1 //===- InstCombineAddSub.cpp ----------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements the visit functions for add, fadd, sub, and fsub. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "InstCombine.h" 15 #include "llvm/ADT/STLExtras.h" 16 #include "llvm/Analysis/InstructionSimplify.h" 17 #include "llvm/IR/DataLayout.h" 18 #include "llvm/IR/GetElementPtrTypeIterator.h" 19 #include "llvm/IR/PatternMatch.h" 20 using namespace llvm; 21 using namespace PatternMatch; 22 23 #define DEBUG_TYPE "instcombine" 24 25 namespace { 26 27 /// Class representing coefficient of floating-point addend. 28 /// This class needs to be highly efficient, which is especially true for 29 /// the constructor. As of I write this comment, the cost of the default 30 /// constructor is merely 4-byte-store-zero (Assuming compiler is able to 31 /// perform write-merging). 32 /// 33 class FAddendCoef { 34 public: 35 // The constructor has to initialize a APFloat, which is uncessary for 36 // most addends which have coefficient either 1 or -1. So, the constructor 37 // is expensive. In order to avoid the cost of the constructor, we should 38 // reuse some instances whenever possible. The pre-created instances 39 // FAddCombine::Add[0-5] embodies this idea. 40 // 41 FAddendCoef() : IsFp(false), BufHasFpVal(false), IntVal(0) {} 42 ~FAddendCoef(); 43 44 void set(short C) { 45 assert(!insaneIntVal(C) && "Insane coefficient"); 46 IsFp = false; IntVal = C; 47 } 48 49 void set(const APFloat& C); 50 51 void negate(); 52 53 bool isZero() const { return isInt() ? !IntVal : getFpVal().isZero(); } 54 Value *getValue(Type *) const; 55 56 // If possible, don't define operator+/operator- etc because these 57 // operators inevitably call FAddendCoef's constructor which is not cheap. 58 void operator=(const FAddendCoef &A); 59 void operator+=(const FAddendCoef &A); 60 void operator-=(const FAddendCoef &A); 61 void operator*=(const FAddendCoef &S); 62 63 bool isOne() const { return isInt() && IntVal == 1; } 64 bool isTwo() const { return isInt() && IntVal == 2; } 65 bool isMinusOne() const { return isInt() && IntVal == -1; } 66 bool isMinusTwo() const { return isInt() && IntVal == -2; } 67 68 private: 69 bool insaneIntVal(int V) { return V > 4 || V < -4; } 70 APFloat *getFpValPtr(void) 71 { return reinterpret_cast<APFloat*>(&FpValBuf.buffer[0]); } 72 const APFloat *getFpValPtr(void) const 73 { return reinterpret_cast<const APFloat*>(&FpValBuf.buffer[0]); } 74 75 const APFloat &getFpVal(void) const { 76 assert(IsFp && BufHasFpVal && "Incorret state"); 77 return *getFpValPtr(); 78 } 79 80 APFloat &getFpVal(void) { 81 assert(IsFp && BufHasFpVal && "Incorret state"); 82 return *getFpValPtr(); 83 } 84 85 bool isInt() const { return !IsFp; } 86 87 // If the coefficient is represented by an integer, promote it to a 88 // floating point. 89 void convertToFpType(const fltSemantics &Sem); 90 91 // Construct an APFloat from a signed integer. 92 // TODO: We should get rid of this function when APFloat can be constructed 93 // from an *SIGNED* integer. 94 APFloat createAPFloatFromInt(const fltSemantics &Sem, int Val); 95 private: 96 97 bool IsFp; 98 99 // True iff FpValBuf contains an instance of APFloat. 100 bool BufHasFpVal; 101 102 // The integer coefficient of an individual addend is either 1 or -1, 103 // and we try to simplify at most 4 addends from neighboring at most 104 // two instructions. So the range of <IntVal> falls in [-4, 4]. APInt 105 // is overkill of this end. 106 short IntVal; 107 108 AlignedCharArrayUnion<APFloat> FpValBuf; 109 }; 110 111 /// FAddend is used to represent floating-point addend. An addend is 112 /// represented as <C, V>, where the V is a symbolic value, and C is a 113 /// constant coefficient. A constant addend is represented as <C, 0>. 114 /// 115 class FAddend { 116 public: 117 FAddend() { Val = nullptr; } 118 119 Value *getSymVal (void) const { return Val; } 120 const FAddendCoef &getCoef(void) const { return Coeff; } 121 122 bool isConstant() const { return Val == nullptr; } 123 bool isZero() const { return Coeff.isZero(); } 124 125 void set(short Coefficient, Value *V) { Coeff.set(Coefficient), Val = V; } 126 void set(const APFloat& Coefficient, Value *V) 127 { Coeff.set(Coefficient); Val = V; } 128 void set(const ConstantFP* Coefficient, Value *V) 129 { Coeff.set(Coefficient->getValueAPF()); Val = V; } 130 131 void negate() { Coeff.negate(); } 132 133 /// Drill down the U-D chain one step to find the definition of V, and 134 /// try to break the definition into one or two addends. 135 static unsigned drillValueDownOneStep(Value* V, FAddend &A0, FAddend &A1); 136 137 /// Similar to FAddend::drillDownOneStep() except that the value being 138 /// splitted is the addend itself. 139 unsigned drillAddendDownOneStep(FAddend &Addend0, FAddend &Addend1) const; 140 141 void operator+=(const FAddend &T) { 142 assert((Val == T.Val) && "Symbolic-values disagree"); 143 Coeff += T.Coeff; 144 } 145 146 private: 147 void Scale(const FAddendCoef& ScaleAmt) { Coeff *= ScaleAmt; } 148 149 // This addend has the value of "Coeff * Val". 150 Value *Val; 151 FAddendCoef Coeff; 152 }; 153 154 /// FAddCombine is the class for optimizing an unsafe fadd/fsub along 155 /// with its neighboring at most two instructions. 156 /// 157 class FAddCombine { 158 public: 159 FAddCombine(InstCombiner::BuilderTy *B) : Builder(B), Instr(nullptr) {} 160 Value *simplify(Instruction *FAdd); 161 162 private: 163 typedef SmallVector<const FAddend*, 4> AddendVect; 164 165 Value *simplifyFAdd(AddendVect& V, unsigned InstrQuota); 166 167 Value *performFactorization(Instruction *I); 168 169 /// Convert given addend to a Value 170 Value *createAddendVal(const FAddend &A, bool& NeedNeg); 171 172 /// Return the number of instructions needed to emit the N-ary addition. 173 unsigned calcInstrNumber(const AddendVect& Vect); 174 Value *createFSub(Value *Opnd0, Value *Opnd1); 175 Value *createFAdd(Value *Opnd0, Value *Opnd1); 176 Value *createFMul(Value *Opnd0, Value *Opnd1); 177 Value *createFDiv(Value *Opnd0, Value *Opnd1); 178 Value *createFNeg(Value *V); 179 Value *createNaryFAdd(const AddendVect& Opnds, unsigned InstrQuota); 180 void createInstPostProc(Instruction *NewInst, bool NoNumber = false); 181 182 InstCombiner::BuilderTy *Builder; 183 Instruction *Instr; 184 185 private: 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 } 197 198 //===----------------------------------------------------------------------===// 199 // 200 // Implementation of 201 // {FAddendCoef, FAddend, FAddition, FAddCombine}. 