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/Support/PatternMatch.h"
18 using namespace PatternMatch;
20 /// CheapToScalarize - Return true if the value is cheaper to scalarize than it
21 /// is to leave as a vector operation. isConstant indicates whether we're
22 /// extracting one known element. If false we're extracting a variable index.
23 static bool CheapToScalarize(Value *V, bool isConstant) {
24 if (Constant *C = dyn_cast<Constant>(V)) {
25 if (isConstant) return true;
27 // If all elts are the same, we can extract it and use any of the values.
28 Constant *Op0 = C->getAggregateElement(0U);
29 for (unsigned i = 1, e = V->getType()->getVectorNumElements(); i != e; ++i)
30 if (C->getAggregateElement(i) != Op0)
34 Instruction *I = dyn_cast<Instruction>(V);
37 // Insert element gets simplified to the inserted element or is deleted if
38 // this is constant idx extract element and its a constant idx insertelt.
39 if (I->getOpcode() == Instruction::InsertElement && isConstant &&
40 isa<ConstantInt>(I->getOperand(2)))
42 if (I->getOpcode() == Instruction::Load && I->hasOneUse())
44 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I))
45 if (BO->hasOneUse() &&
46 (CheapToScalarize(BO->getOperand(0), isConstant) ||
47 CheapToScalarize(BO->getOperand(1), isConstant)))
49 if (CmpInst *CI = dyn_cast<CmpInst>(I))
50 if (CI->hasOneUse() &&
51 (CheapToScalarize(CI->getOperand(0), isConstant) ||
52 CheapToScalarize(CI->getOperand(1), isConstant)))
58 /// FindScalarElement - Given a vector and an element number, see if the scalar
59 /// value is already around as a register, for example if it were inserted then
60 /// extracted from the vector.
61 static Value *FindScalarElement(Value *V, unsigned EltNo) {
62 assert(V->getType()->isVectorTy() && "Not looking at a vector?");
63 VectorType *VTy = cast<VectorType>(V->getType());
64 unsigned Width = VTy->getNumElements();
65 if (EltNo >= Width) // Out of range access.
66 return UndefValue::get(VTy->getElementType());
68 if (Constant *C = dyn_cast<Constant>(V))
69 return C->getAggregateElement(EltNo);
71 if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) {
72 // If this is an insert to a variable element, we don't know what it is.
73 if (!isa<ConstantInt>(III->getOperand(2)))
75 unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue();
77 // If this is an insert to the element we are looking for, return the
80 return III->getOperand(1);
82 // Otherwise, the insertelement doesn't modify the value, recurse on its
84 return FindScalarElement(III->getOperand(0), EltNo);
87 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) {
88 unsigned LHSWidth = SVI->getOperand(0)->getType()->getVectorNumElements();
89 int InEl = SVI->getMaskValue(EltNo);
91 return UndefValue::get(VTy->getElementType());
92 if (InEl < (int)LHSWidth)
93 return FindScalarElement(SVI->getOperand(0), InEl);
94 return FindScalarElement(SVI->getOperand(1), InEl - LHSWidth);
97 // Extract a value from a vector add operation with a constant zero.
98 Value *Val = 0; Constant *Con = 0;
99 if (match(V, m_Add(m_Value(Val), m_Constant(Con)))) {
100 if (Con->getAggregateElement(EltNo)->isNullValue())
101 return FindScalarElement(Val, EltNo);
104 // Otherwise, we don't know.
108 // If we have a PHI node with a vector type that has only 2 uses: feed
109 // itself and be an operand of extractelemnt at a constant location,
110 // try to replace the PHI of the vector type with a PHI of a scalar type
111 Instruction *InstCombiner::scalarizePHI(ExtractElementInst &EI, PHINode *PN) {
112 // Verify that the PHI node has exactly 2 uses. Otherwise return NULL.
