1//===- InstCombineVectorOps.cpp -------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements instcombine for ExtractElement, InsertElement and
10// ShuffleVector.
11//
12//===----------------------------------------------------------------------===//
13
14#include "InstCombineInternal.h"
15#include "llvm/ADT/APInt.h"
16#include "llvm/ADT/ArrayRef.h"
17#include "llvm/ADT/DenseMap.h"
18#include "llvm/ADT/STLExtras.h"
19#include "llvm/ADT/SmallBitVector.h"
20#include "llvm/ADT/SmallVector.h"
21#include "llvm/ADT/Statistic.h"
22#include "llvm/Analysis/InstructionSimplify.h"
23#include "llvm/Analysis/VectorUtils.h"
24#include "llvm/IR/BasicBlock.h"
25#include "llvm/IR/Constant.h"
26#include "llvm/IR/Constants.h"
27#include "llvm/IR/DerivedTypes.h"
28#include "llvm/IR/InstrTypes.h"
29#include "llvm/IR/Instruction.h"
30#include "llvm/IR/Instructions.h"
31#include "llvm/IR/Operator.h"
32#include "llvm/IR/PatternMatch.h"
33#include "llvm/IR/Type.h"
34#include "llvm/IR/User.h"
35#include "llvm/IR/Value.h"
36#include "llvm/Support/Casting.h"
37#include "llvm/Support/ErrorHandling.h"
38#include "llvm/Transforms/InstCombine/InstCombiner.h"
39#include <cassert>
40#include <cstdint>
41#include <iterator>
42#include <utility>
43
44#define DEBUG_TYPE "instcombine"
45
46using namespace llvm;
47using namespace PatternMatch;
48
49STATISTIC(NumAggregateReconstructionsSimplified,
50 "Number of aggregate reconstructions turned into reuse of the "
51 "original aggregate");
52
53/// Return true if the value is cheaper to scalarize than it is to leave as a
54/// vector operation. If the extract index \p EI is a constant integer then
55/// some operations may be cheap to scalarize.
56///
57/// FIXME: It's possible to create more instructions than previously existed.
58static bool cheapToScalarize(Value *V, Value *EI) {
59 ConstantInt *CEI = dyn_cast<ConstantInt>(Val: EI);
60
61 // If we can pick a scalar constant value out of a vector, that is free.
62 if (auto *C = dyn_cast<Constant>(Val: V))
63 return CEI || C->getSplatValue();
64
65 if (CEI && match(V, P: m_Intrinsic<Intrinsic::experimental_stepvector>())) {
66 ElementCount EC = cast<VectorType>(Val: V->getType())->getElementCount();
67 // Index needs to be lower than the minimum size of the vector, because
68 // for scalable vector, the vector size is known at run time.
69 return CEI->getValue().ult(RHS: EC.getKnownMinValue());
70 }
71
72 // An insertelement to the same constant index as our extract will simplify
73 // to the scalar inserted element. An insertelement to a different constant
74 // index is irrelevant to our extract.
75 if (match(V, P: m_InsertElt(Val: m_Value(), Elt: m_Value(), Idx: m_ConstantInt())))
76 return CEI;
77
78 if (match(V, P: m_OneUse(SubPattern: m_Load(Op: m_Value()))))
79 return true;
80
81 if (match(V, P: m_OneUse(SubPattern: m_UnOp())))
82 return true;
83
84 Value *V0, *V1;
85 if (match(V, P: m_OneUse(SubPattern: m_BinOp(L: m_Value(V&: V0), R: m_Value(V&: V1)))))
86 if (cheapToScalarize(V: V0, EI) || cheapToScalarize(V: V1, EI))
87 return true;
88
89 CmpInst::Predicate UnusedPred;
90 if (match(V, P: m_OneUse(SubPattern: m_Cmp(Pred&: UnusedPred, L: m_Value(V&: V0), R: m_Value(V&: V1)))))
91 if (cheapToScalarize(V: V0, EI) || cheapToScalarize(V: V1, EI))
92 return true;
93
94 return false;
95}
96
97// If we have a PHI node with a vector type that is only used to feed
98// itself and be an operand of extractelement at a constant location,
99// try to replace the PHI of the vector type with a PHI of a scalar type.
100Instruction *InstCombinerImpl::scalarizePHI(ExtractElementInst &EI,
101 PHINode *PN) {
102 SmallVector<Instruction *, 2> Extracts;
103 // The users we want the PHI to have are:
104 // 1) The EI ExtractElement (we already know this)
105 // 2) Possibly more ExtractElements with the same index.
106 // 3) Another operand, which will feed back into the PHI.
107 Instruction *PHIUser = nullptr;
108 for (auto *U : PN->users()) {
109 if (ExtractElementInst *EU = dyn_cast<ExtractElementInst>(Val: U)) {
110 if (EI.getIndexOperand() == EU->getIndexOperand())
111 Extracts.push_back(Elt: EU);
112 else
113 return nullptr;
114 } else if (!PHIUser) {
115 PHIUser = cast<Instruction>(Val: U);
116 } else {
117 return nullptr;
118 }
119 }
120
121 if (!PHIUser)
122 return nullptr;
123
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 nullptr.
127 if (!PHIUser->hasOneUse() || !(PHIUser->user_back() == PN) ||
128 !(isa<BinaryOperator>(Val: PHIUser)) ||
129 !cheapToScalarize(V: PHIUser, EI: EI.getIndexOperand()))
130 return nullptr;
131
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>(Val: InsertNewInstWith(
135 New: PHINode::Create(Ty: EI.getType(), NumReservedValues: PN->getNumIncomingValues(), NameStr: ""), Old: PN->getIterator()));
136 // Scalarize each PHI operand.
137 for (unsigned i = 0; i < PN->getNumIncomingValues(); i++) {
138 Value *PHIInVal = PN->getIncomingValue(i);
139 BasicBlock *inBB = PN->getIncomingBlock(i);
140 Value *Elt = EI.getIndexOperand();
141 // If the operand is the PHI induction variable:
142 if (PHIInVal == PHIUser) {
143 // Scalarize the binary operation. Its first operand is the
144 // scalar PHI, and the second operand is extracted from the other
145 // vector operand.
146 BinaryOperator *B0 = cast<BinaryOperator>(Val: PHIUser);
147 unsigned opId = (B0->getOperand(i_nocapture: 0) == PN) ? 1 : 0;
148 Value *Op = InsertNewInstWith(
149 New: ExtractElementInst::Create(Vec: B0->getOperand(i_nocapture: opId), Idx: Elt,
150 NameStr: B0->getOperand(i_nocapture: opId)->getName() + ".Elt"),
151 Old: B0->getIterator());
152 Value *newPHIUser = InsertNewInstWith(
153 New: BinaryOperator::CreateWithCopiedFlags(Opc: B0->getOpcode(),
154 V1: scalarPHI, V2: Op, CopyO: B0), Old: B0->getIterator());
155 scalarPHI->addIncoming(V: newPHIUser, BB: inBB);
156 } else {
157 // Scalarize PHI input:
158 Instruction *newEI = ExtractElementInst::Create(Vec: PHIInVal, Idx: Elt, NameStr: "");
159 // Insert the new instruction into the predecessor basic block.
160 Instruction *pos = dyn_cast<Instruction>(Val: PHIInVal);
161 BasicBlock::iterator InsertPos;
162 if (pos && !isa<PHINode>(Val: pos)) {
163 InsertPos = ++pos->getIterator();
164 } else {
165 InsertPos = inBB->getFirstInsertionPt();
166 }
167
168 InsertNewInstWith(New: newEI, Old: InsertPos);
169
170 scalarPHI->addIncoming(V: newEI, BB: inBB);
171 }
172 }
173
174 for (auto *E : Extracts) {
175 replaceInstUsesWith(I&: *E, V: scalarPHI);
176 // Add old extract to worklist for DCE.
177 addToWorklist(I: E);
178 }
179
180 return &EI;
181}
182
183Instruction *InstCombinerImpl::foldBitcastExtElt(ExtractElementInst &Ext) {
184 Value *X;
185 uint64_t ExtIndexC;
186 if (!match(V: Ext.getVectorOperand(), P: m_BitCast(Op: m_Value(V&: X))) ||
187 !match(V: Ext.getIndexOperand(), P: m_ConstantInt(V&: ExtIndexC)))
188 return nullptr;
189
190 ElementCount NumElts =
191 cast<VectorType>(Val: Ext.getVectorOperandType())->getElementCount();
192 Type *DestTy = Ext.getType();
193 unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
194 bool IsBigEndian = DL.isBigEndian();
195
196 // If we are casting an integer to vector and extracting a portion, that is
197 // a shift-right and truncate.
198 if (X->getType()->isIntegerTy()) {
199 assert(isa<FixedVectorType>(Ext.getVectorOperand()->getType()) &&
200 "Expected fixed vector type for bitcast from scalar integer");
201
202 // Big endian requires adjusting the extract index since MSB is at index 0.
203 // LittleEndian: extelt (bitcast i32 X to v4i8), 0 -> trunc i32 X to i8
204 // BigEndian: extelt (bitcast i32 X to v4i8), 0 -> trunc i32 (X >> 24) to i8
205 if (IsBigEndian)
206 ExtIndexC = NumElts.getKnownMinValue() - 1 - ExtIndexC;
207 unsigned ShiftAmountC = ExtIndexC * DestWidth;
208 if (!ShiftAmountC ||
209 (isDesirableIntType(BitWidth: X->getType()->getPrimitiveSizeInBits()) &&
210 Ext.getVectorOperand()->hasOneUse())) {
211 if (ShiftAmountC)
212 X = Builder.CreateLShr(LHS: X, RHS: ShiftAmountC, Name: "extelt.offset");
213 if (DestTy->isFloatingPointTy()) {
214 Type *DstIntTy = IntegerType::getIntNTy(C&: X->getContext(), N: DestWidth);
215 Value *Trunc = Builder.CreateTrunc(V: X, DestTy: DstIntTy);
216 return new BitCastInst(Trunc, DestTy);
217 }
218 return new TruncInst(X, DestTy);
219 }
220 }
221
222 if (!X->getType()->isVectorTy())
223 return nullptr;
224
225 // If this extractelement is using a bitcast from a vector of the same number
226 // of elements, see if we can find the source element from the source vector:
227 // extelt (bitcast VecX), IndexC --> bitcast X[IndexC]
228 auto *SrcTy = cast<VectorType>(Val: X->getType());
229 ElementCount NumSrcElts = SrcTy->getElementCount();
230 if (NumSrcElts == NumElts)
231 if (Value *Elt = findScalarElement(V: X, EltNo: ExtIndexC))
232 return new BitCastInst(Elt, DestTy);
233
234 assert(NumSrcElts.isScalable() == NumElts.isScalable() &&
235 "Src and Dst must be the same sort of vector type");
236
237 // If the source elements are wider than the destination, try to shift and
238 // truncate a subset of scalar bits of an insert op.
239 if (NumSrcElts.getKnownMinValue() < NumElts.getKnownMinValue()) {
240 Value *Scalar;
241 Value *Vec;
242 uint64_t InsIndexC;
243 if (!match(V: X, P: m_InsertElt(Val: m_Value(V&: Vec), Elt: m_Value(V&: Scalar),
244 Idx: m_ConstantInt(V&: InsIndexC))))
245 return nullptr;
246
247 // The extract must be from the subset of vector elements that we inserted
248 // into. Example: if we inserted element 1 of a <2 x i64> and we are
249 // extracting an i16 (narrowing ratio = 4), then this extract must be from 1
250 // of elements 4-7 of the bitcasted vector.
251 unsigned NarrowingRatio =
252 NumElts.getKnownMinValue() / NumSrcElts.getKnownMinValue();
253
254 if (ExtIndexC / NarrowingRatio != InsIndexC) {
255 // Remove insertelement, if we don't use the inserted element.
256 // extractelement (bitcast (insertelement (Vec, b)), a) ->
257 // extractelement (bitcast (Vec), a)
258 // FIXME: this should be removed to SimplifyDemandedVectorElts,
259 // once scale vectors are supported.
260 if (X->hasOneUse() && Ext.getVectorOperand()->hasOneUse()) {
261 Value *NewBC = Builder.CreateBitCast(V: Vec, DestTy: Ext.getVectorOperandType());
262 return ExtractElementInst::Create(Vec: NewBC, Idx: Ext.getIndexOperand());
263 }
264 return nullptr;
265 }
266
267 // We are extracting part of the original scalar. How that scalar is
268 // inserted into the vector depends on the endian-ness. Example:
269 // Vector Byte Elt Index: 0 1 2 3 4 5 6 7
270 // +--+--+--+--+--+--+--+--+
271 // inselt <2 x i32> V, <i32> S, 1: |V0|V1|V2|V3|S0|S1|S2|S3|
272 // extelt <4 x i16> V', 3: | |S2|S3|
273 // +--+--+--+--+--+--+--+--+
274 // If this is little-endian, S2|S3 are the MSB of the 32-bit 'S' value.
275 // If this is big-endian, S2|S3 are the LSB of the 32-bit 'S' value.
276 // In this example, we must right-shift little-endian. Big-endian is just a
277 // truncate.
278 unsigned Chunk = ExtIndexC % NarrowingRatio;
279 if (IsBigEndian)
280 Chunk = NarrowingRatio - 1 - Chunk;
281
282 // Bail out if this is an FP vector to FP vector sequence. That would take
283 // more instructions than we started with unless there is no shift, and it
284 // may not be handled as well in the backend.
285 bool NeedSrcBitcast = SrcTy->getScalarType()->isFloatingPointTy();
286 bool NeedDestBitcast = DestTy->isFloatingPointTy();
287 if (NeedSrcBitcast && NeedDestBitcast)
288 return nullptr;
289
290 unsigned SrcWidth = SrcTy->getScalarSizeInBits();
291 unsigned ShAmt = Chunk * DestWidth;
292
293 // TODO: This limitation is more strict than necessary. We could sum the
294 // number of new instructions and subtract the number eliminated to know if
295 // we can proceed.
296 if (!X->hasOneUse() || !Ext.getVectorOperand()->hasOneUse())
297 if (NeedSrcBitcast || NeedDestBitcast)
298 return nullptr;
299
300 if (NeedSrcBitcast) {
301 Type *SrcIntTy = IntegerType::getIntNTy(C&: Scalar->getContext(), N: SrcWidth);
302 Scalar = Builder.CreateBitCast(V: Scalar, DestTy: SrcIntTy);
303 }
304
305 if (ShAmt) {
306 // Bail out if we could end with more instructions than we started with.
307 if (!Ext.getVectorOperand()->hasOneUse())
308 return nullptr;
309 Scalar = Builder.CreateLShr(LHS: Scalar, RHS: ShAmt);
310 }
311
312 if (NeedDestBitcast) {
313 Type *DestIntTy = IntegerType::getIntNTy(C&: Scalar->getContext(), N: DestWidth);
314 return new BitCastInst(Builder.CreateTrunc(V: Scalar, DestTy: DestIntTy), DestTy);
315 }
316 return new TruncInst(Scalar, DestTy);
317 }
318
319 return nullptr;
320}
321
322/// Find elements of V demanded by UserInstr.
323static APInt findDemandedEltsBySingleUser(Value *V, Instruction *UserInstr) {
324 unsigned VWidth = cast<FixedVectorType>(Val: V->getType())->getNumElements();
325
326 // Conservatively assume that all elements are needed.
327 APInt UsedElts(APInt::getAllOnes(numBits: VWidth));
328
329 switch (UserInstr->getOpcode()) {
330 case Instruction::ExtractElement: {
331 ExtractElementInst *EEI = cast<ExtractElementInst>(Val: UserInstr);
332 assert(EEI->getVectorOperand() == V);
333 ConstantInt *EEIIndexC = dyn_cast<ConstantInt>(Val: EEI->getIndexOperand());
334 if (EEIIndexC && EEIIndexC->getValue().ult(RHS: VWidth)) {
335 UsedElts = APInt::getOneBitSet(numBits: VWidth, BitNo: EEIIndexC->getZExtValue());
336 }
337 break;
338 }
339 case Instruction::ShuffleVector: {
340 ShuffleVectorInst *Shuffle = cast<ShuffleVectorInst>(Val: UserInstr);
341 unsigned MaskNumElts =
342 cast<FixedVectorType>(Val: UserInstr->getType())->getNumElements();
343
344 UsedElts = APInt(VWidth, 0);
345 for (unsigned i = 0; i < MaskNumElts; i++) {
346 unsigned MaskVal = Shuffle->getMaskValue(Elt: i);
347 if (MaskVal == -1u || MaskVal >= 2 * VWidth)
348 continue;
349 if (Shuffle->getOperand(i_nocapture: 0) == V && (MaskVal < VWidth))
350 UsedElts.setBit(MaskVal);
351 if (Shuffle->getOperand(i_nocapture: 1) == V &&
352 ((MaskVal >= VWidth) && (MaskVal < 2 * VWidth)))
353 UsedElts.setBit(MaskVal - VWidth);
354 }
355 break;
356 }
357 default:
358 break;
359 }
360 return UsedElts;
361}
362
363/// Find union of elements of V demanded by all its users.
364/// If it is known by querying findDemandedEltsBySingleUser that
365/// no user demands an element of V, then the corresponding bit
366/// remains unset in the returned value.
367static APInt findDemandedEltsByAllUsers(Value *V) {
368 unsigned VWidth = cast<FixedVectorType>(Val: V->getType())->getNumElements();
369
370 APInt UnionUsedElts(VWidth, 0);
371 for (const Use &U : V->uses()) {
372 if (Instruction *I = dyn_cast<Instruction>(Val: U.getUser())) {
373 UnionUsedElts |= findDemandedEltsBySingleUser(V, UserInstr: I);
374 } else {
375 UnionUsedElts = APInt::getAllOnes(numBits: VWidth);
376 break;
377 }
378
379 if (UnionUsedElts.isAllOnes())
380 break;
381 }
382
383 return UnionUsedElts;
384}
385
386/// Given a constant index for a extractelement or insertelement instruction,
387/// return it with the canonical type if it isn't already canonical. We
388/// arbitrarily pick 64 bit as our canonical type. The actual bitwidth doesn't
389/// matter, we just want a consistent type to simplify CSE.
390static ConstantInt *getPreferredVectorIndex(ConstantInt *IndexC) {
391 const unsigned IndexBW = IndexC->getBitWidth();
392 if (IndexBW == 64 || IndexC->getValue().getActiveBits() > 64)
393 return nullptr;
394 return ConstantInt::get(Context&: IndexC->getContext(),
395 V: IndexC->getValue().zextOrTrunc(width: 64));
396}
397
398Instruction *InstCombinerImpl::visitExtractElementInst(ExtractElementInst &EI) {
399 Value *SrcVec = EI.getVectorOperand();
400 Value *Index = EI.getIndexOperand();
401 if (Value *V = simplifyExtractElementInst(Vec: SrcVec, Idx: Index,
402 Q: SQ.getWithInstruction(I: &EI)))
403 return replaceInstUsesWith(I&: EI, V);
404
405 // extractelt (select %x, %vec1, %vec2), %const ->
406 // select %x, %vec1[%const], %vec2[%const]
407 // TODO: Support constant folding of multiple select operands:
408 // extractelt (select %x, %vec1, %vec2), (select %x, %c1, %c2)
409 // If the extractelement will for instance try to do out of bounds accesses
410 // because of the values of %c1 and/or %c2, the sequence could be optimized
411 // early. This is currently not possible because constant folding will reach
412 // an unreachable assertion if it doesn't find a constant operand.
413 if (SelectInst *SI = dyn_cast<SelectInst>(Val: EI.getVectorOperand()))
414 if (SI->getCondition()->getType()->isIntegerTy() &&
415 isa<Constant>(Val: EI.getIndexOperand()))
416 if (Instruction *R = FoldOpIntoSelect(Op&: EI, SI))
417 return R;
418
419 // If extracting a specified index from the vector, see if we can recursively
420 // find a previously computed scalar that was inserted into the vector.
421 auto *IndexC = dyn_cast<ConstantInt>(Val: Index);
422 bool HasKnownValidIndex = false;
423 if (IndexC) {
424 // Canonicalize type of constant indices to i64 to simplify CSE
425 if (auto *NewIdx = getPreferredVectorIndex(IndexC))
426 return replaceOperand(I&: EI, OpNum: 1, V: NewIdx);
427
428 ElementCount EC = EI.getVectorOperandType()->getElementCount();
429 unsigned NumElts = EC.getKnownMinValue();
430 HasKnownValidIndex = IndexC->getValue().ult(RHS: NumElts);
431
432 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Val: SrcVec)) {
433 Intrinsic::ID IID = II->getIntrinsicID();
434 // Index needs to be lower than the minimum size of the vector, because
435 // for scalable vector, the vector size is known at run time.
