1 //===- InstCombineVectorOps.cpp -------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements instcombine for ExtractElement, InsertElement and
13 //===----------------------------------------------------------------------===//
15 #include "InstCombine.h"
16 #include "llvm/IR/PatternMatch.h"
18 using namespace PatternMatch;
20 #define DEBUG_TYPE "instcombine"
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.
25 static bool CheapToScalarize(Value *V, bool isConstant) {
26 if (Constant *C = dyn_cast<Constant>(V)) {
27 if (isConstant) return true;
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;
33 if (C->getAggregateElement(i) != Op0)
38 Instruction *I = dyn_cast<Instruction>(V);
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)))
46 if (I->getOpcode() == Instruction::Load && I->hasOneUse())
48 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I))
49 if (BO->hasOneUse() &&
50 (CheapToScalarize(BO->getOperand(0), isConstant) ||
51 CheapToScalarize(BO->getOperand(1), isConstant)))
53 if (CmpInst *CI = dyn_cast<CmpInst>(I))
54 if (CI->hasOneUse() &&
55 (CheapToScalarize(CI->getOperand(0), isConstant) ||
56 CheapToScalarize(CI->getOperand(1), isConstant)))
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.
65 static 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());
72 if (Constant *C = dyn_cast<Constant>(V))
73 return C->getAggregateElement(EltNo);
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)))
79 unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue();
81 // If this is an insert to the element we are looking for, return the
84 return III->getOperand(1);
86 // Otherwise, the insertelement doesn't modify the value, recurse on its
88 return FindScalarElement(III->getOperand(0), EltNo);
91 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) {
92 unsigned LHSWidth = SVI->getOperand(0)->getType()->getVectorNumElements();
93 int InEl = SVI->getMaskValue(EltNo);
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);
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);
108 // Otherwise, we don't know.
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.
115 Instruction *InstCombiner::scalarizePHI(ExtractElementInst &EI, PHINode *PN) {
116 // Verify that the PHI node has exactly 2 uses. Otherwise return NULL.
117 if (!PN->hasNUses(2))
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
123 auto iu = PN->user_begin();
124 Instruction *PHIUser = dyn_cast<Instruction>(*iu);
125 if (PHIUser == cast<Instruction>(&EI))
126 PHIUser = cast<Instruction>(*(++iu));
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))
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
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"),
155 Value *newPHIUser = InsertNewInstWith(
156 BinaryOperator::Create(B0->getOpcode(), scalarPHI, Op), *B0);
157 scalarPHI->addIncoming(newPHIUser, inBB);
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)) {
168 InsertPos = inBB->getFirstInsertionPt();
171 InsertNewInstWith(newEI, *InsertPos);
173 scalarPHI->addIncoming(newEI, inBB);
176 return ReplaceInstUsesWith(EI, scalarPHI);
179 Instruction *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));
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();
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()));
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
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)) {
211 if (Value *Elt = FindScalarElement(EI.getOperand(0), IndexVal))
212 return ReplaceInstUsesWith(EI, Elt);
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());
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);
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)))) {
240 Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1),
241 EI.getName()+".lhs");
243 Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1),
244 EI.getName()+".rhs");
245 return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1);
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));
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());
265 SVI->getOperand(0)->getType()->getVectorNumElements();
268 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
269 if (SrcIdx < (int)LHSWidth)
270 Src = SVI->getOperand(0);
273 Src = SVI->getOperand(1);
275 Type *Int32Ty = Type::getInt32Ty(EI.getContext());
276 return ExtractElementInst::Create(Src,
277 ConstantInt::get(Int32Ty,
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());
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.
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();
300 Value *Cond = SI->getCondition();
301 if (Cond->getType()->isVectorTy()) {
302 Cond = Builder->CreateExtractElement(Cond,
303 EI.getIndexOperand(),
304 Cond->getName() + ".elt");
308 = Builder->CreateExtractElement(TrueVal,
309 EI.getIndexOperand(),
310 TrueVal->getName() + ".elt");
313 = Builder->CreateExtractElement(FalseVal,
314 EI.getIndexOperand(),
315 FalseVal->getName() + ".elt");
316 return SelectInst::Create(Cond,
319 SI->getName() + ".elt");
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.
329 static 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();
335 if (isa<UndefValue>(V)) {
336 Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext())));
341 for (unsigned i = 0; i != NumElts; ++i)
342 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), i));
347 for (unsigned i = 0; i != NumElts; ++i)
348 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()),
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);
359 if (!isa<ConstantInt>(IdxOp))
361 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
363 if (isa<UndefValue>(ScalarOp)) { // inserting undef into vector.
364 // We can handle this if the vector we are inserting into is
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()));
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();
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
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()),
388 assert(EI->getOperand(0) == RHS);
389 Mask[InsertedIdx % NumElts] =
390 ConstantInt::get(Type::getInt32Ty(V->getContext()),
391 ExtractedIdx + NumLHSElts);
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.