113 if (!PN->hasNUses(2))
116 // If so, it's known at this point that one operand is PHI and the other is
117 // an extractelement node. Find the PHI user that is not the extractelement
119 Value::use_iterator iu = PN->use_begin();
120 Instruction *PHIUser = dyn_cast<Instruction>(*iu);
121 if (PHIUser == cast<Instruction>(&EI))
122 PHIUser = cast<Instruction>(*(++iu));
124 // Verify that this PHI user has one use, which is the PHI itself,
125 // and that it is a binary operation which is cheap to scalarize.
126 // otherwise return NULL.
127 if (!PHIUser->hasOneUse() || !(PHIUser->use_back() == PN) ||
128 !(isa<BinaryOperator>(PHIUser)) ||
129 !CheapToScalarize(PHIUser, true))
132 // Create a scalar PHI node that will replace the vector PHI node
133 // just before the current PHI node.
134 PHINode * scalarPHI = cast<PHINode>(
135 InsertNewInstWith(PHINode::Create(EI.getType(),
136 PN->getNumIncomingValues(), ""), *PN));
137 // Scalarize each PHI operand.
138 for (unsigned i=0; i < PN->getNumIncomingValues(); i++) {
139 Value *PHIInVal = PN->getIncomingValue(i);
140 BasicBlock *inBB = PN->getIncomingBlock(i);
141 Value *Elt = EI.getIndexOperand();
142 // If the operand is the PHI induction variable:
143 if (PHIInVal == PHIUser) {
144 // Scalarize the binary operation. Its first operand is the
145 // scalar PHI and the second operand is extracted from the other
147 BinaryOperator *B0 = cast<BinaryOperator>(PHIUser);
148 unsigned opId = (B0->getOperand(0) == PN) ? 1: 0;
149 Value *Op = Builder->CreateExtractElement(
150 B0->getOperand(opId), Elt, B0->getOperand(opId)->getName()+".Elt");
151 Value *newPHIUser = InsertNewInstWith(
152 BinaryOperator::Create(B0->getOpcode(), scalarPHI,Op),
154 scalarPHI->addIncoming(newPHIUser, inBB);
156 // Scalarize PHI input:
158 ExtractElementInst::Create(PHIInVal, Elt, "");
159 // Insert the new instruction into the predecessor basic block.
160 Instruction *pos = dyn_cast<Instruction>(PHIInVal);
161 BasicBlock::iterator InsertPos;
162 if (pos && !isa<PHINode>(pos)) {
166 InsertPos = inBB->getFirstInsertionPt();
169 InsertNewInstWith(newEI, *InsertPos);
171 scalarPHI->addIncoming(newEI, inBB);
174 return ReplaceInstUsesWith(EI, scalarPHI);
177 Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
178 // If vector val is constant with all elements the same, replace EI with
179 // that element. We handle a known element # below.
180 if (Constant *C = dyn_cast<Constant>(EI.getOperand(0)))
181 if (CheapToScalarize(C, false))
182 return ReplaceInstUsesWith(EI, C->getAggregateElement(0U));
184 // If extracting a specified index from the vector, see if we can recursively
185 // find a previously computed scalar that was inserted into the vector.
186 if (ConstantInt *IdxC = dyn_cast<ConstantInt>(EI.getOperand(1))) {
187 unsigned IndexVal = IdxC->getZExtValue();
188 unsigned VectorWidth = EI.getVectorOperandType()->getNumElements();
190 // If this is extracting an invalid index, turn this into undef, to avoid
191 // crashing the code below.
192 if (IndexVal >= VectorWidth)
193 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
195 // This instruction only demands the single element from the input vector.
196 // If the input vector has a single use, simplify it based on this use
198 if (EI.getOperand(0)->hasOneUse() && VectorWidth != 1) {
199 APInt UndefElts(VectorWidth, 0);
200 APInt DemandedMask(VectorWidth, 0);
201 DemandedMask.setBit(IndexVal);
202 if (Value *V = SimplifyDemandedVectorElts(EI.getOperand(0),
203 DemandedMask, UndefElts)) {
209 if (Value *Elt = FindScalarElement(EI.getOperand(0), IndexVal))
210 return ReplaceInstUsesWith(EI, Elt);
212 // If the this extractelement is directly using a bitcast from a vector of
213 // the same number of elements, see if we can find the source element from
214 // it. In this case, we will end up needing to bitcast the scalars.
