-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathInstCombineCasts.cpp
2158 lines (1891 loc) · 89.1 KB
/
InstCombineCasts.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
//===- InstCombineCasts.cpp -----------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the visit functions for cast operations.
//
//===----------------------------------------------------------------------===//
#include "InstCombineInternal.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Crellvm/ValidationUnit.h"
#include "llvm/Crellvm/Structure.h"
#include "llvm/Crellvm/Infrules.h"
#include "llvm/Crellvm/InstCombine/InfrulesCasts.h"
#include "llvm/Crellvm/Hintgen.h"
using namespace llvm;
using namespace PatternMatch;
#define DEBUG_TYPE "instcombine"
/// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear
/// expression. If so, decompose it, returning some value X, such that Val is
/// X*Scale+Offset.
///
static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
uint64_t &Offset) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) {
Offset = CI->getZExtValue();
Scale = 0;
return ConstantInt::get(Val->getType(), 0);
}
if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
// Cannot look past anything that might overflow.
OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val);
if (OBI && !OBI->hasNoUnsignedWrap() && !OBI->hasNoSignedWrap()) {
Scale = 1;
Offset = 0;
return Val;
}
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'.
Scale = UINT64_C(1) << RHS->getZExtValue();
Offset = 0;
return I->getOperand(0);
}
if (I->getOpcode() == Instruction::Mul) {
// This value is scaled by 'RHS'.
Scale = RHS->getZExtValue();
Offset = 0;
return I->getOperand(0);
}
if (I->getOpcode() == Instruction::Add) {
// We have X+C. Check to see if we really have (X*C2)+C1,
// where C1 is divisible by C2.
unsigned SubScale;
Value *SubVal =
DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset);
Offset += RHS->getZExtValue();
Scale = SubScale;
return SubVal;
}
}
}
// Otherwise, we can't look past this.
Scale = 1;
Offset = 0;
return Val;
}
/// PromoteCastOfAllocation - If we find a cast of an allocation instruction,
/// try to eliminate the cast by moving the type information into the alloc.
Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
AllocaInst &AI) {
PointerType *PTy = cast<PointerType>(CI.getType());
BuilderTy AllocaBuilder(*Builder);
AllocaBuilder.SetInsertPoint(AI.getParent(), &AI);
// Get the type really allocated and the type casted to.
Type *AllocElTy = AI.getAllocatedType();
Type *CastElTy = PTy->getElementType();
if (!AllocElTy->isSized() || !CastElTy->isSized()) return nullptr;
unsigned AllocElTyAlign = DL.getABITypeAlignment(AllocElTy);
unsigned CastElTyAlign = DL.getABITypeAlignment(CastElTy);
if (CastElTyAlign < AllocElTyAlign) return nullptr;
// If the allocation has multiple uses, only promote it if we are strictly
// increasing the alignment of the resultant allocation. If we keep it the
// same, we open the door to infinite loops of various kinds.
if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return nullptr;
uint64_t AllocElTySize = DL.getTypeAllocSize(AllocElTy);
uint64_t CastElTySize = DL.getTypeAllocSize(CastElTy);
if (CastElTySize == 0 || AllocElTySize == 0) return nullptr;
// If the allocation has multiple uses, only promote it if we're not
// shrinking the amount of memory being allocated.
uint64_t AllocElTyStoreSize = DL.getTypeStoreSize(AllocElTy);
uint64_t CastElTyStoreSize = DL.getTypeStoreSize(CastElTy);
if (!AI.hasOneUse() && CastElTyStoreSize < AllocElTyStoreSize) return nullptr;
// See if we can satisfy the modulus by pulling a scale out of the array
// size argument.
unsigned ArraySizeScale;
uint64_t ArrayOffset;
Value *NumElements = // See if the array size is a decomposable linear expr.
DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset);
// If we can now satisfy the modulus, by using a non-1 scale, we really can
// do the xform.
if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
(AllocElTySize*ArrayOffset ) % CastElTySize != 0) return nullptr;
unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
Value *Amt = nullptr;
if (Scale == 1) {
Amt = NumElements;
} else {
Amt = ConstantInt::get(AI.getArraySize()->getType(), Scale);
// Insert before the alloca, not before the cast.
