1//===- InstCombineVectorOps.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 instcombine for ExtractElement, InsertElement and 11// ShuffleVector. 12// 13//===----------------------------------------------------------------------===// 14 15#include "InstCombine.h" 16#include "llvm/IR/PatternMatch.h" 17using namespace llvm; 18using namespace PatternMatch; 19 20#define DEBUG_TYPE "instcombine" 21 22/// CheapToScalarize - Return true if the value is cheaper to scalarize than it 23/// is to leave as a vector operation. isConstant indicates whether we're 24/// extracting one known element. If false we're extracting a variable index. 25static bool CheapToScalarize(Value *V, bool isConstant) { 26 if (Constant *C = dyn_cast<Constant>(V)) { 27 if (isConstant) return true; 28 29 // If all elts are the same, we can extract it and use any of the values. 30 if (Constant *Op0 = C->getAggregateElement(0U)) { 31 for (unsigned i = 1, e = V->getType()->getVectorNumElements(); i != e; 32 ++i) 33 if (C->getAggregateElement(i) != Op0) 34 return false; 35 return true; 36 } 37 } 38 Instruction *I = dyn_cast<Instruction>(V); 39 if (!I) return false; 40 41 // Insert element gets simplified to the inserted element or is deleted if 42 // this is constant idx extract element and its a constant idx insertelt. 43 if (I->getOpcode() == Instruction::InsertElement && isConstant && 44 isa<ConstantInt>(I->getOperand(2))) 45 return true; 46 if (I->getOpcode() == Instruction::Load && I->hasOneUse()) 47 return true; 48 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) 49 if (BO->hasOneUse() && 50 (CheapToScalarize(BO->getOperand(0), isConstant) || 51 CheapToScalarize(BO->getOperand(1), isConstant))) 52 return true; 53 if (CmpInst *CI = dyn_cast<CmpInst>(I)) 54 if (CI->hasOneUse() && 55 (CheapToScalarize(CI->getOperand(0), isConstant) || 56 CheapToScalarize(CI->getOperand(1), isConstant))) 57 return true; 58 59 return false; 60} 61 62/// FindScalarElement - Given a vector and an element number, see if the scalar 63/// value is already around as a register, for example if it were inserted then 64/// extracted from the vector. 65static Value *FindScalarElement(Value *V, unsigned EltNo) { 66 assert(V->getType()->isVectorTy() && "Not looking at a vector?"); 67 VectorType *VTy = cast<VectorType>(V->getType()); 68 unsigned Width = VTy->getNumElements(); 69 if (EltNo >= Width) // Out of range access. 70 return UndefValue::get(VTy->getElementType()); 71 72 if (Constant *C = dyn_cast<Constant>(V)) 73 return C->getAggregateElement(EltNo); 74 75 if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) { 76 // If this is an insert to a variable element, we don't know what it is. 77 if (!isa<ConstantInt>(III->getOperand(2))) 78 return nullptr; 79 unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue(); 80 81 // If this is an insert to the element we are looking for, return the 82 // inserted value. 83 if (EltNo == IIElt) 84 return III->getOperand(1); 85 86 // Otherwise, the insertelement doesn't modify the value, recurse on its 87 // vector input. 88 return FindScalarElement(III->getOperand(0), EltNo); 89 } 90 91 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) { 92 unsigned LHSWidth = SVI->getOperand(0)->getType()->getVectorNumElements(); 93 int InEl = SVI->getMaskValue(EltNo); 94 if (InEl < 0) 95 return UndefValue::get(VTy->getElementType()); 96 if (InEl < (int)LHSWidth) 97 return FindScalarElement(SVI->getOperand(0), InEl); 98 return FindScalarElement(SVI->getOperand(1), InEl - LHSWidth); 99 } 100 101 // Extract a value from a vector add operation with a constant zero. 102 Value *Val = nullptr; Constant *Con = nullptr; 103 if (match(V, m_Add(m_Value(Val), m_Constant(Con)))) { 104 if (Con->getAggregateElement(EltNo)->isNullValue()) 105 return FindScalarElement(Val, EltNo); 106 } 107 108 // Otherwise, we don't know. 109 return nullptr; 110} 111 112// If we have a PHI node with a vector type that has only 2 uses: feed 113// itself and be an operand of extractelement at a constant location, 114// try to replace the PHI of the vector type with a PHI of a scalar type. 115Instruction *InstCombiner::scalarizePHI(ExtractElementInst &EI, PHINode *PN) { 116 // Verify that the PHI node has exactly 2 uses. Otherwise return NULL. 117 if (!PN->hasNUses(2)) 118 return nullptr; 119 120 // If so, it's known at this point that one operand is PHI and the other is 121 // an extractelement node. Find the PHI user that is not the extractelement 122 // node. 123 auto iu = PN->user_begin(); 124 Instruction *PHIUser = dyn_cast<Instruction>(*iu); 125 if (PHIUser == cast<Instruction>(&EI)) 126 PHIUser = cast<Instruction>(*(++iu)); 127 128 // Verify that this PHI user has one use, which is the PHI itself, 129 // and that it is a binary operation which is cheap to scalarize. 130 // otherwise return NULL. 131 if (!PHIUser->hasOneUse() || !(PHIUser->user_back() == PN) || 132 !(isa<BinaryOperator>(PHIUser)) || !CheapToScalarize(PHIUser, true)) 133 return nullptr; 134 135 // Create a scalar PHI node that will replace the vector PHI node 136 // just before the current PHI node. 137 PHINode *scalarPHI = cast<PHINode>(InsertNewInstWith( 138 PHINode::Create(EI.getType(), PN->getNumIncomingValues(), ""), *PN)); 139 // Scalarize each PHI operand. 