436 if (IID == Intrinsic::experimental_stepvector &&
437 IndexC->getValue().ult(RHS: NumElts)) {
438 Type *Ty = EI.getType();
439 unsigned BitWidth = Ty->getIntegerBitWidth();
440 Value *Idx;
441 // Return index when its value does not exceed the allowed limit
442 // for the element type of the vector, otherwise return undefined.
443 if (IndexC->getValue().getActiveBits() <= BitWidth)
444 Idx = ConstantInt::get(Ty, V: IndexC->getValue().zextOrTrunc(width: BitWidth));
445 else
446 Idx = PoisonValue::get(T: Ty);
447 return replaceInstUsesWith(I&: EI, V: Idx);
448 }
449 }
450
451 // InstSimplify should handle cases where the index is invalid.
452 // For fixed-length vector, it's invalid to extract out-of-range element.
453 if (!EC.isScalable() && IndexC->getValue().uge(RHS: NumElts))
454 return nullptr;
455
456 if (Instruction *I = foldBitcastExtElt(Ext&: EI))
457 return I;
458
459 // If there's a vector PHI feeding a scalar use through this extractelement
460 // instruction, try to scalarize the PHI.
461 if (auto *Phi = dyn_cast<PHINode>(Val: SrcVec))
462 if (Instruction *ScalarPHI = scalarizePHI(EI, PN: Phi))
463 return ScalarPHI;
464 }
465
466 // TODO come up with a n-ary matcher that subsumes both unary and
467 // binary matchers.
468 UnaryOperator *UO;
469 if (match(V: SrcVec, P: m_UnOp(I&: UO)) && cheapToScalarize(V: SrcVec, EI: Index)) {
470 // extelt (unop X), Index --> unop (extelt X, Index)
471 Value *X = UO->getOperand(i_nocapture: 0);
472 Value *E = Builder.CreateExtractElement(Vec: X, Idx: Index);
473 return UnaryOperator::CreateWithCopiedFlags(Opc: UO->getOpcode(), V: E, CopyO: UO);
474 }
475
476 // If the binop is not speculatable, we cannot hoist the extractelement if
477 // it may make the operand poison.
478 BinaryOperator *BO;
479 if (match(V: SrcVec, P: m_BinOp(I&: BO)) && cheapToScalarize(V: SrcVec, EI: Index) &&
480 (HasKnownValidIndex || isSafeToSpeculativelyExecute(I: BO))) {
481 // extelt (binop X, Y), Index --> binop (extelt X, Index), (extelt Y, Index)
482 Value *X = BO->getOperand(i_nocapture: 0), *Y = BO->getOperand(i_nocapture: 1);
483 Value *E0 = Builder.CreateExtractElement(Vec: X, Idx: Index);
484 Value *E1 = Builder.CreateExtractElement(Vec: Y, Idx: Index);
485 return BinaryOperator::CreateWithCopiedFlags(Opc: BO->getOpcode(), V1: E0, V2: E1, CopyO: BO);
486 }
487
488 Value *X, *Y;
489 CmpInst::Predicate Pred;
490 if (match(V: SrcVec, P: m_Cmp(Pred, L: m_Value(V&: X), R: m_Value(V&: Y))) &&
491 cheapToScalarize(V: SrcVec, EI: Index)) {
492 // extelt (cmp X, Y), Index --> cmp (extelt X, Index), (extelt Y, Index)
493 Value *E0 = Builder.CreateExtractElement(Vec: X, Idx: Index);
494 Value *E1 = Builder.CreateExtractElement(Vec: Y, Idx: Index);
495 CmpInst *SrcCmpInst = cast<CmpInst>(Val: SrcVec);
496 return CmpInst::CreateWithCopiedFlags(Op: SrcCmpInst->getOpcode(), Pred, S1: E0, S2: E1,
497 FlagsSource: SrcCmpInst);
498 }
499
500 if (auto *I = dyn_cast<Instruction>(Val: SrcVec)) {
501 if (auto *IE = dyn_cast<InsertElementInst>(Val: I)) {
502 // instsimplify already handled the case where the indices are constants
503 // and equal by value, if both are constants, they must not be the same
504 // value, extract from the pre-inserted value instead.
505 if (isa<Constant>(Val: IE->getOperand(i_nocapture: 2)) && IndexC)
506 return replaceOperand(I&: EI, OpNum: 0, V: IE->getOperand(i_nocapture: 0));
507 } else if (auto *GEP = dyn_cast<GetElementPtrInst>(Val: I)) {
508 auto *VecType = cast<VectorType>(Val: GEP->getType());
509 ElementCount EC = VecType->getElementCount();
510 uint64_t IdxVal = IndexC ? IndexC->getZExtValue() : 0;
511 if (IndexC && IdxVal < EC.getKnownMinValue() && GEP->hasOneUse()) {
512 // Find out why we have a vector result - these are a few examples:
513 // 1. We have a scalar pointer and a vector of indices, or
514 // 2. We have a vector of pointers and a scalar index, or
515 // 3. We have a vector of pointers and a vector of indices, etc.
516 // Here we only consider combining when there is exactly one vector
517 // operand, since the optimization is less obviously a win due to
518 // needing more than one extractelements.
519
520 unsigned VectorOps =
521 llvm::count_if(Range: GEP->operands(), P: [](const Value *V) {
522 return isa<VectorType>(Val: V->getType());
523 });
524 if (VectorOps == 1) {
525 Value *NewPtr = GEP->getPointerOperand();
526 if (isa<VectorType>(Val: NewPtr->getType()))
527 NewPtr = Builder.CreateExtractElement(Vec: NewPtr, Idx: IndexC);
528
529 SmallVector<Value *> NewOps;
530 for (unsigned I = 1; I != GEP->getNumOperands(); ++I) {
531 Value *Op = GEP->getOperand(i_nocapture: I);
532 if (isa<VectorType>(Val: Op->getType()))
533 NewOps.push_back(Elt: Builder.CreateExtractElement(Vec: Op, Idx: IndexC));
534 else
535 NewOps.push_back(Elt: Op);
536 }
537
538 GetElementPtrInst *NewGEP = GetElementPtrInst::Create(
539 PointeeType: GEP->getSourceElementType(), Ptr: NewPtr, IdxList: NewOps);
540 NewGEP->setIsInBounds(GEP->isInBounds());
541 return NewGEP;
542 }
543 }
544 } else if (auto *SVI = dyn_cast<ShuffleVectorInst>(Val: I)) {
545 // If this is extracting an element from a shufflevector, figure out where
546 // it came from and extract from the appropriate input element instead.
547 // Restrict the following transformation to fixed-length vector.
548 if (isa<FixedVectorType>(Val: SVI->getType()) && isa<ConstantInt>(Val: Index)) {
549 int SrcIdx =
550 SVI->getMaskValue(Elt: cast<ConstantInt>(Val: Index)->getZExtValue());
551 Value *Src;
552 unsigned LHSWidth = cast<FixedVectorType>(Val: SVI->getOperand(i_nocapture: 0)->getType())
553 ->getNumElements();
554
555 if (SrcIdx < 0)
556 return replaceInstUsesWith(I&: EI, V: PoisonValue::get(T: EI.getType()));
557 if (SrcIdx < (int)LHSWidth)
558 Src = SVI->getOperand(i_nocapture: 0);
559 else {
560 SrcIdx -= LHSWidth;
561 Src = SVI->getOperand(i_nocapture: 1);
562 }
563 Type *Int64Ty = Type::getInt64Ty(C&: EI.getContext());
564 return ExtractElementInst::Create(
565 Vec: Src, Idx: ConstantInt::get(Ty: Int64Ty, V: SrcIdx, IsSigned: false));
566 }
567 } else if (auto *CI = dyn_cast<CastInst>(Val: I)) {
568 // Canonicalize extractelement(cast) -> cast(extractelement).
569 // Bitcasts can change the number of vector elements, and they cost
570 // nothing.
571 if (CI->hasOneUse() && (CI->getOpcode() != Instruction::BitCast)) {
572 Value *EE = Builder.CreateExtractElement(Vec: CI->getOperand(i_nocapture: 0), Idx: Index);
573 return CastInst::Create(CI->getOpcode(), S: EE, Ty: EI.getType());
574 }
575 }
576 }
577
578 // Run demanded elements after other transforms as this can drop flags on
579 // binops. If there's two paths to the same final result, we prefer the
580 // one which doesn't force us to drop flags.
581 if (IndexC) {
582 ElementCount EC = EI.getVectorOperandType()->getElementCount();
583 unsigned NumElts = EC.getKnownMinValue();
584 // This instruction only demands the single element from the input vector.
585 // Skip for scalable type, the number of elements is unknown at
586 // compile-time.
587 if (!EC.isScalable() && NumElts != 1) {
588 // If the input vector has a single use, simplify it based on this use
589 // property.
590 if (SrcVec->hasOneUse()) {
591 APInt PoisonElts(NumElts, 0);
592 APInt DemandedElts(NumElts, 0);
593 DemandedElts.setBit(IndexC->getZExtValue());
594 if (Value *V =
595 SimplifyDemandedVectorElts(V: SrcVec, DemandedElts, PoisonElts))
596 return replaceOperand(I&: EI, OpNum: 0, V);
597 } else {
598 // If the input vector has multiple uses, simplify it based on a union
599 // of all elements used.
600 APInt DemandedElts = findDemandedEltsByAllUsers(V: SrcVec);
601 if (!DemandedElts.isAllOnes()) {
602 APInt PoisonElts(NumElts, 0);
603 if (Value *V = SimplifyDemandedVectorElts(
604 V: SrcVec, DemandedElts, PoisonElts, Depth: 0 /* Depth */,
605 AllowMultipleUsers: true /* AllowMultipleUsers */)) {
606 if (V != SrcVec) {
607 Worklist.addValue(V: SrcVec);
608 SrcVec->replaceAllUsesWith(V);
609 return &EI;
610 }
611 }
612 }
613 }
614 }
615 }
616 return nullptr;
617}
618
619/// If V is a shuffle of values that ONLY returns elements from either LHS or
620/// RHS, return the shuffle mask and true. Otherwise, return false.
621static bool collectSingleShuffleElements(Value *V, Value *LHS, Value *RHS,
622 SmallVectorImpl<int> &Mask) {
623 assert(LHS->getType() == RHS->getType() &&
624 "Invalid CollectSingleShuffleElements");
625 unsigned NumElts = cast<FixedVectorType>(Val: V->getType())->getNumElements();
626
627 if (match(V, P: m_Poison())) {
628 Mask.assign(NumElts, Elt: -1);
629 return true;
630 }
631
632 if (V == LHS) {
633 for (unsigned i = 0; i != NumElts; ++i)
634 Mask.push_back(Elt: i);
635 return true;
636 }
637
638 if (V == RHS) {
639 for (unsigned i = 0; i != NumElts; ++i)
640 Mask.push_back(Elt: i + NumElts);
641 return true;
642 }
643
644 if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(Val: V)) {
645 // If this is an insert of an extract from some other vector, include it.
646 Value *VecOp = IEI->getOperand(i_nocapture: 0);
647 Value *ScalarOp = IEI->getOperand(i_nocapture: 1);
648 Value *IdxOp = IEI->getOperand(i_nocapture: 2);
649
650 if (!isa<ConstantInt>(Val: IdxOp))
651 return false;
652 unsigned InsertedIdx = cast<ConstantInt>(Val: IdxOp)->getZExtValue();
653
654 if (isa<PoisonValue>(Val: ScalarOp)) { // inserting poison into vector.
655 // We can handle this if the vector we are inserting into is
656 // transitively ok.
657 if (collectSingleShuffleElements(V: VecOp, LHS, RHS, Mask)) {
658 // If so, update the mask to reflect the inserted poison.
659 Mask[InsertedIdx] = -1;
660 return true;
661 }
662 } else if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(Val: ScalarOp)){
663 if (isa<ConstantInt>(Val: EI->getOperand(i_nocapture: 1))) {
664 unsigned ExtractedIdx =
665 cast<ConstantInt>(Val: EI->getOperand(i_nocapture: 1))->getZExtValue();
666 unsigned NumLHSElts =
667 cast<FixedVectorType>(Val: LHS->getType())->getNumElements();
668
669 // This must be extracting from either LHS or RHS.
670 if (EI->getOperand(i_nocapture: 0) == LHS || EI->getOperand(i_nocapture: 0) == RHS) {
671 // We can handle this if the vector we are inserting into is
672 // transitively ok.
673 if (collectSingleShuffleElements(V: VecOp, LHS, RHS, Mask)) {
674 // If so, update the mask to reflect the inserted value.
675 if (EI->getOperand(i_nocapture: 0) == LHS) {
676 Mask[InsertedIdx % NumElts] = ExtractedIdx;
677 } else {
678 assert(EI->getOperand(0) == RHS);
679 Mask[InsertedIdx % NumElts] = ExtractedIdx + NumLHSElts;
680 }
681 return true;
682 }
683 }
684 }
685 }
686 }
687
688 return false;
689}
690
691/// If we have insertion into a vector that is wider than the vector that we
692/// are extracting from, try to widen the source vector to allow a single
693/// shufflevector to replace one or more insert/extract pairs.
694static bool replaceExtractElements(InsertElementInst *InsElt,
695 ExtractElementInst *ExtElt,
696 InstCombinerImpl &IC) {
697 auto *InsVecType = cast<FixedVectorType>(Val: InsElt->getType());
698 auto *ExtVecType = cast<FixedVectorType>(Val: ExtElt->getVectorOperandType());
699 unsigned NumInsElts = InsVecType->getNumElements();
700 unsigned NumExtElts = ExtVecType->getNumElements();
701
702 // The inserted-to vector must be wider than the extracted-from vector.
703 if (InsVecType->getElementType() != ExtVecType->getElementType() ||
704 NumExtElts >= NumInsElts)
705 return false;
706
707 // Create a shuffle mask to widen the extended-from vector using poison
708 // values. The mask selects all of the values of the original vector followed
709 // by as many poison values as needed to create a vector of the same length
710 // as the inserted-to vector.
711 SmallVector<int, 16> ExtendMask;
712 for (unsigned i = 0; i < NumExtElts; ++i)
713 ExtendMask.push_back(Elt: i);
714 for (unsigned i = NumExtElts; i < NumInsElts; ++i)
715 ExtendMask.push_back(Elt: -1);
716
717 Value *ExtVecOp = ExtElt->getVectorOperand();
718 auto *ExtVecOpInst = dyn_cast<Instruction>(Val: ExtVecOp);
719 BasicBlock *InsertionBlock = (ExtVecOpInst && !isa<PHINode>(Val: ExtVecOpInst))
720 ? ExtVecOpInst->getParent()
721 : ExtElt->getParent();
722
723 // TODO: This restriction matches the basic block check below when creating
724 // new extractelement instructions. If that limitation is removed, this one
725 // could also be removed. But for now, we just bail out to ensure that we
726 // will replace the extractelement instruction that is feeding our
727 // insertelement instruction. This allows the insertelement to then be
728 // replaced by a shufflevector. If the insertelement is not replaced, we can
729 // induce infinite looping because there's an optimization for extractelement
730 // that will delete our widening shuffle. This would trigger another attempt
731 // here to create that shuffle, and we spin forever.
732 if (InsertionBlock != InsElt->getParent())
733 return false;
734
735 // TODO: This restriction matches the check in visitInsertElementInst() and
736 // prevents an infinite loop caused by not turning the extract/insert pair
737 // into a shuffle. We really should not need either check, but we're lacking
738 // folds for shufflevectors because we're afraid to generate shuffle masks
739 // that the backend can't handle.
740 if (InsElt->hasOneUse() && isa<InsertElementInst>(Val: InsElt->user_back()))
741 return false;
742
743 auto *WideVec = new ShuffleVectorInst(ExtVecOp, ExtendMask);
744
745 // Insert the new shuffle after the vector operand of the extract is defined
746 // (as long as it's not a PHI) or at the start of the basic block of the
747 // extract, so any subsequent extracts in the same basic block can use it.
748 // TODO: Insert before the earliest ExtractElementInst that is replaced.
749 if (ExtVecOpInst && !isa<PHINode>(Val: ExtVecOpInst))
750 WideVec->insertAfter(InsertPos: ExtVecOpInst);
751 else
752 IC.InsertNewInstWith(New: WideVec, Old: ExtElt->getParent()->getFirstInsertionPt());
753
754 // Replace extracts from the original narrow vector with extracts from the new
755 // wide vector.
756 for (User *U : ExtVecOp->users()) {
757 ExtractElementInst *OldExt = dyn_cast<ExtractElementInst>(Val: U);
758 if (!OldExt || OldExt->getParent() != WideVec->getParent())
759 continue;
760 auto *NewExt = ExtractElementInst::Create(Vec: WideVec, Idx: OldExt->getOperand(i_nocapture: 1));
761 IC.InsertNewInstWith(New: NewExt, Old: OldExt->getIterator());
762 IC.replaceInstUsesWith(I&: *OldExt, V: NewExt);
763 // Add the old extracts to the worklist for DCE. We can't remove the
764 // extracts directly, because they may still be used by the calling code.
765 IC.addToWorklist(I: OldExt);
766 }
767
768 return true;
769}
770
771/// We are building a shuffle to create V, which is a sequence of insertelement,
772/// extractelement pairs. If PermittedRHS is set, then we must either use it or
773/// not rely on the second vector source. Return a std::pair containing the
774/// left and right vectors of the proposed shuffle (or 0), and set the Mask
775/// parameter as required.
776///
777/// Note: we intentionally don't try to fold earlier shuffles since they have
778/// often been chosen carefully to be efficiently implementable on the target.
779using ShuffleOps = std::pair<Value *, Value *>;
780
781static ShuffleOps collectShuffleElements(Value *V, SmallVectorImpl<int> &Mask,
782 Value *PermittedRHS,
783 InstCombinerImpl &IC, bool &Rerun) {
784 assert(V->getType()->isVectorTy() && "Invalid shuffle!");
785 unsigned NumElts = cast<FixedVectorType>(Val: V->getType())->getNumElements();
786
787 if (match(V, P: m_Poison())) {
788 Mask.assign(NumElts, Elt: -1);
789 return std::make_pair(
790 x: PermittedRHS ? PoisonValue::get(T: PermittedRHS->getType()) : V, y: nullptr);
791 }
792
793 if (isa<ConstantAggregateZero>(Val: V)) {
794 Mask.assign(NumElts, Elt: 0);
795 return std::make_pair(x&: V, y: nullptr);
796 }
797
798 if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(Val: V)) {
799 // If this is an insert of an extract from some other vector, include it.
800 Value *VecOp = IEI->getOperand(i_nocapture: 0);
801 Value *ScalarOp = IEI->getOperand(i_nocapture: 1);
802 Value *IdxOp = IEI->getOperand(i_nocapture: 2);
803
804 if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(Val: ScalarOp)) {
805 if (isa<ConstantInt>(Val: EI->getOperand(i_nocapture: 1)) && isa<ConstantInt>(Val: IdxOp)) {
806 unsigned ExtractedIdx =
807 cast<ConstantInt>(Val: EI->getOperand(i_nocapture: 1))->getZExtValue();
808 unsigned InsertedIdx = cast<ConstantInt>(Val: IdxOp)->getZExtValue();
809
810 // Either the extracted from or inserted into vector must be RHSVec,
811 // otherwise we'd end up with a shuffle of three inputs.
812 if (EI->getOperand(i_nocapture: 0) == PermittedRHS || PermittedRHS == nullptr) {
813 Value *RHS = EI->getOperand(i_nocapture: 0);
814 ShuffleOps LR = collectShuffleElements(V: VecOp, Mask, PermittedRHS: RHS, IC, Rerun);
815 assert(LR.second == nullptr || LR.second == RHS);
816
817 if (LR.first->getType() != RHS->getType()) {
818 // Although we are giving up for now, see if we can create extracts
819 // that match the inserts for another round of combining.
820 if (replaceExtractElements(InsElt: IEI, ExtElt: EI, IC))
821 Rerun = true;
822
823 // We tried our best, but we can't find anything compatible with RHS
824 // further up the chain. Return a trivial shuffle.
825 for (unsigned i = 0; i < NumElts; ++i)
826 Mask[i] = i;
827 return std::make_pair(x&: V, y: nullptr);
828 }
829
830 unsigned NumLHSElts =
831 cast<FixedVectorType>(Val: RHS->getType())->getNumElements();
832 Mask[InsertedIdx % NumElts] = NumLHSElts + ExtractedIdx;
833 return std::make_pair(x&: LR.first, y&: RHS);
834 }
835
836 if (VecOp == PermittedRHS) {
837 // We've gone as far as we can: anything on the other side of the
838 // extractelement will already have been converted into a shuffle.