Amt = AllocaBuilder.CreateMul(Amt, NumElements);
}
if (uint64_t Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
Value *Off = ConstantInt::get(AI.getArraySize()->getType(),
Offset, true);
Amt = AllocaBuilder.CreateAdd(Amt, Off);
}
AllocaInst *New = AllocaBuilder.CreateAlloca(CastElTy, Amt);
New->setAlignment(AI.getAlignment());
New->takeName(&AI);
New->setUsedWithInAlloca(AI.isUsedWithInAlloca());
// If the allocation has multiple real uses, insert a cast and change all
// things that used it to use the new cast. This will also hack on CI, but it
// will die soon.
if (!AI.hasOneUse()) {
// New is the allocation instruction, pointer typed. AI is the original
// allocation instruction, also pointer typed. Thus, cast to use is BitCast.
Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast");
ReplaceInstUsesWith(AI, NewCast);
}
return ReplaceInstUsesWith(CI, New);
}
/// EvaluateInDifferentType - Given an expression that
/// CanEvaluateTruncated or CanEvaluateSExtd returns true for, actually
/// insert the code to evaluate the expression.
Value *InstCombiner::EvaluateInDifferentType(Value *V, Type *Ty,
bool isSigned) {
if (Constant *C = dyn_cast<Constant>(V)) {
C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/);
// If we got a constantexpr back, try to simplify it with DL info.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
C = ConstantFoldConstantExpression(CE, DL, TLI);
return C;
}
// Otherwise, it must be an instruction.
Instruction *I = cast<Instruction>(V);
Instruction *Res = nullptr;
unsigned Opc = I->getOpcode();
switch (Opc) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::AShr:
case Instruction::LShr:
case Instruction::Shl:
case Instruction::UDiv:
case Instruction::URem: {
Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
break;
}
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
// If the source type of the cast is the type we're trying for then we can
// just return the source. There's no need to insert it because it is not
// new.
if (I->getOperand(0)->getType() == Ty)
return I->getOperand(0);
// Otherwise, must be the same type of cast, so just reinsert a new one.
// This also handles the case of zext(trunc(x)) -> zext(x).
Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty,
Opc == Instruction::SExt);
break;
case Instruction::Select: {
Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned);
Res = SelectInst::Create(I->getOperand(0), True, False);
break;
}
case Instruction::PHI: {
PHINode *OPN = cast<PHINode>(I);
PHINode *NPN = PHINode::Create(Ty, OPN->getNumIncomingValues());
for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) {
Value *V =
EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned);
NPN->addIncoming(V, OPN->getIncomingBlock(i));
}
Res = NPN;
break;
}
default:
// TODO: Can handle more cases here.
llvm_unreachable("Unreachable!");
}
Res->takeName(I);
return InsertNewInstWith(Res, *I);
}
/// This function is a wrapper around CastInst::isEliminableCastPair. It
/// simply extracts arguments and returns what that function returns.
static Instruction::CastOps
isEliminableCastPair(const CastInst *CI, ///< First cast instruction
unsigned opcode, ///< Opcode for the second cast
Type *DstTy, ///< Target type for the second cast
const DataLayout &DL) {
Type *SrcTy = CI->getOperand(0)->getType(); // A from above
Type *MidTy = CI->getType(); // B from above
// Get the opcodes of the two Cast instructions
Instruction::CastOps firstOp = Instruction::CastOps(CI->getOpcode());
Instruction::CastOps secondOp = Instruction::CastOps(opcode);
Type *SrcIntPtrTy =
SrcTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(SrcTy) : nullptr;
Type *MidIntPtrTy =
MidTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(MidTy) : nullptr;
Type *DstIntPtrTy =
DstTy->isPtrOrPtrVectorTy() ? DL.getIntPtrType(DstTy) : nullptr;
unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy,
DstTy, SrcIntPtrTy, MidIntPtrTy,
DstIntPtrTy);
// We don't want to form an inttoptr or ptrtoint that converts to an integer
// type that differs from the pointer size.
if ((Res == Instruction::IntToPtr && SrcTy != DstIntPtrTy) ||
(Res == Instruction::PtrToInt && DstTy != SrcIntPtrTy))
Res = 0;
return Instruction::CastOps(Res);
}
/// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
/// results in any code being generated and is interesting to optimize out. If
/// the cast can be eliminated by some other simple transformation, we prefer
/// to do the simplification first.
bool InstCombiner::ShouldOptimizeCast(Instruction::CastOps opc, const Value *V,
Type *Ty) {
// Noop casts and casts of constants should be eliminated trivially.
if (V->getType() == Ty || isa<Constant>(V)) return false;
// If this is another cast that can be eliminated, we prefer to have it
// eliminated.
if (const CastInst *CI = dyn_cast<CastInst>(V))
if (isEliminableCastPair(CI, opc, Ty, DL))
return false;
// If this is a vector sext from a compare, then we don't want to break the
// idiom where each element of the extended vector is either zero or all ones.
if (opc == Instruction::SExt && isa<CmpInst>(V) && Ty->isVectorTy())
return false;
return true;
}
/// @brief Implement the transforms common to all CastInst visitors.
Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
Value *Src = CI.getOperand(0);
// Many cases of "cast of a cast" are eliminable. If it's eliminable we just
// eliminate it now.
if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
if (Instruction::CastOps opc =
isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), DL)) {
// The first cast (CSrc) is eliminable so we need to fix up or replace
// the second cast (CI). CSrc will then have a good chance of being dead.
crellvm::ValidationUnit::Begin("cast_cast", CI);
INTRUDE(CAPTURE(&CI, &CSrc), {
// <src> | <tgt>
// mid = <opcode1> srcty src to midty | mod = <opcode1> srcty src to midty
// dst = <opcode2> midty mid to dstty | dst = <opcode'> srcty src to dstty
Value *src = CSrc->getOperand(0);
CastInst *mid = CSrc;
CastInst *dst = &CI;
Type *srcty = src->getType();
Type *midty = mid->getType();
Type *dstty = dst->getType();
auto _create_infrule_name = [](CastInst *fst, CastInst *snd){
return std::string(snd->getOpcodeName()) + "_" + fst->getOpcodeName();
};
std::function<std::shared_ptr<crellvm::TyInfrule>(std::shared_ptr<crellvm::TyValue>,
std::shared_ptr<crellvm::TyValue>, std::shared_ptr<crellvm::TyValue>,
std::shared_ptr<crellvm::TyValueType>, std::shared_ptr<crellvm::TyValueType>,
std::shared_ptr<crellvm::TyValueType>) >
makeInfruleFunc = nullptr;
std::string new_optname;
crellvm::propagateInstruction(hints, mid, dst, SRC);
if (llvm::isa<BitCastInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastBitcast::make;
else if (llvm::isa<FPExtInst>(dst))
makeInfruleFunc = crellvm::ConsFpextBitcast::make;
else if (llvm::isa<FPToSIInst>(dst))
makeInfruleFunc = crellvm::ConsFptosiBitcast::make;
else if (llvm::isa<FPToUIInst>(dst))
makeInfruleFunc = crellvm::ConsFptouiBitcast::make;
else if (llvm::isa<FPTruncInst>(dst))
makeInfruleFunc = crellvm::ConsFptruncBitcast::make;
else if (llvm::isa<IntToPtrInst>(dst))
makeInfruleFunc = crellvm::ConsInttoptrBitcast::make;
else if (llvm::isa<PtrToIntInst>(dst))
makeInfruleFunc = crellvm::ConsPtrtointBitcast::make;
else if (llvm::isa<SExtInst>(dst))
makeInfruleFunc = crellvm::ConsSextBitcast::make;
else if (llvm::isa<SIToFPInst>(dst))
makeInfruleFunc = crellvm::ConsSitofpBitcast::make;
else if (llvm::isa<TruncInst>(dst))
makeInfruleFunc = crellvm::ConsTruncBitcast::make;
else if (llvm::isa<UIToFPInst>(dst))
makeInfruleFunc = crellvm::ConsUitofpBitcast::make;
else if (llvm::isa<ZExtInst>(dst))
makeInfruleFunc = crellvm::ConsZextBitcast::make;
} else if (llvm::isa<FPExtInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastFpext::make;
else if (llvm::isa<FPExtInst>(dst))
makeInfruleFunc = crellvm::ConsFpextFpext::make;
else if (llvm::isa<FPToSIInst>(dst))
makeInfruleFunc = crellvm::ConsFptosiFpext::make;
else if (llvm::isa<FPToUIInst>(dst))
makeInfruleFunc = crellvm::ConsFptouiFpext::make;
else if (llvm::isa<FPTruncInst>(dst))
makeInfruleFunc = crellvm::ConsFptruncFpext::make;
} else if (llvm::isa<FPToSIInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastFptosi::make;
} else if (llvm::isa<FPToUIInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastFptoui::make;
} else if (llvm::isa<FPTruncInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastFptrunc::make;
} else if (llvm::isa<IntToPtrInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastInttoptr::make;
else if (llvm::isa<PtrToIntInst>(dst))
makeInfruleFunc = crellvm::ConsPtrtointInttoptr::make;
} else if (llvm::isa<PtrToIntInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastPtrtoint::make;
else if (llvm::isa<IntToPtrInst>(dst))
makeInfruleFunc = crellvm::ConsInttoptrPtrtoint::make;
else if (llvm::isa<TruncInst>(dst))
makeInfruleFunc = crellvm::ConsTruncPtrtoint::make;
} else if (llvm::isa<SExtInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastSext::make;
