFloat. 101 bool BufHasFpVal; 102 103 // The integer coefficient of an individual addend is either 1 or -1, 104 // and we try to simplify at most 4 addends from neighboring at most 105 // two instructions. So the range of <IntVal> falls in [-4, 4]. APInt 106 // is overkill of this end. 107 short IntVal; 108 109 AlignedCharArrayUnion<APFloat> FpValBuf; 110 }; 111 112 /// FAddend is used to represent floating-point addend. An addend is 113 /// represented as <C, V>, where the V is a symbolic value, and C is a 114 /// constant coefficient. A constant addend is represented as <C, 0>. 115 /// 116 class FAddend { 117 public: 118 FAddend() : Val(nullptr) {} 119 120 Value *getSymVal() const { return Val; } 121 const FAddendCoef &getCoef() const { return Coeff; } 122 123 bool isConstant() const { return Val == nullptr; } 124 bool isZero() const { return Coeff.isZero(); } 125 126 void set(short Coefficient, Value *V) { Coeff.set(Coefficient), Val = V; } 127 void set(const APFloat& Coefficient, Value *V) 128 { Coeff.set(Coefficient); Val = V; } 129 void set(const ConstantFP* Coefficient, Value *V) 130 { Coeff.set(Coefficient->getValueAPF()); Val = V; } 131 132 void negate() { Coeff.negate(); } 133 134 /// Drill down the U-D chain one step to find the definition of V, and 135 /// try to break the definition into one or two addends. 136 static unsigned drillValueDownOneStep(Value* V, FAddend &A0, FAddend &A1); 137 138 /// Similar to FAddend::drillDownOneStep() except that the value being 139 /// splitted is the addend itself. 140 unsigned drillAddendDownOneStep(FAddend &Addend0, FAddend &Addend1) const; 141 142 void operator+=(const FAddend &T) { 143 assert((Val == T.Val) && "Symbolic-values disagree"); 144 Coeff += T.Coeff; 145 } 146 147 private: 148 void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; } 149 150 // This addend has the value of "Coeff * Val". 151 Value *Val; 152 FAddendCoef Coeff; 153 }; 154 155 /// FAddCombine is the class for optimizing an unsafe fadd/fsub along 156 /// with its neighboring at most two instructions. 157 /// 158 class FAddCombine { 159 public: 160 FAddCombine(InstCombiner::BuilderTy *B) : Builder(B), Instr(nullptr) {} 161 Value *simplify(Instruction *FAdd); 162 163 private: 164 typedef SmallVector<const FAddend*, 4> AddendVect; 165 166 Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota); 167 168 Value *performFactorization(Instruction *I); 169 170 /// Convert given addend to a Value 171 Value *createAddendVal(const FAddend &A, bool& NeedNeg); 172 173 /// Return the number of instructions needed to emit the N-ary addition. 174 unsigned calcInstrNumber(const AddendVect& Vect); 175 Value *createFSub(Value *Opnd0, Value *Opnd1); 176 Value *createFAdd(Value *Opnd0, Value *Opnd1); 177 Value *createFMul(Value *Opnd0, Value *Opnd1); 178 Value *createFDiv(Value *Opnd0, Value *Opnd1); 179 Value *createFNeg(Value *V); 180 Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota); 181 void createInstPostProc(Instruction *NewInst, bool NoNumber = false); 182 183 InstCombiner::BuilderTy *Builder; 184 Instruction *Instr; 185 186 // Debugging stuff are clustered here. 187 #ifndef NDEBUG 188 unsigned CreateInstrNum; 189 void initCreateInstNum() { CreateInstrNum = 0; } 190 void incCreateInstNum() { CreateInstrNum++; } 191 #else 192 void initCreateInstNum() {} 193 void incCreateInstNum() {} 194 #endif 195 }; 196 197 } // anonymous namespace 198 199 //===----------------------------------------------------------------------===// 200 // 201 // Implementation of 202 // {FAddendCoef, FAddend, FAddition, FAddCombine}. 203 // 204 //===----------------------------------------------------------------------===// 205 FAddendCoef::~FAddendCoef() { 206 if (BufHasFpVal) 207 getFpValPtr()->~APFloat(); 208 } 209 210 void FAddendCoef::set(const APFloat& C) { 211 APFloat *P = getFpValPtr(); 212 213 if (isInt()) { 214 // As the buffer is meanless byte stream, we cannot call 215 // APFloat::operator=(). 216 new(P) APFloat(C); 217 } else 218 *P = C; 219 220 IsFp = BufHasFpVal = true; 221 } 222 223 void FAddendCoef::convertToFpType(const fltSemantics &Sem) { 224 if (!isInt()) 225 return; 226 227 APFloat *P = getFpValPtr(); 228 if (IntVal > 0) 229 new(P) APFloat(Sem, IntVal); 230 else { 231 new(P) APFloat(Sem, 0 - IntVal); 232 P->changeSign(); 233 } 234 IsFp = BufHasFpVal = true; 235 } 236 237 APFloat FAddendCoef::createAPFloatFromInt(const fltSemantics &Sem, int Val) { 238 if (Val >= 0) 239 return APFloat(Sem, Val); 240 241 APFloat T(Sem, 0 - Val); 242 T.changeSign(); 243 244 return T; 245 } 246 247 void FAddendCoef::operator=(const FAddendCoef &That) { 248 if (That.isInt()) 249 set(That.IntVal); 250 else 251 set(That.getFpVal()); 252 } 253 254 void FAddendCoef::operator+=(const FAddendCoef &That) { 255 enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven; 256 if (isInt() == That.isInt()) { 257 if (isInt()) 258 IntVal += That.IntVal; 259 else 260 getFpVal().add(That.getFpVal(), RndMode); 261 return; 262 } 263 264 if (isInt()) { 265 const APFloat &T = That.getFpVal(); 266 convertToFpType(T.getSemantics()); 267 getFpVal().add(T, RndMode); 268 return; 269 } 270 271 APFloat &T = getFpVal(); 272 T.add(createAPFloatFromInt(T.getSemantics(), That.IntVal), RndMode); 273 } 274 275 void FAddendCoef::operator-=(const FAddendCoef &That) { 276 enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven; 277 if (isInt() == That.isInt()) { 278 if (isInt()) 279 IntVal -= That.IntVal; 280 else 281 getFpVal().subtract(That.getFpVal(), RndMode); 282 return; 283 } 284 285 if (isInt()) { 286 const APFloat &T = That.getFpVal(); 287 convertToFpType(T.getSemantics()); 288 getFpVal().subtract(T, RndMode); 289 return; 290 } 291 292 APFloat &T = getFpVal(); 293 T.subtract(createAPFloatFromInt(T.getSemantics(), IntVal), RndMode); 294 } 295 296 void FAddendCoef::operator*=(const FAddendCoef &That) { 297 if (That.isOne()) 298 return; 299 300 if (That.isMinusOne()) { 301 negate(); 302 return; 303 } 304 305 if (isInt() && That.isInt()) { 306 int Res = IntVal * (int)That.IntVal; 307 assert(!insaneIntVal(Res) && "Insane int value"); 308 IntVal = Res; 309 return; 310 } 311 312 const fltSemantics &Semantic = 313 isInt() ? That.getFpVal().getSemantics() : getFpVal().getSemantics(); 314 315 if (isInt()) 316 convertToFpType(Semantic); 317 APFloat &F0 = getFpVal(); 318 319 if (That.isInt()) 320 F0.multiply(createAPFloatFromInt(Semantic, That.IntVal), 321 APFloat::rmNearestTiesToEven); 322 else 323 F0.multiply(That.getFpVal(), APFloat::rmNearestTiesToEven); 324 325 return; 326 } 327 328 void FAddendCoef::negate() { 329 if (isInt()) 330 IntVal = 0 - IntVal; 331 else 332 getFpVal().changeSign(); 333 } 334 335 Value *FAddendCoef::getValue(Type *Ty) const { 336 return isInt() ? 