839 unsigned NumLHSElts =
840 cast<FixedVectorType>(Val: EI->getOperand(i_nocapture: 0)->getType())
841 ->getNumElements();
842 for (unsigned i = 0; i != NumElts; ++i)
843 Mask.push_back(Elt: i == InsertedIdx ? ExtractedIdx : NumLHSElts + i);
844 return std::make_pair(x: EI->getOperand(i_nocapture: 0), y&: PermittedRHS);
845 }
846
847 // If this insertelement is a chain that comes from exactly these two
848 // vectors, return the vector and the effective shuffle.
849 if (EI->getOperand(i_nocapture: 0)->getType() == PermittedRHS->getType() &&
850 collectSingleShuffleElements(V: IEI, LHS: EI->getOperand(i_nocapture: 0), RHS: PermittedRHS,
851 Mask))
852 return std::make_pair(x: EI->getOperand(i_nocapture: 0), y&: PermittedRHS);
853 }
854 }
855 }
856
857 // Otherwise, we can't do anything fancy. Return an identity vector.
858 for (unsigned i = 0; i != NumElts; ++i)
859 Mask.push_back(Elt: i);
860 return std::make_pair(x&: V, y: nullptr);
861}
862
863/// Look for chain of insertvalue's that fully define an aggregate, and trace
864/// back the values inserted, see if they are all were extractvalue'd from
865/// the same source aggregate from the exact same element indexes.
866/// If they were, just reuse the source aggregate.
867/// This potentially deals with PHI indirections.
868Instruction *InstCombinerImpl::foldAggregateConstructionIntoAggregateReuse(
869 InsertValueInst &OrigIVI) {
870 Type *AggTy = OrigIVI.getType();
871 unsigned NumAggElts;
872 switch (AggTy->getTypeID()) {
873 case Type::StructTyID:
874 NumAggElts = AggTy->getStructNumElements();
875 break;
876 case Type::ArrayTyID:
877 NumAggElts = AggTy->getArrayNumElements();
878 break;
879 default:
880 llvm_unreachable("Unhandled aggregate type?");
881 }
882
883 // Arbitrary aggregate size cut-off. Motivation for limit of 2 is to be able
884 // to handle clang C++ exception struct (which is hardcoded as {i8*, i32}),
885 // FIXME: any interesting patterns to be caught with larger limit?
886 assert(NumAggElts > 0 && "Aggregate should have elements.");
887 if (NumAggElts > 2)
888 return nullptr;
889
890 static constexpr auto NotFound = std::nullopt;
891 static constexpr auto FoundMismatch = nullptr;
892
893 // Try to find a value of each element of an aggregate.
894 // FIXME: deal with more complex, not one-dimensional, aggregate types
895 SmallVector<std::optional<Instruction *>, 2> AggElts(NumAggElts, NotFound);
896
897 // Do we know values for each element of the aggregate?
898 auto KnowAllElts = [&AggElts]() {
899 return !llvm::is_contained(Range&: AggElts, Element: NotFound);
900 };
901
902 int Depth = 0;
903
904 // Arbitrary `insertvalue` visitation depth limit. Let's be okay with
905 // every element being overwritten twice, which should never happen.
906 static const int DepthLimit = 2 * NumAggElts;
907
908 // Recurse up the chain of `insertvalue` aggregate operands until either we've
909 // reconstructed full initializer or can't visit any more `insertvalue`'s.
910 for (InsertValueInst *CurrIVI = &OrigIVI;
911 Depth < DepthLimit && CurrIVI && !KnowAllElts();
912 CurrIVI = dyn_cast<InsertValueInst>(Val: CurrIVI->getAggregateOperand()),
913 ++Depth) {
914 auto *InsertedValue =
915 dyn_cast<Instruction>(Val: CurrIVI->getInsertedValueOperand());
916 if (!InsertedValue)
917 return nullptr; // Inserted value must be produced by an instruction.
918
919 ArrayRef<unsigned int> Indices = CurrIVI->getIndices();
920
921 // Don't bother with more than single-level aggregates.
922 if (Indices.size() != 1)
923 return nullptr; // FIXME: deal with more complex aggregates?
924
925 // Now, we may have already previously recorded the value for this element
926 // of an aggregate. If we did, that means the CurrIVI will later be
927 // overwritten with the already-recorded value. But if not, let's record it!
928 std::optional<Instruction *> &Elt = AggElts[Indices.front()];
929 Elt = Elt.value_or(u&: InsertedValue);
930
931 // FIXME: should we handle chain-terminating undef base operand?
932 }
933
934 // Was that sufficient to deduce the full initializer for the aggregate?
935 if (!KnowAllElts())
936 return nullptr; // Give up then.
937
938 // We now want to find the source[s] of the aggregate elements we've found.
939 // And with "source" we mean the original aggregate[s] from which
940 // the inserted elements were extracted. This may require PHI translation.
941
942 enum class AggregateDescription {
943 /// When analyzing the value that was inserted into an aggregate, we did
944 /// not manage to find defining `extractvalue` instruction to analyze.
945 NotFound,
946 /// When analyzing the value that was inserted into an aggregate, we did
947 /// manage to find defining `extractvalue` instruction[s], and everything
948 /// matched perfectly - aggregate type, element insertion/extraction index.
949 Found,
950 /// When analyzing the value that was inserted into an aggregate, we did
951 /// manage to find defining `extractvalue` instruction, but there was
952 /// a mismatch: either the source type from which the extraction was didn't
953 /// match the aggregate type into which the insertion was,
954 /// or the extraction/insertion channels mismatched,
955 /// or different elements had different source aggregates.
956 FoundMismatch
957 };
958 auto Describe = [](std::optional<Value *> SourceAggregate) {
959 if (SourceAggregate == NotFound)
960 return AggregateDescription::NotFound;
961 if (*SourceAggregate == FoundMismatch)
962 return AggregateDescription::FoundMismatch;
963 return AggregateDescription::Found;
964 };
965
966 // Given the value \p Elt that was being inserted into element \p EltIdx of an
967 // aggregate AggTy, see if \p Elt was originally defined by an
968 // appropriate extractvalue (same element index, same aggregate type).
969 // If found, return the source aggregate from which the extraction was.
970 // If \p PredBB is provided, does PHI translation of an \p Elt first.
971 auto FindSourceAggregate =
972 [&](Instruction *Elt, unsigned EltIdx, std::optional<BasicBlock *> UseBB,
973 std::optional<BasicBlock *> PredBB) -> std::optional<Value *> {
974 // For now(?), only deal with, at most, a single level of PHI indirection.
975 if (UseBB && PredBB)
976 Elt = dyn_cast<Instruction>(Val: Elt->DoPHITranslation(CurBB: *UseBB, PredBB: *PredBB));
977 // FIXME: deal with multiple levels of PHI indirection?
978
979 // Did we find an extraction?
980 auto *EVI = dyn_cast_or_null<ExtractValueInst>(Val: Elt);
981 if (!EVI)
982 return NotFound;
983
984 Value *SourceAggregate = EVI->getAggregateOperand();
985
986 // Is the extraction from the same type into which the insertion was?
987 if (SourceAggregate->getType() != AggTy)
988 return FoundMismatch;
989 // And the element index doesn't change between extraction and insertion?
990 if (EVI->getNumIndices() != 1 || EltIdx != EVI->getIndices().front())
991 return FoundMismatch;
992
993 return SourceAggregate; // AggregateDescription::Found
994 };
995
996 // Given elements AggElts that were constructing an aggregate OrigIVI,
997 // see if we can find appropriate source aggregate for each of the elements,
998 // and see it's the same aggregate for each element. If so, return it.
999 auto FindCommonSourceAggregate =
1000 [&](std::optional<BasicBlock *> UseBB,
1001 std::optional<BasicBlock *> PredBB) -> std::optional<Value *> {
1002 std::optional<Value *> SourceAggregate;
1003
1004 for (auto I : enumerate(First&: AggElts)) {
1005 assert(Describe(SourceAggregate) != AggregateDescription::FoundMismatch &&
1006 "We don't store nullptr in SourceAggregate!");
1007 assert((Describe(SourceAggregate) == AggregateDescription::Found) ==
1008 (I.index() != 0) &&
1009 "SourceAggregate should be valid after the first element,");
1010
1011 // For this element, is there a plausible source aggregate?
1012 // FIXME: we could special-case undef element, IFF we know that in the
1013 // source aggregate said element isn't poison.
1014 std::optional<Value *> SourceAggregateForElement =
1015 FindSourceAggregate(*I.value(), I.index(), UseBB, PredBB);
1016
1017 // Okay, what have we found? Does that correlate with previous findings?
1018
1019 // Regardless of whether or not we have previously found source
1020 // aggregate for previous elements (if any), if we didn't find one for
1021 // this element, passthrough whatever we have just found.
1022 if (Describe(SourceAggregateForElement) != AggregateDescription::Found)
1023 return SourceAggregateForElement;
1024
1025 // Okay, we have found source aggregate for this element.
1026 // Let's see what we already know from previous elements, if any.
1027 switch (Describe(SourceAggregate)) {
1028 case AggregateDescription::NotFound:
1029 // This is apparently the first element that we have examined.
1030 SourceAggregate = SourceAggregateForElement; // Record the aggregate!
1031 continue; // Great, now look at next element.
1032 case AggregateDescription::Found:
1033 // We have previously already successfully examined other elements.
1034 // Is this the same source aggregate we've found for other elements?
1035 if (*SourceAggregateForElement != *SourceAggregate)
1036 return FoundMismatch;
1037 continue; // Still the same aggregate, look at next element.
1038 case AggregateDescription::FoundMismatch:
1039 llvm_unreachable("Can't happen. We would have early-exited then.");
1040 };
1041 }
1042
1043 assert(Describe(SourceAggregate) == AggregateDescription::Found &&
1044 "Must be a valid Value");
1045 return *SourceAggregate;
1046 };
1047
1048 std::optional<Value *> SourceAggregate;
1049
1050 // Can we find the source aggregate without looking at predecessors?
1051 SourceAggregate = FindCommonSourceAggregate(/*UseBB=*/std::nullopt,
1052 /*PredBB=*/std::nullopt);
1053 if (Describe(SourceAggregate) != AggregateDescription::NotFound) {
1054 if (Describe(SourceAggregate) == AggregateDescription::FoundMismatch)
1055 return nullptr; // Conflicting source aggregates!
1056 ++NumAggregateReconstructionsSimplified;
1057 return replaceInstUsesWith(I&: OrigIVI, V: *SourceAggregate);
1058 }
1059
1060 // Okay, apparently we need to look at predecessors.
1061
1062 // We should be smart about picking the "use" basic block, which will be the
1063 // merge point for aggregate, where we'll insert the final PHI that will be
1064 // used instead of OrigIVI. Basic block of OrigIVI is *not* the right choice.
1065 // We should look in which blocks each of the AggElts is being defined,
1066 // they all should be defined in the same basic block.
1067 BasicBlock *UseBB = nullptr;
1068
1069 for (const std::optional<Instruction *> &I : AggElts) {
1070 BasicBlock *BB = (*I)->getParent();
1071 // If it's the first instruction we've encountered, record the basic block.
1072 if (!UseBB) {
1073 UseBB = BB;
1074 continue;
1075 }
1076 // Otherwise, this must be the same basic block we've seen previously.
1077 if (UseBB != BB)
1078 return nullptr;
1079 }
1080
1081 // If *all* of the elements are basic-block-independent, meaning they are
1082 // either function arguments, or constant expressions, then if we didn't
1083 // handle them without predecessor-aware handling, we won't handle them now.
1084 if (!UseBB)
1085 return nullptr;
1086
1087 // If we didn't manage to find source aggregate without looking at
1088 // predecessors, and there are no predecessors to look at, then we're done.
1089 if (pred_empty(BB: UseBB))
1090 return nullptr;
1091
1092 // Arbitrary predecessor count limit.
1093 static const int PredCountLimit = 64;
1094
1095 // Cache the (non-uniqified!) list of predecessors in a vector,
1096 // checking the limit at the same time for efficiency.
1097 SmallVector<BasicBlock *, 4> Preds; // May have duplicates!
1098 for (BasicBlock *Pred : predecessors(BB: UseBB)) {
1099 // Don't bother if there are too many predecessors.
1100 if (Preds.size() >= PredCountLimit) // FIXME: only count duplicates once?
1101 return nullptr;
1102 Preds.emplace_back(Args&: Pred);
1103 }
1104
1105 // For each predecessor, what is the source aggregate,
1106 // from which all the elements were originally extracted from?
1107 // Note that we want for the map to have stable iteration order!
1108 SmallDenseMap<BasicBlock *, Value *, 4> SourceAggregates;
1109 for (BasicBlock *Pred : Preds) {
1110 std::pair<decltype(SourceAggregates)::iterator, bool> IV =
1111 SourceAggregates.insert(KV: {Pred, nullptr});
1112 // Did we already evaluate this predecessor?
1113 if (!IV.second)
1114 continue;
1115
1116 // Let's hope that when coming from predecessor Pred, all elements of the
1117 // aggregate produced by OrigIVI must have been originally extracted from
1118 // the same aggregate. Is that so? Can we find said original aggregate?
1119 SourceAggregate = FindCommonSourceAggregate(UseBB, Pred);
1120 if (Describe(SourceAggregate) != AggregateDescription::Found)
1121 return nullptr; // Give up.
1122 IV.first->second = *SourceAggregate;
1123 }
1124
1125 // All good! Now we just need to thread the source aggregates here.
1126 // Note that we have to insert the new PHI here, ourselves, because we can't
1127 // rely on InstCombinerImpl::run() inserting it into the right basic block.
1128 // Note that the same block can be a predecessor more than once,
1129 // and we need to preserve that invariant for the PHI node.
1130 BuilderTy::InsertPointGuard Guard(Builder);
1131 Builder.SetInsertPoint(TheBB: UseBB, IP: UseBB->getFirstNonPHIIt());
1132 auto *PHI =
1133 Builder.CreatePHI(Ty: AggTy, NumReservedValues: Preds.size(), Name: OrigIVI.getName() + ".merged");
1134 for (BasicBlock *Pred : Preds)
1135 PHI->addIncoming(V: SourceAggregates[Pred], BB: Pred);
1136
1137 ++NumAggregateReconstructionsSimplified;
1138 return replaceInstUsesWith(I&: OrigIVI, V: PHI);
1139}
1140
1141/// Try to find redundant insertvalue instructions, like the following ones:
1142/// %0 = insertvalue { i8, i32 } undef, i8 %x, 0
1143/// %1 = insertvalue { i8, i32 } %0, i8 %y, 0
1144/// Here the second instruction inserts values at the same indices, as the
1145/// first one, making the first one redundant.
1146/// It should be transformed to:
1147/// %0 = insertvalue { i8, i32 } undef, i8 %y, 0
1148Instruction *InstCombinerImpl::visitInsertValueInst(InsertValueInst &I) {
1149 if (Value *V = simplifyInsertValueInst(
1150 Agg: I.getAggregateOperand(), Val: I.getInsertedValueOperand(), Idxs: I.getIndices(),
1151 Q: SQ.getWithInstruction(I: &I)))
1152 return replaceInstUsesWith(I, V);
1153
1154 bool IsRedundant = false;
1155 ArrayRef<unsigned int> FirstIndices = I.getIndices();
1156
1157 // If there is a chain of insertvalue instructions (each of them except the
1158 // last one has only one use and it's another insertvalue insn from this
1159 // chain), check if any of the 'children' uses the same indices as the first
1160 // instruction. In this case, the first one is redundant.
1161 Value *V = &I;
1162 unsigned Depth = 0;
1163 while (V->hasOneUse() && Depth < 10) {
1164 User *U = V->user_back();
1165 auto UserInsInst = dyn_cast<InsertValueInst>(Val: U);
1166 if (!UserInsInst || U->getOperand(i: 0) != V)
1167 break;
1168 if (UserInsInst->getIndices() == FirstIndices) {
1169 IsRedundant = true;
1170 break;
1171 }
1172 V = UserInsInst;
1173 Depth++;
1174 }
1175
1176 if (IsRedundant)
1177 return replaceInstUsesWith(I, V: I.getOperand(i_nocapture: 0));
1178
1179 if (Instruction *NewI = foldAggregateConstructionIntoAggregateReuse(OrigIVI&: I))
1180 return NewI;
1181
1182 return nullptr;
1183}
1184
1185static bool isShuffleEquivalentToSelect(ShuffleVectorInst &Shuf) {
1186 // Can not analyze scalable type, the number of elements is not a compile-time
1187 // constant.
1188 if (isa<ScalableVectorType>(Val: Shuf.getOperand(i_nocapture: 0)->getType()))
1189 return false;
1190
1191 int MaskSize = Shuf.getShuffleMask().size();
1192 int VecSize =
1193 cast<FixedVectorType>(Val: Shuf.getOperand(i_nocapture: 0)->getType())->getNumElements();
1194
1195 // A vector select does not change the size of the operands.
1196 if (MaskSize != VecSize)
1197 return false;
1198
1199 // Each mask element must be undefined or choose a vector element from one of
1200 // the source operands without crossing vector lanes.
1201 for (int i = 0; i != MaskSize; ++i) {
1202 int Elt = Shuf.getMaskValue(Elt: i);
1203 if (Elt != -1 && Elt != i && Elt != i + VecSize)
1204 return false;
1205 }
1206
1207 return true;
1208}
1209
1210/// Turn a chain of inserts that splats a value into an insert + shuffle:
1211/// insertelt(insertelt(insertelt(insertelt X, %k, 0), %k, 1), %k, 2) ... ->
1212/// shufflevector(insertelt(X, %k, 0), poison, zero)
1213static Instruction *foldInsSequenceIntoSplat(InsertElementInst &InsElt) {
1214 // We are interested in the last insert in a chain. So if this insert has a
1215 // single user and that user is an insert, bail.
1216 if (InsElt.hasOneUse() && isa<InsertElementInst>(Val: InsElt.user_back()))
1217 return nullptr;
1218
1219 VectorType *VecTy = InsElt.getType();
1220 // Can not handle scalable type, the number of elements is not a compile-time
1221 // constant.
1222 if (isa<ScalableVectorType>(Val: VecTy))
1223 return nullptr;
1224 unsigned NumElements = cast<FixedVectorType>(Val: VecTy)->getNumElements();
1225
1226 // Do not try to do this for a one-element vector, since that's a nop,
1227 // and will cause an inf-loop.
1228 if (NumElements == 1)
1229 return nullptr;
1230
1231 Value *SplatVal = InsElt.getOperand(i_nocapture: 1);
1232 InsertElementInst *CurrIE = &InsElt;
1233 SmallBitVector ElementPresent(NumElements, false);
1234 InsertElementInst *FirstIE = nullptr;
1235
1236 // Walk the chain backwards, keeping track of which indices we inserted into,
1237 // until we hit something that isn't an insert of the splatted value.
1238 while (CurrIE) {
1239 auto *Idx = dyn_cast<ConstantInt>(Val: CurrIE->getOperand(i_nocapture: 2));
1240 if (!Idx || CurrIE->getOperand(i_nocapture: 1) != SplatVal)
1241 return nullptr;
1242
1243 auto *NextIE = dyn_cast<InsertElementInst>(Val: CurrIE->getOperand(i_nocapture: 0));
1244 // Check none of the intermediate steps have any additional uses, except
1245 // for the root insertelement instruction, which can be re-used, if it
1246 // inserts at position 0.
1247 if (CurrIE != &InsElt &&
1248 (!CurrIE->hasOneUse() && (NextIE != nullptr || !Idx->isZero())))
1249 return nullptr;
1250
1251 ElementPresent[Idx->getZExtValue()] = true;
1252 FirstIE = CurrIE;
1253 CurrIE = NextIE;
1254 }
1255
1256 // If this is just a single insertelement (not a sequence), we are done.
1257 if (FirstIE == &InsElt)
1258 return nullptr;
1259
1260 // If we are not inserting into a poison vector, make sure we've seen an
1261 // insert into every element.
1262 // TODO: If the base vector is not undef, it might be better to create a splat
1263 // and then a select-shuffle (blend) with the base vector.
1264 if (!match(V: FirstIE->getOperand(i_nocapture: 0), P: m_Poison()))
1265 if (!ElementPresent.all())
1266 return nullptr;
1267
1268 // Create the insert + shuffle.