else if (llvm::isa<SExtInst>(dst))
makeInfruleFunc = crellvm::ConsSextSext::make;
else if (llvm::isa<SIToFPInst>(dst))
makeInfruleFunc = crellvm::ConsSitofpSext::make;
else if (llvm::isa<TruncInst>(dst))
makeInfruleFunc = crellvm::ConsTruncSext::make;
} else if (llvm::isa<SIToFPInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastSitofp::make;
} else if (llvm::isa<TruncInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastTrunc::make;
else if (llvm::isa<TruncInst>(dst))
makeInfruleFunc = crellvm::ConsTruncTrunc::make;
} else if (llvm::isa<UIToFPInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastUitofp::make;
} else if (llvm::isa<ZExtInst>(mid)) {
if (llvm::isa<BitCastInst>(dst))
makeInfruleFunc = crellvm::ConsBitcastZext::make;
else if (llvm::isa<SExtInst>(dst))
makeInfruleFunc = crellvm::ConsSextZext::make;
else if (llvm::isa<SIToFPInst>(dst))
makeInfruleFunc = crellvm::ConsSitofpZext::make;
else if (llvm::isa<TruncInst>(dst))
makeInfruleFunc = crellvm::ConsTruncZext::make;
else if (llvm::isa<UIToFPInst>(dst))
makeInfruleFunc = crellvm::ConsUitofpZext::make;
else if (llvm::isa<ZExtInst>(dst))
makeInfruleFunc = crellvm::ConsZextZext::make;
}
if (!(makeInfruleFunc == nullptr)) {
new_optname = _create_infrule_name(mid, dst);
crellvm::ValidationUnit::GetInstance()->setOptimizationName(new_optname);
INFRULE(INSTPOS(SRC, dst), makeInfruleFunc(VAL(src), VAL(mid),
VAL(dst), VALTYPE(srcty), VALTYPE(midty), VALTYPE(dstty)));
} else {
crellvm::ValidationUnit::Abort();
}
});
return CastInst::Create(opc, CSrc->getOperand(0), CI.getType());
}
}
// If we are casting a select then fold the cast into the select
if (SelectInst *SI = dyn_cast<SelectInst>(Src))
if (Instruction *NV = FoldOpIntoSelect(CI, SI))
return NV;
// If we are casting a PHI then fold the cast into the PHI
if (isa<PHINode>(Src)) {
// We don't do this if this would create a PHI node with an illegal type if
// it is currently legal.
if (!Src->getType()->isIntegerTy() || !CI.getType()->isIntegerTy() ||
ShouldChangeType(CI.getType(), Src->getType()))
if (Instruction *NV = FoldOpIntoPhi(CI))
return NV;
}
return nullptr;
}
/// CanEvaluateTruncated - Return true if we can evaluate the specified
/// expression tree as type Ty instead of its larger type, and arrive with the
/// same value. This is used by code that tries to eliminate truncates.
///
/// Ty will always be a type smaller than V. We should return true if trunc(V)
/// can be computed by computing V in the smaller type. If V is an instruction,
/// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only
/// makes sense if x and y can be efficiently truncated.
///
/// This function works on both vectors and scalars.
///
static bool CanEvaluateTruncated(Value *V, Type *Ty, InstCombiner &IC,
Instruction *CxtI) {
// We can always evaluate constants in another type.
if (isa<Constant>(V))
return true;
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false;
Type *OrigTy = V->getType();
// If this is an extension from the dest type, we can eliminate it, even if it
// has multiple uses.
if ((isa<ZExtInst>(I) || isa<SExtInst>(I)) &&
I->getOperand(0)->getType() == Ty)
return true;
// We can't extend or shrink something that has multiple uses: doing so would
// require duplicating the instruction in general, which isn't profitable.
if (!I->hasOneUse()) return false;
unsigned Opc = I->getOpcode();
switch (Opc) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// These operators can all arbitrarily be extended or truncated.
return CanEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&
CanEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);
case Instruction::UDiv:
case Instruction::URem: {
// UDiv and URem can be truncated if all the truncated bits are zero.