202 // 203 //===----------------------------------------------------------------------===// 204 FAddendCoef::~FAddendCoef() { 205 if (BufHasFpVal) 206 getFpValPtr()->~APFloat(); 207 } 208 209 void FAddendCoef::set(const APFloat& C) { 210 APFloat *P = getFpValPtr(); 211 212 if (isInt()) { 213 // As the buffer is meanless byte stream, we cannot call 214 // APFloat::operator=(). 215 new(P) APFloat(C); 216 } else 217 *P = C; 218 219 IsFp = BufHasFpVal = true; 220 } 221 222 void FAddendCoef::convertToFpType(const fltSemantics &Sem) { 223 if (!isInt()) 224 return; 225 226 APFloat *P = getFpValPtr(); 227 if (IntVal > 0) 228 new(P) APFloat(Sem, IntVal); 229 else { 230 new(P) APFloat(Sem, 0 - IntVal); 231 P->changeSign(); 232 } 233 IsFp = BufHasFpVal = true; 234 } 235 236 APFloat FAddendCoef::createAPFloatFromInt(const fltSemantics &Sem, int Val) { 237 if (Val >= 0) 238 return APFloat(Sem, Val); 239 240 APFloat T(Sem, 0 - Val); 241 T.changeSign(); 242 243 return T; 244 } 245 246 void FAddendCoef::operator=(const FAddendCoef &That) { 247 if (That.isInt()) 248 set(That.IntVal); 249 else 250 set(That.getFpVal()); 251 } 252 253 void FAddendCoef::operator+=(const FAddendCoef &That) { 254 enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven; 255 if (isInt() == That.isInt()) { 256 if (isInt()) 257 IntVal += That.IntVal; 258 else 259 getFpVal().add(That.getFpVal(), RndMode); 260 return; 261 } 262 263 if (isInt()) { 264 const APFloat &T = That.getFpVal(); 265 convertToFpType(T.getSemantics()); 266 getFpVal().add(T, RndMode); 267 return; 268 } 269 270 APFloat &T = getFpVal(); 271 T.add(createAPFloatFromInt(T.getSemantics(), That.IntVal), RndMode); 272 } 273 274 void FAddendCoef::operator-=(const FAddendCoef &That) { 275 enum APFloat::roundingMode RndMode = APFloat::rmNearestTiesToEven; 276 if (isInt() == That.isInt()) { 277 if (isInt()) 278 IntVal -= That.IntVal; 279 else 280 getFpVal().subtract(That.getFpVal(), RndMode); 281 return; 282 } 283 284 if (isInt()) { 285 const APFloat &T = That.getFpVal(); 286 convertToFpType(T.getSemantics()); 287 getFpVal().subtract(T, RndMode); 288 return; 289 } 290 291 APFloat &T = getFpVal(); 292 T.subtract(createAPFloatFromInt(T.getSemantics(), IntVal), RndMode); 293 } 294 295 void FAddendCoef::operator*=(const FAddendCoef &That) { 296 if (That.isOne()) 297 return; 298 299 if (That.isMinusOne()) { 300 negate(); 301 return; 302 } 303 304 if (isInt() && That.isInt()) { 305 int Res = IntVal * (int)That.IntVal; 306 assert(!insaneIntVal(Res) && "Insane int value"); 307 IntVal = Res; 308 return; 309 } 310 311 const fltSemantics &Semantic = 312 isInt() ? That.getFpVal().getSemantics() : getFpVal().getSemantics(); 313 314 if (isInt()) 315 convertToFpType(Semantic); 316 APFloat &F0 = getFpVal(); 317 318 if (That.isInt()) 319 F0.multiply(createAPFloatFromInt(Semantic, That.IntVal), 320 APFloat::rmNearestTiesToEven); 321 else 322 F0.multiply(That.getFpVal(), APFloat::rmNearestTiesToEven); 323 324 return; 325 } 326 327 void FAddendCoef::negate() { 328 if (isInt()) 329 IntVal = 0 - IntVal; 330 else 331 getFpVal().changeSign(); 332 } 333 334 Value *FAddendCoef::getValue(Type *Ty) const { 335 return isInt() ? 336 ConstantFP::get(Ty, float(IntVal)) : 337 ConstantFP::get(Ty->getContext(), getFpVal()); 338 } 339 340 // The definition of <Val> Addends 341 // ========================================= 342 // A + B <1, A>, <1,B> 343 // A - B <1, A>, <1,B> 344 // 0 - B <-1, B> 345 // C * A, <C, A> 346 // A + C <1, A> <C, NULL> 347 // 0 +/- 0 <0, NULL> (corner case) 348 // 349 // Legend: A and B are not constant, C is constant 350 // 351 unsigned FAddend::drillValueDownOneStep 352 (Value *Val, FAddend &Addend0, FAddend &Addend1) { 353 Instruction *I = nullptr; 354 if (!Val || !(I = dyn_cast<Instruction>(Val))) 355 return 0; 356 357 unsigned Opcode = I->getOpcode(); 358 359 if (Opcode == Instruction::FAdd || Opcode == Instruction::FSub) { 360 ConstantFP *C0, *C1; 361 Value *Opnd0 = I->getOperand(0); 362 Value *Opnd1 = I->getOperand(1); 363 if ((C0 = dyn_cast<ConstantFP>(Opnd0)) && C0->isZero()) 364 Opnd0 = nullptr; 365 366 if ((C1 = dyn_cast<ConstantFP>(Opnd1)) && C1->isZero()) 367 Opnd1 = nullptr; 368 369 if (Opnd0) { 370 if (!C0) 371 Addend0.set(1, Opnd0); 372 else 373 Addend0.set(C0, nullptr); 374 } 375 376 if (Opnd1) { 377 FAddend &Addend = Opnd0 ? Addend1 : Addend0; 378 if (!C1) 379 Addend.set(1, Opnd1); 380 else 381 Addend.set(C1, nullptr); 382 if (Opcode == Instruction::FSub) 383 Addend.negate(); 384 } 385 386 if (Opnd0 || Opnd1) 387 return Opnd0 && Opnd1 ? 2 : 1; 388 389 // Both operands are zero. Weird! 390 Addend0.set(APFloat(C0->getValueAPF().getSemantics()), nullptr); 391 return 1; 392 } 393 394 if (I->getOpcode() == Instruction::FMul) { 395 Value *V0 = I->getOperand(0); 396 Value *V1 = I->getOperand(1); 397 if (ConstantFP *C = dyn_cast<ConstantFP>(V0)) { 398 Addend0.set(C, V1); 399 return 1; 400 } 401 402 if (ConstantFP *C = dyn_cast<ConstantFP>(V1)) { 403 Addend0.set(C, V0); 404 return 1; 405 } 406 } 407 408 return 0; 409 } 410 411 // Try to break *this* addend into two addends. e.g. Suppose this addend is 412 // <2.3, V>, and V = X + Y, by calling this function, we obtain two addends, 413 // i.e. <2.3, X> and <2.3, Y>. 414 // 415 unsigned FAddend::drillAddendDownOneStep 416 (FAddend &Addend0, FAddend &Addend1) const { 417 if (isConstant()) 418 return 0; 419 420 unsigned BreakNum = FAddend::drillValueDownOneStep(Val, Addend0, Addend1); 421 if (!BreakNum || Coeff.isOne()) 422 return BreakNum; 423 424 Addend0.Scale(Coeff); 425 426 if (BreakNum == 2) 427 Addend1.Scale(Coeff); 428 429 return BreakNum; 430 } 431 432 // Try to perform following optimization on the input instruction I. Return the 433 // simplified expression if was successful; otherwise, return 0. 