337 ConstantFP::get(Ty, float(IntVal)) : 338 ConstantFP::get(Ty->getContext(), getFpVal()); 339 } 340 341 // The definition of <Val> Addends 342 // ========================================= 343 // A + B <1, A>, <1,B> 344 // A - B <1, A>, <1,B> 345 // 0 - B <-1, B> 346 // C * A, <C, A> 347 // A + C <1, A> <C, NULL> 348 // 0 +/- 0 <0, NULL> (corner case) 349 // 350 // Legend: A and B are not constant, C is constant 351 // 352 unsigned FAddend::drillValueDownOneStep 353 (Value *Val, FAddend &Addend0, FAddend &Addend1) { 354 Instruction *I = nullptr; 355 if (!Val || !(I = dyn_cast<Instruction>(Val))) 356 return 0; 357 358 unsigned Opcode = I->getOpcode(); 359 360 if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub) { 361 ConstantFP *C0, *C1; 362 Value *Opnd0 = I->getOperand(0); 363 Value *Opnd1 = I->getOperand(1); 364 if ((C0 = dyn_cast<ConstantFP>(Opnd0)) && C0->isZero()) 365 Opnd0 = nullptr; 366 367 if ((C1 = dyn_cast<ConstantFP>(Opnd1)) && C1->isZero()) 368 Opnd1 = nullptr; 369 370 if (Opnd0) { 371 if (!C0) 372 Addend0.set(1, Opnd0); 373 else 374 Addend0.set(C0, nullptr); 375 } 376 377 if (Opnd1) { 378 FAddend &Addend = Opnd0 ? Addend1 : Addend0; 379 if (!C1) 380 Addend.set(1, Opnd1); 381 else 382 Addend.set(C1, nullptr); 383 if (Opcode == Instruction::FSub) 384 Addend.negate(); 385 } 386 387 if (Opnd0 || Opnd1) 388 return Opnd0 && Opnd1 ? 2 : 1; 389 390 // Both operands are zero. Weird! 391 Addend0.set(APFloat(C0->getValueAPF().getSemantics()), nullptr); 392 return 1; 393 } 394 395 if (I->getOpcode() == Instruction::FMul) { 396 Value *V0 = I->getOperand(0); 397 Value *V1 = I->getOperand(1); 398 if (ConstantFP *C = dyn_cast<ConstantFP>(V0)) { 399 Addend0.set(C, V1); 400 return 1; 401 } 402 403 if (ConstantFP *C = dyn_cast<ConstantFP>(V1)) { 404 Addend0.set(C, V0); 405 return 1; 406 } 407 } 408 409 return 0; 410 } 411 412 // Try to break *this* addend into two addends. e.g. Suppose this addend is 413 // <2.3, V>, and V = X + Y, by calling this function, we obtain two addends, 414 // i.e. <2.3, X> and <2.3, Y>. 415 // 416 unsigned FAddend::drillAddendDownOneStep 417 (FAddend &Addend0, FAddend &Addend1) const { 418 if (isConstant()) 419 return 0; 420 421 unsigned BreakNum = FAddend::drillValueDownOneStep(Val, Addend0, Addend1); 422 if (!BreakNum || Coeff.isOne()) 423 return BreakNum; 424 425 Addend0.Scale(Coeff); 426 427 if (BreakNum == 2) 428 Addend1.Scale(Coeff); 429 430 return BreakNum; 431 } 432 433 // Try to perform following optimization on the input instruction I. Return the 434 // simplified expression if was successful; otherwise, return 0. 435 // 436 // Instruction "I" is Simplified into 437 // ------------------------------------------------------- 438 // (x * y) +/- (x * z) x * (y +/- z) 439 // (y / x) +/- (z / x) (y +/- z) / x 440 // 441 Value *FAddCombine::performFactorization(Instruction *I) { 442 assert((I->getOpcode() == Instruction::FAdd || 443 I->getOpcode() == Instruction::FSub) && "Expect add/sub"); 444 445 Instruction *I0 = dyn_cast<Instruction>(I->getOperand(0)); 446 Instruction *I1 = dyn_cast<Instruction>(I->getOperand(1)); 447 448 if (!I0 || !I1 || I0->getOpcode() != I1->getOpcode()) 449 return nullptr; 450 451 bool isMpy = false; 452 if (I0->getOpcode() == Instruction::FMul) 453 isMpy = true; 454 else if (I0->getOpcode() != Instruction::FDiv) 455 return nullptr; 456 457 Value *Opnd0_0 = I0->getOperand(0); 458 Value *Opnd0_1 = I0->getOperand(1); 459 Value *Opnd1_0 = I1->getOperand(0); 460 Value *Opnd1_1 = I1->getOperand(1); 461 462 // Input Instr I Factor AddSub0 AddSub1 463 // ---------------------------------------------- 464 // (x*y) +/- (x*z) x y z 465 // (y/x) +/- (z/x) x y z 466 // 467 Value *Factor = nullptr; 468 Value *AddSub0 = nullptr, *AddSub1 = nullptr; 469 470 if (isMpy) { 471 if (Opnd0_0 == Opnd1_0 || Opnd0_0 == Opnd1_1) 472 Factor = Opnd0_0; 473 else if (Opnd0_1 == Opnd1_0 || Opnd0_1 == Opnd1_1) 474 Factor = Opnd0_1; 475 476 if (Factor) { 477 AddSub0 = (Factor == Opnd0_0) ? Opnd0_1 : Opnd0_0; 478 AddSub1 = (Factor == Opnd1_0) ? Opnd1_1 : Opnd1_0; 479 } 480 } else if (Opnd0_1 == Opnd1_1) { 481 Factor = Opnd0_1; 482 AddSub0 = Opnd0_0; 483 AddSub1 = Opnd1_0; 484 } 485 486 if (!Factor) 487 return nullptr; 488 489 FastMathFlags Flags; 490 Flags.setUnsafeAlgebra(); 491 if (I0) Flags &= I->getFastMathFlags(); 492 if (I1) Flags &= I->getFastMathFlags(); 493 494 // Create expression "NewAddSub = AddSub0 +/- AddsSub1" 495 Value *NewAddSub = (I->getOpcode() == Instruction::FAdd) ? 496 createFAdd(AddSub0, AddSub1) : 497 createFSub(AddSub0, AddSub1); 498 if (ConstantFP *CFP = dyn_cast<ConstantFP>(NewAddSub)) { 499 const APFloat &F = CFP->getValueAPF(); 500 if (!F.isNormal()) 501 return nullptr; 502 } else if (Instruction *II = dyn_cast<Instruction>(NewAddSub)) 503 II->setFastMathFlags(Flags); 504 505 if (isMpy) { 506 Value *RI = createFMul(Factor, NewAddSub); 507 if (Instruction *II = dyn_cast<Instruction>(RI)) 508 II->setFastMathFlags(Flags); 509 return RI; 510 } 511 512 Value *RI = createFDiv(NewAddSub, Factor); 513 if (Instruction *II = dyn_cast<Instruction>(RI)) 514 II->setFastMathFlags(Flags); 515 return RI; 516 } 517 518 Value *FAddCombine::simplify(Instruction *I) { 519 assert(I->hasUnsafeAlgebra() && "Should be in unsafe mode"); 520 521 // Currently we are not able to handle vector type. 522 if (I->getType()->isVectorTy()) 523 return nullptr; 524 525 assert((I->getOpcode() == Instruction::FAdd || 526 I->getOpcode() == Instruction::FSub) && "Expect add/sub"); 527 528 // Save the instruction before calling other member-functions. 529 Instr = I; 530 531 FAddend Opnd0, Opnd1, Opnd0_0, Opnd0_1, Opnd1_0, Opnd1_1; 532 533 unsigned OpndNum = FAddend::drillValueDownOneStep(I, Opnd0, Opnd1); 534 535 // Step 1: Expand the 1st addend into Opnd0_0 and Opnd0_1. 536 unsigned Opnd0_ExpNum = 0; 537 unsigned Opnd1_ExpNum = 0; 538 539 if (!Opnd0.isConstant()) 540 Opnd0_ExpNum = Opnd0.drillAddendDownOneStep(Opnd0_0, Opnd0_1); 541 542 // Step 2: Expand the 2nd addend into Opnd1_0 and Opnd1_1. 543 if (OpndNum == 2 && !Opnd1.isConstant()) 544 Opnd1_ExpNum = Opnd1.drillAddendDownOneStep(Opnd1_0, Opnd1_1); 545 546 // Step 3: Try to optimize Opnd0_0 + Opnd0_1 + Opnd1_0 + Opnd1_1 547 if (Opnd0_ExpNum && Opnd1_ExpNum) { 548 AddendVect AllOpnds; 549 AllOpnds.push_back(&Opnd0_0); 550 AllOpnds.push_back(&Opnd1_0); 551 if (Opnd0_ExpNum == 2) 552 AllOpnds.push_back(&Opnd0_1); 553 if (Opnd1_ExpNum == 2) 554 AllOpnds.push_back(&Opnd1_1); 555 556 // Compute instruction quota. We should save at least one instruction. 557 unsigned InstQuota = 0; 558 559 Value *V0 = I->getOperand(0); 560 Value *V1 = I->getOperand(1); 561 InstQuota = ((!isa<Constant>(V0) && V0->hasOneUse()) && 562 (!isa<Constant>(V1) && V1->hasOneUse())) ? 2 : 1; 563 564 if (Value *R = simplifyFAdd(AllOpnds, InstQuota)) 565 return R; 566 } 567 568 if (OpndNum != 2) { 569 // The input instruction is : "I=0.0 +/- V". If the "V" were able to be 570 // splitted into two addends, say "V = X - Y", the instruction would have 571 // been optimized into "I = Y - X" in the previous steps. 