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.
412 typedef std::pair<Value *, Value *> ShuffleOps;
414 static 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();
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);
426 if (isa<ConstantAggregateZero>(V)) {
427 Mask.assign(NumElts, ConstantInt::get(Type::getInt32Ty(V->getContext()),0));
428 return std::make_pair(V, nullptr);
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);
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();
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);
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);
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);
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);
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,
482 return std::make_pair(EI->getOperand(0), PermittedRHS);
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);
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
500 Instruction *InstCombiner::visitInsertValueInst(InsertValueInst &I) {
501 bool IsRedundant = false;
502 ArrayRef<unsigned int> FirstIndices = I.getIndices();
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.
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)
515 if (UserInsInst->getIndices() == FirstIndices) {
524 return ReplaceInstUsesWith(I, I.getOperand(0));
528 Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
529 Value *VecOp = IE.getOperand(0);
530 Value *ScalarOp = IE.getOperand(1);
531 Value *IdxOp = IE.getOperand(2);
533 // Inserting an undef or into an undefined place, remove this.
534 if (isa<UndefValue>(ScalarOp) || isa<UndefValue>(IdxOp))
535 ReplaceInstUsesWith(IE, VecOp);
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();
548 if (ExtractedIdx >= NumExtractVectorElts) // Out of range extract.
549 return ReplaceInstUsesWith(IE, VecOp);
551 if (InsertedIdx >= NumInsertVectorElts) // Out of range insert.
552 return ReplaceInstUsesWith(IE, UndefValue::get(IE.getType()));
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);
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);
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));
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)) {
583 return ReplaceInstUsesWith(IE, V);
590 /// Return true if we can evaluate the specified expression tree if the vector
591 /// elements were shuffled in a different order.
592 static 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))
598 // We won't reorder vector arguments. No IPO here.
599 Instruction *I = dyn_cast<Instruction>(V);
600 if (!I) return false;
602 // Two users may expect different orders of the elements. Don't try it.
606 if (Depth == 0) return false;
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))
645 case Instruction::InsertElement: {
646 ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(2));
647 if (!CI) return false;
648 int ElementNumber = CI->getLimitedValue();
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) {
660 return CanEvaluateShuffled(I->getOperand(0), Mask, Depth-1);
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.
668 static 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());
699 if (isa<PossiblyExactOperator>(BO)) {
700 New->setIsExact(BO->isExact());
702 if (isa<FPMathOperator>(BO))
703 New->copyFastMathFlags(I);
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.
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,
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());
740 llvm_unreachable("failed to rebuild vector instructions");
744 InstCombiner::EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask) {
745 // Mask.size() does not need to be equal to the number of vector elements.
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(),
752 if (isa<ConstantAggregateZero>(V)) {
753 return ConstantAggregateZero::get(
754 VectorType::get(V->getType()->getScalarType(),
757 if (Constant *C = dyn_cast<Constant>(V)) {
758 SmallVector<Constant *, 16> MaskValues;
759 for (int i = 0, e = Mask.size(); i != e; ++i) {
761 MaskValues.push_back(UndefValue::get(Builder->getInt32Ty()));
763 MaskValues.push_back(Builder->getInt32(Mask[i]));
765 return ConstantExpr::getShuffleVector(C, UndefValue::get(C->getType()),
766 ConstantVector::get(MaskValues));
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);
807 NeedsRebuild |= (V != I->getOperand(i));
810 return BuildNew(I, NewOps);
814 case Instruction::InsertElement: {
815 int Element = cast<ConstantInt>(I->getOperand(2))->getLimitedValue();
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.
822 for (int e = Mask.size(); Index != e; ++Index) {
823 if (Mask[Index] == Element) {
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.
832 return EvaluateInDifferentElementOrder(I->getOperand(0), Mask);
834 Value *V = EvaluateInDifferentElementOrder(I->getOperand(0), Mask);
835 return InsertElementInst::Create(V, I->getOperand(1),
836 Builder->getInt32(Index), "", I);
839 llvm_unreachable("failed to reorder elements of vector instruction!");
842 static void RecognizeIdentityMask(const SmallVectorImpl<int> &Mask,
843 bool &isLHSID, bool &isRHSID) {
844 isLHSID = isRHSID = true;
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);
851 // Is this an identity shuffle of the RHS value?
852 isRHSID &= (Mask[i]-e == i);
856 Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
857 Value *LHS = SVI.getOperand(0);
858 Value *RHS = SVI.getOperand(1);
859 SmallVector<int, 16> Mask = SVI.getShuffleMask();
861 bool MadeChange = false;
863 // Undefined shuffle mask -> undefined value.