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (BitWidth < OrigBitWidth) {
APInt Mask = APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth);
if (IC.MaskedValueIsZero(I->getOperand(0), Mask, 0, CxtI) &&
IC.MaskedValueIsZero(I->getOperand(1), Mask, 0, CxtI)) {
return CanEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&
CanEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);
}
}
break;
}
case Instruction::Shl:
// If we are truncating the result of this SHL, and if it's a shift of a
// constant amount, we can always perform a SHL in a smaller type.
if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (CI->getLimitedValue(BitWidth) < BitWidth)
return CanEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI);
}
break;
case Instruction::LShr:
// If this is a truncate of a logical shr, we can truncate it to a smaller
// lshr iff we know that the bits we would otherwise be shifting in are
// already zeros.
if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits();
uint32_t BitWidth = Ty->getScalarSizeInBits();
if (IC.MaskedValueIsZero(I->getOperand(0),
APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth), 0, CxtI) &&
CI->getLimitedValue(BitWidth) < BitWidth) {
return CanEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI);
}
}
break;
case Instruction::Trunc:
// trunc(trunc(x)) -> trunc(x)
return true;
case Instruction::ZExt:
case Instruction::SExt:
// trunc(ext(x)) -> ext(x) if the source type is smaller than the new dest
// trunc(ext(x)) -> trunc(x) if the source type is larger than the new dest
return true;
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
return CanEvaluateTruncated(SI->getTrueValue(), Ty, IC, CxtI) &&
CanEvaluateTruncated(SI->getFalseValue(), Ty, IC, CxtI);
}
case Instruction::PHI: {
// We can change a phi if we can change all operands. Note that we never
// get into trouble with cyclic PHIs here because we only consider
// instructions with a single use.
PHINode *PN = cast<PHINode>(I);
for (Value *IncValue : PN->incoming_values())
if (!CanEvaluateTruncated(IncValue, Ty, IC, CxtI))
return false;
return true;
}
default:
// TODO: Can handle more cases here.
break;
}
return false;
}
Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
if (Instruction *Result = commonCastTransforms(CI))
return Result;
// Test if the trunc is the user of a select which is part of a
// minimum or maximum operation. If so, don't do any more simplification.
// Even simplifying demanded bits can break the canonical form of a
// min/max.
Value *LHS, *RHS;
if (SelectInst *SI = dyn_cast<SelectInst>(CI.getOperand(0)))
if (matchSelectPattern(SI, LHS, RHS) != SPF_UNKNOWN)
return nullptr;
// See if we can simplify any instructions used by the input whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(CI))
return &CI;
Value *Src = CI.getOperand(0);
Type *DestTy = CI.getType(), *SrcTy = Src->getType();
// Attempt to truncate the entire input expression tree to the destination
// type. Only do this if the dest type is a simple type, don't convert the
// expression tree to something weird like i93 unless the source is also
// strange.
if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
CanEvaluateTruncated(Src, DestTy, *this, &CI)) {
// If this cast is a truncate, evaluting in a different type always
// eliminates the cast, so it is always a win.
DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid cast: " << CI << '\n');
Value *Res = EvaluateInDifferentType(Src, DestTy, false);
assert(Res->getType() == DestTy);
return ReplaceInstUsesWith(CI, Res);
}
// Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0), likewise for vector.
if (DestTy->getScalarSizeInBits() == 1) {
// XXX : trunc_onebit ValidationUnit
crellvm::ValidationUnit::Begin("trunc_onebit", CI);
Constant *One = ConstantInt::get(Src->getType(), 1);
Src = Builder->CreateAnd(Src, One);
INTRUDE(CAPTURE(&CI, &Src), {
crellvm::name_instructions(*CI.getParent()->getParent());
// <src> <tgt>
// | y = and x, 1
// z = trunc x to i1 | z = icmp ne y, 0
TruncInst *Z = dyn_cast<TruncInst>(&CI);
BinaryOperator *Y = dyn_cast<BinaryOperator>(Src);
Value *X = CI.getOperand(0);
crellvm::insertSrcNopAtTgtI(hints, Y);
PROPAGATE(MAYDIFF(crellvm::getVariable(*Y), Physical), crellvm::ConsGlobal::make());
crellvm::propagateInstruction(hints, Y, Z, TGT);
INFRULE(INSTPOS(TGT, Z), crellvm::ConsTruncOnebit::make(
VAL(Z), VAL(X), VAL(Y), BITSIZE(*X)));
});
Value *Zero = Constant::getNullValue(Src->getType());
return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero);
}
// Transform trunc(lshr (zext A), Cst) to eliminate one type conversion.