572 // 573 const FAddendCoef &CE = Opnd0.getCoef(); 574 return CE.isOne() ? Opnd0.getSymVal() : nullptr; 575 } 576 577 // step 4: Try to optimize Opnd0 + Opnd1_0 [+ Opnd1_1] 578 if (Opnd1_ExpNum) { 579 AddendVect AllOpnds; 580 AllOpnds.push_back(&Opnd0); 581 AllOpnds.push_back(&Opnd1_0); 582 if (Opnd1_ExpNum == 2) 583 AllOpnds.push_back(&Opnd1_1); 584 585 if (Value *R = simplifyFAdd(AllOpnds, 1)) 586 return R; 587 } 588 589 // step 5: Try to optimize Opnd1 + Opnd0_0 [+ Opnd0_1] 590 if (Opnd0_ExpNum) { 591 AddendVect AllOpnds; 592 AllOpnds.push_back(&Opnd1); 593 AllOpnds.push_back(&Opnd0_0); 594 if (Opnd0_ExpNum == 2) 595 AllOpnds.push_back(&Opnd0_1); 596 597 if (Value *R = simplifyFAdd(AllOpnds, 1)) 598 return R; 599 } 600 601 // step 6: Try factorization as the last resort, 602 return performFactorization(I); 603 } 604 605 Value *FAddCombine::simplifyFAdd(AddendVect& Addends, unsigned InstrQuota) { 606 unsigned AddendNum = Addends.size(); 607 assert(AddendNum <= 4 && "Too many addends"); 608 609 // For saving intermediate results; 610 unsigned NextTmpIdx = 0; 611 FAddend TmpResult[3]; 612 613 // Points to the constant addend of the resulting simplified expression. 614 // If the resulting expr has constant-addend, this constant-addend is 615 // desirable to reside at the top of the resulting expression tree. Placing 616 // constant close to supper-expr(s) will potentially reveal some optimization 617 // opportunities in super-expr(s). 618 // 619 const FAddend *ConstAdd = nullptr; 620 621 // Simplified addends are placed <SimpVect>. 622 AddendVect SimpVect; 623 624 // The outer loop works on one symbolic-value at a time. Suppose the input 625 // addends are : <a1, x>, <b1, y>, <a2, x>, <c1, z>, <b2, y>, ... 626 // The symbolic-values will be processed in this order: x, y, z. 627 // 628 for (unsigned SymIdx = 0; SymIdx < AddendNum; SymIdx++) { 629 630 const FAddend *ThisAddend = Addends[SymIdx]; 631 if (!ThisAddend) { 632 // This addend was processed before. 633 continue; 634 } 635 636 Value *Val = ThisAddend->getSymVal(); 637 unsigned StartIdx = SimpVect.size(); 638 SimpVect.push_back(ThisAddend); 639 640 // The inner loop collects addends sharing same symbolic-value, and these 641 // addends will be later on folded into a single addend. Following above 642 // example, if the symbolic value "y" is being processed, the inner loop 643 // will collect two addends "<b1,y>" and "<b2,Y>". These two addends will 644 // be later on folded into "<b1+b2, y>". 645 // 646 for (unsigned SameSymIdx = SymIdx + 1; 647 SameSymIdx < AddendNum; SameSymIdx++) { 648 const FAddend *T = Addends[SameSymIdx]; 649 if (T && T->getSymVal() == Val) { 650 // Set null such that next iteration of the outer loop will not process 651 // this addend again. 652 Addends[SameSymIdx] = nullptr; 653 SimpVect.push_back(T); 654 } 655 } 656 657 // If multiple addends share same symbolic value, fold them together. 658 if (StartIdx + 1 != SimpVect.size()) { 659 FAddend &R = TmpResult[NextTmpIdx ++]; 660 R = *SimpVect[StartIdx]; 661 for (unsigned Idx = StartIdx + 1; Idx < SimpVect.size(); Idx++) 662 R += *SimpVect[Idx]; 663 664 // Pop all addends being folded and push the resulting folded addend. 665 SimpVect.resize(StartIdx); 666 if (Val) { 667 if (!R.isZero()) { 668 SimpVect.push_back(&R); 669 } 670 } else { 671 // Don't push constant addend at this time. It will be the last element 672 // of <SimpVect>. 673 ConstAdd = &R; 674 } 675 } 676 } 677 678 assert((NextTmpIdx <= array_lengthof(TmpResult) + 1) && 679 "out-of-bound access"); 680 681 if (ConstAdd) 682 SimpVect.push_back(ConstAdd); 683 684 Value *Result; 685 if (!SimpVect.empty()) 686 Result = createNaryFAdd(SimpVect, InstrQuota); 687 else { 688 // The addition is folded to 0.0. 689 Result = ConstantFP::get(Instr->getType(), 0.0); 690 } 691 692 return Result; 693 } 694 695 Value *FAddCombine::createNaryFAdd 696 (const AddendVect &Opnds, unsigned InstrQuota) { 697 assert(!Opnds.empty() && "Expect at least one addend"); 698 699 // Step 1: Check if the # of instructions needed exceeds the quota. 700 // 701 unsigned InstrNeeded = calcInstrNumber(Opnds); 702 if (InstrNeeded > InstrQuota) 703 return nullptr; 704 705 initCreateInstNum(); 706 707 // step 2: Emit the N-ary addition. 708 // Note that at most three instructions are involved in Fadd-InstCombine: the 709 // addition in question, and at most two neighboring instructions. 710 // The resulting optimized addition should have at least one less instruction 711 // than the original addition expression tree. This implies that the resulting 712 // N-ary addition has at most two instructions, and we don't need to worry 713 // about tree-height when constructing the N-ary addition. 714 715 Value *LastVal = nullptr; 716 bool LastValNeedNeg = false; 717 718 // Iterate the addends, creating fadd/fsub using adjacent two addends. 719 for (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end(); 720 I != E; I++) { 721 bool NeedNeg; 722 Value *V = createAddendVal(**I, NeedNeg); 723 if (!LastVal) { 724 LastVal = V; 725 LastValNeedNeg = NeedNeg; 726 continue; 727 } 728 729 if (LastValNeedNeg == NeedNeg) { 730 LastVal = createFAdd(LastVal, V); 731 continue; 732 } 733 734 if (LastValNeedNeg) 735 LastVal = createFSub(V, LastVal); 736 else 737 LastVal = createFSub(LastVal, V); 738 739 LastValNeedNeg = false; 740 } 741 742 if (LastValNeedNeg) { 743 LastVal = createFNeg(LastVal); 744 } 745 746 #ifndef NDEBUG 747 assert(CreateInstrNum == InstrNeeded && 748 "Inconsistent in instruction numbers"); 749 #endif 750 751 return LastVal; 752 } 753 754 Value *FAddCombine::createFSub(Value *Opnd0, Value *Opnd1) { 755 Value *V = Builder->CreateFSub(Opnd0, Opnd1); 756 if (Instruction *I = dyn_cast<Instruction>(V)) 757 createInstPostProc(I); 758 return V; 759 } 760 761 Value *FAddCombine::createFNeg(Value *V) { 762 Value *Zero = cast<Value>(ConstantFP::getZeroValueForNegation(V->getType())); 763 Value *NewV = createFSub(Zero, V); 764 if (Instruction *I = dyn_cast<Instruction>(NewV)) 765 createInstPostProc(I, true); // fneg's don't receive instruction numbers. 766 return NewV; 767 } 768 769 Value *FAddCombine::createFAdd(Value *Opnd0, Value *Opnd1) { 770 Value *V = Builder->CreateFAdd(Opnd0, Opnd1); 771 if (Instruction *I = dyn_cast<Instruction>(V)) 772 createInstPostProc(I); 773 return V; 774 } 775 776 Value *FAddCombine::createFMul(Value *Opnd0, Value *Opnd1) { 777 Value *V = Builder->CreateFMul(Opnd0, Opnd1); 778 if (Instruction *I = dyn_cast<Instruction>(V)) 779 createInstPostProc(I); 780 return V; 781 } 782 783 Value *FAddCombine::createFDiv(Value *Opnd0, Value *Opnd1) { 784 Value *V = Builder->CreateFDiv(Opnd0, Opnd1); 785 if (Instruction *I = dyn_cast<Instruction>(V)) 786 createInstPostProc(I); 787 return V; 788 } 789 790 void FAddCombine::createInstPostProc(Instruction *NewInstr, bool NoNumber) { 791 NewInstr->setDebugLoc(Instr->getDebugLoc()); 792 793 // Keep track of the number of instruction created. 