864 if (isa<UndefValue>(SVI.getOperand(2)))
865 return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
867 unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements();
869 APInt UndefElts(VWidth, 0);
870 APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
871 if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
873 return ReplaceInstUsesWith(SVI, V);
874 LHS = SVI.getOperand(0);
875 RHS = SVI.getOperand(1);
879 unsigned LHSWidth = cast<VectorType>(LHS->getType())->getNumElements();
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);
891 // Remap any references to RHS to use LHS.
892 SmallVector<Constant*, 16> Elts;
893 for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) {
895 Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
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())));
904 Mask[i] = Mask[i] % e; // Force to LHS.
905 Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
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);
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);
922 // Eliminate identity shuffles.
923 if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
924 if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
927 if (isa<UndefValue>(RHS) && CanEvaluateShuffled(LHS, Mask)) {
928 Value *V = EvaluateInDifferentElementOrder(LHS, Mask);
929 return ReplaceInstUsesWith(SVI, V);
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:
936 // x1=shuffle(v1,v2,mask1)
937 // x=shuffle(x1,undef,mask)
939 // x=shuffle(v1,undef,newMask)
940 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : -1
942 // x1=shuffle(v1,undef,mask1)
943 // x=shuffle(x1,x2,mask)
944 // where v1.size() == mask1.size()
946 // x=shuffle(v1,x2,newMask)
947 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : mask[i]
949 // x2=shuffle(v2,undef,mask2)
950 // x=shuffle(x1,x2,mask)
951 // where v2.size() == mask2.size()
953 // x=shuffle(x1,v2,newMask)
954 // newMask[i] = (mask[i] < x1.size())
955 // ? mask[i] : mask2[mask[i]-x1.size()]+x1.size()
957 // x1=shuffle(v1,undef,mask1)
958 // x2=shuffle(v2,undef,mask2)
959 // x=shuffle(x1,x2,mask)
960 // where v1.size() == v2.size()
962 // x=shuffle(v1,v2,newMask)
963 // newMask[i] = (mask[i] < x1.size())
964 // ? mask1[mask[i]] : mask2[mask[i]-x1.size()]+v1.size()
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);
978 if (!isa<UndefValue>(LHSShuffle->getOperand(1)) && !isa<UndefValue>(RHS))
979 LHSShuffle = nullptr;
981 if (!isa<UndefValue>(RHSShuffle->getOperand(1)))
982 RHSShuffle = nullptr;
983 if (!LHSShuffle && !RHSShuffle)
984 return MadeChange ? &SVI : nullptr;
986 Value* LHSOp0 = nullptr;
987 Value* LHSOp1 = nullptr;
988 Value* RHSOp0 = nullptr;
989 unsigned LHSOp0Width = 0;
990 unsigned RHSOp0Width = 0;
992 LHSOp0 = LHSShuffle->getOperand(0);
993 LHSOp1 = LHSShuffle->getOperand(1);
994 LHSOp0Width = cast<VectorType>(LHSOp0->getType())->getNumElements();
997 RHSOp0 = RHSShuffle->getOperand(0);
998 RHSOp0Width = cast<VectorType>(RHSOp0->getType())->getNumElements();
1000 Value* newLHS = LHS;
1001 Value* newRHS = RHS;
1004 if (isa<UndefValue>(RHS)) {
1009 else if (LHSOp0Width == LHSWidth) {
1014 if (RHSShuffle && RHSOp0Width == LHSWidth) {
1018 if (LHSOp0 == RHSOp0) {
1023 if (newLHS == LHS && newRHS == RHS)
1024 return MadeChange ? &SVI : nullptr;
1026 SmallVector<int, 16> LHSMask;
1027 SmallVector<int, 16> RHSMask;
1029 LHSMask = LHSShuffle->getShuffleMask();
1030 if (RHSShuffle && newRHS != RHS)
1031 RHSMask = RHSShuffle->getShuffleMask();
1033 unsigned newLHSWidth = (newLHS != LHS) ? LHSOp0Width : LHSWidth;
1034 SmallVector<int, 16> newMask;
1035 bool isSplat = true;
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) {
1042 // This element is an undef value.
1044 } else if (Mask[i] < (int)LHSWidth) {
1045 // This element is from left hand side vector operand.
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))
1058 // This element is from right hand side vector operand
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))
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");
1076 eltMask = Mask[i]-LHSWidth;
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;
1088 // Check if this could still be a splat.
1090 if (SplatElt >= 0 && SplatElt != eltMask)
1095 newMask.push_back(eltMask);
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));
1107 Elts.push_back(ConstantInt::get(Int32Ty, newMask[i]));
1111 newRHS = UndefValue::get(newLHS->getType());
1112 return new ShuffleVectorInst(newLHS, newRHS, ConstantVector::get(Elts));
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);
1122 return MadeChange ? &SVI : nullptr;