Value *A = nullptr; ConstantInt *Cst = nullptr;
if (Src->hasOneUse() &&
match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) {
// We have three types to worry about here, the type of A, the source of
// the truncate (MidSize), and the destination of the truncate. We know that
// ASize < MidSize and MidSize > ResultSize, but don't know the relation
// between ASize and ResultSize.
unsigned ASize = A->getType()->getPrimitiveSizeInBits();
// If the shift amount is larger than the size of A, then the result is
// known to be zero because all the input bits got shifted out.
if (Cst->getZExtValue() >= ASize)
return ReplaceInstUsesWith(CI, Constant::getNullValue(CI.getType()));
// Since we're doing an lshr and a zero extend, and know that the shift
// amount is smaller than ASize, it is always safe to do the shift in A's
// type, then zero extend or truncate to the result.
Value *Shift = Builder->CreateLShr(A, Cst->getZExtValue());
Shift->takeName(Src);
return CastInst::CreateIntegerCast(Shift, CI.getType(), false);
}
// Transform "trunc (and X, cst)" -> "and (trunc X), cst" so long as the dest
// type isn't non-native.
if (Src->hasOneUse() && isa<IntegerType>(Src->getType()) &&
ShouldChangeType(Src->getType(), CI.getType()) &&
match(Src, m_And(m_Value(A), m_ConstantInt(Cst)))) {
Value *NewTrunc = Builder->CreateTrunc(A, CI.getType(), A->getName()+".tr");
return BinaryOperator::CreateAnd(NewTrunc,
ConstantExpr::getTrunc(Cst, CI.getType()));
}
return nullptr;
}
/// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations
/// in order to eliminate the icmp.
Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI,
bool DoXform) {
// If we are just checking for a icmp eq of a single bit and zext'ing it
// to an integer, then shift the bit to the appropriate place and then
// cast to integer to avoid the comparison.
if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
const APInt &Op1CV = Op1C->getValue();
// zext (x <s 0) to i32 --> x>>u31 true if signbit set.
// zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
(ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) {
if (!DoXform) return ICI;
Value *In = ICI->getOperand(0);
Value *Sh = ConstantInt::get(In->getType(),
In->getType()->getScalarSizeInBits()-1);
In = Builder->CreateLShr(In, Sh, In->getName()+".lobit");
if (In->getType() != CI.getType())
In = Builder->CreateIntCast(In, CI.getType(), false/*ZExt*/);
if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
Constant *One = ConstantInt::get(In->getType(), 1);
In = Builder->CreateXor(In, One, In->getName()+".not");
}
return ReplaceInstUsesWith(CI, In);
}
// zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
// zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
// zext (X == 1) to i32 --> X iff X has only the low bit set.
// zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set.
// zext (X != 0) to i32 --> X iff X has only the low bit set.
// zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set.
// zext (X != 1) to i32 --> X^1 iff X has only the low bit set.
// zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
if ((Op1CV == 0 || Op1CV.isPowerOf2()) &&
// This only works for EQ and NE
ICI->isEquality()) {
// If Op1C some other power of two, convert:
uint32_t BitWidth = Op1C->getType()->getBitWidth();
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
computeKnownBits(ICI->getOperand(0), KnownZero, KnownOne, 0, &CI);
APInt KnownZeroMask(~KnownZero);
if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
if (!DoXform) return ICI;
bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE;
if (Op1CV != 0 && (Op1CV != KnownZeroMask)) {
// (X&4) == 2 --> false
// (X&4) != 2 --> true
Constant *Res = ConstantInt::get(Type::getInt1Ty(CI.getContext()),
isNE);
Res = ConstantExpr::getZExt(Res, CI.getType());
return ReplaceInstUsesWith(CI, Res);
}
uint32_t ShiftAmt = KnownZeroMask.logBase2();
Value *In = ICI->getOperand(0);
if (ShiftAmt) {
// Perform a logical shr by shiftamt.
// Insert the shift to put the result in the low bit.
In = Builder->CreateLShr(In, ConstantInt::get(In->getType(),ShiftAmt),
In->getName()+".lobit");
}
if ((Op1CV != 0) == isNE) { // Toggle the low bit.