794 if (!NoNumber) 795 incCreateInstNum(); 796 797 // Propagate fast-math flags 798 NewInstr->setFastMathFlags(Instr->getFastMathFlags()); 799 } 800 801 // Return the number of instruction needed to emit the N-ary addition. 802 // NOTE: Keep this function in sync with createAddendVal(). 803 unsigned FAddCombine::calcInstrNumber(const AddendVect &Opnds) { 804 unsigned OpndNum = Opnds.size(); 805 unsigned InstrNeeded = OpndNum - 1; 806 807 // The number of addends in the form of "(-1)*x". 808 unsigned NegOpndNum = 0; 809 810 // Adjust the number of instructions needed to emit the N-ary add. 811 for (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end(); 812 I != E; I++) { 813 const FAddend *Opnd = *I; 814 if (Opnd->isConstant()) 815 continue; 816 817 const FAddendCoef &CE = Opnd->getCoef(); 818 if (CE.isMinusOne() || CE.isMinusTwo()) 819 NegOpndNum++; 820 821 // Let the addend be "c * x". If "c == +/-1", the value of the addend 822 // is immediately available; otherwise, it needs exactly one instruction 823 // to evaluate the value. 824 if (!CE.isMinusOne() && !CE.isOne()) 825 InstrNeeded++; 826 } 827 if (NegOpndNum == OpndNum) 828 InstrNeeded++; 829 return InstrNeeded; 830 } 831 832 // Input Addend Value NeedNeg(output) 833 // ================================================================ 834 // Constant C C false 835 // <+/-1, V> V coefficient is -1 836 // <2/-2, V> "fadd V, V" coefficient is -2 837 // <C, V> "fmul V, C" false 838 // 839 // NOTE: Keep this function in sync with FAddCombine::calcInstrNumber. 840 Value *FAddCombine::createAddendVal(const FAddend &Opnd, bool &NeedNeg) { 841 const FAddendCoef &Coeff = Opnd.getCoef(); 842 843 if (Opnd.isConstant()) { 844 NeedNeg = false; 845 return Coeff.getValue(Instr->getType()); 846 } 847 848 Value *OpndVal = Opnd.getSymVal(); 849 850 if (Coeff.isMinusOne() || Coeff.isOne()) { 851 NeedNeg = Coeff.isMinusOne(); 852 return OpndVal; 853 } 854 855 if (Coeff.isTwo() || Coeff.isMinusTwo()) { 856 NeedNeg = Coeff.isMinusTwo(); 857 return createFAdd(OpndVal, OpndVal); 858 } 859 860 NeedNeg = false; 861 return createFMul(OpndVal, Coeff.getValue(Instr->getType())); 862 } 863 864 // If one of the operands only has one non-zero bit, and if the other 865 // operand has a known-zero bit in a more significant place than it (not 866 // including the sign bit) the ripple may go up to and fill the zero, but 867 // won't change the sign. For example, (X & ~4) + 1. 868 static bool checkRippleForAdd(const APInt &Op0KnownZero, 869 const APInt &Op1KnownZero) { 870 APInt Op1MaybeOne = ~Op1KnownZero; 871 // Make sure that one of the operand has at most one bit set to 1. 872 if (Op1MaybeOne.countPopulation() != 1) 873 return false; 874 875 // Find the most significant known 0 other than the sign bit. 876 int BitWidth = Op0KnownZero.getBitWidth(); 877 APInt Op0KnownZeroTemp(Op0KnownZero); 878 Op0KnownZeroTemp.clearBit(BitWidth - 1); 879 int Op0ZeroPosition = BitWidth - Op0KnownZeroTemp.countLeadingZeros() - 1; 880 881 int Op1OnePosition = BitWidth - Op1MaybeOne.countLeadingZeros() - 1; 882 assert(Op1OnePosition >= 0); 883 884 // This also covers the case of no known zero, since in that case 885 // Op0ZeroPosition is -1. 886 return Op0ZeroPosition >= Op1OnePosition; 887 } 888 889 /// Return true if we can prove that: 890 /// (sext (add LHS, RHS)) === (add (sext LHS), (sext RHS)) 891 /// This basically requires proving that the add in the original type would not 892 /// overflow to change the sign bit or have a carry out. 893 bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS, 894 Instruction &CxtI) { 895 // There are different heuristics we can use for this. Here are some simple 896 // ones. 897 898 // If LHS and RHS each have at least two sign bits, the addition will look 899 // like 900 // 901 // XX..... + 902 // YY..... 903 // 904 // If the carry into the most significant position is 0, X and Y can't both 905 // be 1 and therefore the carry out of the addition is also 0. 906 // 907 // If the carry into the most significant position is 1, X and Y can't both 908 // be 0 and therefore the carry out of the addition is also 1. 909 // 910 // Since the carry into the most significant position is always equal to 911 // the carry out of the addition, there is no signed overflow. 912 if (ComputeNumSignBits(LHS, 0, &CxtI) > 1 && 913 ComputeNumSignBits(RHS, 0, &CxtI) > 1) 914 return true; 915 916 unsigned BitWidth = LHS->getType()->getScalarSizeInBits(); 917 APInt LHSKnownZero(BitWidth, 0); 918 APInt LHSKnownOne(BitWidth, 0); 919 computeKnownBits(LHS, LHSKnownZero, LHSKnownOne, 0, &CxtI); 920 921 APInt RHSKnownZero(BitWidth, 0); 922 APInt RHSKnownOne(BitWidth, 0); 923 computeKnownBits(RHS, RHSKnownZero, RHSKnownOne, 0, &CxtI); 924 925 // Addition of two 2's compliment numbers having opposite signs will never 926 // overflow. 927 if ((LHSKnownOne[BitWidth - 1] && RHSKnownZero[BitWidth - 1]) || 928 (LHSKnownZero[BitWidth - 1] && RHSKnownOne[BitWidth - 1])) 929 return true; 930 931 // Check if carry bit of addition will not cause overflow. 932 if (checkRippleForAdd(LHSKnownZero, RHSKnownZero)) 933 return true; 934 if (checkRippleForAdd(RHSKnownZero, LHSKnownZero)) 935 return true; 936 937 return false; 938 } 939 940 /// \brief Return true if we can prove that: 941 /// (sub LHS, RHS) === (sub nsw LHS, RHS) 942 /// This basically requires proving that the add in the original type would not 943 /// overflow to change the sign bit or have a carry out. 944 /// TODO: Handle this for Vectors. 945 bool InstCombiner::WillNotOverflowSignedSub(Value *LHS, Value *RHS, 946 Instruction &CxtI) { 947 // If LHS and RHS each have at least two sign bits, the subtraction 948 // cannot overflow. 949 if (ComputeNumSignBits(LHS, 0, &CxtI) > 1 && 950 ComputeNumSignBits(RHS, 0, &CxtI) > 1) 951 return true; 952 953 unsigned BitWidth = LHS->getType()->getScalarSizeInBits(); 954 APInt LHSKnownZero(BitWidth, 0); 955 APInt LHSKnownOne(BitWidth, 0); 956 computeKnownBits(LHS, LHSKnownZero, LHSKnownOne, 0, &CxtI); 957 958 APInt RHSKnownZero(BitWidth, 0); 959 APInt RHSKnownOne(BitWidth, 0); 960 computeKnownBits(RHS, RHSKnownZero, RHSKnownOne, 0, &CxtI); 961 962 // Subtraction of two 2's compliment numbers having identical signs will 963 // never overflow. 964 if ((LHSKnownOne[BitWidth - 1] && RHSKnownOne[BitWidth - 1]) || 965 (LHSKnownZero[BitWidth - 1] && RHSKnownZero[BitWidth - 1])) 966 return true; 967 968 // TODO: implement logic similar to checkRippleForAdd 969 return false; 970 } 971 972 /// \brief Return true if we can prove that: 973 /// (sub LHS, RHS) === (sub nuw LHS, RHS) 974 bool InstCombiner::WillNotOverflowUnsignedSub(Value *LHS, Value *RHS, 975 Instruction &CxtI) { 976 // If the LHS is negative and the RHS is non-negative, no unsigned wrap. 977 bool LHSKnownNonNegative, LHSKnownNegative; 978 bool RHSKnownNonNegative, RHSKnownNegative; 979 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, /*Depth=*/0, 980 &CxtI); 981 ComputeSignBit(RHS, RHSKnownNonNegative, RHSKnownNegative, /*Depth=*/0, 982 &CxtI); 983 if (LHSKnownNegative && RHSKnownNonNegative) 984 return true; 985 986 return false; 987 } 988 989 // Checks if any operand is negative and we can convert add to sub. 990 // This function checks for following negative patterns 991 // ADD(XOR(OR(Z, NOT(C)), C)), 1) == NEG(AND(Z, C)) 992 // ADD(XOR(AND(Z, C), C), 1) == NEG(OR(Z, ~C)) 993 // XOR(AND(Z, C), (C + 1)) == NEG(OR(Z, ~C)) if C is even 994 static Value *checkForNegativeOperand(BinaryOperator &I, 995 InstCombiner::BuilderTy *Builder) { 996 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 997 998 // This function creates 2 instructions to replace ADD, we need at least one 999 // of LHS or RHS to have one use to ensure benefit in transform. 