140 for (unsigned i = 0; i < PN->getNumIncomingValues(); i++) { 141 Value *PHIInVal = PN->getIncomingValue(i); 142 BasicBlock *inBB = PN->getIncomingBlock(i); 143 Value *Elt = EI.getIndexOperand(); 144 // If the operand is the PHI induction variable: 145 if (PHIInVal == PHIUser) { 146 // Scalarize the binary operation. Its first operand is the 147 // scalar PHI, and the second operand is extracted from the other 148 // vector operand. 149 BinaryOperator *B0 = cast<BinaryOperator>(PHIUser); 150 unsigned opId = (B0->getOperand(0) == PN) ? 1 : 0; 151 Value *Op = InsertNewInstWith( 152 ExtractElementInst::Create(B0->getOperand(opId), Elt, 153 B0->getOperand(opId)->getName() + ".Elt"), 154 *B0); 155 Value *newPHIUser = InsertNewInstWith( 156 BinaryOperator::Create(B0->getOpcode(), scalarPHI, Op), *B0); 157 scalarPHI->addIncoming(newPHIUser, inBB); 158 } else { 159 // Scalarize PHI input: 160 Instruction *newEI = ExtractElementInst::Create(PHIInVal, Elt, ""); 161 // Insert the new instruction into the predecessor basic block. 162 Instruction *pos = dyn_cast<Instruction>(PHIInVal); 163 BasicBlock::iterator InsertPos; 164 if (pos && !isa<PHINode>(pos)) { 165 InsertPos = pos; 166 ++InsertPos; 167 } else { 168 InsertPos = inBB->getFirstInsertionPt(); 169 } 170 171 InsertNewInstWith(newEI, *InsertPos); 172 173 scalarPHI->addIncoming(newEI, inBB); 174 } 175 } 176 return ReplaceInstUsesWith(EI, scalarPHI); 177} 178 179Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) { 180 // If vector val is constant with all elements the same, replace EI with 181 // that element. We handle a known element # below. 182 if (Constant *C = dyn_cast<Constant>(EI.getOperand(0))) 183 if (CheapToScalarize(C, false)) 184 return ReplaceInstUsesWith(EI, C->getAggregateElement(0U)); 185 186 // If extracting a specified index from the vector, see if we can recursively 187 // find a previously computed scalar that was inserted into the vector. 188 if (ConstantInt *IdxC = dyn_cast<ConstantInt>(EI.getOperand(1))) { 189 unsigned IndexVal = IdxC->getZExtValue(); 190 unsigned VectorWidth = EI.getVectorOperandType()->getNumElements(); 191 192 // If this is extracting an invalid index, turn this into undef, to avoid 193 // crashing the code below. 194 if (IndexVal >= VectorWidth) 195 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType())); 196 197 // This instruction only demands the single element from the input vector. 198 // If the input vector has a single use, simplify it based on this use 199 // property. 200 if (EI.getOperand(0)->hasOneUse() && VectorWidth != 1) { 201 APInt UndefElts(VectorWidth, 0); 202 APInt DemandedMask(VectorWidth, 0); 203 DemandedMask.setBit(IndexVal); 204 if (Value *V = SimplifyDemandedVectorElts(EI.getOperand(0), 205 DemandedMask, UndefElts)) { 206 EI.setOperand(0, V); 207 return &EI; 208 } 209 } 210 211 if (Value *Elt = FindScalarElement(EI.getOperand(0), IndexVal)) 212 return ReplaceInstUsesWith(EI, Elt); 213 214 // If the this extractelement is directly using a bitcast from a vector of 215 // the same number of elements, see if we can find the source element from 216 // it. In this case, we will end up needing to bitcast the scalars. 217 if (BitCastInst *BCI = dyn_cast<BitCastInst>(EI.getOperand(0))) { 218 if (VectorType *VT = dyn_cast<VectorType>(BCI->getOperand(0)->getType())) 219 if (VT->getNumElements() == VectorWidth) 220 if (Value *Elt = FindScalarElement(BCI->getOperand(0), IndexVal)) 221 return new BitCastInst(Elt, EI.getType()); 222 } 223 224 // If there's a vector PHI feeding a scalar use through this extractelement 225 // instruction, try to scalarize the PHI. 226 if (PHINode *PN = dyn_cast<PHINode>(EI.getOperand(0))) { 227 Instruction *scalarPHI = scalarizePHI(EI, PN); 228 if (scalarPHI) 229 return scalarPHI; 230 } 231 } 232 233 if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) { 234 // Push extractelement into predecessor operation if legal and 235 // profitable to do so 236 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) { 237 if (I->hasOneUse() && 238 CheapToScalarize(BO, isa<ConstantInt>(EI.getOperand(1)))) { 239 Value *newEI0 = 240 Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1), 241 EI.getName()+".lhs"); 242 Value *newEI1 = 243 Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1), 244 EI.getName()+".rhs"); 245 return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1); 246 } 247 } else if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) { 248 // Extracting the inserted element? 249 if (IE->getOperand(2) == EI.getOperand(1)) 250 return ReplaceInstUsesWith(EI, IE->getOperand(1)); 251 // If the inserted and extracted elements are constants, they must not 252 // be the same value, extract from the pre-inserted value instead. 253 if (isa<Constant>(IE->getOperand(2)) && isa<Constant>(EI.getOperand(1))) { 254 Worklist.AddValue(EI.getOperand(0)); 255 EI.setOperand(0, IE->getOperand(0)); 256 return &EI; 257 } 258 } else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I)) { 259 // If this is extracting an element from a shufflevector, figure out where 260 // it came from and extract from the appropriate input element instead. 