Constant *One = ConstantInt::get(In->getType(), 1);
In = Builder->CreateXor(In, One);
}
if (CI.getType() == In->getType())
return ReplaceInstUsesWith(CI, In);
return CastInst::CreateIntegerCast(In, CI.getType(), false/*ZExt*/);
}
}
}
// icmp ne A, B is equal to xor A, B when A and B only really have one bit.
// It is also profitable to transform icmp eq into not(xor(A, B)) because that
// may lead to additional simplifications.
if (ICI->isEquality() && CI.getType() == ICI->getOperand(0)->getType()) {
if (IntegerType *ITy = dyn_cast<IntegerType>(CI.getType())) {
uint32_t BitWidth = ITy->getBitWidth();
Value *LHS = ICI->getOperand(0);
Value *RHS = ICI->getOperand(1);
APInt KnownZeroLHS(BitWidth, 0), KnownOneLHS(BitWidth, 0);
APInt KnownZeroRHS(BitWidth, 0), KnownOneRHS(BitWidth, 0);
computeKnownBits(LHS, KnownZeroLHS, KnownOneLHS, 0, &CI);
computeKnownBits(RHS, KnownZeroRHS, KnownOneRHS, 0, &CI);
if (KnownZeroLHS == KnownZeroRHS && KnownOneLHS == KnownOneRHS) {
APInt KnownBits = KnownZeroLHS | KnownOneLHS;
APInt UnknownBit = ~KnownBits;
if (UnknownBit.countPopulation() == 1) {
if (!DoXform) return ICI;
Value *Result = Builder->CreateXor(LHS, RHS);
// Mask off any bits that are set and won't be shifted away.
if (KnownOneLHS.uge(UnknownBit))
Result = Builder->CreateAnd(Result,
ConstantInt::get(ITy, UnknownBit));
// Shift the bit we're testing down to the lsb.
Result = Builder->CreateLShr(
Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros()));
if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
Result = Builder->CreateXor(Result, ConstantInt::get(ITy, 1));
Result->takeName(ICI);
return ReplaceInstUsesWith(CI, Result);
}
}
}
}
return nullptr;
}
/// CanEvaluateZExtd - Determine if the specified value can be computed in the
/// specified wider type and produce the same low bits. If not, return false.
///
/// If this function returns true, it can also return a non-zero number of bits
/// (in BitsToClear) which indicates that the value it computes is correct for
/// the zero extend, but that the additional BitsToClear bits need to be zero'd
/// out. For example, to promote something like:
///
/// %B = trunc i64 %A to i32
/// %C = lshr i32 %B, 8
/// %E = zext i32 %C to i64
///
/// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be
/// set to 8 to indicate that the promoted value needs to have bits 24-31
/// cleared in addition to bits 32-63. Since an 'and' will be generated to
/// clear the top bits anyway, doing this has no extra cost.
///
/// This function works on both vectors and scalars.
static bool CanEvaluateZExtd(Value *V, Type *Ty, unsigned &BitsToClear,
InstCombiner &IC, Instruction *CxtI) {
BitsToClear = 0;
if (isa<Constant>(V))
return true;
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false;
// If the input is a truncate from the destination type, we can trivially
// eliminate it.
if (isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty)
return true;
// We can't extend or shrink something that has multiple uses: doing so would
// require duplicating the instruction in general, which isn't profitable.
if (!I->hasOneUse()) return false;
unsigned Opc = I->getOpcode(), Tmp;
switch (Opc) {
case Instruction::ZExt: // zext(zext(x)) -> zext(x).
case Instruction::SExt: // zext(sext(x)) -> sext(x).
case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x)
return true;
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI) ||
!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp, IC, CxtI))
return false;
// These can all be promoted if neither operand has 'bits to clear'.
if (BitsToClear == 0 && Tmp == 0)
return true;
// If the operation is an AND/OR/XOR and the bits to clear are zero in the
// other side, BitsToClear is ok.
if (Tmp == 0 &&
(Opc == Instruction::And || Opc == Instruction::Or ||
Opc == Instruction::Xor)) {
// We use MaskedValueIsZero here for generality, but the case we care
// about the most is constant RHS.
unsigned VSize = V->getType()->getScalarSizeInBits();
if (IC.MaskedValueIsZero(I->getOperand(1),
APInt::getHighBitsSet(VSize, BitsToClear),
0, CxtI))
return true;
}
// Otherwise, we don't know how to analyze this BitsToClear case yet.