1000 if (!LHS->hasOneUse() && !RHS->hasOneUse()) 1001 return nullptr; 1002 1003 Value *X = nullptr, *Y = nullptr, *Z = nullptr; 1004 const APInt *C1 = nullptr, *C2 = nullptr; 1005 1006 // if ONE is on other side, swap 1007 if (match(RHS, m_Add(m_Value(X), m_One()))) 1008 std::swap(LHS, RHS); 1009 1010 if (match(LHS, m_Add(m_Value(X), m_One()))) { 1011 // if XOR on other side, swap 1012 if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1)))) 1013 std::swap(X, RHS); 1014 1015 if (match(X, m_Xor(m_Value(Y), m_APInt(C1)))) { 1016 // X = XOR(Y, C1), Y = OR(Z, C2), C2 = NOT(C1) ==> X == NOT(AND(Z, C1)) 1017 // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, AND(Z, C1)) 1018 if (match(Y, m_Or(m_Value(Z), m_APInt(C2))) && (*C2 == ~(*C1))) { 1019 Value *NewAnd = Builder->CreateAnd(Z, *C1); 1020 return Builder->CreateSub(RHS, NewAnd, "sub"); 1021 } else if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && (*C1 == *C2)) { 1022 // X = XOR(Y, C1), Y = AND(Z, C2), C2 == C1 ==> X == NOT(OR(Z, ~C1)) 1023 // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, OR(Z, ~C1)) 1024 Value *NewOr = Builder->CreateOr(Z, ~(*C1)); 1025 return Builder->CreateSub(RHS, NewOr, "sub"); 1026 } 1027 } 1028 } 1029 1030 // Restore LHS and RHS 1031 LHS = I.getOperand(0); 1032 RHS = I.getOperand(1); 1033 1034 // if XOR is on other side, swap 1035 if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1)))) 1036 std::swap(LHS, RHS); 1037 1038 // C2 is ODD 1039 // LHS = XOR(Y, C1), Y = AND(Z, C2), C1 == (C2 + 1) => LHS == NEG(OR(Z, ~C2)) 1040 // ADD(LHS, RHS) == SUB(RHS, OR(Z, ~C2)) 1041 if (match(LHS, m_Xor(m_Value(Y), m_APInt(C1)))) 1042 if (C1->countTrailingZeros() == 0) 1043 if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && *C1 == (*C2 + 1)) { 1044 Value *NewOr = Builder->CreateOr(Z, ~(*C2)); 1045 return Builder->CreateSub(RHS, NewOr, "sub"); 1046 } 1047 return nullptr; 1048 } 1049 1050 Instruction *InstCombiner::visitAdd(BinaryOperator &I) { 1051 bool Changed = SimplifyAssociativeOrCommutative(I); 1052 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 1053 1054 if (Value *V = SimplifyVectorOp(I)) 1055 return ReplaceInstUsesWith(I, V); 1056 1057 if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(), 1058 I.hasNoUnsignedWrap(), DL, TLI, DT, AC)) 1059 return ReplaceInstUsesWith(I, V); 1060 1061 // (A*B)+(A*C) -> A*(B+C) etc 1062 if (Value *V = SimplifyUsingDistributiveLaws(I)) 1063 return ReplaceInstUsesWith(I, V); 1064 1065 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1066 // X + (signbit) --> X ^ signbit 1067 const APInt &Val = CI->getValue(); 1068 if (Val.isSignBit()) 1069 return BinaryOperator::CreateXor(LHS, RHS); 1070 1071 // See if SimplifyDemandedBits can simplify this. This handles stuff like 1072 // (X & 254)+1 -> (X&254)|1 1073 if (SimplifyDemandedInstructionBits(I)) 1074 return &I; 1075 1076 // zext(bool) + C -> bool ? C + 1 : C 1077 if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS)) 1078 if (ZI->getSrcTy()->isIntegerTy(1)) 1079 return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI); 1080 1081 Value *XorLHS = nullptr; ConstantInt *XorRHS = nullptr; 1082 if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) { 1083 uint32_t TySizeBits = I.getType()->getScalarSizeInBits(); 1084 const APInt &RHSVal = CI->getValue(); 1085 unsigned ExtendAmt = 0; 1086 // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext. 1087 // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext. 1088 if (XorRHS->getValue() == -RHSVal) { 1089 if (RHSVal.isPowerOf2()) 1090 ExtendAmt = TySizeBits - RHSVal.logBase2() - 1; 1091 else if (XorRHS->getValue().isPowerOf2()) 1092 ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1; 1093 } 1094 1095 if (ExtendAmt) { 1096 APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt); 1097 if (!MaskedValueIsZero(XorLHS, Mask, 0, &I)) 1098 ExtendAmt = 0; 1099 } 1100 1101 if (ExtendAmt) { 1102 Constant *ShAmt = ConstantInt::get(I.getType(), ExtendAmt); 1103 Value *NewShl = Builder->CreateShl(XorLHS, ShAmt, "sext"); 1104 return BinaryOperator::CreateAShr(NewShl, ShAmt); 1105 } 1106 1107 // If this is a xor that was canonicalized from a sub, turn it back into 1108 // a sub and fuse this add with it. 1109 if (LHS->hasOneUse() && (XorRHS->getValue()+1).isPowerOf2()) { 1110 IntegerType *IT = cast<IntegerType>(I.getType()); 1111 APInt LHSKnownOne(IT->getBitWidth(), 0); 1112 APInt LHSKnownZero(IT->getBitWidth(), 0); 1113 computeKnownBits(XorLHS, LHSKnownZero, LHSKnownOne, 0, &I); 1114 if ((XorRHS->getValue() | LHSKnownZero).isAllOnesValue()) 1115 return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI), 1116 XorLHS); 1117 } 1118 // (X + signbit) + C could have gotten canonicalized to (X ^ signbit) + C, 1119 // transform them into (X + (signbit ^ C)) 1120 if (XorRHS->getValue().isSignBit()) 1121 return BinaryOperator::CreateAdd(XorLHS, 1122 ConstantExpr::getXor(XorRHS, CI)); 1123 } 1124 } 1125 1126 if (isa<Constant>(RHS) && isa<PHINode>(LHS)) 1127 if (Instruction *NV = FoldOpIntoPhi(I)) 1128 return NV; 1129 1130 if (I.getType()->getScalarType()->isIntegerTy(1)) 1131 return BinaryOperator::CreateXor(LHS, RHS); 1132 1133 // X + X --> X << 1 1134 if (LHS == RHS) { 1135 BinaryOperator *New = 1136 BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1)); 1137 New->setHasNoSignedWrap(I.hasNoSignedWrap()); 1138 New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); 1139 return New; 1140 } 1141 1142 // -A + B --> B - A 1143 // -A + -B --> -(A + B) 1144 if (Value *LHSV = dyn_castNegVal(LHS)) { 1145 if (!isa<Constant>(RHS)) 1146 if (Value *RHSV = dyn_castNegVal(RHS)) { 1147 Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum"); 1148 return BinaryOperator::CreateNeg(NewAdd); 1149 } 1150 1151 return BinaryOperator::CreateSub(RHS, LHSV); 1152 } 1153 1154 // A + -B --> A - B 1155 if (!isa<Constant>(RHS)) 1156 if (Value *V = dyn_castNegVal(RHS)) 1157 return BinaryOperator::CreateSub(LHS, V); 1158 1159 if (Value *V = checkForNegativeOperand(I, Builder)) 1160 return ReplaceInstUsesWith(I, V); 1161 1162 // A+B --> A|B iff A and B have no bits set in common. 