434 // 435 // Instruction "I" is Simplified into 436 // ------------------------------------------------------- 437 // (x * y) +/- (x * z) x * (y +/- z) 438 // (y / x) +/- (z / x) (y +/- z) / x 439 // 440 Value *FAddCombine::performFactorization(Instruction *I) { 441 assert((I->getOpcode() == Instruction::FAdd || 442 I->getOpcode() == Instruction::FSub) && "Expect add/sub"); 443 444 Instruction *I0 = dyn_cast<Instruction>(I->getOperand(0)); 445 Instruction *I1 = dyn_cast<Instruction>(I->getOperand(1)); 446 447 if (!I0 || !I1 || I0->getOpcode() != I1->getOpcode()) 448 return nullptr; 449 450 bool isMpy = false; 451 if (I0->getOpcode() == Instruction::FMul) 452 isMpy = true; 453 else if (I0->getOpcode() != Instruction::FDiv) 454 return nullptr; 455 456 Value *Opnd0_0 = I0->getOperand(0); 457 Value *Opnd0_1 = I0->getOperand(1); 458 Value *Opnd1_0 = I1->getOperand(0); 459 Value *Opnd1_1 = I1->getOperand(1); 460 461 // Input Instr I Factor AddSub0 AddSub1 462 // ---------------------------------------------- 463 // (x*y) +/- (x*z) x y z 464 // (y/x) +/- (z/x) x y z 465 // 466 Value *Factor = nullptr; 467 Value *AddSub0 = nullptr, *AddSub1 = nullptr; 468 469 if (isMpy) { 470 if (Opnd0_0 == Opnd1_0 || Opnd0_0 == Opnd1_1) 471 Factor = Opnd0_0; 472 else if (Opnd0_1 == Opnd1_0 || Opnd0_1 == Opnd1_1) 473 Factor = Opnd0_1; 474 475 if (Factor) { 476 AddSub0 = (Factor == Opnd0_0) ? Opnd0_1 : Opnd0_0; 477 AddSub1 = (Factor == Opnd1_0) ? Opnd1_1 : Opnd1_0; 478 } 479 } else if (Opnd0_1 == Opnd1_1) { 480 Factor = Opnd0_1; 481 AddSub0 = Opnd0_0; 482 AddSub1 = Opnd1_0; 483 } 484 485 if (!Factor) 486 return nullptr; 487 488 FastMathFlags Flags; 489 Flags.setUnsafeAlgebra(); 490 if (I0) Flags &= I->getFastMathFlags(); 491 if (I1) Flags &= I->getFastMathFlags(); 492 493 // Create expression "NewAddSub = AddSub0 +/- AddsSub1" 494 Value *NewAddSub = (I->getOpcode() == Instruction::FAdd) ? 495 createFAdd(AddSub0, AddSub1) : 496 createFSub(AddSub0, AddSub1); 497 if (ConstantFP *CFP = dyn_cast<ConstantFP>(NewAddSub)) { 498 const APFloat &F = CFP->getValueAPF(); 499 if (!F.isNormal()) 500 return nullptr; 501 } else if (Instruction *II = dyn_cast<Instruction>(NewAddSub)) 502 II->setFastMathFlags(Flags); 503 504 if (isMpy) { 505 Value *RI = createFMul(Factor, NewAddSub); 506 if (Instruction *II = dyn_cast<Instruction>(RI)) 507 II->setFastMathFlags(Flags); 508 return RI; 509 } 510 511 Value *RI = createFDiv(NewAddSub, Factor); 512 if (Instruction *II = dyn_cast<Instruction>(RI)) 513 II->setFastMathFlags(Flags); 514 return RI; 515 } 516 517 Value *FAddCombine::simplify(Instruction *I) { 518 assert(I->hasUnsafeAlgebra() && "Should be in unsafe mode"); 519 520 // Currently we are not able to handle vector type. 521 if (I->getType()->isVectorTy()) 522 return nullptr; 523 524 assert((I->getOpcode() == Instruction::FAdd || 525 I->getOpcode() == Instruction::FSub) && "Expect add/sub"); 526 527 // Save the instruction before calling other member-functions. 528 Instr = I; 529 530 FAddend Opnd0, Opnd1, Opnd0_0, Opnd0_1, Opnd1_0, Opnd1_1; 531 532 unsigned OpndNum = FAddend::drillValueDownOneStep(I, Opnd0, Opnd1); 533 534 // Step 1: Expand the 1st addend into Opnd0_0 and Opnd0_1. 535 unsigned Opnd0_ExpNum = 0; 536 unsigned Opnd1_ExpNum = 0; 537 538 if (!Opnd0.isConstant()) 539 Opnd0_ExpNum = Opnd0.drillAddendDownOneStep(Opnd0_0, Opnd0_1); 540 541 // Step 2: Expand the 2nd addend into Opnd1_0 and Opnd1_1. 542 if (OpndNum == 2 && !Opnd1.isConstant()) 543 Opnd1_ExpNum = Opnd1.drillAddendDownOneStep(Opnd1_0, Opnd1_1); 544 545 // Step 3: Try to optimize Opnd0_0 + Opnd0_1 + Opnd1_0 + Opnd1_1 546 if (Opnd0_ExpNum && Opnd1_ExpNum) { 547 AddendVect AllOpnds; 548 AllOpnds.push_back(&Opnd0_0); 549 AllOpnds.push_back(&Opnd1_0); 550 if (Opnd0_ExpNum == 2) 551 AllOpnds.push_back(&Opnd0_1); 552 if (Opnd1_ExpNum == 2) 553 AllOpnds.push_back(&Opnd1_1); 554 555 // Compute instruction quota. We should save at least one instruction. 556 unsigned InstQuota = 0; 557 558 Value *V0 = I->getOperand(0); 559 Value *V1 = I->getOperand(1); 560 InstQuota = ((!isa<Constant>(V0) && V0->hasOneUse()) && 561 (!isa<Constant>(V1) && V1->hasOneUse())) ? 2 : 1; 562 563 if (Value *R = simplifyFAdd(AllOpnds, InstQuota)) 564 return R; 565 } 566 567 if (OpndNum != 2) { 568 // The input instruction is : "I=0.0 +/- V". If the "V" were able to be 569 // splitted into two addends, say "V = X - Y", the instruction would have 570 // been optimized into "I = Y - X" in the previous steps. 571 // 572 const FAddendCoef &CE = Opnd0.getCoef(); 573 return CE.isOne() ? Opnd0.getSymVal() : nullptr; 574 } 575 576 // step 4: Try to optimize Opnd0 + Opnd1_0 [+ Opnd1_1] 577 if (Opnd1_ExpNum) { 578 AddendVect AllOpnds; 579 AllOpnds.push_back(&Opnd0); 580 AllOpnds.push_back(&Opnd1_0); 581 if (Opnd1_ExpNum == 2) 582 AllOpnds.push_back(&Opnd1_1); 583 584 if (Value *R = simplifyFAdd(AllOpnds, 1)) 585 return R; 586 } 587 588 // step 5: Try to optimize Opnd1 + Opnd0_0 [+ Opnd0_1] 589 if (Opnd0_ExpNum) { 590 AddendVect AllOpnds; 591 AllOpnds.push_back(&Opnd1); 592 AllOpnds.push_back(&Opnd0_0); 593 if (Opnd0_ExpNum == 2) 594 AllOpnds.push_back(&Opnd0_1); 595 596 if (Value *R = simplifyFAdd(AllOpnds, 1)) 597 return R; 598 } 599 600 // step 6: Try factorization as the last resort, 601 return performFactorization(I); 602 } 603 604 Value *FAddCombine::simplifyFAdd(AddendVect& Addends, unsigned InstrQuota) { 605 606 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 755 (Value *Opnd0, Value *Opnd1) { 756 Value *V = Builder->CreateFSub(Opnd0, Opnd1); 757 if (Instruction *I = dyn_cast<Instruction>(V)) 758 createInstPostProc(I); 759 return V; 760 } 761 762 Value *FAddCombine::createFNeg(Value *V) { 763 Value *Zero = cast<Value>(ConstantFP::get(V->getType(), 0.0)); 764 Value *NewV = createFSub(Zero, V); 765 if (Instruction *I = dyn_cast<Instruction>(NewV)) 766 createInstPostProc(I, true); // fneg's don't receive instruction numbers. 767 return NewV; 768 } 769 770 Value *FAddCombine::createFAdd 771 (Value *Opnd0, Value *Opnd1) { 772 Value *V = Builder->CreateFAdd(Opnd0, Opnd1); 773 if (Instruction *I = dyn_cast<Instruction>(V)) 774 createInstPostProc(I); 775 return V; 776 } 777 778 Value *FAddCombine::createFMul(Value *Opnd0, Value *Opnd1) { 779 Value *V = Builder->CreateFMul(Opnd0, Opnd1); 780 if (Instruction *I = dyn_cast<Instruction>(V)) 781 createInstPostProc(I); 782 return V; 783 } 784 785 Value *FAddCombine::createFDiv(Value *Opnd0, Value *Opnd1) { 786 Value *V = Builder->CreateFDiv(Opnd0, Opnd1); 787 if (Instruction *I = dyn_cast<Instruction>(V)) 788 createInstPostProc(I); 789 return V; 790 } 791 792 void FAddCombine::createInstPostProc(Instruction *NewInstr, 793 bool NoNumber) { 794 NewInstr->setDebugLoc(Instr->getDebugLoc()); 795 796 // Keep track of the number of instruction created. 