215 if (BitCastInst *BCI = dyn_cast<BitCastInst>(EI.getOperand(0))) {
216 if (VectorType *VT = dyn_cast<VectorType>(BCI->getOperand(0)->getType()))
217 if (VT->getNumElements() == VectorWidth)
218 if (Value *Elt = FindScalarElement(BCI->getOperand(0), IndexVal))
219 return new BitCastInst(Elt, EI.getType());
222 // If there's a vector PHI feeding a scalar use through this extractelement
223 // instruction, try to scalarize the PHI.
224 if (PHINode *PN = dyn_cast<PHINode>(EI.getOperand(0))) {
225 Instruction *scalarPHI = scalarizePHI(EI, PN);
231 if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) {
232 // Push extractelement into predecessor operation if legal and
233 // profitable to do so
234 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
235 if (I->hasOneUse() &&
236 CheapToScalarize(BO, isa<ConstantInt>(EI.getOperand(1)))) {
238 Builder->CreateExtractElement(BO->getOperand(0), EI.getOperand(1),
239 EI.getName()+".lhs");
241 Builder->CreateExtractElement(BO->getOperand(1), EI.getOperand(1),
242 EI.getName()+".rhs");
243 return BinaryOperator::Create(BO->getOpcode(), newEI0, newEI1);
245 } else if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
246 // Extracting the inserted element?
247 if (IE->getOperand(2) == EI.getOperand(1))
248 return ReplaceInstUsesWith(EI, IE->getOperand(1));
249 // If the inserted and extracted elements are constants, they must not
250 // be the same value, extract from the pre-inserted value instead.
251 if (isa<Constant>(IE->getOperand(2)) && isa<Constant>(EI.getOperand(1))) {
252 Worklist.AddValue(EI.getOperand(0));
253 EI.setOperand(0, IE->getOperand(0));
256 } else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I)) {
257 // If this is extracting an element from a shufflevector, figure out where
258 // it came from and extract from the appropriate input element instead.
259 if (ConstantInt *Elt = dyn_cast<ConstantInt>(EI.getOperand(1))) {
260 int SrcIdx = SVI->getMaskValue(Elt->getZExtValue());
263 SVI->getOperand(0)->getType()->getVectorNumElements();
266 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
267 if (SrcIdx < (int)LHSWidth)
268 Src = SVI->getOperand(0);
271 Src = SVI->getOperand(1);
273 Type *Int32Ty = Type::getInt32Ty(EI.getContext());
274 return ExtractElementInst::Create(Src,
275 ConstantInt::get(Int32Ty,
278 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
279 // Canonicalize extractelement(cast) -> cast(extractelement)
280 // bitcasts can change the number of vector elements and they cost nothing
281 if (CI->hasOneUse() && EI.hasOneUse() &&
282 (CI->getOpcode() != Instruction::BitCast)) {
283 Value *EE = Builder->CreateExtractElement(CI->getOperand(0),
284 EI.getIndexOperand());
285 return CastInst::Create(CI->getOpcode(), EE, EI.getType());
292 /// CollectSingleShuffleElements - If V is a shuffle of values that ONLY returns
293 /// elements from either LHS or RHS, return the shuffle mask and true.
294 /// Otherwise, return false.
295 static bool CollectSingleShuffleElements(Value *V, Value *LHS, Value *RHS,
296 SmallVectorImpl<Constant*> &Mask) {
297 assert(V->getType() == LHS->getType() && V->getType() == RHS->getType() &&
298 "Invalid CollectSingleShuffleElements");
299 unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
301 if (isa<UndefValue>(V)) {
302 Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext())));
307 for (unsigned i = 0; i != NumElts; ++i)
308 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), i));
313 for (unsigned i = 0; i != NumElts; ++i)
314 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()),
319 if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
320 // If this is an insert of an extract from some other vector, include it.