261 if (ConstantInt *Elt = dyn_cast<ConstantInt>(EI.getOperand(1))) { 262 int SrcIdx = SVI->getMaskValue(Elt->getZExtValue()); 263 Value *Src; 264 unsigned LHSWidth = 265 SVI->getOperand(0)->getType()->getVectorNumElements(); 266 267 if (SrcIdx < 0) 268 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType())); 269 if (SrcIdx < (int)LHSWidth) 270 Src = SVI->getOperand(0); 271 else { 272 SrcIdx -= LHSWidth; 273 Src = SVI->getOperand(1); 274 } 275 Type *Int32Ty = Type::getInt32Ty(EI.getContext()); 276 return ExtractElementInst::Create(Src, 277 ConstantInt::get(Int32Ty, 278 SrcIdx, false)); 279 } 280 } else if (CastInst *CI = dyn_cast<CastInst>(I)) { 281 // Canonicalize extractelement(cast) -> cast(extractelement) 282 // bitcasts can change the number of vector elements and they cost nothing 283 if (CI->hasOneUse() && (CI->getOpcode() != Instruction::BitCast)) { 284 Value *EE = Builder->CreateExtractElement(CI->getOperand(0), 285 EI.getIndexOperand()); 286 Worklist.AddValue(EE); 287 return CastInst::Create(CI->getOpcode(), EE, EI.getType()); 288 } 289 } else if (SelectInst *SI = dyn_cast<SelectInst>(I)) { 290 if (SI->hasOneUse()) { 291 // TODO: For a select on vectors, it might be useful to do this if it 292 // has multiple extractelement uses. For vector select, that seems to 293 // fight the vectorizer. 294 295 // If we are extracting an element from a vector select or a select on 296 // vectors, a select on the scalars extracted from the vector arguments. 297 Value *TrueVal = SI->getTrueValue(); 298 Value *FalseVal = SI->getFalseValue(); 299 300 Value *Cond = SI->getCondition(); 301 if (Cond->getType()->isVectorTy()) { 302 Cond = Builder->CreateExtractElement(Cond, 303 EI.getIndexOperand(), 304 Cond->getName() + ".elt"); 305 } 306 307 Value *V1Elem 308 = Builder->CreateExtractElement(TrueVal, 309 EI.getIndexOperand(), 310 TrueVal->getName() + ".elt"); 311 312 Value *V2Elem 313 = Builder->CreateExtractElement(FalseVal, 314 EI.getIndexOperand(), 315 FalseVal->getName() + ".elt"); 316 return SelectInst::Create(Cond, 317 V1Elem, 318 V2Elem, 319 SI->getName() + ".elt"); 320 } 321 } 322 } 323 return nullptr; 324} 325 326/// CollectSingleShuffleElements - If V is a shuffle of values that ONLY returns 327/// elements from either LHS or RHS, return the shuffle mask and true. 328/// Otherwise, return false. 329static bool CollectSingleShuffleElements(Value *V, Value *LHS, Value *RHS, 330 SmallVectorImpl<Constant*> &Mask) { 331 assert(LHS->getType() == RHS->getType() && 332 "Invalid CollectSingleShuffleElements"); 333 unsigned NumElts = V->getType()->getVectorNumElements(); 334 335 if (isa<UndefValue>(V)) { 336 Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext()))); 337 return true; 338 } 339 340 if (V == LHS) { 341 for (unsigned i = 0; i != NumElts; ++i) 342 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), i)); 343 return true; 344 } 345 346 if (V == RHS) { 347 for (unsigned i = 0; i != NumElts; ++i) 348 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), 349 i+NumElts)); 350 return true; 351 } 352 353 if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) { 354 // If this is an insert of an extract from some other vector, include it. 355 Value *VecOp = IEI->getOperand(0); 356 Value *ScalarOp = IEI->getOperand(1); 357 Value *IdxOp = IEI->getOperand(2); 358 359 if (!isa<ConstantInt>(IdxOp)) 360 return false; 361 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue(); 362 363 if (isa<UndefValue>(ScalarOp)) { // inserting undef into vector. 364 // We can handle this if the vector we are inserting into is 365 // transitively ok. 366 if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) { 367 // If so, update the mask to reflect the inserted undef. 368 Mask[InsertedIdx] = UndefValue::get(Type::getInt32Ty(V->getContext())); 369 return true; 370 } 371 } else if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)){ 372 if (isa<ConstantInt>(EI->getOperand(1))) { 373 unsigned ExtractedIdx = 374 cast<ConstantInt>(EI->getOperand(1))->getZExtValue(); 375 unsigned NumLHSElts = LHS->getType()->getVectorNumElements(); 376 377 // This must be extracting from either LHS or RHS. 378 if (EI->getOperand(0) == LHS || EI->getOperand(0) == RHS) { 379 // We can handle this if the vector we are inserting into is 380 // transitively ok. 381 if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) { 382 // If so, update the mask to reflect the inserted value. 383 if (EI->getOperand(0) == LHS) { 384 Mask[InsertedIdx % NumElts] = 385 ConstantInt::get(Type::getInt32Ty(V->getContext()), 386 ExtractedIdx); 387 } else { 388 assert(EI->getOperand(0) == RHS); 389 Mask[InsertedIdx % NumElts] = 390 ConstantInt::get(Type::getInt32Ty(V->getContext()), 391 ExtractedIdx + NumLHSElts); 392 } 393 return true; 394 } 395 } 396 } 397 } 398 } 399 400 return false; 401} 402 403 404/// We are building a shuffle to create V, which is a sequence of insertelement, 405/// extractelement pairs. If PermittedRHS is set, then we must either use it or 406/// not rely on the second vector source. Return a std::pair containing the 407/// left and right vectors of the proposed shuffle (or 0), and set the Mask 408/// parameter as required. 