1269 Type *Int64Ty = Type::getInt64Ty(C&: InsElt.getContext());
1270 PoisonValue *PoisonVec = PoisonValue::get(T: VecTy);
1271 Constant *Zero = ConstantInt::get(Ty: Int64Ty, V: 0);
1272 if (!cast<ConstantInt>(Val: FirstIE->getOperand(i_nocapture: 2))->isZero())
1273 FirstIE = InsertElementInst::Create(Vec: PoisonVec, NewElt: SplatVal, Idx: Zero, NameStr: "",
1274 InsertBefore: InsElt.getIterator());
1275
1276 // Splat from element 0, but replace absent elements with poison in the mask.
1277 SmallVector<int, 16> Mask(NumElements, 0);
1278 for (unsigned i = 0; i != NumElements; ++i)
1279 if (!ElementPresent[i])
1280 Mask[i] = -1;
1281
1282 return new ShuffleVectorInst(FirstIE, Mask);
1283}
1284
1285/// Try to fold an insert element into an existing splat shuffle by changing
1286/// the shuffle's mask to include the index of this insert element.
1287static Instruction *foldInsEltIntoSplat(InsertElementInst &InsElt) {
1288 // Check if the vector operand of this insert is a canonical splat shuffle.
1289 auto *Shuf = dyn_cast<ShuffleVectorInst>(Val: InsElt.getOperand(i_nocapture: 0));
1290 if (!Shuf || !Shuf->isZeroEltSplat())
1291 return nullptr;
1292
1293 // Bail out early if shuffle is scalable type. The number of elements in
1294 // shuffle mask is unknown at compile-time.
1295 if (isa<ScalableVectorType>(Val: Shuf->getType()))
1296 return nullptr;
1297
1298 // Check for a constant insertion index.
1299 uint64_t IdxC;
1300 if (!match(V: InsElt.getOperand(i_nocapture: 2), P: m_ConstantInt(V&: IdxC)))
1301 return nullptr;
1302
1303 // Check if the splat shuffle's input is the same as this insert's scalar op.
1304 Value *X = InsElt.getOperand(i_nocapture: 1);
1305 Value *Op0 = Shuf->getOperand(i_nocapture: 0);
1306 if (!match(V: Op0, P: m_InsertElt(Val: m_Undef(), Elt: m_Specific(V: X), Idx: m_ZeroInt())))
1307 return nullptr;
1308
1309 // Replace the shuffle mask element at the index of this insert with a zero.
1310 // For example:
1311 // inselt (shuf (inselt undef, X, 0), _, <0,undef,0,undef>), X, 1
1312 // --> shuf (inselt undef, X, 0), poison, <0,0,0,undef>
1313 unsigned NumMaskElts =
1314 cast<FixedVectorType>(Val: Shuf->getType())->getNumElements();
1315 SmallVector<int, 16> NewMask(NumMaskElts);
1316 for (unsigned i = 0; i != NumMaskElts; ++i)
1317 NewMask[i] = i == IdxC ? 0 : Shuf->getMaskValue(Elt: i);
1318
1319 return new ShuffleVectorInst(Op0, NewMask);
1320}
1321
1322/// Try to fold an extract+insert element into an existing identity shuffle by
1323/// changing the shuffle's mask to include the index of this insert element.
1324static Instruction *foldInsEltIntoIdentityShuffle(InsertElementInst &InsElt) {
1325 // Check if the vector operand of this insert is an identity shuffle.
1326 auto *Shuf = dyn_cast<ShuffleVectorInst>(Val: InsElt.getOperand(i_nocapture: 0));
1327 if (!Shuf || !match(V: Shuf->getOperand(i_nocapture: 1), P: m_Poison()) ||
1328 !(Shuf->isIdentityWithExtract() || Shuf->isIdentityWithPadding()))
1329 return nullptr;
1330
1331 // Bail out early if shuffle is scalable type. The number of elements in
1332 // shuffle mask is unknown at compile-time.
1333 if (isa<ScalableVectorType>(Val: Shuf->getType()))
1334 return nullptr;
1335
1336 // Check for a constant insertion index.
1337 uint64_t IdxC;
1338 if (!match(V: InsElt.getOperand(i_nocapture: 2), P: m_ConstantInt(V&: IdxC)))
1339 return nullptr;
1340
1341 // Check if this insert's scalar op is extracted from the identity shuffle's
1342 // input vector.
1343 Value *Scalar = InsElt.getOperand(i_nocapture: 1);
1344 Value *X = Shuf->getOperand(i_nocapture: 0);
1345 if (!match(V: Scalar, P: m_ExtractElt(Val: m_Specific(V: X), Idx: m_SpecificInt(V: IdxC))))
1346 return nullptr;
1347
1348 // Replace the shuffle mask element at the index of this extract+insert with
1349 // that same index value.
1350 // For example:
1351 // inselt (shuf X, IdMask), (extelt X, IdxC), IdxC --> shuf X, IdMask'
1352 unsigned NumMaskElts =
1353 cast<FixedVectorType>(Val: Shuf->getType())->getNumElements();
1354 SmallVector<int, 16> NewMask(NumMaskElts);
1355 ArrayRef<int> OldMask = Shuf->getShuffleMask();
1356 for (unsigned i = 0; i != NumMaskElts; ++i) {
1357 if (i != IdxC) {
1358 // All mask elements besides the inserted element remain the same.
1359 NewMask[i] = OldMask[i];
1360 } else if (OldMask[i] == (int)IdxC) {
1361 // If the mask element was already set, there's nothing to do
1362 // (demanded elements analysis may unset it later).
1363 return nullptr;
1364 } else {
1365 assert(OldMask[i] == PoisonMaskElem &&
1366 "Unexpected shuffle mask element for identity shuffle");
1367 NewMask[i] = IdxC;
1368 }
1369 }
1370
1371 return new ShuffleVectorInst(X, Shuf->getOperand(i_nocapture: 1), NewMask);
1372}
1373
1374/// If we have an insertelement instruction feeding into another insertelement
1375/// and the 2nd is inserting a constant into the vector, canonicalize that
1376/// constant insertion before the insertion of a variable:
1377///
1378/// insertelement (insertelement X, Y, IdxC1), ScalarC, IdxC2 -->
1379/// insertelement (insertelement X, ScalarC, IdxC2), Y, IdxC1
1380///
1381/// This has the potential of eliminating the 2nd insertelement instruction
1382/// via constant folding of the scalar constant into a vector constant.
1383static Instruction *hoistInsEltConst(InsertElementInst &InsElt2,
1384 InstCombiner::BuilderTy &Builder) {
1385 auto *InsElt1 = dyn_cast<InsertElementInst>(Val: InsElt2.getOperand(i_nocapture: 0));
1386 if (!InsElt1 || !InsElt1->hasOneUse())
1387 return nullptr;
1388
1389 Value *X, *Y;
1390 Constant *ScalarC;
1391 ConstantInt *IdxC1, *IdxC2;
1392 if (match(V: InsElt1->getOperand(i_nocapture: 0), P: m_Value(V&: X)) &&
1393 match(V: InsElt1->getOperand(i_nocapture: 1), P: m_Value(V&: Y)) && !isa<Constant>(Val: Y) &&
1394 match(V: InsElt1->getOperand(i_nocapture: 2), P: m_ConstantInt(CI&: IdxC1)) &&
1395 match(V: InsElt2.getOperand(i_nocapture: 1), P: m_Constant(C&: ScalarC)) &&
1396 match(V: InsElt2.getOperand(i_nocapture: 2), P: m_ConstantInt(CI&: IdxC2)) && IdxC1 != IdxC2) {
1397 Value *NewInsElt1 = Builder.CreateInsertElement(Vec: X, NewElt: ScalarC, Idx: IdxC2);
1398 return InsertElementInst::Create(Vec: NewInsElt1, NewElt: Y, Idx: IdxC1);
1399 }
1400
1401 return nullptr;
1402}
1403
1404/// insertelt (shufflevector X, CVec, Mask|insertelt X, C1, CIndex1), C, CIndex
1405/// --> shufflevector X, CVec', Mask'
1406static Instruction *foldConstantInsEltIntoShuffle(InsertElementInst &InsElt) {
1407 auto *Inst = dyn_cast<Instruction>(Val: InsElt.getOperand(i_nocapture: 0));
1408 // Bail out if the parent has more than one use. In that case, we'd be
1409 // replacing the insertelt with a shuffle, and that's not a clear win.
1410 if (!Inst || !Inst->hasOneUse())
1411 return nullptr;
1412 if (auto *Shuf = dyn_cast<ShuffleVectorInst>(Val: InsElt.getOperand(i_nocapture: 0))) {
1413 // The shuffle must have a constant vector operand. The insertelt must have
1414 // a constant scalar being inserted at a constant position in the vector.
1415 Constant *ShufConstVec, *InsEltScalar;
1416 uint64_t InsEltIndex;
1417 if (!match(V: Shuf->getOperand(i_nocapture: 1), P: m_Constant(C&: ShufConstVec)) ||
1418 !match(V: InsElt.getOperand(i_nocapture: 1), P: m_Constant(C&: InsEltScalar)) ||
1419 !match(V: InsElt.getOperand(i_nocapture: 2), P: m_ConstantInt(V&: InsEltIndex)))
1420 return nullptr;
1421
1422 // Adding an element to an arbitrary shuffle could be expensive, but a
1423 // shuffle that selects elements from vectors without crossing lanes is
1424 // assumed cheap.
1425 // If we're just adding a constant into that shuffle, it will still be
1426 // cheap.
1427 if (!isShuffleEquivalentToSelect(Shuf&: *Shuf))
1428 return nullptr;
1429
1430 // From the above 'select' check, we know that the mask has the same number
1431 // of elements as the vector input operands. We also know that each constant
1432 // input element is used in its lane and can not be used more than once by
1433 // the shuffle. Therefore, replace the constant in the shuffle's constant
1434 // vector with the insertelt constant. Replace the constant in the shuffle's
1435 // mask vector with the insertelt index plus the length of the vector
1436 // (because the constant vector operand of a shuffle is always the 2nd
1437 // operand).
1438 ArrayRef<int> Mask = Shuf->getShuffleMask();
1439 unsigned NumElts = Mask.size();
1440 SmallVector<Constant *, 16> NewShufElts(NumElts);
1441 SmallVector<int, 16> NewMaskElts(NumElts);
1442 for (unsigned I = 0; I != NumElts; ++I) {
1443 if (I == InsEltIndex) {
1444 NewShufElts[I] = InsEltScalar;
1445 NewMaskElts[I] = InsEltIndex + NumElts;
1446 } else {
1447 // Copy over the existing values.
1448 NewShufElts[I] = ShufConstVec->getAggregateElement(Elt: I);
1449 NewMaskElts[I] = Mask[I];
1450 }
1451
1452 // Bail if we failed to find an element.
1453 if (!NewShufElts[I])
1454 return nullptr;
1455 }
1456
1457 // Create new operands for a shuffle that includes the constant of the
1458 // original insertelt. The old shuffle will be dead now.
1459 return new ShuffleVectorInst(Shuf->getOperand(i_nocapture: 0),
1460 ConstantVector::get(V: NewShufElts), NewMaskElts);
1461 } else if (auto *IEI = dyn_cast<InsertElementInst>(Val: Inst)) {
1462 // Transform sequences of insertelements ops with constant data/indexes into
1463 // a single shuffle op.
1464 // Can not handle scalable type, the number of elements needed to create
1465 // shuffle mask is not a compile-time constant.
1466 if (isa<ScalableVectorType>(Val: InsElt.getType()))
1467 return nullptr;
1468 unsigned NumElts =
1469 cast<FixedVectorType>(Val: InsElt.getType())->getNumElements();
1470
1471 uint64_t InsertIdx[2];
1472 Constant *Val[2];
1473 if (!match(V: InsElt.getOperand(i_nocapture: 2), P: m_ConstantInt(V&: InsertIdx[0])) ||
1474 !match(V: InsElt.getOperand(i_nocapture: 1), P: m_Constant(C&: Val[0])) ||
1475 !match(V: IEI->getOperand(i_nocapture: 2), P: m_ConstantInt(V&: InsertIdx[1])) ||
1476 !match(V: IEI->getOperand(i_nocapture: 1), P: m_Constant(C&: Val[1])))
1477 return nullptr;
1478 SmallVector<Constant *, 16> Values(NumElts);
1479 SmallVector<int, 16> Mask(NumElts);
1480 auto ValI = std::begin(arr&: Val);
1481 // Generate new constant vector and mask.
1482 // We have 2 values/masks from the insertelements instructions. Insert them
1483 // into new value/mask vectors.
1484 for (uint64_t I : InsertIdx) {
1485 if (!Values[I]) {
1486 Values[I] = *ValI;
1487 Mask[I] = NumElts + I;
1488 }
1489 ++ValI;
1490 }
1491 // Remaining values are filled with 'poison' values.
1492 for (unsigned I = 0; I < NumElts; ++I) {
1493 if (!Values[I]) {
1494 Values[I] = PoisonValue::get(T: InsElt.getType()->getElementType());
1495 Mask[I] = I;
1496 }
1497 }
1498 // Create new operands for a shuffle that includes the constant of the
1499 // original insertelt.
1500 return new ShuffleVectorInst(IEI->getOperand(i_nocapture: 0),
1501 ConstantVector::get(V: Values), Mask);
1502 }
1503 return nullptr;
1504}
1505
1506/// If both the base vector and the inserted element are extended from the same
1507/// type, do the insert element in the narrow source type followed by extend.
1508/// TODO: This can be extended to include other cast opcodes, but particularly
1509/// if we create a wider insertelement, make sure codegen is not harmed.
1510static Instruction *narrowInsElt(InsertElementInst &InsElt,
1511 InstCombiner::BuilderTy &Builder) {
1512 // We are creating a vector extend. If the original vector extend has another
1513 // use, that would mean we end up with 2 vector extends, so avoid that.
1514 // TODO: We could ease the use-clause to "if at least one op has one use"
1515 // (assuming that the source types match - see next TODO comment).
1516 Value *Vec = InsElt.getOperand(i_nocapture: 0);
1517 if (!Vec->hasOneUse())
1518 return nullptr;
1519
1520 Value *Scalar = InsElt.getOperand(i_nocapture: 1);
1521 Value *X, *Y;
1522 CastInst::CastOps CastOpcode;
1523 if (match(V: Vec, P: m_FPExt(Op: m_Value(V&: X))) && match(V: Scalar, P: m_FPExt(Op: m_Value(V&: Y))))
1524 CastOpcode = Instruction::FPExt;
1525 else if (match(V: Vec, P: m_SExt(Op: m_Value(V&: X))) && match(V: Scalar, P: m_SExt(Op: m_Value(V&: Y))))
1526 CastOpcode = Instruction::SExt;
1527 else if (match(V: Vec, P: m_ZExt(Op: m_Value(V&: X))) && match(V: Scalar, P: m_ZExt(Op: m_Value(V&: Y))))
1528 CastOpcode = Instruction::ZExt;
1529 else
1530 return nullptr;
1531
1532 // TODO: We can allow mismatched types by creating an intermediate cast.
1533 if (X->getType()->getScalarType() != Y->getType())
1534 return nullptr;
1535
1536 // inselt (ext X), (ext Y), Index --> ext (inselt X, Y, Index)
1537 Value *NewInsElt = Builder.CreateInsertElement(Vec: X, NewElt: Y, Idx: InsElt.getOperand(i_nocapture: 2));
1538 return CastInst::Create(CastOpcode, S: NewInsElt, Ty: InsElt.getType());
1539}
1540
1541/// If we are inserting 2 halves of a value into adjacent elements of a vector,
1542/// try to convert to a single insert with appropriate bitcasts.
1543static Instruction *foldTruncInsEltPair(InsertElementInst &InsElt,
1544 bool IsBigEndian,
1545 InstCombiner::BuilderTy &Builder) {
1546 Value *VecOp = InsElt.getOperand(i_nocapture: 0);
1547 Value *ScalarOp = InsElt.getOperand(i_nocapture: 1);
1548 Value *IndexOp = InsElt.getOperand(i_nocapture: 2);
1549
1550 // Pattern depends on endian because we expect lower index is inserted first.
1551 // Big endian:
1552 // inselt (inselt BaseVec, (trunc (lshr X, BW/2), Index0), (trunc X), Index1
1553 // Little endian:
1554 // inselt (inselt BaseVec, (trunc X), Index0), (trunc (lshr X, BW/2)), Index1
1555 // Note: It is not safe to do this transform with an arbitrary base vector
1556 // because the bitcast of that vector to fewer/larger elements could
1557 // allow poison to spill into an element that was not poison before.
1558 // TODO: Detect smaller fractions of the scalar.
1559 // TODO: One-use checks are conservative.
1560 auto *VTy = dyn_cast<FixedVectorType>(Val: InsElt.getType());
1561 Value *Scalar0, *BaseVec;
1562 uint64_t Index0, Index1;
1563 if (!VTy || (VTy->getNumElements() & 1) ||
1564 !match(V: IndexOp, P: m_ConstantInt(V&: Index1)) ||
1565 !match(V: VecOp, P: m_InsertElt(Val: m_Value(V&: BaseVec), Elt: m_Value(V&: Scalar0),
1566 Idx: m_ConstantInt(V&: Index0))) ||
1567 !match(V: BaseVec, P: m_Undef()))
1568 return nullptr;
1569
1570 // The first insert must be to the index one less than this one, and
1571 // the first insert must be to an even index.
1572 if (Index0 + 1 != Index1 || Index0 & 1)
1573 return nullptr;
1574
1575 // For big endian, the high half of the value should be inserted first.
1576 // For little endian, the low half of the value should be inserted first.
1577 Value *X;
1578 uint64_t ShAmt;
1579 if (IsBigEndian) {
1580 if (!match(V: ScalarOp, P: m_Trunc(Op: m_Value(V&: X))) ||
1581 !match(V: Scalar0, P: m_Trunc(Op: m_LShr(L: m_Specific(V: X), R: m_ConstantInt(V&: ShAmt)))))
1582 return nullptr;
1583 } else {
1584 if (!match(V: Scalar0, P: m_Trunc(Op: m_Value(V&: X))) ||
1585 !match(V: ScalarOp, P: m_Trunc(Op: m_LShr(L: m_Specific(V: X), R: m_ConstantInt(V&: ShAmt)))))
1586 return nullptr;
1587 }
1588
1589 Type *SrcTy = X->getType();
1590 unsigned ScalarWidth = SrcTy->getScalarSizeInBits();
1591 unsigned VecEltWidth = VTy->getScalarSizeInBits();
1592 if (ScalarWidth != VecEltWidth * 2 || ShAmt != VecEltWidth)
1593 return nullptr;
1594
1595 // Bitcast the base vector to a vector type with the source element type.
1596 Type *CastTy = FixedVectorType::get(ElementType: SrcTy, NumElts: VTy->getNumElements() / 2);
1597 Value *CastBaseVec = Builder.CreateBitCast(V: BaseVec, DestTy: CastTy);
1598
1599 // Scale the insert index for a vector with half as many elements.
1600 // bitcast (inselt (bitcast BaseVec), X, NewIndex)
1601 uint64_t NewIndex = IsBigEndian ? Index1 / 2 : Index0 / 2;
1602 Value *NewInsert = Builder.CreateInsertElement(Vec: CastBaseVec, NewElt: X, Idx: NewIndex);
1603 return new BitCastInst(NewInsert, VTy);
1604}
1605
1606Instruction *InstCombinerImpl::visitInsertElementInst(InsertElementInst &IE) {
1607 Value *VecOp = IE.getOperand(i_nocapture: 0);
1608 Value *ScalarOp = IE.getOperand(i_nocapture: 1);
1609 Value *IdxOp = IE.getOperand(i_nocapture: 2);
1610
1611 if (auto *V = simplifyInsertElementInst(
1612 Vec: VecOp, Elt: ScalarOp, Idx: IdxOp, Q: SQ.getWithInstruction(I: &IE)))
1613 return replaceInstUsesWith(I&: IE, V);
1614
1615 // Canonicalize type of constant indices to i64 to simplify CSE
1616 if (auto *IndexC = dyn_cast<ConstantInt>(Val: IdxOp)) {
1617 if (auto *NewIdx = getPreferredVectorIndex(IndexC))
1618 return replaceOperand(I&: IE, OpNum: 2, V: NewIdx);
1619
1620 Value *BaseVec, *OtherScalar;
1621 uint64_t OtherIndexVal;
1622 if (match(V: VecOp, P: m_OneUse(SubPattern: m_InsertElt(Val: m_Value(V&: BaseVec),
1623 Elt: m_Value(V&: OtherScalar),
1624 Idx: m_ConstantInt(V&: OtherIndexVal)))) &&
1625 !isa<Constant>(Val: OtherScalar) && OtherIndexVal > IndexC->getZExtValue()) {
1626 Value *NewIns = Builder.CreateInsertElement(Vec: BaseVec, NewElt: ScalarOp, Idx: IdxOp);
1627 return InsertElementInst::Create(Vec: NewIns, NewElt: OtherScalar,
1628 Idx: Builder.getInt64(C: OtherIndexVal));
1629 }
1630 }
1631
1632 // If the scalar is bitcast and inserted into undef, do the insert in the
1633 // source type followed by bitcast.