321 Value *VecOp = IEI->getOperand(0);
322 Value *ScalarOp = IEI->getOperand(1);
323 Value *IdxOp = IEI->getOperand(2);
325 if (!isa<ConstantInt>(IdxOp))
327 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
329 if (isa<UndefValue>(ScalarOp)) { // inserting undef into vector.
330 // Okay, we can handle this if the vector we are insertinting into is
332 if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) {
333 // If so, update the mask to reflect the inserted undef.
334 Mask[InsertedIdx] = UndefValue::get(Type::getInt32Ty(V->getContext()));
337 } else if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)){
338 if (isa<ConstantInt>(EI->getOperand(1)) &&
339 EI->getOperand(0)->getType() == V->getType()) {
340 unsigned ExtractedIdx =
341 cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
343 // This must be extracting from either LHS or RHS.
344 if (EI->getOperand(0) == LHS || EI->getOperand(0) == RHS) {
345 // Okay, we can handle this if the vector we are insertinting into is
347 if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) {
348 // If so, update the mask to reflect the inserted value.
349 if (EI->getOperand(0) == LHS) {
350 Mask[InsertedIdx % NumElts] =
351 ConstantInt::get(Type::getInt32Ty(V->getContext()),
354 assert(EI->getOperand(0) == RHS);
355 Mask[InsertedIdx % NumElts] =
356 ConstantInt::get(Type::getInt32Ty(V->getContext()),
357 ExtractedIdx+NumElts);
365 // TODO: Handle shufflevector here!
370 /// CollectShuffleElements - We are building a shuffle of V, using RHS as the
371 /// RHS of the shuffle instruction, if it is not null. Return a shuffle mask
372 /// that computes V and the LHS value of the shuffle.
373 static Value *CollectShuffleElements(Value *V, SmallVectorImpl<Constant*> &Mask,
375 assert(V->getType()->isVectorTy() &&
376 (RHS == 0 || V->getType() == RHS->getType()) &&
378 unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
380 if (isa<UndefValue>(V)) {
381 Mask.assign(NumElts, UndefValue::get(Type::getInt32Ty(V->getContext())));
385 if (isa<ConstantAggregateZero>(V)) {
386 Mask.assign(NumElts, ConstantInt::get(Type::getInt32Ty(V->getContext()),0));
390 if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
391 // If this is an insert of an extract from some other vector, include it.
392 Value *VecOp = IEI->getOperand(0);
393 Value *ScalarOp = IEI->getOperand(1);
394 Value *IdxOp = IEI->getOperand(2);
396 if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
397 if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
398 EI->getOperand(0)->getType() == V->getType()) {
399 unsigned ExtractedIdx =
400 cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
401 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
403 // Either the extracted from or inserted into vector must be RHSVec,
404 // otherwise we'd end up with a shuffle of three inputs.
405 if (EI->getOperand(0) == RHS || RHS == 0) {
406 RHS = EI->getOperand(0);
407 Value *V = CollectShuffleElements(VecOp, Mask, RHS);
408 Mask[InsertedIdx % NumElts] =
409 ConstantInt::get(Type::getInt32Ty(V->getContext()),
410 NumElts+ExtractedIdx);
415 Value *V = CollectShuffleElements(EI->getOperand(0), Mask, RHS);
416 // Update Mask to reflect that `ScalarOp' has been inserted at
417 // position `InsertedIdx' within the vector returned by IEI.
418 Mask[InsertedIdx % NumElts] = Mask[ExtractedIdx];
420 // Everything but the extracted element is replaced with the RHS.
421 for (unsigned i = 0; i != NumElts; ++i) {
422 if (i != InsertedIdx)
423 Mask[i] = ConstantInt::get(Type::getInt32Ty(V->getContext()),
429 // If this insertelement is a chain that comes from exactly these two
430 // vectors, return the vector and the effective shuffle.