409/// 410/// Note: we intentionally don't try to fold earlier shuffles since they have 411/// often been chosen carefully to be efficiently implementable on the target. 412typedef std::pair<Value *, Value *> ShuffleOps; 413 414static ShuffleOps CollectShuffleElements(Value *V, 415 SmallVectorImpl<Constant *> &Mask, 416 Value *PermittedRHS) { 417 assert(V->getType()->isVectorTy() && "Invalid shuffle!"); 418 unsigned NumElts = cast<VectorType>(V->getType())->getNumElements(); 419 420 if (isa<UndefValue>(V)) { 421 Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext()))); 422 return std::make_pair( 423 PermittedRHS ? UndefValue::get(PermittedRHS->getType()) : V, nullptr); 424 } 425 426 if (isa<ConstantAggregateZero>(V)) { 427 Mask.assign(NumElts, ConstantInt::get(Type::getInt32Ty(V->getContext()),0)); 428 return std::make_pair(V, nullptr); 429 } 430 431 if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) { 432 // If this is an insert of an extract from some other vector, include it. 433 Value *VecOp = IEI->getOperand(0); 434 Value *ScalarOp = IEI->getOperand(1); 435 Value *IdxOp = IEI->getOperand(2); 436 437 if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) { 438 if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp)) { 439 unsigned ExtractedIdx = 440 cast<ConstantInt>(EI->getOperand(1))->getZExtValue(); 441 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue(); 442 443 // Either the extracted from or inserted into vector must be RHSVec, 444 // otherwise we'd end up with a shuffle of three inputs. 445 if (EI->getOperand(0) == PermittedRHS || PermittedRHS == nullptr) { 446 Value *RHS = EI->getOperand(0); 447 ShuffleOps LR = CollectShuffleElements(VecOp, Mask, RHS); 448 assert(LR.second == nullptr || LR.second == RHS); 449 450 if (LR.first->getType() != RHS->getType()) { 451 // We tried our best, but we can't find anything compatible with RHS 452 // further up the chain. Return a trivial shuffle. 453 for (unsigned i = 0; i < NumElts; ++i) 454 Mask[i] = ConstantInt::get(Type::getInt32Ty(V->getContext()), i); 455 return std::make_pair(V, nullptr); 456 } 457 458 unsigned NumLHSElts = RHS->getType()->getVectorNumElements(); 459 Mask[InsertedIdx % NumElts] = 460 ConstantInt::get(Type::getInt32Ty(V->getContext()), 461 NumLHSElts+ExtractedIdx); 462 return std::make_pair(LR.first, RHS); 463 } 464 465 if (VecOp == PermittedRHS) { 466 // We've gone as far as we can: anything on the other side of the 467 // extractelement will already have been converted into a shuffle. 468 unsigned NumLHSElts = 469 EI->getOperand(0)->getType()->getVectorNumElements(); 470 for (unsigned i = 0; i != NumElts; ++i) 471 Mask.push_back(ConstantInt::get( 472 Type::getInt32Ty(V->getContext()), 473 i == InsertedIdx ? ExtractedIdx : NumLHSElts + i)); 474 return std::make_pair(EI->getOperand(0), PermittedRHS); 475 } 476 477 // If this insertelement is a chain that comes from exactly these two 478 // vectors, return the vector and the effective shuffle. 479 if (EI->getOperand(0)->getType() == PermittedRHS->getType() && 480 CollectSingleShuffleElements(IEI, EI->getOperand(0), PermittedRHS, 481 Mask)) 482 return std::make_pair(EI->getOperand(0), PermittedRHS); 483 } 484 } 485 } 486 487 // Otherwise, can't do anything fancy. Return an identity vector. 488 for (unsigned i = 0; i != NumElts; ++i) 489 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), i)); 490 return std::make_pair(V, nullptr); 491} 492 493/// Try to find redundant insertvalue instructions, like the following ones: 494/// %0 = insertvalue { i8, i32 } undef, i8 %x, 0 495/// %1 = insertvalue { i8, i32 } %0, i8 %y, 0 496/// Here the second instruction inserts values at the same indices, as the 497/// first one, making the first one redundant. 498/// It should be transformed to: 499/// %0 = insertvalue { i8, i32 } undef, i8 %y, 0 500Instruction *InstCombiner::visitInsertValueInst(InsertValueInst &I) { 501 bool IsRedundant = false; 502 ArrayRef<unsigned int> FirstIndices = I.getIndices(); 503 504 // If there is a chain of insertvalue instructions (each of them except the 505 // last one has only one use and it's another insertvalue insn from this 506 // chain), check if any of the 'children' uses the same indices as the first 507 // instruction. In this case, the first one is redundant. 508 Value *V = &I; 509 unsigned Depth = 0; 510 while (V->hasOneUse() && Depth < 10) { 511 User *U = V->user_back(); 512 auto UserInsInst = dyn_cast<InsertValueInst>(U); 513 if (!UserInsInst || U->getOperand(0) != V) 514 break; 515 if (UserInsInst->getIndices() == FirstIndices) { 516 IsRedundant = true; 517 break; 518 } 519 V = UserInsInst; 520 Depth++; 521 } 522 523 if (IsRedundant) 524 return ReplaceInstUsesWith(I, I.getOperand(0)); 525 return nullptr; 526} 527 528Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) { 529 Value *VecOp = IE.getOperand(0); 530 Value *ScalarOp = IE.getOperand(1); 531 Value *IdxOp = IE.getOperand(2); 532 533 // Inserting an undef or into an undefined place, remove this. 534 if (isa<UndefValue>(ScalarOp) || isa<UndefValue>(IdxOp)) 535 ReplaceInstUsesWith(IE, VecOp); 536 537 // If the inserted element was extracted from some other vector, and if the 538 // indexes are constant, try to turn this into a shufflevector operation. 