797 if (!NoNumber) 798 incCreateInstNum(); 799 800 // Propagate fast-math flags 801 NewInstr->setFastMathFlags(Instr->getFastMathFlags()); 802 } 803 804 // Return the number of instruction needed to emit the N-ary addition. 805 // NOTE: Keep this function in sync with createAddendVal(). 806 unsigned FAddCombine::calcInstrNumber(const AddendVect &Opnds) { 807 unsigned OpndNum = Opnds.size(); 808 unsigned InstrNeeded = OpndNum - 1; 809 810 // The number of addends in the form of "(-1)*x". 811 unsigned NegOpndNum = 0; 812 813 // Adjust the number of instructions needed to emit the N-ary add. 814 for (AddendVect::const_iterator I = Opnds.begin(), E = Opnds.end(); 815 I != E; I++) { 816 const FAddend *Opnd = *I; 817 if (Opnd->isConstant()) 818 continue; 819 820 const FAddendCoef &CE = Opnd->getCoef(); 821 if (CE.isMinusOne() || CE.isMinusTwo()) 822 NegOpndNum++; 823 824 // Let the addend be "c * x". If "c == +/-1", the value of the addend 825 // is immediately available; otherwise, it needs exactly one instruction 826 // to evaluate the value. 827 if (!CE.isMinusOne() && !CE.isOne()) 828 InstrNeeded++; 829 } 830 if (NegOpndNum == OpndNum) 831 InstrNeeded++; 832 return InstrNeeded; 833 } 834 835 // Input Addend Value NeedNeg(output) 836 // ================================================================ 837 // Constant C C false 838 // <+/-1, V> V coefficient is -1 839 // <2/-2, V> "fadd V, V" coefficient is -2 840 // <C, V> "fmul V, C" false 841 // 842 // NOTE: Keep this function in sync with FAddCombine::calcInstrNumber. 843 Value *FAddCombine::createAddendVal 844 (const FAddend &Opnd, bool &NeedNeg) { 845 const FAddendCoef &Coeff = Opnd.getCoef(); 846 847 if (Opnd.isConstant()) { 848 NeedNeg = false; 849 return Coeff.getValue(Instr->getType()); 850 } 851 852 Value *OpndVal = Opnd.getSymVal(); 853 854 if (Coeff.isMinusOne() || Coeff.isOne()) { 855 NeedNeg = Coeff.isMinusOne(); 856 return OpndVal; 857 } 858 859 if (Coeff.isTwo() || Coeff.isMinusTwo()) { 860 NeedNeg = Coeff.isMinusTwo(); 861 return createFAdd(OpndVal, OpndVal); 862 } 863 864 NeedNeg = false; 865 return createFMul(OpndVal, Coeff.getValue(Instr->getType())); 866 } 867 868 // If one of the operands only has one non-zero bit, and if the other 869 // operand has a known-zero bit in a more significant place than it (not 870 // including the sign bit) the ripple may go up to and fill the zero, but 871 // won't change the sign. For example, (X & ~4) + 1. 872 static bool checkRippleForAdd(const APInt &Op0KnownZero, 873 const APInt &Op1KnownZero) { 874 APInt Op1MaybeOne = ~Op1KnownZero; 875 // Make sure that one of the operand has at most one bit set to 1. 876 if (Op1MaybeOne.countPopulation() != 1) 877 return false; 878 879 // Find the most significant known 0 other than the sign bit. 880 int BitWidth = Op0KnownZero.getBitWidth(); 881 APInt Op0KnownZeroTemp(Op0KnownZero); 882 Op0KnownZeroTemp.clearBit(BitWidth - 1); 883 int Op0ZeroPosition = BitWidth - Op0KnownZeroTemp.countLeadingZeros() - 1; 884 885 int Op1OnePosition = BitWidth - Op1MaybeOne.countLeadingZeros() - 1; 886 assert(Op1OnePosition >= 0); 887 888 // This also covers the case of no known zero, since in that case 889 // Op0ZeroPosition is -1. 890 return Op0ZeroPosition >= Op1OnePosition; 891 } 892 893 /// WillNotOverflowSignedAdd - Return true if we can prove that: 894 /// (sext (add LHS, RHS)) === (add (sext LHS), (sext RHS)) 895 /// This basically requires proving that the add in the original type would not 896 /// overflow to change the sign bit or have a carry out. 897 /// TODO: Handle this for Vectors. 898 bool InstCombiner::WillNotOverflowSignedAdd(Value *LHS, Value *RHS) { 899 // There are different heuristics we can use for this. Here are some simple 900 // ones. 901 902 // If LHS and RHS each have at least two sign bits, the addition will look 903 // like 904 // 905 // XX..... + 906 // YY..... 907 // 908 // If the carry into the most significant position is 0, X and Y can't both 909 // be 1 and therefore the carry out of the addition is also 0. 910 // 911 // If the carry into the most significant position is 1, X and Y can't both 912 // be 0 and therefore the carry out of the addition is also 1. 913 // 914 // Since the carry into the most significant position is always equal to 915 // the carry out of the addition, there is no signed overflow. 916 if (ComputeNumSignBits(LHS) > 1 && ComputeNumSignBits(RHS) > 1) 917 return true; 918 919 if (IntegerType *IT = dyn_cast<IntegerType>(LHS->getType())) { 920 int BitWidth = IT->getBitWidth(); 921 APInt LHSKnownZero(BitWidth, 0); 922 APInt LHSKnownOne(BitWidth, 0); 923 computeKnownBits(LHS, LHSKnownZero, LHSKnownOne); 924 925 APInt RHSKnownZero(BitWidth, 0); 926 APInt RHSKnownOne(BitWidth, 0); 927 computeKnownBits(RHS, RHSKnownZero, RHSKnownOne); 928 929 // Addition of two 2's compliment numbers having opposite signs will never 930 // overflow. 931 if ((LHSKnownOne[BitWidth - 1] && RHSKnownZero[BitWidth - 1]) || 932 (LHSKnownZero[BitWidth - 1] && RHSKnownOne[BitWidth - 1])) 933 return true; 934 935 // Check if carry bit of addition will not cause overflow. 936 if (checkRippleForAdd(LHSKnownZero, RHSKnownZero)) 937 return true; 938 if (checkRippleForAdd(RHSKnownZero, LHSKnownZero)) 939 return true; 940 } 941 return false; 942 } 943 944 /// WillNotOverflowUnsignedAdd - Return true if we can prove that: 945 /// (zext (add LHS, RHS)) === (add (zext LHS), (zext RHS)) 946 bool InstCombiner::WillNotOverflowUnsignedAdd(Value *LHS, Value *RHS) { 947 // There are different heuristics we can use for this. Here is a simple one. 948 // If the sign bit of LHS and that of RHS are both zero, no unsigned wrap. 949 bool LHSKnownNonNegative, LHSKnownNegative; 950 bool RHSKnownNonNegative, RHSKnownNegative; 951 ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, DL, 0); 952 ComputeSignBit(RHS, RHSKnownNonNegative, RHSKnownNegative, DL, 0); 953 if (LHSKnownNonNegative && RHSKnownNonNegative) 954 return true; 955 956 return false; 957 } 958 959 // Checks if any operand is negative and we can convert add to sub. 960 // This function checks for following negative patterns 961 // ADD(XOR(OR(Z, NOT(C)), C)), 1) == NEG(AND(Z, C)) 962 // ADD(XOR(AND(Z, C), C), 1) == NEG(OR(Z, ~C)) 963 // XOR(AND(Z, C), (C + 1)) == NEG(OR(Z, ~C)) if C is even 964 static Value *checkForNegativeOperand(BinaryOperator &I, 965 InstCombiner::BuilderTy *Builder) { 966 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 967 968 // This function creates 2 instructions to replace ADD, we need at least one 969 // of LHS or RHS to have one use to ensure benefit in transform. 