1634 // TODO: Generalize for insert into any constant, not just undef?
1635 Value *ScalarSrc;
1636 if (match(V: VecOp, P: m_Undef()) &&
1637 match(V: ScalarOp, P: m_OneUse(SubPattern: m_BitCast(Op: m_Value(V&: ScalarSrc)))) &&
1638 (ScalarSrc->getType()->isIntegerTy() ||
1639 ScalarSrc->getType()->isFloatingPointTy())) {
1640 // inselt undef, (bitcast ScalarSrc), IdxOp -->
1641 // bitcast (inselt undef, ScalarSrc, IdxOp)
1642 Type *ScalarTy = ScalarSrc->getType();
1643 Type *VecTy = VectorType::get(ElementType: ScalarTy, EC: IE.getType()->getElementCount());
1644 Constant *NewUndef = isa<PoisonValue>(Val: VecOp) ? PoisonValue::get(T: VecTy)
1645 : UndefValue::get(T: VecTy);
1646 Value *NewInsElt = Builder.CreateInsertElement(Vec: NewUndef, NewElt: ScalarSrc, Idx: IdxOp);
1647 return new BitCastInst(NewInsElt, IE.getType());
1648 }
1649
1650 // If the vector and scalar are both bitcast from the same element type, do
1651 // the insert in that source type followed by bitcast.
1652 Value *VecSrc;
1653 if (match(V: VecOp, P: m_BitCast(Op: m_Value(V&: VecSrc))) &&
1654 match(V: ScalarOp, P: m_BitCast(Op: m_Value(V&: ScalarSrc))) &&
1655 (VecOp->hasOneUse() || ScalarOp->hasOneUse()) &&
1656 VecSrc->getType()->isVectorTy() && !ScalarSrc->getType()->isVectorTy() &&
1657 cast<VectorType>(Val: VecSrc->getType())->getElementType() ==
1658 ScalarSrc->getType()) {
1659 // inselt (bitcast VecSrc), (bitcast ScalarSrc), IdxOp -->
1660 // bitcast (inselt VecSrc, ScalarSrc, IdxOp)
1661 Value *NewInsElt = Builder.CreateInsertElement(Vec: VecSrc, NewElt: ScalarSrc, Idx: IdxOp);
1662 return new BitCastInst(NewInsElt, IE.getType());
1663 }
1664
1665 // If the inserted element was extracted from some other fixed-length vector
1666 // and both indexes are valid constants, try to turn this into a shuffle.
1667 // Can not handle scalable vector type, the number of elements needed to
1668 // create shuffle mask is not a compile-time constant.
1669 uint64_t InsertedIdx, ExtractedIdx;
1670 Value *ExtVecOp;
1671 if (isa<FixedVectorType>(Val: IE.getType()) &&
1672 match(V: IdxOp, P: m_ConstantInt(V&: InsertedIdx)) &&
1673 match(V: ScalarOp,
1674 P: m_ExtractElt(Val: m_Value(V&: ExtVecOp), Idx: m_ConstantInt(V&: ExtractedIdx))) &&
1675 isa<FixedVectorType>(Val: ExtVecOp->getType()) &&
1676 ExtractedIdx <
1677 cast<FixedVectorType>(Val: ExtVecOp->getType())->getNumElements()) {
1678 // TODO: Looking at the user(s) to determine if this insert is a
1679 // fold-to-shuffle opportunity does not match the usual instcombine
1680 // constraints. We should decide if the transform is worthy based only
1681 // on this instruction and its operands, but that may not work currently.
1682 //
1683 // Here, we are trying to avoid creating shuffles before reaching
1684 // the end of a chain of extract-insert pairs. This is complicated because
1685 // we do not generally form arbitrary shuffle masks in instcombine
1686 // (because those may codegen poorly), but collectShuffleElements() does
1687 // exactly that.
1688 //
1689 // The rules for determining what is an acceptable target-independent
1690 // shuffle mask are fuzzy because they evolve based on the backend's
1691 // capabilities and real-world impact.
1692 auto isShuffleRootCandidate = [](InsertElementInst &Insert) {
1693 if (!Insert.hasOneUse())
1694 return true;
1695 auto *InsertUser = dyn_cast<InsertElementInst>(Val: Insert.user_back());
1696 if (!InsertUser)
1697 return true;
1698 return false;
1699 };
1700
1701 // Try to form a shuffle from a chain of extract-insert ops.
1702 if (isShuffleRootCandidate(IE)) {
1703 bool Rerun = true;
1704 while (Rerun) {
1705 Rerun = false;
1706
1707 SmallVector<int, 16> Mask;
1708 ShuffleOps LR =
1709 collectShuffleElements(V: &IE, Mask, PermittedRHS: nullptr, IC&: *this, Rerun);
1710
1711 // The proposed shuffle may be trivial, in which case we shouldn't
1712 // perform the combine.
1713 if (LR.first != &IE && LR.second != &IE) {
1714 // We now have a shuffle of LHS, RHS, Mask.
1715 if (LR.second == nullptr)
1716 LR.second = PoisonValue::get(T: LR.first->getType());
1717 return new ShuffleVectorInst(LR.first, LR.second, Mask);
1718 }
1719 }
1720 }
1721 }
1722
1723 if (auto VecTy = dyn_cast<FixedVectorType>(Val: VecOp->getType())) {
1724 unsigned VWidth = VecTy->getNumElements();
1725 APInt PoisonElts(VWidth, 0);
1726 APInt AllOnesEltMask(APInt::getAllOnes(numBits: VWidth));
1727 if (Value *V = SimplifyDemandedVectorElts(V: &IE, DemandedElts: AllOnesEltMask,
1728 PoisonElts)) {
1729 if (V != &IE)
1730 return replaceInstUsesWith(I&: IE, V);
1731 return &IE;
1732 }
1733 }
1734
1735 if (Instruction *Shuf = foldConstantInsEltIntoShuffle(InsElt&: IE))
1736 return Shuf;
1737
1738 if (Instruction *NewInsElt = hoistInsEltConst(InsElt2&: IE, Builder))
1739 return NewInsElt;
1740
1741 if (Instruction *Broadcast = foldInsSequenceIntoSplat(InsElt&: IE))
1742 return Broadcast;
1743
1744 if (Instruction *Splat = foldInsEltIntoSplat(InsElt&: IE))
1745 return Splat;
1746
1747 if (Instruction *IdentityShuf = foldInsEltIntoIdentityShuffle(InsElt&: IE))
1748 return IdentityShuf;
1749
1750 if (Instruction *Ext = narrowInsElt(InsElt&: IE, Builder))
1751 return Ext;
1752
1753 if (Instruction *Ext = foldTruncInsEltPair(InsElt&: IE, IsBigEndian: DL.isBigEndian(), Builder))
1754 return Ext;
1755
1756 return nullptr;
1757}
1758
1759/// Return true if we can evaluate the specified expression tree if the vector
1760/// elements were shuffled in a different order.
1761static bool canEvaluateShuffled(Value *V, ArrayRef<int> Mask,
1762 unsigned Depth = 5) {
1763 // We can always reorder the elements of a constant.
1764 if (isa<Constant>(Val: V))
1765 return true;
1766
1767 // We won't reorder vector arguments. No IPO here.
1768 Instruction *I = dyn_cast<Instruction>(Val: V);
1769 if (!I) return false;
1770
1771 // Two users may expect different orders of the elements. Don't try it.
1772 if (!I->hasOneUse())
1773 return false;
1774
1775 if (Depth == 0) return false;
1776
1777 switch (I->getOpcode()) {
1778 case Instruction::UDiv:
1779 case Instruction::SDiv:
1780 case Instruction::URem:
1781 case Instruction::SRem:
1782 // Propagating an undefined shuffle mask element to integer div/rem is not
1783 // allowed because those opcodes can create immediate undefined behavior
1784 // from an undefined element in an operand.
1785 if (llvm::is_contained(Range&: Mask, Element: -1))
1786 return false;
1787 [[fallthrough]];
1788 case Instruction::Add:
1789 case Instruction::FAdd:
1790 case Instruction::Sub:
1791 case Instruction::FSub:
1792 case Instruction::Mul:
1793 case Instruction::FMul:
1794 case Instruction::FDiv:
1795 case Instruction::FRem:
1796 case Instruction::Shl:
1797 case Instruction::LShr:
1798 case Instruction::AShr:
1799 case Instruction::And:
1800 case Instruction::Or:
1801 case Instruction::Xor:
1802 case Instruction::ICmp:
1803 case Instruction::FCmp:
1804 case Instruction::Trunc:
1805 case Instruction::ZExt:
1806 case Instruction::SExt:
1807 case Instruction::FPToUI:
1808 case Instruction::FPToSI:
1809 case Instruction::UIToFP:
1810 case Instruction::SIToFP:
1811 case Instruction::FPTrunc:
1812 case Instruction::FPExt:
1813 case Instruction::GetElementPtr: {
1814 // Bail out if we would create longer vector ops. We could allow creating
1815 // longer vector ops, but that may result in more expensive codegen.
1816 Type *ITy = I->getType();
1817 if (ITy->isVectorTy() &&
1818 Mask.size() > cast<FixedVectorType>(Val: ITy)->getNumElements())
1819 return false;
1820 for (Value *Operand : I->operands()) {
1821 if (!canEvaluateShuffled(V: Operand, Mask, Depth: Depth - 1))
1822 return false;
1823 }
1824 return true;
1825 }
1826 case Instruction::InsertElement: {
1827 ConstantInt *CI = dyn_cast<ConstantInt>(Val: I->getOperand(i: 2));
1828 if (!CI) return false;
1829 int ElementNumber = CI->getLimitedValue();
1830
1831 // Verify that 'CI' does not occur twice in Mask. A single 'insertelement'
1832 // can't put an element into multiple indices.
1833 bool SeenOnce = false;
1834 for (int I : Mask) {
1835 if (I == ElementNumber) {
1836 if (SeenOnce)
1837 return false;
1838 SeenOnce = true;
1839 }
1840 }
1841 return canEvaluateShuffled(V: I->getOperand(i: 0), Mask, Depth: Depth - 1);
1842 }
1843 }
1844 return false;
1845}
1846
1847/// Rebuild a new instruction just like 'I' but with the new operands given.
1848/// In the event of type mismatch, the type of the operands is correct.
1849static Value *buildNew(Instruction *I, ArrayRef<Value*> NewOps,
1850 IRBuilderBase &Builder) {
1851 Builder.SetInsertPoint(I);
1852 switch (I->getOpcode()) {
1853 case Instruction::Add:
1854 case Instruction::FAdd:
1855 case Instruction::Sub:
1856 case Instruction::FSub:
1857 case Instruction::Mul:
1858 case Instruction::FMul:
1859 case Instruction::UDiv:
1860 case Instruction::SDiv:
1861 case Instruction::FDiv:
1862 case Instruction::URem:
1863 case Instruction::SRem:
1864 case Instruction::FRem:
1865 case Instruction::Shl:
1866 case Instruction::LShr:
1867 case Instruction::AShr:
1868 case Instruction::And:
1869 case Instruction::Or:
1870 case Instruction::Xor: {
1871 BinaryOperator *BO = cast<BinaryOperator>(Val: I);
1872 assert(NewOps.size() == 2 && "binary operator with #ops != 2");
1873 Value *New = Builder.CreateBinOp(Opc: cast<BinaryOperator>(Val: I)->getOpcode(),
1874 LHS: NewOps[0], RHS: NewOps[1]);
1875 if (auto *NewI = dyn_cast<Instruction>(Val: New)) {
1876 if (isa<OverflowingBinaryOperator>(Val: BO)) {
1877 NewI->setHasNoUnsignedWrap(BO->hasNoUnsignedWrap());
1878 NewI->setHasNoSignedWrap(BO->hasNoSignedWrap());
1879 }
1880 if (isa<PossiblyExactOperator>(Val: BO)) {
1881 NewI->setIsExact(BO->isExact());
1882 }
1883 if (isa<FPMathOperator>(Val: BO))
1884 NewI->copyFastMathFlags(I);
1885 }
1886 return New;
1887 }
1888 case Instruction::ICmp:
1889 assert(NewOps.size() == 2 && "icmp with #ops != 2");
1890 return Builder.CreateICmp(P: cast<ICmpInst>(Val: I)->getPredicate(), LHS: NewOps[0],
1891 RHS: NewOps[1]);
1892 case Instruction::FCmp:
1893 assert(NewOps.size() == 2 && "fcmp with #ops != 2");
1894 return Builder.CreateFCmp(P: cast<FCmpInst>(Val: I)->getPredicate(), LHS: NewOps[0],
1895 RHS: NewOps[1]);
1896 case Instruction::Trunc:
1897 case Instruction::ZExt:
1898 case Instruction::SExt:
1899 case Instruction::FPToUI:
1900 case Instruction::FPToSI:
1901 case Instruction::UIToFP:
1902 case Instruction::SIToFP:
1903 case Instruction::FPTrunc:
1904 case Instruction::FPExt: {
1905 // It's possible that the mask has a different number of elements from
1906 // the original cast. We recompute the destination type to match the mask.
1907 Type *DestTy = VectorType::get(
1908 ElementType: I->getType()->getScalarType(),
1909 EC: cast<VectorType>(Val: NewOps[0]->getType())->getElementCount());
1910 assert(NewOps.size() == 1 && "cast with #ops != 1");
1911 return Builder.CreateCast(Op: cast<CastInst>(Val: I)->getOpcode(), V: NewOps[0],
1912 DestTy);
1913 }
1914 case Instruction::GetElementPtr: {
1915 Value *Ptr = NewOps[0];
1916 ArrayRef<Value*> Idx = NewOps.slice(N: 1);
1917 return Builder.CreateGEP(Ty: cast<GEPOperator>(Val: I)->getSourceElementType(),
1918 Ptr, IdxList: Idx, Name: "",
1919 NW: cast<GEPOperator>(Val: I)->isInBounds());
1920 }
1921 }
1922 llvm_unreachable("failed to rebuild vector instructions");
1923}
1924
1925static Value *evaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask,
1926 IRBuilderBase &Builder) {
1927 // Mask.size() does not need to be equal to the number of vector elements.
1928
1929 assert(V->getType()->isVectorTy() && "can't reorder non-vector elements");
1930 Type *EltTy = V->getType()->getScalarType();
1931
1932 if (isa<PoisonValue>(Val: V))
1933 return PoisonValue::get(T: FixedVectorType::get(ElementType: EltTy, NumElts: Mask.size()));
1934
1935 if (match(V, P: m_Undef()))
1936 return UndefValue::get(T: FixedVectorType::get(ElementType: EltTy, NumElts: Mask.size()));
1937
1938 if (isa<ConstantAggregateZero>(Val: V))
1939 return ConstantAggregateZero::get(Ty: FixedVectorType::get(ElementType: EltTy, NumElts: Mask.size()));
1940
1941 if (Constant *C = dyn_cast<Constant>(Val: V))
1942 return ConstantExpr::getShuffleVector(V1: C, V2: PoisonValue::get(T: C->getType()),
1943 Mask);
1944
1945 Instruction *I = cast<Instruction>(Val: V);
1946 switch (I->getOpcode()) {
1947 case Instruction::Add:
1948 case Instruction::FAdd:
1949 case Instruction::Sub:
1950 case Instruction::FSub:
1951 case Instruction::Mul:
1952 case Instruction::FMul:
1953 case Instruction::UDiv:
1954 case Instruction::SDiv:
1955 case Instruction::FDiv:
1956 case Instruction::URem:
1957 case Instruction::SRem:
1958 case Instruction::FRem:
1959 case Instruction::Shl:
1960 case Instruction::LShr:
1961 case Instruction::AShr:
1962 case Instruction::And:
1963 case Instruction::Or:
1964 case Instruction::Xor:
1965 case Instruction::ICmp:
1966 case Instruction::FCmp:
1967 case Instruction::Trunc:
1968 case Instruction::ZExt:
1969 case Instruction::SExt:
1970 case Instruction::FPToUI:
1971 case Instruction::FPToSI:
1972 case Instruction::UIToFP:
1973 case Instruction::SIToFP:
1974 case Instruction::FPTrunc:
1975 case Instruction::FPExt:
1976 case Instruction::Select:
1977 case Instruction::GetElementPtr: {
1978 SmallVector<Value*, 8> NewOps;
1979 bool NeedsRebuild =
1980 (Mask.size() !=
1981 cast<FixedVectorType>(Val: I->getType())->getNumElements());
1982 for (int i = 0, e = I->getNumOperands(); i != e; ++i) {
1983 Value *V;
1984 // Recursively call evaluateInDifferentElementOrder on vector arguments
1985 // as well. E.g. GetElementPtr may have scalar operands even if the
1986 // return value is a vector, so we need to examine the operand type.
1987 if (I->getOperand(i)->getType()->isVectorTy())
1988 V = evaluateInDifferentElementOrder(V: I->getOperand(i), Mask, Builder);
1989 else
1990 V = I->getOperand(i);
1991 NewOps.push_back(Elt: V);
1992 NeedsRebuild |= (V != I->getOperand(i));
1993 }
1994 if (NeedsRebuild)
1995 return buildNew(I, NewOps, Builder);
1996 return I;
1997 }
1998 case Instruction::InsertElement: {
1999 int Element = cast<ConstantInt>(Val: I->getOperand(i: 2))->getLimitedValue();
2000
2001 // The insertelement was inserting at Element. Figure out which element
2002 // that becomes after shuffling. The answer is guaranteed to be unique
2003 // by CanEvaluateShuffled.
2004 bool Found = false;
2005 int Index = 0;
2006 for (int e = Mask.size(); Index != e; ++Index) {
2007 if (Mask[Index] == Element) {
2008 Found = true;
2009 break;
2010 }
2011 }
2012
2013 // If element is not in Mask, no need to handle the operand 1 (element to
2014 // be inserted). Just evaluate values in operand 0 according to Mask.
2015 if (!Found)
2016 return evaluateInDifferentElementOrder(V: I->getOperand(i: 0), Mask, Builder);
2017
2018 Value *V = evaluateInDifferentElementOrder(V: I->getOperand(i: 0), Mask,
2019 Builder);
2020 Builder.SetInsertPoint(I);
2021 return Builder.CreateInsertElement(Vec: V, NewElt: I->getOperand(i: 1), Idx: Index);
2022 }
2023 }
2024 llvm_unreachable("failed to reorder elements of vector instruction!");
2025}
2026
2027// Returns true if the shuffle is extracting a contiguous range of values from
2028// LHS, for example:
2029// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
2030// Input: |AA|BB|CC|DD|EE|FF|GG|HH|II|JJ|KK|LL|MM|NN|OO|PP|
2031// Shuffles to: |EE|FF|GG|HH|
2032// +--+--+--+--+
2033static bool isShuffleExtractingFromLHS(ShuffleVectorInst &SVI,
2034 ArrayRef<int> Mask) {
2035 unsigned LHSElems =
2036 cast<FixedVectorType>(Val: SVI.getOperand(i_nocapture: 0)->getType())->getNumElements();
2037 unsigned MaskElems = Mask.size();
2038 unsigned BegIdx = Mask.front();
2039 unsigned EndIdx = Mask.back();
2040 if (BegIdx > EndIdx || EndIdx >= LHSElems || EndIdx - BegIdx != MaskElems - 1)
2041 return false;
2042 for (unsigned I = 0; I != MaskElems; ++I)
2043 if (static_cast<unsigned>(Mask[I]) != BegIdx + I)
2044 return false;
2045 return true;
2046}
2047
2048/// These are the ingredients in an alternate form binary operator as described
2049/// below.
2050struct BinopElts {
2051 BinaryOperator::BinaryOps Opcode;
2052 Value *Op0;
2053 Value *Op1;
2054 BinopElts(BinaryOperator::BinaryOps Opc = (BinaryOperator::BinaryOps)0,
2055 Value *V0 = nullptr, Value *V1 = nullptr) :
2056 Opcode(Opc), Op0(V0), Op1(V1) {}
2057 operator bool() const { return Opcode != 0; }
2058};
2059
2060/// Binops may be transformed into binops with different opcodes and operands.
2061/// Reverse the usual canonicalization to enable folds with the non-canonical
2062/// form of the binop. If a transform is possible, return the elements of the
2063/// new binop. If not, return invalid elements.