431 if (CollectSingleShuffleElements(IEI, EI->getOperand(0), RHS, Mask))
432 return EI->getOperand(0);
436 // TODO: Handle shufflevector here!
438 // Otherwise, can't do anything fancy. Return an identity vector.
439 for (unsigned i = 0; i != NumElts; ++i)
440 Mask.push_back(ConstantInt::get(Type::getInt32Ty(V->getContext()), i));
444 Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
445 Value *VecOp = IE.getOperand(0);
446 Value *ScalarOp = IE.getOperand(1);
447 Value *IdxOp = IE.getOperand(2);
449 // Inserting an undef or into an undefined place, remove this.
450 if (isa<UndefValue>(ScalarOp) || isa<UndefValue>(IdxOp))
451 ReplaceInstUsesWith(IE, VecOp);
453 // If the inserted element was extracted from some other vector, and if the
454 // indexes are constant, try to turn this into a shufflevector operation.
455 if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
456 if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
457 EI->getOperand(0)->getType() == IE.getType()) {
458 unsigned NumVectorElts = IE.getType()->getNumElements();
459 unsigned ExtractedIdx =
460 cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
461 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
463 if (ExtractedIdx >= NumVectorElts) // Out of range extract.
464 return ReplaceInstUsesWith(IE, VecOp);
466 if (InsertedIdx >= NumVectorElts) // Out of range insert.
467 return ReplaceInstUsesWith(IE, UndefValue::get(IE.getType()));
469 // If we are extracting a value from a vector, then inserting it right
470 // back into the same place, just use the input vector.
471 if (EI->getOperand(0) == VecOp && ExtractedIdx == InsertedIdx)
472 return ReplaceInstUsesWith(IE, VecOp);
474 // If this insertelement isn't used by some other insertelement, turn it
475 // (and any insertelements it points to), into one big shuffle.
476 if (!IE.hasOneUse() || !isa<InsertElementInst>(IE.use_back())) {
477 SmallVector<Constant*, 16> Mask;
479 Value *LHS = CollectShuffleElements(&IE, Mask, RHS);
480 if (RHS == 0) RHS = UndefValue::get(LHS->getType());
481 // We now have a shuffle of LHS, RHS, Mask.
482 return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Mask));
487 unsigned VWidth = cast<VectorType>(VecOp->getType())->getNumElements();
488 APInt UndefElts(VWidth, 0);
489 APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
490 if (Value *V = SimplifyDemandedVectorElts(&IE, AllOnesEltMask, UndefElts)) {
492 return ReplaceInstUsesWith(IE, V);
500 Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
501 Value *LHS = SVI.getOperand(0);
502 Value *RHS = SVI.getOperand(1);
503 SmallVector<int, 16> Mask = SVI.getShuffleMask();
505 bool MadeChange = false;
507 // Undefined shuffle mask -> undefined value.
508 if (isa<UndefValue>(SVI.getOperand(2)))
509 return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
511 unsigned VWidth = cast<VectorType>(SVI.getType())->getNumElements();
513 APInt UndefElts(VWidth, 0);
514 APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
515 if (Value *V = SimplifyDemandedVectorElts(&SVI, AllOnesEltMask, UndefElts)) {
517 return ReplaceInstUsesWith(SVI, V);
518 LHS = SVI.getOperand(0);
519 RHS = SVI.getOperand(1);
523 unsigned LHSWidth = cast<VectorType>(LHS->getType())->getNumElements();
525 // Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
526 // Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
527 if (LHS == RHS || isa<UndefValue>(LHS)) {
528 if (isa<UndefValue>(LHS) && LHS == RHS) {
529 // shuffle(undef,undef,mask) -> undef.
530 Value* result = (VWidth == LHSWidth)
531 ? LHS : UndefValue::get(SVI.getType());
532 return ReplaceInstUsesWith(SVI, result);
535 // Remap any references to RHS to use LHS.