1163 if (haveNoCommonBitsSet(LHS, RHS, DL, AC, &I, DT)) 1164 return BinaryOperator::CreateOr(LHS, RHS); 1165 1166 if (Constant *CRHS = dyn_cast<Constant>(RHS)) { 1167 Value *X; 1168 if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X 1169 return BinaryOperator::CreateSub(SubOne(CRHS), X); 1170 } 1171 1172 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) { 1173 // (X & FF00) + xx00 -> (X+xx00) & FF00 1174 Value *X; 1175 ConstantInt *C2; 1176 if (LHS->hasOneUse() && 1177 match(LHS, m_And(m_Value(X), m_ConstantInt(C2))) && 1178 CRHS->getValue() == (CRHS->getValue() & C2->getValue())) { 1179 // See if all bits from the first bit set in the Add RHS up are included 1180 // in the mask. First, get the rightmost bit. 1181 const APInt &AddRHSV = CRHS->getValue(); 1182 1183 // Form a mask of all bits from the lowest bit added through the top. 1184 APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1)); 1185 1186 // See if the and mask includes all of these bits. 1187 APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue()); 1188 1189 if (AddRHSHighBits == AddRHSHighBitsAnd) { 1190 // Okay, the xform is safe. Insert the new add pronto. 1191 Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName()); 1192 return BinaryOperator::CreateAnd(NewAdd, C2); 1193 } 1194 } 1195 1196 // Try to fold constant add into select arguments. 1197 if (SelectInst *SI = dyn_cast<SelectInst>(LHS)) 1198 if (Instruction *R = FoldOpIntoSelect(I, SI)) 1199 return R; 1200 } 1201 1202 // add (select X 0 (sub n A)) A --> select X A n 1203 { 1204 SelectInst *SI = dyn_cast<SelectInst>(LHS); 1205 Value *A = RHS; 1206 if (!SI) { 1207 SI = dyn_cast<SelectInst>(RHS); 1208 A = LHS; 1209 } 1210 if (SI && SI->hasOneUse()) { 1211 Value *TV = SI->getTrueValue(); 1212 Value *FV = SI->getFalseValue(); 1213 Value *N; 1214 1215 // Can we fold the add into the argument of the select? 1216 // We check both true and false select arguments for a matching subtract. 1217 if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A)))) 1218 // Fold the add into the true select value. 1219 return SelectInst::Create(SI->getCondition(), N, A); 1220 1221 if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A)))) 1222 // Fold the add into the false select value. 1223 return SelectInst::Create(SI->getCondition(), A, N); 1224 } 1225 } 1226 1227 // Check for (add (sext x), y), see if we can merge this into an 1228 // integer add followed by a sext. 1229 if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) { 1230 // (add (sext x), cst) --> (sext (add x, cst')) 1231 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) { 1232 Constant *CI = 1233 ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType()); 1234 if (LHSConv->hasOneUse() && 1235 ConstantExpr::getSExt(CI, I.getType()) == RHSC && 1236 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI, I)) { 1237 // Insert the new, smaller add. 1238 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1239 CI, "addconv"); 1240 return new SExtInst(NewAdd, I.getType()); 1241 } 1242 } 1243 1244 // (add (sext x), (sext y)) --> (sext (add int x, y)) 1245 if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) { 1246 // Only do this if x/y have the same type, if at last one of them has a 1247 // single use (so we don't increase the number of sexts), and if the 1248 // integer add will not overflow. 1249 if (LHSConv->getOperand(0)->getType() == 1250 RHSConv->getOperand(0)->getType() && 1251 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && 1252 WillNotOverflowSignedAdd(LHSConv->getOperand(0), 1253 RHSConv->getOperand(0), I)) { 1254 // Insert the new integer add. 1255 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1256 RHSConv->getOperand(0), "addconv"); 1257 return new SExtInst(NewAdd, I.getType()); 1258 } 1259 } 1260 } 1261 1262 // (add (xor A, B) (and A, B)) --> (or A, B) 1263 { 1264 Value *A = nullptr, *B = nullptr; 1265 if (match(RHS, m_Xor(m_Value(A), m_Value(B))) && 1266 (match(LHS, m_And(m_Specific(A), m_Specific(B))) || 1267 match(LHS, m_And(m_Specific(B), m_Specific(A))))) 1268 return BinaryOperator::CreateOr(A, B); 1269 1270 if (match(LHS, m_Xor(m_Value(A), m_Value(B))) && 1271 (match(RHS, m_And(m_Specific(A), m_Specific(B))) || 1272 match(RHS, m_And(m_Specific(B), m_Specific(A))))) 1273 return BinaryOperator::CreateOr(A, B); 1274 } 1275 1276 // (add (or A, B) (and A, B)) --> (add A, B) 1277 { 1278 Value *A = nullptr, *B = nullptr; 1279 if (match(RHS, m_Or(m_Value(A), m_Value(B))) && 1280 (match(LHS, m_And(m_Specific(A), m_Specific(B))) || 1281 match(LHS, m_And(m_Specific(B), m_Specific(A))))) { 1282 auto *New = BinaryOperator::CreateAdd(A, B); 1283 New->setHasNoSignedWrap(I.hasNoSignedWrap()); 1284 New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); 1285 return New; 1286 } 1287 1288 if (match(LHS, m_Or(m_Value(A), m_Value(B))) && 1289 (match(RHS, m_And(m_Specific(A), m_Specific(B))) || 1290 match(RHS, m_And(m_Specific(B), m_Specific(A))))) { 1291 auto *New = BinaryOperator::CreateAdd(A, B); 1292 New->setHasNoSignedWrap(I.hasNoSignedWrap()); 1293 New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); 1294 return New; 1295 } 1296 } 1297 1298 // TODO(jingyue): Consider WillNotOverflowSignedAdd and 1299 // WillNotOverflowUnsignedAdd to reduce the number of invocations of 1300 // computeKnownBits. 1301 if (!I.hasNoSignedWrap() && WillNotOverflowSignedAdd(LHS, RHS, I)) { 1302 Changed = true; 1303 I.setHasNoSignedWrap(true); 1304 } 1305 if (!I.hasNoUnsignedWrap() && 1306 computeOverflowForUnsignedAdd(LHS, RHS, &I) == 1307 OverflowResult::NeverOverflows) { 1308 Changed = true; 1309 I.setHasNoUnsignedWrap(true); 1310 } 1311 1312 return Changed ? &I : nullptr; 1313 } 1314 1315 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) { 1316 bool Changed = SimplifyAssociativeOrCommutative(I); 1317 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 1318 1319 if (Value *V = SimplifyVectorOp(I)) 1320 return ReplaceInstUsesWith(I, V); 1321 1322 if (Value *V = 1323 SimplifyFAddInst(LHS, RHS, I.getFastMathFlags(), DL, TLI, DT, AC)) 1324 return ReplaceInstUsesWith(I, V); 1325 1326 if (isa<Constant>(RHS)) { 1327 if (isa<PHINode>(LHS)) 1328 if (Instruction *NV = FoldOpIntoPhi(I)) 1329 return NV; 1330 1331 if (SelectInst *SI = dyn_cast<SelectInst>(LHS)) 1332 if (Instruction *NV = FoldOpIntoSelect(I, SI)) 1333 return NV; 1334 } 1335 1336 // -A + B --> B - A 1337 // -A + -B --> -(A + B) 1338 if (Value *LHSV = dyn_castFNegVal(LHS)) { 1339 Instruction *RI = BinaryOperator::CreateFSub(RHS, LHSV); 1340 RI->copyFastMathFlags(&I); 1341 return RI; 1342 } 1343 1344 // A + -B --> A - B 1345 if (!isa<Constant>(RHS)) 1346 if (Value *V = dyn_castFNegVal(RHS)) { 1347 Instruction *RI = BinaryOperator::CreateFSub(LHS, V); 1348 RI->copyFastMathFlags(&I); 1349 return RI; 1350 } 1351 1352 // Check for (fadd double (sitofp x), y), see if we can merge this into an 1353 // integer add followed by a promotion. 1354 if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) { 1355 // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst)) 1356 // ... if the constant fits in the integer value. This is useful for things 1357 // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer 1358 // requires a constant pool load, and generally allows the add to be better 1359 // instcombined. 