970 if (!LHS->hasOneUse() && !RHS->hasOneUse()) 971 return nullptr; 972 973 Value *X = nullptr, *Y = nullptr, *Z = nullptr; 974 const APInt *C1 = nullptr, *C2 = nullptr; 975 976 // if ONE is on other side, swap 977 if (match(RHS, m_Add(m_Value(X), m_One()))) 978 std::swap(LHS, RHS); 979 980 if (match(LHS, m_Add(m_Value(X), m_One()))) { 981 // if XOR on other side, swap 982 if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1)))) 983 std::swap(X, RHS); 984 985 if (match(X, m_Xor(m_Value(Y), m_APInt(C1)))) { 986 // X = XOR(Y, C1), Y = OR(Z, C2), C2 = NOT(C1) ==> X == NOT(AND(Z, C1)) 987 // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, AND(Z, C1)) 988 if (match(Y, m_Or(m_Value(Z), m_APInt(C2))) && (*C2 == ~(*C1))) { 989 Value *NewAnd = Builder->CreateAnd(Z, *C1); 990 return Builder->CreateSub(RHS, NewAnd, "sub"); 991 } else if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && (*C1 == *C2)) { 992 // X = XOR(Y, C1), Y = AND(Z, C2), C2 == C1 ==> X == NOT(OR(Z, ~C1)) 993 // ADD(ADD(X, 1), RHS) == ADD(X, ADD(RHS, 1)) == SUB(RHS, OR(Z, ~C1)) 994 Value *NewOr = Builder->CreateOr(Z, ~(*C1)); 995 return Builder->CreateSub(RHS, NewOr, "sub"); 996 } 997 } 998 } 999 1000 // Restore LHS and RHS 1001 LHS = I.getOperand(0); 1002 RHS = I.getOperand(1); 1003 1004 // if XOR is on other side, swap 1005 if (match(RHS, m_Xor(m_Value(Y), m_APInt(C1)))) 1006 std::swap(LHS, RHS); 1007 1008 // C2 is ODD 1009 // LHS = XOR(Y, C1), Y = AND(Z, C2), C1 == (C2 + 1) => LHS == NEG(OR(Z, ~C2)) 1010 // ADD(LHS, RHS) == SUB(RHS, OR(Z, ~C2)) 1011 if (match(LHS, m_Xor(m_Value(Y), m_APInt(C1)))) 1012 if (C1->countTrailingZeros() == 0) 1013 if (match(Y, m_And(m_Value(Z), m_APInt(C2))) && *C1 == (*C2 + 1)) { 1014 Value *NewOr = Builder->CreateOr(Z, ~(*C2)); 1015 return Builder->CreateSub(RHS, NewOr, "sub"); 1016 } 1017 return nullptr; 1018 } 1019 1020 Instruction *InstCombiner::visitAdd(BinaryOperator &I) { 1021 bool Changed = SimplifyAssociativeOrCommutative(I); 1022 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 1023 1024 if (Value *V = SimplifyVectorOp(I)) 1025 return ReplaceInstUsesWith(I, V); 1026 1027 if (Value *V = SimplifyAddInst(LHS, RHS, I.hasNoSignedWrap(), 1028 I.hasNoUnsignedWrap(), DL)) 1029 return ReplaceInstUsesWith(I, V); 1030 1031 // (A*B)+(A*C) -> A*(B+C) etc 1032 if (Value *V = SimplifyUsingDistributiveLaws(I)) 1033 return ReplaceInstUsesWith(I, V); 1034 1035 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { 1036 // X + (signbit) --> X ^ signbit 1037 const APInt &Val = CI->getValue(); 1038 if (Val.isSignBit()) 1039 return BinaryOperator::CreateXor(LHS, RHS); 1040 1041 // See if SimplifyDemandedBits can simplify this. This handles stuff like 1042 // (X & 254)+1 -> (X&254)|1 1043 if (SimplifyDemandedInstructionBits(I)) 1044 return &I; 1045 1046 // zext(bool) + C -> bool ? C + 1 : C 1047 if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS)) 1048 if (ZI->getSrcTy()->isIntegerTy(1)) 1049 return SelectInst::Create(ZI->getOperand(0), AddOne(CI), CI); 1050 1051 Value *XorLHS = nullptr; ConstantInt *XorRHS = nullptr; 1052 if (match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) { 1053 uint32_t TySizeBits = I.getType()->getScalarSizeInBits(); 1054 const APInt &RHSVal = CI->getValue(); 1055 unsigned ExtendAmt = 0; 1056 // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext. 1057 // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext. 1058 if (XorRHS->getValue() == -RHSVal) { 1059 if (RHSVal.isPowerOf2()) 1060 ExtendAmt = TySizeBits - RHSVal.logBase2() - 1; 1061 else if (XorRHS->getValue().isPowerOf2()) 1062 ExtendAmt = TySizeBits - XorRHS->getValue().logBase2() - 1; 1063 } 1064 1065 if (ExtendAmt) { 1066 APInt Mask = APInt::getHighBitsSet(TySizeBits, ExtendAmt); 1067 if (!MaskedValueIsZero(XorLHS, Mask)) 1068 ExtendAmt = 0; 1069 } 1070 1071 if (ExtendAmt) { 1072 Constant *ShAmt = ConstantInt::get(I.getType(), ExtendAmt); 1073 Value *NewShl = Builder->CreateShl(XorLHS, ShAmt, "sext"); 1074 return BinaryOperator::CreateAShr(NewShl, ShAmt); 1075 } 1076 1077 // If this is a xor that was canonicalized from a sub, turn it back into 1078 // a sub and fuse this add with it. 1079 if (LHS->hasOneUse() && (XorRHS->getValue()+1).isPowerOf2()) { 1080 IntegerType *IT = cast<IntegerType>(I.getType()); 1081 APInt LHSKnownOne(IT->getBitWidth(), 0); 1082 APInt LHSKnownZero(IT->getBitWidth(), 0); 1083 computeKnownBits(XorLHS, LHSKnownZero, LHSKnownOne); 1084 if ((XorRHS->getValue() | LHSKnownZero).isAllOnesValue()) 1085 return BinaryOperator::CreateSub(ConstantExpr::getAdd(XorRHS, CI), 1086 XorLHS); 1087 } 1088 // (X + signbit) + C could have gotten canonicalized to (X ^ signbit) + C, 1089 // transform them into (X + (signbit ^ C)) 1090 if (XorRHS->getValue().isSignBit()) 1091 return BinaryOperator::CreateAdd(XorLHS, 1092 ConstantExpr::getXor(XorRHS, CI)); 1093 } 1094 } 1095 1096 if (isa<Constant>(RHS) && isa<PHINode>(LHS)) 1097 if (Instruction *NV = FoldOpIntoPhi(I)) 1098 return NV; 1099 1100 if (I.getType()->getScalarType()->isIntegerTy(1)) 1101 return BinaryOperator::CreateXor(LHS, RHS); 1102 1103 // X + X --> X << 1 1104 if (LHS == RHS) { 1105 BinaryOperator *New = 1106 BinaryOperator::CreateShl(LHS, ConstantInt::get(I.getType(), 1)); 1107 New->setHasNoSignedWrap(I.hasNoSignedWrap()); 1108 New->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); 1109 return New; 1110 } 1111 1112 // -A + B --> B - A 1113 // -A + -B --> -(A + B) 1114 if (Value *LHSV = dyn_castNegVal(LHS)) { 1115 if (!isa<Constant>(RHS)) 1116 if (Value *RHSV = dyn_castNegVal(RHS)) { 1117 Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum"); 1118 return BinaryOperator::CreateNeg(NewAdd); 1119 } 1120 1121 return BinaryOperator::CreateSub(RHS, LHSV); 1122 } 1123 1124 // A + -B --> A - B 1125 if (!isa<Constant>(RHS)) 1126 if (Value *V = dyn_castNegVal(RHS)) 1127 return BinaryOperator::CreateSub(LHS, V); 1128 1129 if (Value *V = checkForNegativeOperand(I, Builder)) 1130 return ReplaceInstUsesWith(I, V); 1131 1132 // A+B --> A|B iff A and B have no bits set in common. 