539 if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) { 540 if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp)) { 541 unsigned NumInsertVectorElts = IE.getType()->getNumElements(); 542 unsigned NumExtractVectorElts = 543 EI->getOperand(0)->getType()->getVectorNumElements(); 544 unsigned ExtractedIdx = 545 cast<ConstantInt>(EI->getOperand(1))->getZExtValue(); 546 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue(); 547 548 if (ExtractedIdx >= NumExtractVectorElts) // Out of range extract. 549 return ReplaceInstUsesWith(IE, VecOp); 550 551 if (InsertedIdx >= NumInsertVectorElts) // Out of range insert. 552 return ReplaceInstUsesWith(IE, UndefValue::get(IE.getType())); 553 554 // If we are extracting a value from a vector, then inserting it right 555 // back into the same place, just use the input vector. 556 if (EI->getOperand(0) == VecOp && ExtractedIdx == InsertedIdx) 557 return ReplaceInstUsesWith(IE, VecOp); 558 559 // If this insertelement isn't used by some other insertelement, turn it 560 // (and any insertelements it points to), into one big shuffle. 561 if (!IE.hasOneUse() || !isa<InsertElementInst>(IE.user_back())) { 562 SmallVector<Constant*, 16> Mask; 563 ShuffleOps LR = CollectShuffleElements(&IE, Mask, nullptr); 564 565 // The proposed shuffle may be trivial, in which case we shouldn't 566 // perform the combine. 567 if (LR.first != &IE && LR.second != &IE) { 568 // We now have a shuffle of LHS, RHS, Mask. 569 if (LR.second == nullptr) 570 LR.second = UndefValue::get(LR.first->getType()); 571 return new ShuffleVectorInst(LR.first, LR.second, 572 ConstantVector::get(Mask)); 573 } 574 } 575 } 576 } 577 578 unsigned VWidth = cast<VectorType>(VecOp->getType())->getNumElements(); 579 APInt UndefElts(VWidth, 0); 580 APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); 581 if (Value *V = SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts)) { 582 if (V != &IE) 583 return ReplaceInstUsesWith(IE, V); 584 return &IE; 585 } 586 587 return nullptr; 588} 589 590/// Return true if we can evaluate the specified expression tree if the vector 591/// elements were shuffled in a different order. 592static bool CanEvaluateShuffled(Value *V, ArrayRef<int> Mask, 593 unsigned Depth = 5) { 594 // We can always reorder the elements of a constant. 595 if (isa<Constant>(V)) 596 return true; 597 598 // We won't reorder vector arguments. No IPO here. 599 Instruction *I = dyn_cast<Instruction>(V); 600 if (!I) return false; 601 602 // Two users may expect different orders of the elements. Don't try it. 603 if (!I->hasOneUse()) 604 return false; 605 606 if (Depth == 0) return false; 607 608 switch (I->getOpcode()) { 609 case Instruction::Add: 610 case Instruction::FAdd: 611 case Instruction::Sub: 612 case Instruction::FSub: 613 case Instruction::Mul: 614 case Instruction::FMul: 615 case Instruction::UDiv: 616 case Instruction::SDiv: 617 case Instruction::FDiv: 618 case Instruction::URem: 619 case Instruction::SRem: 620 case Instruction::FRem: 621 case Instruction::Shl: 622 case Instruction::LShr: 623 case Instruction::AShr: 624 case Instruction::And: 625 case Instruction::Or: 626 case Instruction::Xor: 627 case Instruction::ICmp: 628 case Instruction::FCmp: 629 case Instruction::Trunc: 630 case Instruction::ZExt: 631 case Instruction::SExt: 632 case Instruction::FPToUI: 633 case Instruction::FPToSI: 634 case Instruction::UIToFP: 635 case Instruction::SIToFP: 636 case Instruction::FPTrunc: 637 case Instruction::FPExt: 638 case Instruction::GetElementPtr: { 639 for (int i = 0, e = I->getNumOperands(); i != e; ++i) { 640 if (!CanEvaluateShuffled(I->getOperand(i), Mask, Depth-1)) 641 return false; 642 } 643 return true; 644 } 645 case Instruction::InsertElement: { 646 ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(2)); 647 if (!CI) return false; 648 int ElementNumber = CI->getLimitedValue(); 649 650 // Verify that 'CI' does not occur twice in Mask. A single 'insertelement' 651 // can't put an element into multiple indices. 652 bool SeenOnce = false; 653 for (int i = 0, e = Mask.size(); i != e; ++i) { 654 if (Mask[i] == ElementNumber) { 655 if (SeenOnce) 656 return false; 657 SeenOnce = true; 658 } 659 } 660 return CanEvaluateShuffled(I->getOperand(0), Mask, Depth-1); 661 } 662 } 663 return false; 664} 665 666/// Rebuild a new instruction just like 'I' but with the new operands given. 667/// In the event of type mismatch, the type of the operands is correct. 668static Value *BuildNew(Instruction *I, ArrayRef<Value*> NewOps) { 669 // We don't want to use the IRBuilder here because we want the replacement 670 // instructions to appear next to 'I', not the builder's insertion point. 