2064static BinopElts getAlternateBinop(BinaryOperator *BO, const DataLayout &DL) {
2065 Value *BO0 = BO->getOperand(i_nocapture: 0), *BO1 = BO->getOperand(i_nocapture: 1);
2066 Type *Ty = BO->getType();
2067 switch (BO->getOpcode()) {
2068 case Instruction::Shl: {
2069 // shl X, C --> mul X, (1 << C)
2070 Constant *C;
2071 if (match(V: BO1, P: m_ImmConstant(C))) {
2072 Constant *ShlOne = ConstantFoldBinaryOpOperands(
2073 Opcode: Instruction::Shl, LHS: ConstantInt::get(Ty, V: 1), RHS: C, DL);
2074 assert(ShlOne && "Constant folding of immediate constants failed");
2075 return {Instruction::Mul, BO0, ShlOne};
2076 }
2077 break;
2078 }
2079 case Instruction::Or: {
2080 // or disjoin X, C --> add X, C
2081 if (cast<PossiblyDisjointInst>(Val: BO)->isDisjoint())
2082 return {Instruction::Add, BO0, BO1};
2083 break;
2084 }
2085 case Instruction::Sub:
2086 // sub 0, X --> mul X, -1
2087 if (match(V: BO0, P: m_ZeroInt()))
2088 return {Instruction::Mul, BO1, ConstantInt::getAllOnesValue(Ty)};
2089 break;
2090 default:
2091 break;
2092 }
2093 return {};
2094}
2095
2096/// A select shuffle of a select shuffle with a shared operand can be reduced
2097/// to a single select shuffle. This is an obvious improvement in IR, and the
2098/// backend is expected to lower select shuffles efficiently.
2099static Instruction *foldSelectShuffleOfSelectShuffle(ShuffleVectorInst &Shuf) {
2100 assert(Shuf.isSelect() && "Must have select-equivalent shuffle");
2101
2102 Value *Op0 = Shuf.getOperand(i_nocapture: 0), *Op1 = Shuf.getOperand(i_nocapture: 1);
2103 SmallVector<int, 16> Mask;
2104 Shuf.getShuffleMask(Result&: Mask);
2105 unsigned NumElts = Mask.size();
2106
2107 // Canonicalize a select shuffle with common operand as Op1.
2108 auto *ShufOp = dyn_cast<ShuffleVectorInst>(Val: Op0);
2109 if (ShufOp && ShufOp->isSelect() &&
2110 (ShufOp->getOperand(i_nocapture: 0) == Op1 || ShufOp->getOperand(i_nocapture: 1) == Op1)) {
2111 std::swap(a&: Op0, b&: Op1);
2112 ShuffleVectorInst::commuteShuffleMask(Mask, InVecNumElts: NumElts);
2113 }
2114
2115 ShufOp = dyn_cast<ShuffleVectorInst>(Val: Op1);
2116 if (!ShufOp || !ShufOp->isSelect() ||
2117 (ShufOp->getOperand(i_nocapture: 0) != Op0 && ShufOp->getOperand(i_nocapture: 1) != Op0))
2118 return nullptr;
2119
2120 Value *X = ShufOp->getOperand(i_nocapture: 0), *Y = ShufOp->getOperand(i_nocapture: 1);
2121 SmallVector<int, 16> Mask1;
2122 ShufOp->getShuffleMask(Result&: Mask1);
2123 assert(Mask1.size() == NumElts && "Vector size changed with select shuffle");
2124
2125 // Canonicalize common operand (Op0) as X (first operand of first shuffle).
2126 if (Y == Op0) {
2127 std::swap(a&: X, b&: Y);
2128 ShuffleVectorInst::commuteShuffleMask(Mask: Mask1, InVecNumElts: NumElts);
2129 }
2130
2131 // If the mask chooses from X (operand 0), it stays the same.
2132 // If the mask chooses from the earlier shuffle, the other mask value is
2133 // transferred to the combined select shuffle:
2134 // shuf X, (shuf X, Y, M1), M --> shuf X, Y, M'
2135 SmallVector<int, 16> NewMask(NumElts);
2136 for (unsigned i = 0; i != NumElts; ++i)
2137 NewMask[i] = Mask[i] < (signed)NumElts ? Mask[i] : Mask1[i];
2138
2139 // A select mask with undef elements might look like an identity mask.
2140 assert((ShuffleVectorInst::isSelectMask(NewMask, NumElts) ||
2141 ShuffleVectorInst::isIdentityMask(NewMask, NumElts)) &&
2142 "Unexpected shuffle mask");
2143 return new ShuffleVectorInst(X, Y, NewMask);
2144}
2145
2146static Instruction *foldSelectShuffleWith1Binop(ShuffleVectorInst &Shuf,
2147 const SimplifyQuery &SQ) {
2148 assert(Shuf.isSelect() && "Must have select-equivalent shuffle");
2149
2150 // Are we shuffling together some value and that same value after it has been
2151 // modified by a binop with a constant?
2152 Value *Op0 = Shuf.getOperand(i_nocapture: 0), *Op1 = Shuf.getOperand(i_nocapture: 1);
2153 Constant *C;
2154 bool Op0IsBinop;
2155 if (match(V: Op0, P: m_BinOp(L: m_Specific(V: Op1), R: m_Constant(C))))
2156 Op0IsBinop = true;
2157 else if (match(V: Op1, P: m_BinOp(L: m_Specific(V: Op0), R: m_Constant(C))))
2158 Op0IsBinop = false;
2159 else
2160 return nullptr;
2161
2162 // The identity constant for a binop leaves a variable operand unchanged. For
2163 // a vector, this is a splat of something like 0, -1, or 1.
2164 // If there's no identity constant for this binop, we're done.
2165 auto *BO = cast<BinaryOperator>(Val: Op0IsBinop ? Op0 : Op1);
2166 BinaryOperator::BinaryOps BOpcode = BO->getOpcode();
2167 Constant *IdC = ConstantExpr::getBinOpIdentity(Opcode: BOpcode, Ty: Shuf.getType(), AllowRHSConstant: true);
2168 if (!IdC)
2169 return nullptr;
2170
2171 Value *X = Op0IsBinop ? Op1 : Op0;
2172
2173 // Prevent folding in the case the non-binop operand might have NaN values.
2174 // If X can have NaN elements then we have that the floating point math
2175 // operation in the transformed code may not preserve the exact NaN
2176 // bit-pattern -- e.g. `fadd sNaN, 0.0 -> qNaN`.
2177 // This makes the transformation incorrect since the original program would
2178 // have preserved the exact NaN bit-pattern.
2179 // Avoid the folding if X can have NaN elements.
2180 if (Shuf.getType()->getElementType()->isFloatingPointTy() &&
2181 !isKnownNeverNaN(V: X, Depth: 0, SQ))
2182 return nullptr;
2183
2184 // Shuffle identity constants into the lanes that return the original value.
2185 // Example: shuf (mul X, {-1,-2,-3,-4}), X, {0,5,6,3} --> mul X, {-1,1,1,-4}
2186 // Example: shuf X, (add X, {-1,-2,-3,-4}), {0,1,6,7} --> add X, {0,0,-3,-4}
2187 // The existing binop constant vector remains in the same operand position.
2188 ArrayRef<int> Mask = Shuf.getShuffleMask();
2189 Constant *NewC = Op0IsBinop ? ConstantExpr::getShuffleVector(V1: C, V2: IdC, Mask) :
2190 ConstantExpr::getShuffleVector(V1: IdC, V2: C, Mask);
2191
2192 bool MightCreatePoisonOrUB =
2193 is_contained(Range&: Mask, Element: PoisonMaskElem) &&
2194 (Instruction::isIntDivRem(Opcode: BOpcode) || Instruction::isShift(Opcode: BOpcode));
2195 if (MightCreatePoisonOrUB)
2196 NewC = InstCombiner::getSafeVectorConstantForBinop(Opcode: BOpcode, In: NewC, IsRHSConstant: true);
2197
2198 // shuf (bop X, C), X, M --> bop X, C'
2199 // shuf X, (bop X, C), M --> bop X, C'
2200 Instruction *NewBO = BinaryOperator::Create(Op: BOpcode, S1: X, S2: NewC);
2201 NewBO->copyIRFlags(V: BO);
2202
2203 // An undef shuffle mask element may propagate as an undef constant element in
2204 // the new binop. That would produce poison where the original code might not.
2205 // If we already made a safe constant, then there's no danger.
2206 if (is_contained(Range&: Mask, Element: PoisonMaskElem) && !MightCreatePoisonOrUB)
2207 NewBO->dropPoisonGeneratingFlags();
2208 return NewBO;
2209}
2210
2211/// If we have an insert of a scalar to a non-zero element of an undefined
2212/// vector and then shuffle that value, that's the same as inserting to the zero
2213/// element and shuffling. Splatting from the zero element is recognized as the
2214/// canonical form of splat.
2215static Instruction *canonicalizeInsertSplat(ShuffleVectorInst &Shuf,
2216 InstCombiner::BuilderTy &Builder) {
2217 Value *Op0 = Shuf.getOperand(i_nocapture: 0), *Op1 = Shuf.getOperand(i_nocapture: 1);
2218 ArrayRef<int> Mask = Shuf.getShuffleMask();
2219 Value *X;
2220 uint64_t IndexC;
2221
2222 // Match a shuffle that is a splat to a non-zero element.
2223 if (!match(V: Op0, P: m_OneUse(SubPattern: m_InsertElt(Val: m_Poison(), Elt: m_Value(V&: X),
2224 Idx: m_ConstantInt(V&: IndexC)))) ||
2225 !match(V: Op1, P: m_Poison()) || match(Mask, P: m_ZeroMask()) || IndexC == 0)
2226 return nullptr;
2227
2228 // Insert into element 0 of a poison vector.
2229 PoisonValue *PoisonVec = PoisonValue::get(T: Shuf.getType());
2230 Value *NewIns = Builder.CreateInsertElement(Vec: PoisonVec, NewElt: X, Idx: (uint64_t)0);
2231
2232 // Splat from element 0. Any mask element that is poison remains poison.
2233 // For example:
2234 // shuf (inselt poison, X, 2), _, <2,2,undef>
2235 // --> shuf (inselt poison, X, 0), poison, <0,0,undef>
2236 unsigned NumMaskElts =
2237 cast<FixedVectorType>(Val: Shuf.getType())->getNumElements();
2238 SmallVector<int, 16> NewMask(NumMaskElts, 0);
2239 for (unsigned i = 0; i != NumMaskElts; ++i)
2240 if (Mask[i] == PoisonMaskElem)
2241 NewMask[i] = Mask[i];
2242
2243 return new ShuffleVectorInst(NewIns, NewMask);
2244}
2245
2246/// Try to fold shuffles that are the equivalent of a vector select.
2247Instruction *InstCombinerImpl::foldSelectShuffle(ShuffleVectorInst &Shuf) {
2248 if (!Shuf.isSelect())
2249 return nullptr;
2250
2251 // Canonicalize to choose from operand 0 first unless operand 1 is undefined.
2252 // Commuting undef to operand 0 conflicts with another canonicalization.
2253 unsigned NumElts = cast<FixedVectorType>(Val: Shuf.getType())->getNumElements();
2254 if (!match(V: Shuf.getOperand(i_nocapture: 1), P: m_Undef()) &&
2255 Shuf.getMaskValue(Elt: 0) >= (int)NumElts) {
2256 // TODO: Can we assert that both operands of a shuffle-select are not undef
2257 // (otherwise, it would have been folded by instsimplify?
2258 Shuf.commute();
2259 return &Shuf;
2260 }
2261
2262 if (Instruction *I = foldSelectShuffleOfSelectShuffle(Shuf))
2263 return I;
2264
2265 if (Instruction *I = foldSelectShuffleWith1Binop(
2266 Shuf, SQ: getSimplifyQuery().getWithInstruction(I: &Shuf)))
2267 return I;
2268
2269 BinaryOperator *B0, *B1;
2270 if (!match(V: Shuf.getOperand(i_nocapture: 0), P: m_BinOp(I&: B0)) ||
2271 !match(V: Shuf.getOperand(i_nocapture: 1), P: m_BinOp(I&: B1)))
2272 return nullptr;
2273
2274 // If one operand is "0 - X", allow that to be viewed as "X * -1"
2275 // (ConstantsAreOp1) by getAlternateBinop below. If the neg is not paired
2276 // with a multiply, we will exit because C0/C1 will not be set.
2277 Value *X, *Y;
2278 Constant *C0 = nullptr, *C1 = nullptr;
2279 bool ConstantsAreOp1;
2280 if (match(V: B0, P: m_BinOp(L: m_Constant(C&: C0), R: m_Value(V&: X))) &&
2281 match(V: B1, P: m_BinOp(L: m_Constant(C&: C1), R: m_Value(V&: Y))))
2282 ConstantsAreOp1 = false;
2283 else if (match(V: B0, P: m_CombineOr(L: m_BinOp(L: m_Value(V&: X), R: m_Constant(C&: C0)),
2284 R: m_Neg(V: m_Value(V&: X)))) &&
2285 match(V: B1, P: m_CombineOr(L: m_BinOp(L: m_Value(V&: Y), R: m_Constant(C&: C1)),
2286 R: m_Neg(V: m_Value(V&: Y)))))
2287 ConstantsAreOp1 = true;
2288 else
2289 return nullptr;
2290
2291 // We need matching binops to fold the lanes together.
2292 BinaryOperator::BinaryOps Opc0 = B0->getOpcode();
2293 BinaryOperator::BinaryOps Opc1 = B1->getOpcode();
2294 bool DropNSW = false;
2295 if (ConstantsAreOp1 && Opc0 != Opc1) {
2296 // TODO: We drop "nsw" if shift is converted into multiply because it may
2297 // not be correct when the shift amount is BitWidth - 1. We could examine
2298 // each vector element to determine if it is safe to keep that flag.
2299 if (Opc0 == Instruction::Shl || Opc1 == Instruction::Shl)
2300 DropNSW = true;
2301 if (BinopElts AltB0 = getAlternateBinop(BO: B0, DL)) {
2302 assert(isa<Constant>(AltB0.Op1) && "Expecting constant with alt binop");
2303 Opc0 = AltB0.Opcode;
2304 C0 = cast<Constant>(Val: AltB0.Op1);
2305 } else if (BinopElts AltB1 = getAlternateBinop(BO: B1, DL)) {
2306 assert(isa<Constant>(AltB1.Op1) && "Expecting constant with alt binop");
2307 Opc1 = AltB1.Opcode;
2308 C1 = cast<Constant>(Val: AltB1.Op1);
2309 }
2310 }
2311
2312 if (Opc0 != Opc1 || !C0 || !C1)
2313 return nullptr;
2314
2315 // The opcodes must be the same. Use a new name to make that clear.
2316 BinaryOperator::BinaryOps BOpc = Opc0;
2317
2318 // Select the constant elements needed for the single binop.
2319 ArrayRef<int> Mask = Shuf.getShuffleMask();
2320 Constant *NewC = ConstantExpr::getShuffleVector(V1: C0, V2: C1, Mask);
2321
2322 // We are moving a binop after a shuffle. When a shuffle has an undefined
2323 // mask element, the result is undefined, but it is not poison or undefined
2324 // behavior. That is not necessarily true for div/rem/shift.
2325 bool MightCreatePoisonOrUB =
2326 is_contained(Range&: Mask, Element: PoisonMaskElem) &&
2327 (Instruction::isIntDivRem(Opcode: BOpc) || Instruction::isShift(Opcode: BOpc));
2328 if (MightCreatePoisonOrUB)
2329 NewC = InstCombiner::getSafeVectorConstantForBinop(Opcode: BOpc, In: NewC,
2330 IsRHSConstant: ConstantsAreOp1);
2331
2332 Value *V;
2333 if (X == Y) {
2334 // Remove a binop and the shuffle by rearranging the constant:
2335 // shuffle (op V, C0), (op V, C1), M --> op V, C'
2336 // shuffle (op C0, V), (op C1, V), M --> op C', V
2337 V = X;
2338 } else {
2339 // If there are 2 different variable operands, we must create a new shuffle
2340 // (select) first, so check uses to ensure that we don't end up with more
2341 // instructions than we started with.
2342 if (!B0->hasOneUse() && !B1->hasOneUse())
2343 return nullptr;
2344
2345 // If we use the original shuffle mask and op1 is *variable*, we would be
2346 // putting an undef into operand 1 of div/rem/shift. This is either UB or
2347 // poison. We do not have to guard against UB when *constants* are op1
2348 // because safe constants guarantee that we do not overflow sdiv/srem (and
2349 // there's no danger for other opcodes).
2350 // TODO: To allow this case, create a new shuffle mask with no undefs.
2351 if (MightCreatePoisonOrUB && !ConstantsAreOp1)
2352 return nullptr;
2353
2354 // Note: In general, we do not create new shuffles in InstCombine because we
2355 // do not know if a target can lower an arbitrary shuffle optimally. In this
2356 // case, the shuffle uses the existing mask, so there is no additional risk.
2357
2358 // Select the variable vectors first, then perform the binop:
2359 // shuffle (op X, C0), (op Y, C1), M --> op (shuffle X, Y, M), C'
2360 // shuffle (op C0, X), (op C1, Y), M --> op C', (shuffle X, Y, M)
2361 V = Builder.CreateShuffleVector(V1: X, V2: Y, Mask);
2362 }
2363
2364 Value *NewBO = ConstantsAreOp1 ? Builder.CreateBinOp(Opc: BOpc, LHS: V, RHS: NewC) :
2365 Builder.CreateBinOp(Opc: BOpc, LHS: NewC, RHS: V);
2366
2367 // Flags are intersected from the 2 source binops. But there are 2 exceptions:
2368 // 1. If we changed an opcode, poison conditions might have changed.
2369 // 2. If the shuffle had undef mask elements, the new binop might have undefs
2370 // where the original code did not. But if we already made a safe constant,
2371 // then there's no danger.
2372 if (auto *NewI = dyn_cast<Instruction>(Val: NewBO)) {
2373 NewI->copyIRFlags(V: B0);
2374 NewI->andIRFlags(V: B1);
2375 if (DropNSW)
2376 NewI->setHasNoSignedWrap(false);
2377 if (is_contained(Range&: Mask, Element: PoisonMaskElem) && !MightCreatePoisonOrUB)
2378 NewI->dropPoisonGeneratingFlags();
2379 }
2380 return replaceInstUsesWith(I&: Shuf, V: NewBO);
2381}
2382
2383/// Convert a narrowing shuffle of a bitcasted vector into a vector truncate.
2384/// Example (little endian):
2385/// shuf (bitcast <4 x i16> X to <8 x i8>), <0, 2, 4, 6> --> trunc X to <4 x i8>
2386static Instruction *foldTruncShuffle(ShuffleVectorInst &Shuf,
2387 bool IsBigEndian) {
2388 // This must be a bitcasted shuffle of 1 vector integer operand.
2389 Type *DestType = Shuf.getType();
2390 Value *X;
2391 if (!match(V: Shuf.getOperand(i_nocapture: 0), P: m_BitCast(Op: m_Value(V&: X))) ||
2392 !match(V: Shuf.getOperand(i_nocapture: 1), P: m_Poison()) || !DestType->isIntOrIntVectorTy())
2393 return nullptr;
2394
2395 // The source type must have the same number of elements as the shuffle,
2396 // and the source element type must be larger than the shuffle element type.
2397 Type *SrcType = X->getType();
2398 if (!SrcType->isVectorTy() || !SrcType->isIntOrIntVectorTy() ||
2399 cast<FixedVectorType>(Val: SrcType)->getNumElements() !=
2400 cast<FixedVectorType>(Val: DestType)->getNumElements() ||
2401 SrcType->getScalarSizeInBits() % DestType->getScalarSizeInBits() != 0)
2402 return nullptr;
2403
2404 assert(Shuf.changesLength() && !Shuf.increasesLength() &&
2405 "Expected a shuffle that decreases length");
2406
2407 // Last, check that the mask chooses the correct low bits for each narrow
2408 // element in the result.
2409 uint64_t TruncRatio =
2410 SrcType->getScalarSizeInBits() / DestType->getScalarSizeInBits();
2411 ArrayRef<int> Mask = Shuf.getShuffleMask();
2412 for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
2413 if (Mask[i] == PoisonMaskElem)
2414 continue;
2415 uint64_t LSBIndex = IsBigEndian ? (i + 1) * TruncRatio - 1 : i * TruncRatio;
2416 assert(LSBIndex <= INT32_MAX && "Overflowed 32-bits");
2417 if (Mask[i] != (int)LSBIndex)
2418 return nullptr;
2419 }
2420
2421 return new TruncInst(X, DestType);
2422}
2423
2424/// Match a shuffle-select-shuffle pattern where the shuffles are widening and
2425/// narrowing (concatenating with poison and extracting back to the original
2426/// length). This allows replacing the wide select with a narrow select.