1360 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) { 1361 Constant *CI = 1362 ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType()); 1363 if (LHSConv->hasOneUse() && 1364 ConstantExpr::getSIToFP(CI, I.getType()) == CFP && 1365 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI, I)) { 1366 // Insert the new integer add. 1367 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1368 CI, "addconv"); 1369 return new SIToFPInst(NewAdd, I.getType()); 1370 } 1371 } 1372 1373 // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y)) 1374 if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) { 1375 // Only do this if x/y have the same type, if at last one of them has a 1376 // single use (so we don't increase the number of int->fp conversions), 1377 // and if the integer add will not overflow. 1378 if (LHSConv->getOperand(0)->getType() == 1379 RHSConv->getOperand(0)->getType() && 1380 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && 1381 WillNotOverflowSignedAdd(LHSConv->getOperand(0), 1382 RHSConv->getOperand(0), I)) { 1383 // Insert the new integer add. 1384 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1385 RHSConv->getOperand(0),"addconv"); 1386 return new SIToFPInst(NewAdd, I.getType()); 1387 } 1388 } 1389 } 1390 1391 // select C, 0, B + select C, A, 0 -> select C, A, B 1392 { 1393 Value *A1, *B1, *C1, *A2, *B2, *C2; 1394 if (match(LHS, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) && 1395 match(RHS, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) { 1396 if (C1 == C2) { 1397 Constant *Z1=nullptr, *Z2=nullptr; 1398 Value *A, *B, *C=C1; 1399 if (match(A1, m_AnyZero()) && match(B2, m_AnyZero())) { 1400 Z1 = dyn_cast<Constant>(A1); A = A2; 1401 Z2 = dyn_cast<Constant>(B2); B = B1; 1402 } else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) { 1403 Z1 = dyn_cast<Constant>(B1); B = B2; 1404 Z2 = dyn_cast<Constant>(A2); A = A1; 1405 } 1406 1407 if (Z1 && Z2 && 1408 (I.hasNoSignedZeros() || 1409 (Z1->isNegativeZeroValue() && Z2->isNegativeZeroValue()))) { 1410 return SelectInst::Create(C, A, B); 1411 } 1412 } 1413 } 1414 } 1415 1416 if (I.hasUnsafeAlgebra()) { 1417 if (Value *V = FAddCombine(Builder).simplify(&I)) 1418 return ReplaceInstUsesWith(I, V); 1419 } 1420 1421 return Changed ? &I : nullptr; 1422 } 1423 1424 /// Optimize pointer differences into the same array into a size. Consider: 1425 /// &A[10] - &A[0]: we should compile this to "10". LHS/RHS are the pointer 1426 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract. 1427 /// 1428 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS, 1429 Type *Ty) { 1430 // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize 1431 // this. 1432 bool Swapped = false; 1433 GEPOperator *GEP1 = nullptr, *GEP2 = nullptr; 1434 1435 // For now we require one side to be the base pointer "A" or a constant 1436 // GEP derived from it. 1437 if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) { 1438 // (gep X, ...) - X 1439 if (LHSGEP->getOperand(0) == RHS) { 1440 GEP1 = LHSGEP; 1441 Swapped = false; 1442 } else if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) { 1443 // (gep X, ...) - (gep X, ...) 1444 if (LHSGEP->getOperand(0)->stripPointerCasts() == 1445 RHSGEP->getOperand(0)->stripPointerCasts()) { 1446 GEP2 = RHSGEP; 1447 GEP1 = LHSGEP; 1448 Swapped = false; 1449 } 1450 } 1451 } 1452 1453 if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) { 1454 // X - (gep X, ...) 1455 if (RHSGEP->getOperand(0) == LHS) { 1456 GEP1 = RHSGEP; 1457 Swapped = true; 1458 } else if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) { 1459 // (gep X, ...) - (gep X, ...) 1460 if (RHSGEP->getOperand(0)->stripPointerCasts() == 1461 LHSGEP->getOperand(0)->stripPointerCasts()) { 1462 GEP2 = LHSGEP; 1463 GEP1 = RHSGEP; 1464 Swapped = true; 1465 } 1466 } 1467 } 1468 1469 // Avoid duplicating the arithmetic if GEP2 has non-constant indices and 1470 // multiple users. 1471 if (!GEP1 || 1472 (GEP2 && !GEP2->hasAllConstantIndices() && !GEP2->hasOneUse())) 1473 return nullptr; 1474 1475 // Emit the offset of the GEP and an intptr_t. 1476 Value *Result = EmitGEPOffset(GEP1); 1477 1478 // If we had a constant expression GEP on the other side offsetting the 1479 // pointer, subtract it from the offset we have. 1480 if (GEP2) { 1481 Value *Offset = EmitGEPOffset(GEP2); 1482 Result = Builder->CreateSub(Result, Offset); 1483 } 1484 1485 // If we have p - gep(p, ...) then we have to negate the result. 1486 if (Swapped) 1487 Result = Builder->CreateNeg(Result, "diff.neg"); 1488 1489 return Builder->CreateIntCast(Result, Ty, true); 1490 } 1491 1492 Instruction *InstCombiner::visitSub(BinaryOperator &I) { 1493 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 1494 1495 if (Value *V = SimplifyVectorOp(I)) 1496 return ReplaceInstUsesWith(I, V); 1497 1498 if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(), 1499 I.hasNoUnsignedWrap(), DL, TLI, DT, AC)) 1500 return ReplaceInstUsesWith(I, V); 1501 1502 // (A*B)-(A*C) -> A*(B-C) etc 1503 if (Value *V = SimplifyUsingDistributiveLaws(I)) 1504 return ReplaceInstUsesWith(I, V); 1505 1506 // If this is a 'B = x-(-A)', change to B = x+A. 1507 if (Value *V = dyn_castNegVal(Op1)) { 1508 BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V); 1509 1510 if (const auto *BO = dyn_cast<BinaryOperator>(Op1)) { 1511 assert(BO->getOpcode() == Instruction::Sub && 1512 "Expected a subtraction operator!"); 1513 if (BO->hasNoSignedWrap() && I.hasNoSignedWrap()) 1514 Res->setHasNoSignedWrap(true); 1515 } else { 1516 if (cast<Constant>(Op1)->isNotMinSignedValue() && I.hasNoSignedWrap()) 1517 Res->setHasNoSignedWrap(true); 1518 } 1519 1520 return Res; 1521 } 1522 1523 if (I.getType()->isIntegerTy(1)) 1524 return BinaryOperator::CreateXor(Op0, Op1); 1525 1526 // Replace (-1 - A) with (~A). 1527 if (match(Op0, m_AllOnes())) 1528 return BinaryOperator::CreateNot(Op1); 1529 1530 if (Constant *C = dyn_cast<Constant>(Op0)) { 1531 // C - ~X == X + (1+C) 1532 Value *X = nullptr; 1533 if (match(Op1, m_Not(m_Value(X)))) 1534 return BinaryOperator::CreateAdd(X, AddOne(C)); 1535 1536 // Try to fold constant sub into select arguments. 