536 SmallVector<Constant*, 16> Elts;
537 for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) {
539 Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
543 if ((Mask[i] >= (int)e && isa<UndefValue>(RHS)) ||
544 (Mask[i] < (int)e && isa<UndefValue>(LHS))) {
545 Mask[i] = -1; // Turn into undef.
546 Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext())));
548 Mask[i] = Mask[i] % e; // Force to LHS.
549 Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()),
553 SVI.setOperand(0, SVI.getOperand(1));
554 SVI.setOperand(1, UndefValue::get(RHS->getType()));
555 SVI.setOperand(2, ConstantVector::get(Elts));
556 LHS = SVI.getOperand(0);
557 RHS = SVI.getOperand(1);
561 if (VWidth == LHSWidth) {
562 // Analyze the shuffle, are the LHS or RHS and identity shuffles?
563 bool isLHSID = true, isRHSID = true;
565 for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
566 if (Mask[i] < 0) continue; // Ignore undef values.
567 // Is this an identity shuffle of the LHS value?
568 isLHSID &= (Mask[i] == (int)i);
570 // Is this an identity shuffle of the RHS value?
571 isRHSID &= (Mask[i]-e == i);
574 // Eliminate identity shuffles.
575 if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
576 if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
579 // If the LHS is a shufflevector itself, see if we can combine it with this
580 // one without producing an unusual shuffle.
581 // Cases that might be simplified:
583 // x1=shuffle(v1,v2,mask1)
584 // x=shuffle(x1,undef,mask)
586 // x=shuffle(v1,undef,newMask)
587 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : -1
589 // x1=shuffle(v1,undef,mask1)
590 // x=shuffle(x1,x2,mask)
591 // where v1.size() == mask1.size()
593 // x=shuffle(v1,x2,newMask)
594 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : mask[i]
596 // x2=shuffle(v2,undef,mask2)
597 // x=shuffle(x1,x2,mask)
598 // where v2.size() == mask2.size()
600 // x=shuffle(x1,v2,newMask)
601 // newMask[i] = (mask[i] < x1.size())
602 // ? mask[i] : mask2[mask[i]-x1.size()]+x1.size()
604 // x1=shuffle(v1,undef,mask1)
605 // x2=shuffle(v2,undef,mask2)
606 // x=shuffle(x1,x2,mask)
607 // where v1.size() == v2.size()
609 // x=shuffle(v1,v2,newMask)
610 // newMask[i] = (mask[i] < x1.size())
611 // ? mask1[mask[i]] : mask2[mask[i]-x1.size()]+v1.size()
613 // Here we are really conservative:
614 // we are absolutely afraid of producing a shuffle mask not in the input
615 // program, because the code gen may not be smart enough to turn a merged
616 // shuffle into two specific shuffles: it may produce worse code. As such,
617 // we only merge two shuffles if the result is either a splat or one of the
618 // input shuffle masks. In this case, merging the shuffles just removes
619 // one instruction, which we know is safe. This is good for things like
620 // turning: (splat(splat)) -> splat, or
621 // merge(V[0..n], V[n+1..2n]) -> V[0..2n]
622 ShuffleVectorInst* LHSShuffle = dyn_cast<ShuffleVectorInst>(LHS);
623 ShuffleVectorInst* RHSShuffle = dyn_cast<ShuffleVectorInst>(RHS);
625 if (!isa<UndefValue>(LHSShuffle->getOperand(1)) && !isa<UndefValue>(RHS))
628 if (!isa<UndefValue>(RHSShuffle->getOperand(1)))
630 if (!LHSShuffle && !RHSShuffle)
631 return MadeChange ? &SVI : 0;
633 Value* LHSOp0 = NULL;
634 Value* LHSOp1 = NULL;
635 Value* RHSOp0 = NULL;
636 unsigned LHSOp0Width = 0;