2427static Instruction *narrowVectorSelect(ShuffleVectorInst &Shuf,
2428 InstCombiner::BuilderTy &Builder) {
2429 // This must be a narrowing identity shuffle. It extracts the 1st N elements
2430 // of the 1st vector operand of a shuffle.
2431 if (!match(V: Shuf.getOperand(i_nocapture: 1), P: m_Poison()) || !Shuf.isIdentityWithExtract())
2432 return nullptr;
2433
2434 // The vector being shuffled must be a vector select that we can eliminate.
2435 // TODO: The one-use requirement could be eased if X and/or Y are constants.
2436 Value *Cond, *X, *Y;
2437 if (!match(V: Shuf.getOperand(i_nocapture: 0),
2438 P: m_OneUse(SubPattern: m_Select(C: m_Value(V&: Cond), L: m_Value(V&: X), R: m_Value(V&: Y)))))
2439 return nullptr;
2440
2441 // We need a narrow condition value. It must be extended with poison elements
2442 // and have the same number of elements as this shuffle.
2443 unsigned NarrowNumElts =
2444 cast<FixedVectorType>(Val: Shuf.getType())->getNumElements();
2445 Value *NarrowCond;
2446 if (!match(V: Cond, P: m_OneUse(SubPattern: m_Shuffle(v1: m_Value(V&: NarrowCond), v2: m_Poison()))) ||
2447 cast<FixedVectorType>(Val: NarrowCond->getType())->getNumElements() !=
2448 NarrowNumElts ||
2449 !cast<ShuffleVectorInst>(Val: Cond)->isIdentityWithPadding())
2450 return nullptr;
2451
2452 // shuf (sel (shuf NarrowCond, poison, WideMask), X, Y), poison, NarrowMask)
2453 // -->
2454 // sel NarrowCond, (shuf X, poison, NarrowMask), (shuf Y, poison, NarrowMask)
2455 Value *NarrowX = Builder.CreateShuffleVector(V: X, Mask: Shuf.getShuffleMask());
2456 Value *NarrowY = Builder.CreateShuffleVector(V: Y, Mask: Shuf.getShuffleMask());
2457 return SelectInst::Create(C: NarrowCond, S1: NarrowX, S2: NarrowY);
2458}
2459
2460/// Canonicalize FP negate/abs after shuffle.
2461static Instruction *foldShuffleOfUnaryOps(ShuffleVectorInst &Shuf,
2462 InstCombiner::BuilderTy &Builder) {
2463 auto *S0 = dyn_cast<Instruction>(Val: Shuf.getOperand(i_nocapture: 0));
2464 Value *X;
2465 if (!S0 || !match(V: S0, P: m_CombineOr(L: m_FNeg(X: m_Value(V&: X)), R: m_FAbs(Op0: m_Value(V&: X)))))
2466 return nullptr;
2467
2468 bool IsFNeg = S0->getOpcode() == Instruction::FNeg;
2469
2470 // Match 1-input (unary) shuffle.
2471 // shuffle (fneg/fabs X), Mask --> fneg/fabs (shuffle X, Mask)
2472 if (S0->hasOneUse() && match(V: Shuf.getOperand(i_nocapture: 1), P: m_Poison())) {
2473 Value *NewShuf = Builder.CreateShuffleVector(V: X, Mask: Shuf.getShuffleMask());
2474 if (IsFNeg)
2475 return UnaryOperator::CreateFNegFMF(Op: NewShuf, FMFSource: S0);
2476
2477 Function *FAbs = Intrinsic::getDeclaration(M: Shuf.getModule(),
2478 id: Intrinsic::fabs, Tys: Shuf.getType());
2479 CallInst *NewF = CallInst::Create(Func: FAbs, Args: {NewShuf});
2480 NewF->setFastMathFlags(S0->getFastMathFlags());
2481 return NewF;
2482 }
2483
2484 // Match 2-input (binary) shuffle.
2485 auto *S1 = dyn_cast<Instruction>(Val: Shuf.getOperand(i_nocapture: 1));
2486 Value *Y;
2487 if (!S1 || !match(V: S1, P: m_CombineOr(L: m_FNeg(X: m_Value(V&: Y)), R: m_FAbs(Op0: m_Value(V&: Y)))) ||
2488 S0->getOpcode() != S1->getOpcode() ||
2489 (!S0->hasOneUse() && !S1->hasOneUse()))
2490 return nullptr;
2491
2492 // shuf (fneg/fabs X), (fneg/fabs Y), Mask --> fneg/fabs (shuf X, Y, Mask)
2493 Value *NewShuf = Builder.CreateShuffleVector(V1: X, V2: Y, Mask: Shuf.getShuffleMask());
2494 Instruction *NewF;
2495 if (IsFNeg) {
2496 NewF = UnaryOperator::CreateFNeg(V: NewShuf);
2497 } else {
2498 Function *FAbs = Intrinsic::getDeclaration(M: Shuf.getModule(),
2499 id: Intrinsic::fabs, Tys: Shuf.getType());
2500 NewF = CallInst::Create(Func: FAbs, Args: {NewShuf});
2501 }
2502 NewF->copyIRFlags(V: S0);
2503 NewF->andIRFlags(V: S1);
2504 return NewF;
2505}
2506
2507/// Canonicalize casts after shuffle.
2508static Instruction *foldCastShuffle(ShuffleVectorInst &Shuf,
2509 InstCombiner::BuilderTy &Builder) {
2510 // Do we have 2 matching cast operands?
2511 auto *Cast0 = dyn_cast<CastInst>(Val: Shuf.getOperand(i_nocapture: 0));
2512 auto *Cast1 = dyn_cast<CastInst>(Val: Shuf.getOperand(i_nocapture: 1));
2513 if (!Cast0 || !Cast1 || Cast0->getOpcode() != Cast1->getOpcode() ||
2514 Cast0->getSrcTy() != Cast1->getSrcTy())
2515 return nullptr;
2516
2517 // TODO: Allow other opcodes? That would require easing the type restrictions
2518 // below here.
2519 CastInst::CastOps CastOpcode = Cast0->getOpcode();
2520 switch (CastOpcode) {
2521 case Instruction::FPToSI:
2522 case Instruction::FPToUI:
2523 case Instruction::SIToFP:
2524 case Instruction::UIToFP:
2525 break;
2526 default:
2527 return nullptr;
2528 }
2529
2530 VectorType *ShufTy = Shuf.getType();
2531 VectorType *ShufOpTy = cast<VectorType>(Val: Shuf.getOperand(i_nocapture: 0)->getType());
2532 VectorType *CastSrcTy = cast<VectorType>(Val: Cast0->getSrcTy());
2533
2534 // TODO: Allow length-increasing shuffles?
2535 if (ShufTy->getElementCount().getKnownMinValue() >
2536 ShufOpTy->getElementCount().getKnownMinValue())
2537 return nullptr;
2538
2539 // TODO: Allow element-size-decreasing casts (ex: fptosi float to i8)?
2540 assert(isa<FixedVectorType>(CastSrcTy) && isa<FixedVectorType>(ShufOpTy) &&
2541 "Expected fixed vector operands for casts and binary shuffle");
2542 if (CastSrcTy->getPrimitiveSizeInBits() > ShufOpTy->getPrimitiveSizeInBits())
2543 return nullptr;
2544
2545 // At least one of the operands must have only one use (the shuffle).
2546 if (!Cast0->hasOneUse() && !Cast1->hasOneUse())
2547 return nullptr;
2548
2549 // shuffle (cast X), (cast Y), Mask --> cast (shuffle X, Y, Mask)
2550 Value *X = Cast0->getOperand(i_nocapture: 0);
2551 Value *Y = Cast1->getOperand(i_nocapture: 0);
2552 Value *NewShuf = Builder.CreateShuffleVector(V1: X, V2: Y, Mask: Shuf.getShuffleMask());
2553 return CastInst::Create(CastOpcode, S: NewShuf, Ty: ShufTy);
2554}
2555
2556/// Try to fold an extract subvector operation.
2557static Instruction *foldIdentityExtractShuffle(ShuffleVectorInst &Shuf) {
2558 Value *Op0 = Shuf.getOperand(i_nocapture: 0), *Op1 = Shuf.getOperand(i_nocapture: 1);
2559 if (!Shuf.isIdentityWithExtract() || !match(V: Op1, P: m_Poison()))
2560 return nullptr;
2561
2562 // Check if we are extracting all bits of an inserted scalar:
2563 // extract-subvec (bitcast (inselt ?, X, 0) --> bitcast X to subvec type
2564 Value *X;
2565 if (match(V: Op0, P: m_BitCast(Op: m_InsertElt(Val: m_Value(), Elt: m_Value(V&: X), Idx: m_Zero()))) &&
2566 X->getType()->getPrimitiveSizeInBits() ==
2567 Shuf.getType()->getPrimitiveSizeInBits())
2568 return new BitCastInst(X, Shuf.getType());
2569
2570 // Try to combine 2 shuffles into 1 shuffle by concatenating a shuffle mask.
2571 Value *Y;
2572 ArrayRef<int> Mask;
2573 if (!match(V: Op0, P: m_Shuffle(v1: m_Value(V&: X), v2: m_Value(V&: Y), mask: m_Mask(Mask))))
2574 return nullptr;
2575
2576 // Be conservative with shuffle transforms. If we can't kill the 1st shuffle,
2577 // then combining may result in worse codegen.
2578 if (!Op0->hasOneUse())
2579 return nullptr;
2580
2581 // We are extracting a subvector from a shuffle. Remove excess elements from
2582 // the 1st shuffle mask to eliminate the extract.
2583 //
2584 // This transform is conservatively limited to identity extracts because we do
2585 // not allow arbitrary shuffle mask creation as a target-independent transform
2586 // (because we can't guarantee that will lower efficiently).
2587 //
2588 // If the extracting shuffle has an poison mask element, it transfers to the
2589 // new shuffle mask. Otherwise, copy the original mask element. Example:
2590 // shuf (shuf X, Y, <C0, C1, C2, poison, C4>), poison, <0, poison, 2, 3> -->
2591 // shuf X, Y, <C0, poison, C2, poison>
2592 unsigned NumElts = cast<FixedVectorType>(Val: Shuf.getType())->getNumElements();
2593 SmallVector<int, 16> NewMask(NumElts);
2594 assert(NumElts < Mask.size() &&
2595 "Identity with extract must have less elements than its inputs");
2596
2597 for (unsigned i = 0; i != NumElts; ++i) {
2598 int ExtractMaskElt = Shuf.getMaskValue(Elt: i);
2599 int MaskElt = Mask[i];
2600 NewMask[i] = ExtractMaskElt == PoisonMaskElem ? ExtractMaskElt : MaskElt;
2601 }
2602 return new ShuffleVectorInst(X, Y, NewMask);
2603}
2604
2605/// Try to replace a shuffle with an insertelement or try to replace a shuffle
2606/// operand with the operand of an insertelement.
2607static Instruction *foldShuffleWithInsert(ShuffleVectorInst &Shuf,
2608 InstCombinerImpl &IC) {
2609 Value *V0 = Shuf.getOperand(i_nocapture: 0), *V1 = Shuf.getOperand(i_nocapture: 1);
2610 SmallVector<int, 16> Mask;
2611 Shuf.getShuffleMask(Result&: Mask);
2612
2613 int NumElts = Mask.size();
2614 int InpNumElts = cast<FixedVectorType>(Val: V0->getType())->getNumElements();
2615
2616 // This is a specialization of a fold in SimplifyDemandedVectorElts. We may
2617 // not be able to handle it there if the insertelement has >1 use.
2618 // If the shuffle has an insertelement operand but does not choose the
2619 // inserted scalar element from that value, then we can replace that shuffle
2620 // operand with the source vector of the insertelement.
2621 Value *X;
2622 uint64_t IdxC;
2623 if (match(V: V0, P: m_InsertElt(Val: m_Value(V&: X), Elt: m_Value(), Idx: m_ConstantInt(V&: IdxC)))) {
2624 // shuf (inselt X, ?, IdxC), ?, Mask --> shuf X, ?, Mask
2625 if (!is_contained(Range&: Mask, Element: (int)IdxC))
2626 return IC.replaceOperand(I&: Shuf, OpNum: 0, V: X);
2627 }
2628 if (match(V: V1, P: m_InsertElt(Val: m_Value(V&: X), Elt: m_Value(), Idx: m_ConstantInt(V&: IdxC)))) {
2629 // Offset the index constant by the vector width because we are checking for
2630 // accesses to the 2nd vector input of the shuffle.
2631 IdxC += InpNumElts;
2632 // shuf ?, (inselt X, ?, IdxC), Mask --> shuf ?, X, Mask
2633 if (!is_contained(Range&: Mask, Element: (int)IdxC))
2634 return IC.replaceOperand(I&: Shuf, OpNum: 1, V: X);
2635 }
2636 // For the rest of the transform, the shuffle must not change vector sizes.
2637 // TODO: This restriction could be removed if the insert has only one use
2638 // (because the transform would require a new length-changing shuffle).
2639 if (NumElts != InpNumElts)
2640 return nullptr;
2641
2642 // shuffle (insert ?, Scalar, IndexC), V1, Mask --> insert V1, Scalar, IndexC'
2643 auto isShufflingScalarIntoOp1 = [&](Value *&Scalar, ConstantInt *&IndexC) {
2644 // We need an insertelement with a constant index.
2645 if (!match(V: V0, P: m_InsertElt(Val: m_Value(), Elt: m_Value(V&: Scalar),
2646 Idx: m_ConstantInt(CI&: IndexC))))
2647 return false;
2648
2649 // Test the shuffle mask to see if it splices the inserted scalar into the
2650 // operand 1 vector of the shuffle.
2651 int NewInsIndex = -1;
2652 for (int i = 0; i != NumElts; ++i) {
2653 // Ignore undef mask elements.
2654 if (Mask[i] == -1)
2655 continue;
2656
2657 // The shuffle takes elements of operand 1 without lane changes.
2658 if (Mask[i] == NumElts + i)
2659 continue;
2660
2661 // The shuffle must choose the inserted scalar exactly once.
2662 if (NewInsIndex != -1 || Mask[i] != IndexC->getSExtValue())
2663 return false;
2664
2665 // The shuffle is placing the inserted scalar into element i.
2666 NewInsIndex = i;
2667 }
2668
2669 assert(NewInsIndex != -1 && "Did not fold shuffle with unused operand?");
2670
2671 // Index is updated to the potentially translated insertion lane.
2672 IndexC = ConstantInt::get(Ty: IndexC->getIntegerType(), V: NewInsIndex);
2673 return true;
2674 };
2675
2676 // If the shuffle is unnecessary, insert the scalar operand directly into
2677 // operand 1 of the shuffle. Example:
2678 // shuffle (insert ?, S, 1), V1, <1, 5, 6, 7> --> insert V1, S, 0
2679 Value *Scalar;
2680 ConstantInt *IndexC;
2681 if (isShufflingScalarIntoOp1(Scalar, IndexC))
2682 return InsertElementInst::Create(Vec: V1, NewElt: Scalar, Idx: IndexC);
2683
2684 // Try again after commuting shuffle. Example:
2685 // shuffle V0, (insert ?, S, 0), <0, 1, 2, 4> -->
2686 // shuffle (insert ?, S, 0), V0, <4, 5, 6, 0> --> insert V0, S, 3
2687 std::swap(a&: V0, b&: V1);
2688 ShuffleVectorInst::commuteShuffleMask(Mask, InVecNumElts: NumElts);
2689 if (isShufflingScalarIntoOp1(Scalar, IndexC))
2690 return InsertElementInst::Create(Vec: V1, NewElt: Scalar, Idx: IndexC);
2691
2692 return nullptr;
2693}
2694
2695static Instruction *foldIdentityPaddedShuffles(ShuffleVectorInst &Shuf) {
2696 // Match the operands as identity with padding (also known as concatenation
2697 // with undef) shuffles of the same source type. The backend is expected to
2698 // recreate these concatenations from a shuffle of narrow operands.
2699 auto *Shuffle0 = dyn_cast<ShuffleVectorInst>(Val: Shuf.getOperand(i_nocapture: 0));
2700 auto *Shuffle1 = dyn_cast<ShuffleVectorInst>(Val: Shuf.getOperand(i_nocapture: 1));
2701 if (!Shuffle0 || !Shuffle0->isIdentityWithPadding() ||
2702 !Shuffle1 || !Shuffle1->isIdentityWithPadding())
2703 return nullptr;
2704
2705 // We limit this transform to power-of-2 types because we expect that the
2706 // backend can convert the simplified IR patterns to identical nodes as the
2707 // original IR.
2708 // TODO: If we can verify the same behavior for arbitrary types, the
2709 // power-of-2 checks can be removed.
2710 Value *X = Shuffle0->getOperand(i_nocapture: 0);
2711 Value *Y = Shuffle1->getOperand(i_nocapture: 0);
2712 if (X->getType() != Y->getType() ||
2713 !isPowerOf2_32(Value: cast<FixedVectorType>(Val: Shuf.getType())->getNumElements()) ||
2714 !isPowerOf2_32(
2715 Value: cast<FixedVectorType>(Val: Shuffle0->getType())->getNumElements()) ||
2716 !isPowerOf2_32(Value: cast<FixedVectorType>(Val: X->getType())->getNumElements()) ||
2717 match(V: X, P: m_Undef()) || match(V: Y, P: m_Undef()))
2718 return nullptr;
2719 assert(match(Shuffle0->getOperand(1), m_Undef()) &&
2720 match(Shuffle1->getOperand(1), m_Undef()) &&
2721 "Unexpected operand for identity shuffle");
2722
2723 // This is a shuffle of 2 widening shuffles. We can shuffle the narrow source
2724 // operands directly by adjusting the shuffle mask to account for the narrower
2725 // types:
2726 // shuf (widen X), (widen Y), Mask --> shuf X, Y, Mask'
2727 int NarrowElts = cast<FixedVectorType>(Val: X->getType())->getNumElements();
2728 int WideElts = cast<FixedVectorType>(Val: Shuffle0->getType())->getNumElements();
2729 assert(WideElts > NarrowElts && "Unexpected types for identity with padding");
2730
2731 ArrayRef<int> Mask = Shuf.getShuffleMask();
2732 SmallVector<int, 16> NewMask(Mask.size(), -1);
2733 for (int i = 0, e = Mask.size(); i != e; ++i) {
2734 if (Mask[i] == -1)
2735 continue;
2736
2737 // If this shuffle is choosing an undef element from 1 of the sources, that
2738 // element is undef.
2739 if (Mask[i] < WideElts) {
2740 if (Shuffle0->getMaskValue(Elt: Mask[i]) == -1)
2741 continue;
2742 } else {
2743 if (Shuffle1->getMaskValue(Elt: Mask[i] - WideElts) == -1)
2744 continue;
2745 }
2746
2747 // If this shuffle is choosing from the 1st narrow op, the mask element is
2748 // the same. If this shuffle is choosing from the 2nd narrow op, the mask
2749 // element is offset down to adjust for the narrow vector widths.