1133 if (IntegerType *IT = dyn_cast<IntegerType>(I.getType())) { 1134 APInt LHSKnownOne(IT->getBitWidth(), 0); 1135 APInt LHSKnownZero(IT->getBitWidth(), 0); 1136 computeKnownBits(LHS, LHSKnownZero, LHSKnownOne); 1137 if (LHSKnownZero != 0) { 1138 APInt RHSKnownOne(IT->getBitWidth(), 0); 1139 APInt RHSKnownZero(IT->getBitWidth(), 0); 1140 computeKnownBits(RHS, RHSKnownZero, RHSKnownOne); 1141 1142 // No bits in common -> bitwise or. 1143 if ((LHSKnownZero|RHSKnownZero).isAllOnesValue()) 1144 return BinaryOperator::CreateOr(LHS, RHS); 1145 } 1146 } 1147 1148 if (Constant *CRHS = dyn_cast<Constant>(RHS)) { 1149 Value *X; 1150 if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X 1151 return BinaryOperator::CreateSub(SubOne(CRHS), X); 1152 } 1153 1154 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) { 1155 // (X & FF00) + xx00 -> (X+xx00) & FF00 1156 Value *X; 1157 ConstantInt *C2; 1158 if (LHS->hasOneUse() && 1159 match(LHS, m_And(m_Value(X), m_ConstantInt(C2))) && 1160 CRHS->getValue() == (CRHS->getValue() & C2->getValue())) { 1161 // See if all bits from the first bit set in the Add RHS up are included 1162 // in the mask. First, get the rightmost bit. 1163 const APInt &AddRHSV = CRHS->getValue(); 1164 1165 // Form a mask of all bits from the lowest bit added through the top. 1166 APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1)); 1167 1168 // See if the and mask includes all of these bits. 1169 APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue()); 1170 1171 if (AddRHSHighBits == AddRHSHighBitsAnd) { 1172 // Okay, the xform is safe. Insert the new add pronto. 1173 Value *NewAdd = Builder->CreateAdd(X, CRHS, LHS->getName()); 1174 return BinaryOperator::CreateAnd(NewAdd, C2); 1175 } 1176 } 1177 1178 // Try to fold constant add into select arguments. 1179 if (SelectInst *SI = dyn_cast<SelectInst>(LHS)) 1180 if (Instruction *R = FoldOpIntoSelect(I, SI)) 1181 return R; 1182 } 1183 1184 // add (select X 0 (sub n A)) A --> select X A n 1185 { 1186 SelectInst *SI = dyn_cast<SelectInst>(LHS); 1187 Value *A = RHS; 1188 if (!SI) { 1189 SI = dyn_cast<SelectInst>(RHS); 1190 A = LHS; 1191 } 1192 if (SI && SI->hasOneUse()) { 1193 Value *TV = SI->getTrueValue(); 1194 Value *FV = SI->getFalseValue(); 1195 Value *N; 1196 1197 // Can we fold the add into the argument of the select? 1198 // We check both true and false select arguments for a matching subtract. 1199 if (match(FV, m_Zero()) && match(TV, m_Sub(m_Value(N), m_Specific(A)))) 1200 // Fold the add into the true select value. 1201 return SelectInst::Create(SI->getCondition(), N, A); 1202 1203 if (match(TV, m_Zero()) && match(FV, m_Sub(m_Value(N), m_Specific(A)))) 1204 // Fold the add into the false select value. 1205 return SelectInst::Create(SI->getCondition(), A, N); 1206 } 1207 } 1208 1209 // Check for (add (sext x), y), see if we can merge this into an 1210 // integer add followed by a sext. 1211 if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) { 1212 // (add (sext x), cst) --> (sext (add x, cst')) 1213 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) { 1214 Constant *CI = 1215 ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType()); 1216 if (LHSConv->hasOneUse() && 1217 ConstantExpr::getSExt(CI, I.getType()) == RHSC && 1218 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) { 1219 // Insert the new, smaller add. 1220 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1221 CI, "addconv"); 1222 return new SExtInst(NewAdd, I.getType()); 1223 } 1224 } 1225 1226 // (add (sext x), (sext y)) --> (sext (add int x, y)) 1227 if (SExtInst *RHSConv = dyn_cast<SExtInst>(RHS)) { 1228 // Only do this if x/y have the same type, if at last one of them has a 1229 // single use (so we don't increase the number of sexts), and if the 1230 // integer add will not overflow. 1231 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&& 1232 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && 1233 WillNotOverflowSignedAdd(LHSConv->getOperand(0), 1234 RHSConv->getOperand(0))) { 1235 // Insert the new integer add. 1236 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1237 RHSConv->getOperand(0), "addconv"); 1238 return new SExtInst(NewAdd, I.getType()); 1239 } 1240 } 1241 } 1242 1243 // Check for (x & y) + (x ^ y) 1244 { 1245 Value *A = nullptr, *B = nullptr; 1246 if (match(RHS, m_Xor(m_Value(A), m_Value(B))) && 1247 (match(LHS, m_And(m_Specific(A), m_Specific(B))) || 1248 match(LHS, m_And(m_Specific(B), m_Specific(A))))) 1249 return BinaryOperator::CreateOr(A, B); 1250 1251 if (match(LHS, m_Xor(m_Value(A), m_Value(B))) && 1252 (match(RHS, m_And(m_Specific(A), m_Specific(B))) || 1253 match(RHS, m_And(m_Specific(B), m_Specific(A))))) 1254 return BinaryOperator::CreateOr(A, B); 1255 } 1256 1257 // TODO(jingyue): Consider WillNotOverflowSignedAdd and 1258 // WillNotOverflowUnsignedAdd to reduce the number of invocations of 1259 // computeKnownBits. 1260 if (!I.hasNoSignedWrap() && WillNotOverflowSignedAdd(LHS, RHS)) { 1261 Changed = true; 1262 I.setHasNoSignedWrap(true); 1263 } 1264 if (!I.hasNoUnsignedWrap() && WillNotOverflowUnsignedAdd(LHS, RHS)) { 1265 Changed = true; 1266 I.setHasNoUnsignedWrap(true); 1267 } 1268 1269 return Changed ? &I : nullptr; 1270 } 1271 1272 Instruction *InstCombiner::visitFAdd(BinaryOperator &I) { 1273 bool Changed = SimplifyAssociativeOrCommutative(I); 1274 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); 1275 1276 if (Value *V = SimplifyVectorOp(I)) 1277 return ReplaceInstUsesWith(I, V); 1278 1279 if (Value *V = SimplifyFAddInst(LHS, RHS, I.getFastMathFlags(), DL)) 1280 return ReplaceInstUsesWith(I, V); 1281 1282 if (isa<Constant>(RHS)) { 1283 if (isa<PHINode>(LHS)) 1284 if (Instruction *NV = FoldOpIntoPhi(I)) 1285 return NV; 1286 1287 if (SelectInst *SI = dyn_cast<SelectInst>(LHS)) 1288 if (Instruction *NV = FoldOpIntoSelect(I, SI)) 1289 return NV; 1290 } 1291 1292 // -A + B --> B - A 1293 // -A + -B --> -(A + B) 1294 if (Value *LHSV = dyn_castFNegVal(LHS)) { 1295 Instruction *RI = BinaryOperator::CreateFSub(RHS, LHSV); 1296 RI->copyFastMathFlags(&I); 1297 return RI; 1298 } 1299 1300 // A + -B --> A - B 1301 if (!isa<Constant>(RHS)) 1302 if (Value *V = dyn_castFNegVal(RHS)) { 1303 Instruction *RI = BinaryOperator::CreateFSub(LHS, V); 1304 RI->copyFastMathFlags(&I); 1305 return RI; 1306 } 1307 1308 // Check for (fadd double (sitofp x), y), see if we can merge this into an 1309 // integer add followed by a promotion. 