671 switch (I->getOpcode()) { 672 case Instruction::Add: 673 case Instruction::FAdd: 674 case Instruction::Sub: 675 case Instruction::FSub: 676 case Instruction::Mul: 677 case Instruction::FMul: 678 case Instruction::UDiv: 679 case Instruction::SDiv: 680 case Instruction::FDiv: 681 case Instruction::URem: 682 case Instruction::SRem: 683 case Instruction::FRem: 684 case Instruction::Shl: 685 case Instruction::LShr: 686 case Instruction::AShr: 687 case Instruction::And: 688 case Instruction::Or: 689 case Instruction::Xor: { 690 BinaryOperator *BO = cast<BinaryOperator>(I); 691 assert(NewOps.size() == 2 && "binary operator with #ops != 2"); 692 BinaryOperator *New = 693 BinaryOperator::Create(cast<BinaryOperator>(I)->getOpcode(), 694 NewOps[0], NewOps[1], "", BO); 695 if (isa<OverflowingBinaryOperator>(BO)) { 696 New->setHasNoUnsignedWrap(BO->hasNoUnsignedWrap()); 697 New->setHasNoSignedWrap(BO->hasNoSignedWrap()); 698 } 699 if (isa<PossiblyExactOperator>(BO)) { 700 New->setIsExact(BO->isExact()); 701 } 702 if (isa<FPMathOperator>(BO)) 703 New->copyFastMathFlags(I); 704 return New; 705 } 706 case Instruction::ICmp: 707 assert(NewOps.size() == 2 && "icmp with #ops != 2"); 708 return new ICmpInst(I, cast<ICmpInst>(I)->getPredicate(), 709 NewOps[0], NewOps[1]); 710 case Instruction::FCmp: 711 assert(NewOps.size() == 2 && "fcmp with #ops != 2"); 712 return new FCmpInst(I, cast<FCmpInst>(I)->getPredicate(), 713 NewOps[0], NewOps[1]); 714 case Instruction::Trunc: 715 case Instruction::ZExt: 716 case Instruction::SExt: 717 case Instruction::FPToUI: 718 case Instruction::FPToSI: 719 case Instruction::UIToFP: 720 case Instruction::SIToFP: 721 case Instruction::FPTrunc: 722 case Instruction::FPExt: { 723 // It's possible that the mask has a different number of elements from 724 // the original cast. We recompute the destination type to match the mask. 725 Type *DestTy = 726 VectorType::get(I->getType()->getScalarType(), 727 NewOps[0]->getType()->getVectorNumElements()); 728 assert(NewOps.size() == 1 && "cast with #ops != 1"); 729 return CastInst::Create(cast<CastInst>(I)->getOpcode(), NewOps[0], DestTy, 730 "", I); 731 } 732 case Instruction::GetElementPtr: { 733 Value *Ptr = NewOps[0]; 734 ArrayRef<Value*> Idx = NewOps.slice(1); 735 GetElementPtrInst *GEP = GetElementPtrInst::Create(Ptr, Idx, "", I); 736 GEP->setIsInBounds(cast<GetElementPtrInst>(I)->isInBounds()); 737 return GEP; 738 } 739 } 740 llvm_unreachable("failed to rebuild vector instructions"); 741} 742 743Value * 744InstCombiner::EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask) { 745 // Mask.size() does not need to be equal to the number of vector elements. 746 747 assert(V->getType()->isVectorTy() && "can't reorder non-vector elements"); 748 if (isa<UndefValue>(V)) { 749 return UndefValue::get(VectorType::get(V->getType()->getScalarType(), 750 Mask.size())); 751 } 752 if (isa<ConstantAggregateZero>(V)) { 753 return ConstantAggregateZero::get( 754 VectorType::get(V->getType()->getScalarType(), 755 Mask.size())); 756 } 757 if (Constant *C = dyn_cast<Constant>(V)) { 758 SmallVector<Constant *, 16> MaskValues; 759 for (int i = 0, e = Mask.size(); i != e; ++i) { 760 if (Mask[i] == -1) 761 MaskValues.push_back(UndefValue::get(Builder->getInt32Ty())); 762 else 763 MaskValues.push_back(Builder->getInt32(Mask[i])); 764 } 765 return ConstantExpr::getShuffleVector(C, UndefValue::get(C->getType()), 766 ConstantVector::get(MaskValues)); 767 } 768 769 Instruction *I = cast<Instruction>(V); 770 switch (I->getOpcode()) { 771 case Instruction::Add: 772 case Instruction::FAdd: 773 case Instruction::Sub: 774 case Instruction::FSub: 775 case Instruction::Mul: 776 case Instruction::FMul: 777 case Instruction::UDiv: 778 case Instruction::SDiv: 779 case Instruction::FDiv: 780 case Instruction::URem: 781 case Instruction::SRem: 782 case Instruction::FRem: 783 case Instruction::Shl: 784 case Instruction::LShr: 785 case Instruction::AShr: 786 case Instruction::And: 787 case Instruction::Or: 788 case Instruction::Xor: 789 case Instruction::ICmp: 790 case Instruction::FCmp: 791 case Instruction::Trunc: 792 case Instruction::ZExt: 793 case Instruction::SExt: 794 case Instruction::FPToUI: 795 case Instruction::FPToSI: 796 case Instruction::UIToFP: 797 case Instruction::SIToFP: 798 case Instruction::FPTrunc: 799 case Instruction::FPExt: 800 case Instruction::Select: 801 case Instruction::GetElementPtr: { 802 SmallVector<Value*, 8> NewOps; 803 bool NeedsRebuild = (Mask.size() != I->getType()->getVectorNumElements()); 804 for (int i = 0, e = I->getNumOperands(); i != e; ++i) { 805 Value *V = EvaluateInDifferentElementOrder(I->getOperand(i), Mask); 806 NewOps.push_back(V); 807 NeedsRebuild |= (V != I->getOperand(i)); 808 } 809 if (NeedsRebuild) { 810 return BuildNew(I, NewOps); 811 } 812 return I; 813 } 814 case Instruction::InsertElement: { 815 int Element = cast<ConstantInt>(I->getOperand(2))->getLimitedValue(); 816 817 // The insertelement was inserting at Element. Figure out which element 818 // that becomes after shuffling. The answer is guaranteed to be unique 819 // by CanEvaluateShuffled. 