637 unsigned RHSOp0Width = 0;
639 LHSOp0 = LHSShuffle->getOperand(0);
640 LHSOp1 = LHSShuffle->getOperand(1);
641 LHSOp0Width = cast<VectorType>(LHSOp0->getType())->getNumElements();
644 RHSOp0 = RHSShuffle->getOperand(0);
645 RHSOp0Width = cast<VectorType>(RHSOp0->getType())->getNumElements();
651 if (isa<UndefValue>(RHS)) {
656 else if (LHSOp0Width == LHSWidth) {
661 if (RHSShuffle && RHSOp0Width == LHSWidth) {
665 if (LHSOp0 == RHSOp0) {
670 if (newLHS == LHS && newRHS == RHS)
671 return MadeChange ? &SVI : 0;
673 SmallVector<int, 16> LHSMask;
674 SmallVector<int, 16> RHSMask;
676 LHSMask = LHSShuffle->getShuffleMask();
677 if (RHSShuffle && newRHS != RHS)
678 RHSMask = RHSShuffle->getShuffleMask();
680 unsigned newLHSWidth = (newLHS != LHS) ? LHSOp0Width : LHSWidth;
681 SmallVector<int, 16> newMask;
684 // Create a new mask for the new ShuffleVectorInst so that the new
685 // ShuffleVectorInst is equivalent to the original one.
686 for (unsigned i = 0; i < VWidth; ++i) {
689 // This element is an undef value.
691 } else if (Mask[i] < (int)LHSWidth) {
692 // This element is from left hand side vector operand.
694 // If LHS is going to be replaced (case 1, 2, or 4), calculate the
695 // new mask value for the element.
697 eltMask = LHSMask[Mask[i]];
698 // If the value selected is an undef value, explicitly specify it
699 // with a -1 mask value.
700 if (eltMask >= (int)LHSOp0Width && isa<UndefValue>(LHSOp1))
705 // This element is from right hand side vector operand
707 // If the value selected is an undef value, explicitly specify it
708 // with a -1 mask value. (case 1)
709 if (isa<UndefValue>(RHS))
711 // If RHS is going to be replaced (case 3 or 4), calculate the
712 // new mask value for the element.
713 else if (newRHS != RHS) {
714 eltMask = RHSMask[Mask[i]-LHSWidth];
715 // If the value selected is an undef value, explicitly specify it
716 // with a -1 mask value.
717 if (eltMask >= (int)RHSOp0Width) {
718 assert(isa<UndefValue>(RHSShuffle->getOperand(1))
719 && "should have been check above");
723 eltMask = Mask[i]-LHSWidth;
725 // If LHS's width is changed, shift the mask value accordingly.
726 // If newRHS == NULL, i.e. LHSOp0 == RHSOp0, we want to remap any
727 // references from RHSOp0 to LHSOp0, so we don't need to shift the mask.
728 // If newRHS == newLHS, we want to remap any references from newRHS to
729 // newLHS so that we can properly identify splats that may occur due to
730 // obfuscation accross the two vectors.
731 if (eltMask >= 0 && newRHS != NULL && newLHS != newRHS)
732 eltMask += newLHSWidth;
735 // Check if this could still be a splat.
737 if (SplatElt >= 0 && SplatElt != eltMask)
742 newMask.push_back(eltMask);
745 // If the result mask is equal to one of the original shuffle masks,
746 // or is a splat, do the replacement.
747 if (isSplat || newMask == LHSMask || newMask == RHSMask || newMask == Mask) {
748 SmallVector<Constant*, 16> Elts;
749 Type *Int32Ty = Type::getInt32Ty(SVI.getContext());
750 for (unsigned i = 0, e = newMask.size(); i != e; ++i) {
751 if (newMask[i] < 0) {
752 Elts.push_back(UndefValue::get(Int32Ty));
754 Elts.push_back(ConstantInt::get(Int32Ty, newMask[i]));
758 newRHS = UndefValue::get(newLHS->getType());
759 return new ShuffleVectorInst(newLHS, newRHS, ConstantVector::get(Elts));
762 return MadeChange ? &SVI : 0;