1310 if (SIToFPInst *LHSConv = dyn_cast<SIToFPInst>(LHS)) { 1311 // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst)) 1312 // ... if the constant fits in the integer value. This is useful for things 1313 // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer 1314 // requires a constant pool load, and generally allows the add to be better 1315 // instcombined. 1316 if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHS)) { 1317 Constant *CI = 1318 ConstantExpr::getFPToSI(CFP, LHSConv->getOperand(0)->getType()); 1319 if (LHSConv->hasOneUse() && 1320 ConstantExpr::getSIToFP(CI, I.getType()) == CFP && 1321 WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI)) { 1322 // Insert the new integer add. 1323 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1324 CI, "addconv"); 1325 return new SIToFPInst(NewAdd, I.getType()); 1326 } 1327 } 1328 1329 // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y)) 1330 if (SIToFPInst *RHSConv = dyn_cast<SIToFPInst>(RHS)) { 1331 // Only do this if x/y have the same type, if at last one of them has a 1332 // single use (so we don't increase the number of int->fp conversions), 1333 // and if the integer add will not overflow. 1334 if (LHSConv->getOperand(0)->getType()==RHSConv->getOperand(0)->getType()&& 1335 (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && 1336 WillNotOverflowSignedAdd(LHSConv->getOperand(0), 1337 RHSConv->getOperand(0))) { 1338 // Insert the new integer add. 1339 Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0), 1340 RHSConv->getOperand(0),"addconv"); 1341 return new SIToFPInst(NewAdd, I.getType()); 1342 } 1343 } 1344 } 1345 1346 // select C, 0, B + select C, A, 0 -> select C, A, B 1347 { 1348 Value *A1, *B1, *C1, *A2, *B2, *C2; 1349 if (match(LHS, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) && 1350 match(RHS, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) { 1351 if (C1 == C2) { 1352 Constant *Z1=nullptr, *Z2=nullptr; 1353 Value *A, *B, *C=C1; 1354 if (match(A1, m_AnyZero()) && match(B2, m_AnyZero())) { 1355 Z1 = dyn_cast<Constant>(A1); A = A2; 1356 Z2 = dyn_cast<Constant>(B2); B = B1; 1357 } else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) { 1358 Z1 = dyn_cast<Constant>(B1); B = B2; 1359 Z2 = dyn_cast<Constant>(A2); A = A1; 1360 } 1361 1362 if (Z1 && Z2 && 1363 (I.hasNoSignedZeros() || 1364 (Z1->isNegativeZeroValue() && Z2->isNegativeZeroValue()))) { 1365 return SelectInst::Create(C, A, B); 1366 } 1367 } 1368 } 1369 } 1370 1371 if (I.hasUnsafeAlgebra()) { 1372 if (Value *V = FAddCombine(Builder).simplify(&I)) 1373 return ReplaceInstUsesWith(I, V); 1374 } 1375 1376 return Changed ? &I : nullptr; 1377 } 1378 1379 1380 /// Optimize pointer differences into the same array into a size. Consider: 1381 /// &A[10] - &A[0]: we should compile this to "10". LHS/RHS are the pointer 1382 /// operands to the ptrtoint instructions for the LHS/RHS of the subtract. 1383 /// 1384 Value *InstCombiner::OptimizePointerDifference(Value *LHS, Value *RHS, 1385 Type *Ty) { 1386 assert(DL && "Must have target data info for this"); 1387 1388 // If LHS is a gep based on RHS or RHS is a gep based on LHS, we can optimize 1389 // this. 1390 bool Swapped = false; 1391 GEPOperator *GEP1 = nullptr, *GEP2 = nullptr; 1392 1393 // For now we require one side to be the base pointer "A" or a constant 1394 // GEP derived from it. 1395 if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) { 1396 // (gep X, ...) - X 1397 if (LHSGEP->getOperand(0) == RHS) { 1398 GEP1 = LHSGEP; 1399 Swapped = false; 1400 } else if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) { 1401 // (gep X, ...) - (gep X, ...) 1402 if (LHSGEP->getOperand(0)->stripPointerCasts() == 1403 RHSGEP->getOperand(0)->stripPointerCasts()) { 1404 GEP2 = RHSGEP; 1405 GEP1 = LHSGEP; 1406 Swapped = false; 1407 } 1408 } 1409 } 1410 1411 if (GEPOperator *RHSGEP = dyn_cast<GEPOperator>(RHS)) { 1412 // X - (gep X, ...) 1413 if (RHSGEP->getOperand(0) == LHS) { 1414 GEP1 = RHSGEP; 1415 Swapped = true; 1416 } else if (GEPOperator *LHSGEP = dyn_cast<GEPOperator>(LHS)) { 1417 // (gep X, ...) - (gep X, ...) 1418 if (RHSGEP->getOperand(0)->stripPointerCasts() == 1419 LHSGEP->getOperand(0)->stripPointerCasts()) { 1420 GEP2 = LHSGEP; 1421 GEP1 = RHSGEP; 1422 Swapped = true; 1423 } 1424 } 1425 } 1426 1427 // Avoid duplicating the arithmetic if GEP2 has non-constant indices and 1428 // multiple users. 1429 if (!GEP1 || 1430 (GEP2 && !GEP2->hasAllConstantIndices() && !GEP2->hasOneUse())) 1431 return nullptr; 1432 1433 // Emit the offset of the GEP and an intptr_t. 1434 Value *Result = EmitGEPOffset(GEP1); 1435 1436 // If we had a constant expression GEP on the other side offsetting the 1437 // pointer, subtract it from the offset we have. 1438 if (GEP2) { 1439 Value *Offset = EmitGEPOffset(GEP2); 1440 Result = Builder->CreateSub(Result, Offset); 1441 } 1442 1443 // If we have p - gep(p, ...) then we have to negate the result. 1444 if (Swapped) 1445 Result = Builder->CreateNeg(Result, "diff.neg"); 1446 1447 return Builder->CreateIntCast(Result, Ty, true); 1448 } 1449 1450 1451 Instruction *InstCombiner::visitSub(BinaryOperator &I) { 1452 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 1453 1454 if (Value *V = SimplifyVectorOp(I)) 1455 return ReplaceInstUsesWith(I, V); 1456 1457 if (Value *V = SimplifySubInst(Op0, Op1, I.hasNoSignedWrap(), 1458 I.hasNoUnsignedWrap(), DL)) 1459 return ReplaceInstUsesWith(I, V); 1460 1461 // (A*B)-(A*C) -> A*(B-C) etc 1462 if (Value *V = SimplifyUsingDistributiveLaws(I)) 1463 return ReplaceInstUsesWith(I, V); 1464 1465 // If this is a 'B = x-(-A)', change to B = x+A. This preserves NSW/NUW. 1466 if (Value *V = dyn_castNegVal(Op1)) { 1467 BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V); 1468 Res->setHasNoSignedWrap(I.hasNoSignedWrap()); 1469 Res->setHasNoUnsignedWrap(I.hasNoUnsignedWrap()); 1470 return Res; 1471 } 1472 1473 if (I.getType()->isIntegerTy(1)) 1474 return BinaryOperator::CreateXor(Op0, Op1); 1475 1476 // Replace (-1 - A) with (~A). 