820 bool Found = false; 821 int Index = 0; 822 for (int e = Mask.size(); Index != e; ++Index) { 823 if (Mask[Index] == Element) { 824 Found = true; 825 break; 826 } 827 } 828 829 // If element is not in Mask, no need to handle the operand 1 (element to 830 // be inserted). Just evaluate values in operand 0 according to Mask. 831 if (!Found) 832 return EvaluateInDifferentElementOrder(I->getOperand(0), Mask); 833 834 Value *V = EvaluateInDifferentElementOrder(I->getOperand(0), Mask); 835 return InsertElementInst::Create(V, I->getOperand(1), 836 Builder->getInt32(Index), "", I); 837 } 838 } 839 llvm_unreachable("failed to reorder elements of vector instruction!"); 840} 841 842static void RecognizeIdentityMask(const SmallVectorImpl<int> &Mask, 843 bool &isLHSID, bool &isRHSID) { 844 isLHSID = isRHSID = true; 845 846 for (unsigned i = 0, e = Mask.size(); i != e; ++i) { 847 if (Mask[i] < 0) continue; // Ignore undef values. 848 // Is this an identity shuffle of the LHS value? 849 isLHSID &= (Mask[i] == (int)i); 850 851 // Is this an identity shuffle of the RHS value? 852 isRHSID &= (Mask[i]-e == i); 853 } 854} 855 856Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { 857 Value *LHS = SVI.getOperand(0); 858 Value *RHS = SVI.getOperand(1); 859 SmallVector<int, 16> Mask = SVI.getShuffleMask(); 860 861 bool MadeChange = false; 862 863 // Undefined shuffle mask -> undefined value. 864 if (isa<UndefValue>(SVI.getOperand(2))) 865 return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType())); 866 867 unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements(); 868 869 APInt UndefElts(VWidth, 0); 870 APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); 871 if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) { 872 if (V != &SVI) 873 return ReplaceInstUsesWith(SVI, V); 874 LHS = SVI.getOperand(0); 875 RHS = SVI.getOperand(1); 876 MadeChange = true; 877 } 878 879 unsigned LHSWidth = cast<VectorType>(LHS->getType())->getNumElements(); 880 881 // Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask') 882 // Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask'). 883 if (LHS == RHS || isa<UndefValue>(LHS)) { 884 if (isa<UndefValue>(LHS) && LHS == RHS) { 885 // shuffle(undef,undef,mask) -> undef. 886 Value *Result = (VWidth == LHSWidth) 887 ? LHS : UndefValue::get(SVI.getType()); 888 return ReplaceInstUsesWith(SVI, Result); 889 } 890 891 // Remap any references to RHS to use LHS. 892 SmallVector<Constant*, 16> Elts; 893 for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) { 894 if (Mask[i] < 0) { 895 Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); 896 continue; 897 } 898 899 if ((Mask[i] >= (int)e && isa<UndefValue>(RHS)) || 900 (Mask[i] < (int)e && isa<UndefValue>(LHS))) { 901 Mask[i] = -1; // Turn into undef. 902 Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); 903 } else { 904 Mask[i] = Mask[i] % e; // Force to LHS. 905 Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), 906 Mask[i])); 907 } 908 } 909 SVI.setOperand(0, SVI.getOperand(1)); 910 SVI.setOperand(1, UndefValue::get(RHS->getType())); 911 SVI.setOperand(2, ConstantVector::get(Elts)); 912 LHS = SVI.getOperand(0); 913 RHS = SVI.getOperand(1); 914 MadeChange = true; 915 } 916 917 if (VWidth == LHSWidth) { 918 // Analyze the shuffle, are the LHS or RHS and identity shuffles? 919 bool isLHSID, isRHSID; 920 RecognizeIdentityMask(Mask, isLHSID, isRHSID); 921 922 // Eliminate identity shuffles. 923 if (isLHSID) return ReplaceInstUsesWith(SVI, LHS); 924 if (isRHSID) return ReplaceInstUsesWith(SVI, RHS); 925 } 926 927 if (isa<UndefValue>(RHS) && CanEvaluateShuffled(LHS, Mask)) { 928 Value *V = EvaluateInDifferentElementOrder(LHS, Mask); 929 return ReplaceInstUsesWith(SVI, V); 930 } 931 932 // If the LHS is a shufflevector itself, see if we can combine it with this 933 // one without producing an unusual shuffle. 934 // Cases that might be simplified: 935 // 1. 936 // x1=shuffle(v1,v2,mask1) 937 // x=shuffle(x1,undef,mask) 938 // ==> 939 // x=shuffle(v1,undef,newMask) 940 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : -1 941 // 2. 942 // x1=shuffle(v1,undef,mask1) 943 // x=shuffle(x1,x2,mask) 944 // where v1.size() == mask1.size() 945 // ==> 946 // x=shuffle(v1,x2,newMask) 947 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : mask[i] 948 // 3. 949 // x2=shuffle(v2,undef,mask2) 950 // x=shuffle(x1,x2,mask) 951 // where v2.size() == mask2.size() 952 // ==> 953 // x=shuffle(x1,v2,newMask) 954 // newMask[i] = (mask[i] < x1.size()) 955 // ? mask[i] : mask2[mask[i]-x1.size()]+x1.size() 956 // 4. 957 // x1=shuffle(v1,undef,mask1) 958 // x2=shuffle(v2,undef,mask2) 959 // x=shuffle(x1,x2,mask) 960 // where v1.size() == v2.size() 961 // ==> 962 // x=shuffle(v1,v2,newMask) 963 // newMask[i] = (mask[i] < x1.size()) 964 // ? mask1[mask[i]] : mask2[mask[i]-x1.size()]+v1.size() 965 // 966 // Here we are really conservative: 967 // we are absolutely afraid of producing a shuffle mask not in the input 968 // program, because the code gen may not be smart enough to turn a merged 969 // shuffle into two specific shuffles: it may produce worse code. As such, 970 // we only merge two shuffles if the result is either a splat or one of the 971 // input shuffle masks. In this case, merging the shuffles just removes 972 // one instruction, which we know is safe. This is good for things like 973 // turning: (splat(splat)) -> splat, or 974 // merge(V[0..n], V[n+1..2n]) -> V[0..2n] 975 ShuffleVectorInst* LHSShuffle = dyn_cast<ShuffleVectorInst>(LHS); 976 ShuffleVectorInst* RHSShuffle = dyn_cast<ShuffleVectorInst>(RHS); 977 if (LHSShuffle) 978 if (!isa<UndefValue>(LHSShuffle->getOperand(1)) && !isa<UndefValue>(RHS)) 979 LHSShuffle = nullptr; 980 if (RHSShuffle) 981 if (!isa<UndefValue>(RHSShuffle->getOperand(1))) 982 RHSShuffle = nullptr; 983 if (!LHSShuffle && !RHSShuffle) 984 return MadeChange ? &SVI : nullptr; 985 986 Value* LHSOp0 = nullptr; 987 Value* LHSOp1 = nullptr; 988 Value* RHSOp0 = nullptr; 989 unsigned LHSOp0Width = 0; 990 unsigned RHSOp0Width = 0; 991 if (LHSShuffle) { 992 LHSOp0 = LHSShuffle->getOperand(0); 993 LHSOp1 = LHSShuffle->getOperand(1); 994 LHSOp0Width = cast<VectorType>(LHSOp0->getType())->getNumElements(); 995 } 996 if (RHSShuffle) { 997 RHSOp0 = RHSShuffle->getOperand(0); 998 RHSOp0Width = cast<VectorType>(RHSOp0->getType())->getNumElements(); 999 } 1000 Value* newLHS = LHS; 1001 Value* newRHS = RHS; 1002 if (LHSShuffle) { 1003 // case 1 1004 if (isa<UndefValue>(RHS)) { 1005 newLHS = LHSOp0; 1006 newRHS = LHSOp1; 1007 } 1008 // case 2 or 4 1009 else if (LHSOp0Width == LHSWidth) { 1010 newLHS = LHSOp0; 1011 } 1012 } 1013 // case 3 or 4 1014 if (RHSShuffle && RHSOp0Width == LHSWidth) { 1015 newRHS = RHSOp0; 1016 } 1017 // case 4 1018 if (LHSOp0 == RHSOp0) { 1019 newLHS = LHSOp0; 1020 newRHS = nullptr; 1021 } 1022 1023 if (newLHS == LHS && newRHS == RHS) 1024 return MadeChange ? &SVI : nullptr; 1025 1026 SmallVector<int, 16> LHSMask; 1027 SmallVector<int, 16> RHSMask; 1028 if (newLHS != LHS) 1029 LHSMask = LHSShuffle->getShuffleMask(); 1030 if (RHSShuffle && newRHS != RHS) 1031 RHSMask = RHSShuffle->getShuffleMask(); 1032 1033 unsigned newLHSWidth = (newLHS != LHS) ? LHSOp0Width : LHSWidth; 1034 SmallVector<int, 16> newMask; 1035 bool isSplat = true; 1036 int SplatElt = -1; 1037 // Create a new mask for the new ShuffleVectorInst so that the new 1038 // ShuffleVectorInst is equivalent to the original one. 1039 for (unsigned i = 0; i < VWidth; ++i) { 1040 int eltMask; 1041 if (Mask[i] < 0) { 1042 // This element is an undef value. 1043 eltMask = -1; 1044 } else if (Mask[i] < (int)LHSWidth) { 1045 // This element is from left hand side vector operand. 1046 // 1047 // If LHS is going to be replaced (case 1, 2, or 4), calculate the 1048 // new mask value for the element. 1049 if (newLHS != LHS) { 1050 eltMask = LHSMask[Mask[i]]; 1051 // If the value selected is an undef value, explicitly specify it 1052 // with a -1 mask value. 1053 if (eltMask >= (int)LHSOp0Width && isa<UndefValue>(LHSOp1)) 1054 eltMask = -1; 1055 } else 1056 eltMask = Mask[i]; 1057 } else { 1058 // This element is from right hand side vector operand 1059 // 1060 // If the value selected is an undef value, explicitly specify it 1061 // with a -1 mask value. (case 1) 1062 if (isa<UndefValue>(RHS)) 1063 eltMask = -1; 1064 // If RHS is going to be replaced (case 3 or 4), calculate the 1065 // new mask value for the element. 1066 else if (newRHS != RHS) { 1067 eltMask = RHSMask[Mask[i]-LHSWidth]; 1068 // If the value selected is an undef value, explicitly specify it 1069 // with a -1 mask value. 1070 if (eltMask >= (int)RHSOp0Width) { 1071 assert(isa<UndefValue>(RHSShuffle->getOperand(1)) 1072 && "should have been check above"); 1073 eltMask = -1; 1074 } 1075 } else 1076 eltMask = Mask[i]-LHSWidth; 1077 1078 // If LHS's width is changed, shift the mask value accordingly. 1079 // If newRHS == NULL, i.e. LHSOp0 == RHSOp0, we want to remap any 1080 // references from RHSOp0 to LHSOp0, so we don't need to shift the mask. 1081 // If newRHS == newLHS, we want to remap any references from newRHS to 1082 // newLHS so that we can properly identify splats that may occur due to 1083 // obfuscation across the two vectors. 1084 if (eltMask >= 0 && newRHS != nullptr && newLHS != newRHS) 1085 eltMask += newLHSWidth; 1086 } 1087 1088 // Check if this could still be a splat. 1089 if (eltMask >= 0) { 1090 if (SplatElt >= 0 && SplatElt != eltMask) 1091 isSplat = false; 1092 SplatElt = eltMask; 1093 } 1094 1095 newMask.push_back(eltMask); 1096 } 1097 1098 // If the result mask is equal to one of the original shuffle masks, 1099 // or is a splat, do the replacement. 1100 if (isSplat || newMask == LHSMask || newMask == RHSMask || newMask == Mask) { 1101 SmallVector<Constant*, 16> Elts; 1102 Type *Int32Ty = Type::getInt32Ty(SVI.getContext()); 1103 for (unsigned i = 0, e = newMask.size(); i != e; ++i) { 1104 if (newMask[i] < 0) { 1105 Elts.push_back(UndefValue::get(Int32Ty)); 1106 } else { 1107 Elts.push_back(ConstantInt::get(Int32Ty, newMask[i])); 1108 } 1109 } 1110 if (!newRHS) 1111 newRHS = UndefValue::get(newLHS->getType()); 1112 return new ShuffleVectorInst(newLHS, newRHS, ConstantVector::get(Elts)); 1113 } 1114 1115 // If the result mask is an identity, replace uses of this instruction with 1116 // corresponding argument. 1117 bool isLHSID, isRHSID; 1118 RecognizeIdentityMask(newMask, isLHSID, isRHSID); 1119 if (isLHSID && VWidth == LHSOp0Width) return ReplaceInstUsesWith(SVI, newLHS); 1120 if (isRHSID && VWidth == RHSOp0Width) return ReplaceInstUsesWith(SVI, newRHS); 1121 1122 return MadeChange ? &SVI : nullptr; 1123} 1124