2750 if (Mask[i] < WideElts) {
2751 assert(Mask[i] < NarrowElts && "Unexpected shuffle mask");
2752 NewMask[i] = Mask[i];
2753 } else {
2754 assert(Mask[i] < (WideElts + NarrowElts) && "Unexpected shuffle mask");
2755 NewMask[i] = Mask[i] - (WideElts - NarrowElts);
2756 }
2757 }
2758 return new ShuffleVectorInst(X, Y, NewMask);
2759}
2760
2761// Splatting the first element of the result of a BinOp, where any of the
2762// BinOp's operands are the result of a first element splat can be simplified to
2763// splatting the first element of the result of the BinOp
2764Instruction *InstCombinerImpl::simplifyBinOpSplats(ShuffleVectorInst &SVI) {
2765 if (!match(V: SVI.getOperand(i_nocapture: 1), P: m_Poison()) ||
2766 !match(Mask: SVI.getShuffleMask(), P: m_ZeroMask()) ||
2767 !SVI.getOperand(i_nocapture: 0)->hasOneUse())
2768 return nullptr;
2769
2770 Value *Op0 = SVI.getOperand(i_nocapture: 0);
2771 Value *X, *Y;
2772 if (!match(V: Op0, P: m_BinOp(L: m_Shuffle(v1: m_Value(V&: X), v2: m_Poison(), mask: m_ZeroMask()),
2773 R: m_Value(V&: Y))) &&
2774 !match(V: Op0, P: m_BinOp(L: m_Value(V&: X),
2775 R: m_Shuffle(v1: m_Value(V&: Y), v2: m_Poison(), mask: m_ZeroMask()))))
2776 return nullptr;
2777 if (X->getType() != Y->getType())
2778 return nullptr;
2779
2780 auto *BinOp = cast<BinaryOperator>(Val: Op0);
2781 if (!isSafeToSpeculativelyExecute(I: BinOp))
2782 return nullptr;
2783
2784 Value *NewBO = Builder.CreateBinOp(Opc: BinOp->getOpcode(), LHS: X, RHS: Y);
2785 if (auto NewBOI = dyn_cast<Instruction>(Val: NewBO))
2786 NewBOI->copyIRFlags(V: BinOp);
2787
2788 return new ShuffleVectorInst(NewBO, SVI.getShuffleMask());
2789}
2790
2791Instruction *InstCombinerImpl::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
2792 Value *LHS = SVI.getOperand(i_nocapture: 0);
2793 Value *RHS = SVI.getOperand(i_nocapture: 1);
2794 SimplifyQuery ShufQuery = SQ.getWithInstruction(I: &SVI);
2795 if (auto *V = simplifyShuffleVectorInst(Op0: LHS, Op1: RHS, Mask: SVI.getShuffleMask(),
2796 RetTy: SVI.getType(), Q: ShufQuery))
2797 return replaceInstUsesWith(I&: SVI, V);
2798
2799 if (Instruction *I = simplifyBinOpSplats(SVI))
2800 return I;
2801
2802 // Canonicalize splat shuffle to use poison RHS. Handle this explicitly in
2803 // order to support scalable vectors.
2804 if (match(Mask: SVI.getShuffleMask(), P: m_ZeroMask()) && !isa<PoisonValue>(Val: RHS))
2805 return replaceOperand(I&: SVI, OpNum: 1, V: PoisonValue::get(T: RHS->getType()));
2806
2807 if (isa<ScalableVectorType>(Val: LHS->getType()))
2808 return nullptr;
2809
2810 unsigned VWidth = cast<FixedVectorType>(Val: SVI.getType())->getNumElements();
2811 unsigned LHSWidth = cast<FixedVectorType>(Val: LHS->getType())->getNumElements();
2812
2813 // shuffle (bitcast X), (bitcast Y), Mask --> bitcast (shuffle X, Y, Mask)
2814 //
2815 // if X and Y are of the same (vector) type, and the element size is not
2816 // changed by the bitcasts, we can distribute the bitcasts through the
2817 // shuffle, hopefully reducing the number of instructions. We make sure that
2818 // at least one bitcast only has one use, so we don't *increase* the number of
2819 // instructions here.
2820 Value *X, *Y;
2821 if (match(V: LHS, P: m_BitCast(Op: m_Value(V&: X))) && match(V: RHS, P: m_BitCast(Op: m_Value(V&: Y))) &&
2822 X->getType()->isVectorTy() && X->getType() == Y->getType() &&
2823 X->getType()->getScalarSizeInBits() ==
2824 SVI.getType()->getScalarSizeInBits() &&
2825 (LHS->hasOneUse() || RHS->hasOneUse())) {
2826 Value *V = Builder.CreateShuffleVector(V1: X, V2: Y, Mask: SVI.getShuffleMask(),
2827 Name: SVI.getName() + ".uncasted");
2828 return new BitCastInst(V, SVI.getType());
2829 }
2830
2831 ArrayRef<int> Mask = SVI.getShuffleMask();
2832
2833 // Peek through a bitcasted shuffle operand by scaling the mask. If the
2834 // simulated shuffle can simplify, then this shuffle is unnecessary:
2835 // shuf (bitcast X), undef, Mask --> bitcast X'
2836 // TODO: This could be extended to allow length-changing shuffles.
2837 // The transform might also be obsoleted if we allowed canonicalization
2838 // of bitcasted shuffles.
2839 if (match(V: LHS, P: m_BitCast(Op: m_Value(V&: X))) && match(V: RHS, P: m_Undef()) &&
2840 X->getType()->isVectorTy() && VWidth == LHSWidth) {
2841 // Try to create a scaled mask constant.
2842 auto *XType = cast<FixedVectorType>(Val: X->getType());
2843 unsigned XNumElts = XType->getNumElements();
2844 SmallVector<int, 16> ScaledMask;
2845 if (scaleShuffleMaskElts(NumDstElts: XNumElts, Mask, ScaledMask)) {
2846 // If the shuffled source vector simplifies, cast that value to this
2847 // shuffle's type.
2848 if (auto *V = simplifyShuffleVectorInst(Op0: X, Op1: UndefValue::get(T: XType),
2849 Mask: ScaledMask, RetTy: XType, Q: ShufQuery))
2850 return BitCastInst::Create(Instruction::BitCast, S: V, Ty: SVI.getType());
2851 }
2852 }
2853
2854 // shuffle x, x, mask --> shuffle x, undef, mask'
2855 if (LHS == RHS) {
2856 assert(!match(RHS, m_Undef()) &&
2857 "Shuffle with 2 undef ops not simplified?");
2858 return new ShuffleVectorInst(LHS, createUnaryMask(Mask, NumElts: LHSWidth));
2859 }
2860
2861 // shuffle undef, x, mask --> shuffle x, undef, mask'
2862 if (match(V: LHS, P: m_Undef())) {
2863 SVI.commute();
2864 return &SVI;
2865 }
2866
2867 if (Instruction *I = canonicalizeInsertSplat(Shuf&: SVI, Builder))
2868 return I;
2869
2870 if (Instruction *I = foldSelectShuffle(Shuf&: SVI))
2871 return I;
2872
2873 if (Instruction *I = foldTruncShuffle(Shuf&: SVI, IsBigEndian: DL.isBigEndian()))
2874 return I;
2875
2876 if (Instruction *I = narrowVectorSelect(Shuf&: SVI, Builder))
2877 return I;
2878
2879 if (Instruction *I = foldShuffleOfUnaryOps(Shuf&: SVI, Builder))
2880 return I;
2881
2882 if (Instruction *I = foldCastShuffle(Shuf&: SVI, Builder))
2883 return I;
2884
2885 APInt PoisonElts(VWidth, 0);
2886 APInt AllOnesEltMask(APInt::getAllOnes(numBits: VWidth));
2887 if (Value *V = SimplifyDemandedVectorElts(V: &SVI, DemandedElts: AllOnesEltMask, PoisonElts)) {
2888 if (V != &SVI)
2889 return replaceInstUsesWith(I&: SVI, V);
2890 return &SVI;
2891 }
2892
2893 if (Instruction *I = foldIdentityExtractShuffle(Shuf&: SVI))
2894 return I;
2895
2896 // These transforms have the potential to lose undef knowledge, so they are
2897 // intentionally placed after SimplifyDemandedVectorElts().
2898 if (Instruction *I = foldShuffleWithInsert(Shuf&: SVI, IC&: *this))
2899 return I;
2900 if (Instruction *I = foldIdentityPaddedShuffles(Shuf&: SVI))
2901 return I;
2902
2903 if (match(V: RHS, P: m_Poison()) && canEvaluateShuffled(V: LHS, Mask)) {
2904 Value *V = evaluateInDifferentElementOrder(V: LHS, Mask, Builder);
2905 return replaceInstUsesWith(I&: SVI, V);
2906 }
2907
2908 // SROA generates shuffle+bitcast when the extracted sub-vector is bitcast to
2909 // a non-vector type. We can instead bitcast the original vector followed by
2910 // an extract of the desired element:
2911 //
2912 // %sroa = shufflevector <16 x i8> %in, <16 x i8> undef,
2913 // <4 x i32> <i32 0, i32 1, i32 2, i32 3>
2914 // %1 = bitcast <4 x i8> %sroa to i32
2915 // Becomes:
2916 // %bc = bitcast <16 x i8> %in to <4 x i32>
2917 // %ext = extractelement <4 x i32> %bc, i32 0
2918 //
2919 // If the shuffle is extracting a contiguous range of values from the input
2920 // vector then each use which is a bitcast of the extracted size can be
2921 // replaced. This will work if the vector types are compatible, and the begin
2922 // index is aligned to a value in the casted vector type. If the begin index
2923 // isn't aligned then we can shuffle the original vector (keeping the same
2924 // vector type) before extracting.
2925 //
2926 // This code will bail out if the target type is fundamentally incompatible
2927 // with vectors of the source type.
2928 //
2929 // Example of <16 x i8>, target type i32:
2930 // Index range [4,8): v-----------v Will work.
2931 // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
2932 // <16 x i8>: | | | | | | | | | | | | | | | | |
2933 // <4 x i32>: | | | | |
2934 // +-----------+-----------+-----------+-----------+
2935 // Index range [6,10): ^-----------^ Needs an extra shuffle.
2936 // Target type i40: ^--------------^ Won't work, bail.
2937 bool MadeChange = false;
2938 if (isShuffleExtractingFromLHS(SVI, Mask)) {
2939 Value *V = LHS;
2940 unsigned MaskElems = Mask.size();
2941 auto *SrcTy = cast<FixedVectorType>(Val: V->getType());
2942 unsigned VecBitWidth = SrcTy->getPrimitiveSizeInBits().getFixedValue();
2943 unsigned SrcElemBitWidth = DL.getTypeSizeInBits(Ty: SrcTy->getElementType());
2944 assert(SrcElemBitWidth && "vector elements must have a bitwidth");
2945 unsigned SrcNumElems = SrcTy->getNumElements();
2946 SmallVector<BitCastInst *, 8> BCs;
2947 DenseMap<Type *, Value *> NewBCs;
2948 for (User *U : SVI.users())
2949 if (BitCastInst *BC = dyn_cast<BitCastInst>(Val: U))
2950 if (!BC->use_empty())
2951 // Only visit bitcasts that weren't previously handled.
2952 BCs.push_back(Elt: BC);
2953 for (BitCastInst *BC : BCs) {
2954 unsigned BegIdx = Mask.front();
2955 Type *TgtTy = BC->getDestTy();
2956 unsigned TgtElemBitWidth = DL.getTypeSizeInBits(Ty: TgtTy);
2957 if (!TgtElemBitWidth)
2958 continue;
2959 unsigned TgtNumElems = VecBitWidth / TgtElemBitWidth;
2960 bool VecBitWidthsEqual = VecBitWidth == TgtNumElems * TgtElemBitWidth;
2961 bool BegIsAligned = 0 == ((SrcElemBitWidth * BegIdx) % TgtElemBitWidth);
2962 if (!VecBitWidthsEqual)
2963 continue;
2964 if (!VectorType::isValidElementType(ElemTy: TgtTy))
2965 continue;
2966 auto *CastSrcTy = FixedVectorType::get(ElementType: TgtTy, NumElts: TgtNumElems);
2967 if (!BegIsAligned) {
2968 // Shuffle the input so [0,NumElements) contains the output, and
2969 // [NumElems,SrcNumElems) is undef.
2970 SmallVector<int, 16> ShuffleMask(SrcNumElems, -1);
2971 for (unsigned I = 0, E = MaskElems, Idx = BegIdx; I != E; ++Idx, ++I)
2972 ShuffleMask[I] = Idx;
2973 V = Builder.CreateShuffleVector(V, Mask: ShuffleMask,
2974 Name: SVI.getName() + ".extract");
2975 BegIdx = 0;
2976 }
2977 unsigned SrcElemsPerTgtElem = TgtElemBitWidth / SrcElemBitWidth;
2978 assert(SrcElemsPerTgtElem);
2979 BegIdx /= SrcElemsPerTgtElem;
2980 bool BCAlreadyExists = NewBCs.contains(Val: CastSrcTy);
2981 auto *NewBC =
2982 BCAlreadyExists
2983 ? NewBCs[CastSrcTy]
2984 : Builder.CreateBitCast(V, DestTy: CastSrcTy, Name: SVI.getName() + ".bc");
2985 if (!BCAlreadyExists)
2986 NewBCs[CastSrcTy] = NewBC;
2987 auto *Ext = Builder.CreateExtractElement(Vec: NewBC, Idx: BegIdx,
2988 Name: SVI.getName() + ".extract");
2989 // The shufflevector isn't being replaced: the bitcast that used it
2990 // is. InstCombine will visit the newly-created instructions.
2991 replaceInstUsesWith(I&: *BC, V: Ext);
2992 MadeChange = true;
2993 }
2994 }
2995
2996 // If the LHS is a shufflevector itself, see if we can combine it with this
2997 // one without producing an unusual shuffle.
2998 // Cases that might be simplified:
2999 // 1.
3000 // x1=shuffle(v1,v2,mask1)
3001 // x=shuffle(x1,undef,mask)
3002 // ==>
3003 // x=shuffle(v1,undef,newMask)
3004 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : -1
3005 // 2.
3006 // x1=shuffle(v1,undef,mask1)
3007 // x=shuffle(x1,x2,mask)
3008 // where v1.size() == mask1.size()
3009 // ==>
3010 // x=shuffle(v1,x2,newMask)
3011 // newMask[i] = (mask[i] < x1.size()) ? mask1[mask[i]] : mask[i]
3012 // 3.
3013 // x2=shuffle(v2,undef,mask2)
3014 // x=shuffle(x1,x2,mask)
3015 // where v2.size() == mask2.size()
3016 // ==>
3017 // x=shuffle(x1,v2,newMask)
3018 // newMask[i] = (mask[i] < x1.size())
3019 // ? mask[i] : mask2[mask[i]-x1.size()]+x1.size()
3020 // 4.
3021 // x1=shuffle(v1,undef,mask1)
3022 // x2=shuffle(v2,undef,mask2)
3023 // x=shuffle(x1,x2,mask)
3024 // where v1.size() == v2.size()
3025 // ==>
3026 // x=shuffle(v1,v2,newMask)
3027 // newMask[i] = (mask[i] < x1.size())
3028 // ? mask1[mask[i]] : mask2[mask[i]-x1.size()]+v1.size()
3029 //
3030 // Here we are really conservative:
3031 // we are absolutely afraid of producing a shuffle mask not in the input
3032 // program, because the code gen may not be smart enough to turn a merged
3033 // shuffle into two specific shuffles: it may produce worse code. As such,
3034 // we only merge two shuffles if the result is either a splat or one of the
3035 // input shuffle masks. In this case, merging the shuffles just removes
3036 // one instruction, which we know is safe. This is good for things like
3037 // turning: (splat(splat)) -> splat, or
3038 // merge(V[0..n], V[n+1..2n]) -> V[0..2n]
3039 ShuffleVectorInst* LHSShuffle = dyn_cast<ShuffleVectorInst>(Val: LHS);
3040 ShuffleVectorInst* RHSShuffle = dyn_cast<ShuffleVectorInst>(Val: RHS);
3041 if (LHSShuffle)
3042 if (!match(V: LHSShuffle->getOperand(i_nocapture: 1), P: m_Poison()) &&
3043 !match(V: RHS, P: m_Poison()))
3044 LHSShuffle = nullptr;
3045 if (RHSShuffle)
3046 if (!match(V: RHSShuffle->getOperand(i_nocapture: 1), P: m_Poison()))
3047 RHSShuffle = nullptr;
3048 if (!LHSShuffle && !RHSShuffle)
3049 return MadeChange ? &SVI : nullptr;
3050
3051 Value* LHSOp0 = nullptr;
3052 Value* LHSOp1 = nullptr;
3053 Value* RHSOp0 = nullptr;
3054 unsigned LHSOp0Width = 0;
3055 unsigned RHSOp0Width = 0;
3056 if (LHSShuffle) {
3057 LHSOp0 = LHSShuffle->getOperand(i_nocapture: 0);
3058 LHSOp1 = LHSShuffle->getOperand(i_nocapture: 1);
3059 LHSOp0Width = cast<FixedVectorType>(Val: LHSOp0->getType())->getNumElements();
3060 }
3061 if (RHSShuffle) {
3062 RHSOp0 = RHSShuffle->getOperand(i_nocapture: 0);
3063 RHSOp0Width = cast<FixedVectorType>(Val: RHSOp0->getType())->getNumElements();
3064 }
3065 Value* newLHS = LHS;
3066 Value* newRHS = RHS;
3067 if (LHSShuffle) {
3068 // case 1
3069 if (match(V: RHS, P: m_Poison())) {
3070 newLHS = LHSOp0;
3071 newRHS = LHSOp1;
3072 }
3073 // case 2 or 4
3074 else if (LHSOp0Width == LHSWidth) {
3075 newLHS = LHSOp0;
3076 }
3077 }
3078 // case 3 or 4
3079 if (RHSShuffle && RHSOp0Width == LHSWidth) {
3080 newRHS = RHSOp0;
3081 }
3082 // case 4
3083 if (LHSOp0 == RHSOp0) {
3084 newLHS = LHSOp0;
3085 newRHS = nullptr;
3086 }
3087
3088 if (newLHS == LHS && newRHS == RHS)
3089 return MadeChange ? &SVI : nullptr;
3090
3091 ArrayRef<int> LHSMask;
3092 ArrayRef<int> RHSMask;
3093 if (newLHS != LHS)
3094 LHSMask = LHSShuffle->getShuffleMask();
3095 if (RHSShuffle && newRHS != RHS)
3096 RHSMask = RHSShuffle->getShuffleMask();
3097
3098 unsigned newLHSWidth = (newLHS != LHS) ? LHSOp0Width : LHSWidth;
3099 SmallVector<int, 16> newMask;
3100 bool isSplat = true;
3101 int SplatElt = -1;
3102 // Create a new mask for the new ShuffleVectorInst so that the new
3103 // ShuffleVectorInst is equivalent to the original one.
3104 for (unsigned i = 0; i < VWidth; ++i) {
3105 int eltMask;
3106 if (Mask[i] < 0) {
3107 // This element is a poison value.
3108 eltMask = -1;
3109 } else if (Mask[i] < (int)LHSWidth) {
3110 // This element is from left hand side vector operand.
3111 //
3112 // If LHS is going to be replaced (case 1, 2, or 4), calculate the
3113 // new mask value for the element.
3114 if (newLHS != LHS) {
3115 eltMask = LHSMask[Mask[i]];
3116 // If the value selected is an poison value, explicitly specify it
3117 // with a -1 mask value.
3118 if (eltMask >= (int)LHSOp0Width && isa<PoisonValue>(Val: LHSOp1))
3119 eltMask = -1;
3120 } else
3121 eltMask = Mask[i];
3122 } else {
3123 // This element is from right hand side vector operand
3124 //
3125 // If the value selected is a poison value, explicitly specify it
3126 // with a -1 mask value. (case 1)
3127 if (match(V: RHS, P: m_Poison()))
3128 eltMask = -1;
3129 // If RHS is going to be replaced (case 3 or 4), calculate the
3130 // new mask value for the element.
3131 else if (newRHS != RHS) {
3132 eltMask = RHSMask[Mask[i]-LHSWidth];
3133 // If the value selected is an poison value, explicitly specify it
3134 // with a -1 mask value.
3135 if (eltMask >= (int)RHSOp0Width) {
3136 assert(match(RHSShuffle->getOperand(1), m_Poison()) &&
3137 "should have been check above");
3138 eltMask = -1;
3139 }
3140 } else
3141 eltMask = Mask[i]-LHSWidth;
3142
3143 // If LHS's width is changed, shift the mask value accordingly.
3144 // If newRHS == nullptr, i.e. LHSOp0 == RHSOp0, we want to remap any
3145 // references from RHSOp0 to LHSOp0, so we don't need to shift the mask.
3146 // If newRHS == newLHS, we want to remap any references from newRHS to
3147 // newLHS so that we can properly identify splats that may occur due to
3148 // obfuscation across the two vectors.
3149 if (eltMask >= 0 && newRHS != nullptr && newLHS != newRHS)
3150 eltMask += newLHSWidth;
3151 }
3152
3153 // Check if this could still be a splat.
3154 if (eltMask >= 0) {
3155 if (SplatElt >= 0 && SplatElt != eltMask)
3156 isSplat = false;
3157 SplatElt = eltMask;
3158 }
3159
3160 newMask.push_back(Elt: eltMask);
3161 }
3162
3163 // If the result mask is equal to one of the original shuffle masks,
3164 // or is a splat, do the replacement.
3165 if (isSplat || newMask == LHSMask || newMask == RHSMask || newMask == Mask) {
3166 if (!newRHS)
3167 newRHS = PoisonValue::get(T: newLHS->getType());
3168 return new ShuffleVectorInst(newLHS, newRHS, newMask);
3169 }
3170
3171 return MadeChange ? &SVI : nullptr;
3172}
3173