1477 if (match(Op0, m_AllOnes())) 1478 return BinaryOperator::CreateNot(Op1); 1479 1480 if (Constant *C = dyn_cast<Constant>(Op0)) { 1481 // C - ~X == X + (1+C) 1482 Value *X = nullptr; 1483 if (match(Op1, m_Not(m_Value(X)))) 1484 return BinaryOperator::CreateAdd(X, AddOne(C)); 1485 1486 // Try to fold constant sub into select arguments. 1487 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) 1488 if (Instruction *R = FoldOpIntoSelect(I, SI)) 1489 return R; 1490 1491 // C-(X+C2) --> (C-C2)-X 1492 Constant *C2; 1493 if (match(Op1, m_Add(m_Value(X), m_Constant(C2)))) 1494 return BinaryOperator::CreateSub(ConstantExpr::getSub(C, C2), X); 1495 1496 if (SimplifyDemandedInstructionBits(I)) 1497 return &I; 1498 1499 // Fold (sub 0, (zext bool to B)) --> (sext bool to B) 1500 if (C->isNullValue() && match(Op1, m_ZExt(m_Value(X)))) 1501 if (X->getType()->getScalarType()->isIntegerTy(1)) 1502 return CastInst::CreateSExtOrBitCast(X, Op1->getType()); 1503 1504 // Fold (sub 0, (sext bool to B)) --> (zext bool to B) 1505 if (C->isNullValue() && match(Op1, m_SExt(m_Value(X)))) 1506 if (X->getType()->getScalarType()->isIntegerTy(1)) 1507 return CastInst::CreateZExtOrBitCast(X, Op1->getType()); 1508 } 1509 1510 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) { 1511 // -(X >>u 31) -> (X >>s 31) 1512 // -(X >>s 31) -> (X >>u 31) 1513 if (C->isZero()) { 1514 Value *X; ConstantInt *CI; 1515 if (match(Op1, m_LShr(m_Value(X), m_ConstantInt(CI))) && 1516 // Verify we are shifting out everything but the sign bit. 1517 CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1) 1518 return BinaryOperator::CreateAShr(X, CI); 1519 1520 if (match(Op1, m_AShr(m_Value(X), m_ConstantInt(CI))) && 1521 // Verify we are shifting out everything but the sign bit. 1522 CI->getValue() == I.getType()->getPrimitiveSizeInBits()-1) 1523 return BinaryOperator::CreateLShr(X, CI); 1524 } 1525 } 1526 1527 1528 { Value *Y; 1529 // X-(X+Y) == -Y X-(Y+X) == -Y 1530 if (match(Op1, m_Add(m_Specific(Op0), m_Value(Y))) || 1531 match(Op1, m_Add(m_Value(Y), m_Specific(Op0)))) 1532 return BinaryOperator::CreateNeg(Y); 1533 1534 // (X-Y)-X == -Y 1535 if (match(Op0, m_Sub(m_Specific(Op1), m_Value(Y)))) 1536 return BinaryOperator::CreateNeg(Y); 1537 } 1538 1539 if (Op1->hasOneUse()) { 1540 Value *X = nullptr, *Y = nullptr, *Z = nullptr; 1541 Constant *C = nullptr; 1542 Constant *CI = nullptr; 1543 1544 // (X - (Y - Z)) --> (X + (Z - Y)). 1545 if (match(Op1, m_Sub(m_Value(Y), m_Value(Z)))) 1546 return BinaryOperator::CreateAdd(Op0, 1547 Builder->CreateSub(Z, Y, Op1->getName())); 1548 1549 // (X - (X & Y)) --> (X & ~Y) 1550 // 1551 if (match(Op1, m_And(m_Value(Y), m_Specific(Op0))) || 1552 match(Op1, m_And(m_Specific(Op0), m_Value(Y)))) 1553 return BinaryOperator::CreateAnd(Op0, 1554 Builder->CreateNot(Y, Y->getName() + ".not")); 1555 1556 // 0 - (X sdiv C) -> (X sdiv -C) provided the negation doesn't overflow. 1557 if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) && match(Op0, m_Zero()) && 1558 !C->isMinSignedValue()) 1559 return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C)); 1560 1561 // 0 - (X << Y) -> (-X << Y) when X is freely negatable. 1562 if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero())) 1563 if (Value *XNeg = dyn_castNegVal(X)) 1564 return BinaryOperator::CreateShl(XNeg, Y); 1565 1566 // X - A*-B -> X + A*B 1567 // X - -A*B -> X + A*B 1568 Value *A, *B; 1569 if (match(Op1, m_Mul(m_Value(A), m_Neg(m_Value(B)))) || 1570 match(Op1, m_Mul(m_Neg(m_Value(A)), m_Value(B)))) 1571 return BinaryOperator::CreateAdd(Op0, Builder->CreateMul(A, B)); 1572 1573 // X - A*CI -> X + A*-CI 1574 // X - CI*A -> X + A*-CI 1575 if (match(Op1, m_Mul(m_Value(A), m_Constant(CI))) || 1576 match(Op1, m_Mul(m_Constant(CI), m_Value(A)))) { 1577 Value *NewMul = Builder->CreateMul(A, ConstantExpr::getNeg(CI)); 1578 return BinaryOperator::CreateAdd(Op0, NewMul); 1579 } 1580 } 1581 1582 // Optimize pointer differences into the same array into a size. Consider: 1583 // &A[10] - &A[0]: we should compile this to "10". 1584 if (DL) { 1585 Value *LHSOp, *RHSOp; 1586 if (match(Op0, m_PtrToInt(m_Value(LHSOp))) && 1587 match(Op1, m_PtrToInt(m_Value(RHSOp)))) 1588 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType())) 1589 return ReplaceInstUsesWith(I, Res); 1590 1591 // trunc(p)-trunc(q) -> trunc(p-q) 1592 if (match(Op0, m_Trunc(m_PtrToInt(m_Value(LHSOp)))) && 1593 match(Op1, m_Trunc(m_PtrToInt(m_Value(RHSOp))))) 1594 if (Value *Res = OptimizePointerDifference(LHSOp, RHSOp, I.getType())) 1595 return ReplaceInstUsesWith(I, Res); 1596 } 1597 1598 return nullptr; 1599 } 1600 1601 Instruction *InstCombiner::visitFSub(BinaryOperator &I) { 1602 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); 1603 1604 if (Value *V = SimplifyVectorOp(I)) 1605 return ReplaceInstUsesWith(I, V); 1606 1607 if (Value *V = SimplifyFSubInst(Op0, Op1, I.getFastMathFlags(), DL)) 1608 return ReplaceInstUsesWith(I, V); 1609 1610 if (isa<Constant>(Op0)) 1611 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) 1612 if (Instruction *NV = FoldOpIntoSelect(I, SI)) 1613 return NV; 1614 1615 // If this is a 'B = x-(-A)', change to B = x+A, potentially looking 1616 // through FP extensions/truncations along the way. 1617 if (Value *V = dyn_castFNegVal(Op1)) { 1618 Instruction *NewI = BinaryOperator::CreateFAdd(Op0, V); 1619 NewI->copyFastMathFlags(&I); 1620 return NewI; 1621 } 1622 if (FPTruncInst *FPTI = dyn_cast<FPTruncInst>(Op1)) { 1623 if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) { 1624 Value *NewTrunc = Builder->CreateFPTrunc(V, I.getType()); 1625 Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewTrunc); 1626 NewI->copyFastMathFlags(&I); 1627 return NewI; 1628 } 1629 } else if (FPExtInst *FPEI = dyn_cast<FPExtInst>(Op1)) { 1630 if (Value *V = dyn_castFNegVal(FPEI->getOperand(0))) { 1631 Value *NewExt = Builder->CreateFPExt(V, I.getType()); 1632 Instruction *NewI = BinaryOperator::CreateFAdd(Op0, NewExt); 1633 NewI->copyFastMathFlags(&I); 1634 return NewI; 1635 } 1636 } 1637 1638 if (I.hasUnsafeAlgebra()) { 1639 if (Value *V = FAddCombine(Builder).simplify(&I)) 1640 return ReplaceInstUsesWith(I, V); 1641 } 1642 1643 return nullptr; 1644 } 1645