1537 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) 1538 if (Instruction *R = FoldOpIntoSelect(I, SI)) 1539 return R; 1540 1541 // C-(X+C2) --> (C-C2)-X 1542 Constant *C2; 1543 if (match(Op1, m_Add(m_Value(X), m_Constant(C2)))) 1544 return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X); 1545 1546 if (SimplifyDemandedInstructionBits(I)) 1547 return &I; 1548 1549 // Fold (sub 0, (zext bool to B)) --> (sext bool to B) 1550 if (C->isNullValue() && match(Op1, m_ZExt(m_Value(X)))) 1551 if (X->getType()->getScalarType()->isIntegerTy(1)) 1552 return CastInst::CreateSExtOrBitCast(X, Op1->getType()); 1553 1554 // Fold (sub 0, (sext bool to B)) --> (zext bool to B) 1555 if (C->isNullValue() && match(Op1, m_SExt(m_Value(X)))) 1556 if (X->getType()->getScalarType()->isIntegerTy(1)) 1557 return CastInst::CreateZExtOrBitCast(X, Op1->getType()); 1558 } 1559 1560 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) { 1561 // -(X >>u 31) -> (X >>s 31) 1562 // -(X >>s 31) -> (X >>u 31) 1563 if (C->isZero()) { 1564 Value *X; 1565 ConstantInt *CI; 1566 if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) && 1567 // Verify we are shifting out everything but the sign bit. 1568 CI->getValue() == I.getType()->getPrimitiveSizeInBits() - 1) 1569 return BinaryOperator::CreateAShr(X, CI); 1570 1571 if (match(Op1, m_AShr(m_Value(X), m_ConstantInt(CI))) && 1572 // Verify we are shifting out everything but the sign bit. 1573 CI->getValue() == I.getType()->getPrimitiveSizeInBits() - 1) 1574 return BinaryOperator::CreateLShr(X, CI); 1575 } 1576 1577 // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known 1578 // zero. 1579 APInt IntVal = C->getValue(); 1580 if ((IntVal + 1).isPowerOf2()) { 1581 unsigned BitWidth = I.getType()->getScalarSizeInBits(); 1582 APInt KnownZero(BitWidth, 0); 1583 APInt KnownOne(BitWidth, 0); 1584 computeKnownBits(&I, KnownZero, KnownOne, 0, &I); 1585 if ((IntVal | KnownZero).isAllOnesValue()) { 1586 return BinaryOperator::CreateXor(Op1, C); 1587 } 1588 } 1589 } 1590 1591 { 1592 Value *Y; 1593 // X-(X+Y) == -Y X-(Y+X) == -Y 1594 if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) || 1595 match(Op1, m_Add(m_Value(Y), m_Specific(Op0)))) 1596 return BinaryOperator::CreateNeg(Y); 1597 1598 // (X-Y)-X == -Y 1599 if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y)))) 1600 return BinaryOperator::CreateNeg(Y); 1601 } 1602 1603 // (sub (or A, B) (xor A, B)) --> (and A, B) 1604 { 1605 Value *A = nullptr, *B = nullptr; 1606 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && 1607 (match(Op0, m_Or(m_Specific(A), m_Specific(B))) || 1608 match(Op0, m_Or(m_Specific(B), m_Specific(A))))) 1609 return BinaryOperator::CreateAnd(A, B); 1610 } 1611 1612 if (Op0->hasOneUse()) { 1613 Value *Y = nullptr; 1614 // ((X | Y) - X) --> (~X & Y) 1615 if (match(Op0, m_Or(m_Value(Y), m_Specific(Op1))) || 1616 match(Op0, m_Or(m_Specific(Op1), m_Value(Y)))) 1617 return BinaryOperator::CreateAnd( 1618 Y, Builder->CreateNot(Op1, Op1->getName() + ".not")); 1619 } 1620 1621 if (Op1->hasOneUse()) { 1622 Value *X = nullptr, *Y = nullptr, *Z = nullptr; 1623 Constant *C = nullptr; 1624 Constant *CI = nullptr; 1625 1626 // (X - (Y - Z)) --> (X + (Z - Y)). 1627 if (match(Op1, m_Sub(m_Value(Y), m_Value(Z)))) 1628 return BinaryOperator::CreateAdd(Op0, 1629 Builder->CreateSub(Z, Y, Op1->getName())); 1630 1631 // (X - (X & Y)) --> (X & ~Y) 1632 // 1633 if (match(Op1, m_And(m_Value(Y), m_Specific(Op0))) || 1634 match(Op1, m_And(m_Specific(Op0), m_Value(Y)))) 1635 return BinaryOperator::CreateAnd(Op0, 1636 Builder->CreateNot(Y, Y->getName() + ".not")); 1637 1638 // 0 - (X sdiv C) -> (X sdiv -C) provided the negation doesn't overflow. 1639 if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) && match(Op0, m_Zero()) && 1640 C->isNotMinSignedValue() && !C->isOneValue()) 1641 return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C)); 1642 1643 // 0 - (X << Y) -> (-X << Y) when X is freely negatable. 1644 if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero())) 1645 if (Value *XNeg = dyn_castNegVal(X)) 1646 return BinaryOperator::CreateShl(XNeg, Y); 1647 1648 // X - A*-B -> X + A*B 1649 // X - -A*B -> X + A*B 1650 Value *A, *B; 1651 if (match(Op1, m_Mul(m_Value(A), m_Neg(m_Value(B)))) || 1652 match(Op1, m_Mul(m_Neg(m_Value(A)), m_Value(B)))) 1653 return BinaryOperator::CreateAdd(Op0, Builder->CreateMul(A, B)); 1654 1655 // X - A*CI -> X + A*-CI 1656 // X - CI*A -> X + A*-CI 1657 if (match(Op1, m_Mul(m_Value(A), m_Constant(CI))) || 1658 match(Op1, m_Mul(m_Constant(CI), m_Value(A)))) { 1659 Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(CI)); 1660 return BinaryOperator::CreateAdd(Op0, NewMul); 1661 } 1662 } 1663 1664 // Optimize pointer differences into the same array into a size. Consider: 1665 // &A[10] - &A[0]: we should compile this to "10". 1666 Value *LHSOp, *RHSOp; 1667 if (match(Op0, m_PtrToInt(m_Value(LHSOp))) && 1668 match(Op1, m_PtrToInt(m_Value(RHSOp)))) 1669 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType())) 1670 return ReplaceInstUsesWith(I, Res); 1671 1672 // trunc(p)-trunc(q) -> trunc(p-q) 1673 if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) && 1674 match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp))))) 1675 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType())) 1676 return ReplaceInstUsesWith(I, Res); 1677 1678 bool Changed = false; 1679 if (!I.hasNoSignedWrap() && WillNotOverflowSignedSub(Op0, Op1, I)) { 1680 Changed = true; 1681 I.setHasNoSignedWrap(true); 1682 } 1683 if (!I.hasNoUnsignedWrap() && WillNotOverflowUnsignedSub(Op0, Op1, I)) { 1684 Changed = true; 1685 I.setHasNoUnsignedWrap(true); 1686 } 1687 1688 return Changed ? &I : nullptr; 1689 } 1690 1691 Instruction *InstCombiner::visitFSub(BinaryOperator &I) { 1692 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 1693 1694 if (Value *V = SimplifyVectorOp(I)) 1695 return ReplaceInstUsesWith(I, V); 1696 1697 if (Value *V = 1698 SimplifyFSubInst(Op0, Op1, I.getFastMathFlags(), DL, TLI, DT, AC)) 1699 return ReplaceInstUsesWith(I, V); 1700 1701 // fsub nsz 0, X ==> fsub nsz -0.0, X 1702 if (I.getFastMathFlags().noSignedZeros() && match(Op0, m_Zero())) { 1703 // Subtraction from -0.0 is the canonical form of fneg. 1704 Instruction *NewI = BinaryOperator::CreateFNeg(Op1); 1705 NewI->copyFastMathFlags(&I); 1706 return NewI; 1707 } 1708 1709 if (isa<Constant>(Op0)) 1710 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) 1711 if (Instruction *NV = FoldOpIntoSelect(I, SI)) 1712 return NV; 1713 1714 // If this is a 'B = x-(-A)', change to B = x+A, potentially looking 1715 // through FP extensions/truncations along the way. 1716 if (Value *V = dyn_castFNegVal(Op1)) { 1717 Instruction *NewI = BinaryOperator::CreateFAdd(Op0, V); 1718 NewI->copyFastMathFlags(&I); 1719 return NewI; 1720 } 1721 if (FPTruncInst *FPTI = dyn_cast<FPTruncInst>(Op1)) { 1722 if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) { 1723 Value *NewTrunc = Builder->CreateFPTrunc(V, I.getType()); 1724 Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewTrunc); 1725 NewI->copyFastMathFlags(&I); 1726 return NewI; 1727 } 1728 } else if (FPExtInst *FPEI = dyn_cast<FPExtInst>(Op1)) { 1729 if (Value *V = dyn_castFNegVal(FPEI->getOperand(0))) { 1730 Value *NewExt = Builder->CreateFPExt(V, I.getType()); 1731 Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewExt); 1732 NewI->copyFastMathFlags(&I); 1733 return NewI; 1734 } 1735 } 1736 1737 if (I.hasUnsafeAlgebra()) { 1738 if (Value *V = FAddCombine(Builder).simplify(&I)) 1739 return ReplaceInstUsesWith(I, V); 1740 } 1741 1742 return nullptr; 1743 } 1744