return false;
case Instruction::Shl:
// We can promote shl(x, cst) if we can promote x. Since shl overwrites the
// upper bits we can reduce BitsToClear by the shift amount.
if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI))
return false;
uint64_t ShiftAmt = Amt->getZExtValue();
BitsToClear = ShiftAmt < BitsToClear ? BitsToClear - ShiftAmt : 0;
return true;
}
return false;
case Instruction::LShr:
// We can promote lshr(x, cst) if we can promote x. This requires the
// ultimate 'and' to clear out the high zero bits we're clearing out though.
if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear, IC, CxtI))
return false;
BitsToClear += Amt->getZExtValue();
if (BitsToClear > V->getType()->getScalarSizeInBits())
BitsToClear = V->getType()->getScalarSizeInBits();
return true;
}
// Cannot promote variable LSHR.
return false;
case Instruction::Select:
if (!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp, IC, CxtI) ||
!CanEvaluateZExtd(I->getOperand(2), Ty, BitsToClear, IC, CxtI) ||
// TODO: If important, we could handle the case when the BitsToClear are
// known zero in the disagreeing side.
Tmp != BitsToClear)
return false;
return true;
case Instruction::PHI: {
// We can change a phi if we can change all operands. Note that we never
// get into trouble with cyclic PHIs here because we only consider
// instructions with a single use.
PHINode *PN = cast<PHINode>(I);
if (!CanEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear, IC, CxtI))
return false;
for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
if (!CanEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp, IC, CxtI) ||
// TODO: If important, we could handle the case when the BitsToClear
// are known zero in the disagreeing input.
Tmp != BitsToClear)
return false;
return true;
}
default:
// TODO: Can handle more cases here.
return false;
}
}
Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
// If this zero extend is only used by a truncate, let the truncate be
// eliminated before we try to optimize this zext.
if (CI.hasOneUse() && isa<TruncInst>(CI.user_back()))
return nullptr;
// If one of the common conversion will work, do it.
if (Instruction *Result = commonCastTransforms(CI))
return Result;
// See if we can simplify any instructions used by the input whose sole
// purpose is to compute bits we don't care about.
if (SimplifyDemandedInstructionBits(CI))
return &CI;
Value *Src = CI.getOperand(0);
Type *SrcTy = Src->getType(), *DestTy = CI.getType();
// Attempt to extend the entire input expression tree to the destination
// type. Only do this if the dest type is a simple type, don't convert the
// expression tree to something weird like i93 unless the source is also
// strange.
unsigned BitsToClear;
if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) &&
CanEvaluateZExtd(Src, DestTy, BitsToClear, *this, &CI)) {
assert(BitsToClear < SrcTy->getScalarSizeInBits() &&
"Unreasonable BitsToClear");
// Okay, we can transform this! Insert the new expression now.
DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type"
" to avoid zero extend: " << CI);
Value *Res = EvaluateInDifferentType(Src, DestTy, false);
assert(Res->getType() == DestTy);
uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear;
uint32_t DestBitSize = DestTy->getScalarSizeInBits();
// If the high bits are already filled with zeros, just replace this
// cast with the result.
if (MaskedValueIsZero(Res,
APInt::getHighBitsSet(DestBitSize,
DestBitSize-SrcBitsKept),
0, &CI))
return ReplaceInstUsesWith(CI, Res);
// We need to emit an AND to clear the high bits.
Constant *C = ConstantInt::get(Res->getType(),
APInt::getLowBitsSet(DestBitSize, SrcBitsKept));
return BinaryOperator::CreateAnd(Res, C);
}
// If this is a TRUNC followed by a ZEXT then we are dealing with integral
// types and if the sizes are just right we can convert this into a logical
// 'and' which will be much cheaper than the pair of casts.
if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast
// TODO: Subsume this into EvaluateInDifferentType.
// Get the sizes of the types involved. We know that the intermediate type
// will be smaller than A or C, but don't know the relation between A and C.
Value *A = CSrc->getOperand(0);
unsigned SrcSize = A->getType()->getScalarSizeInBits();
unsigned MidSize = CSrc->getType()->getScalarSizeInBits();
unsigned DstSize = CI.getType()->getScalarSizeInBits();
// If we're actually extending zero bits, then if
// SrcSize < DstSize: zext(a & mask)
// SrcSize == DstSize: a & mask
// SrcSize > DstSize: trunc(a) & mask
if (SrcSize < DstSize) {
APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
Constant *AndConst = ConstantInt::get(A->getType(), AndValue);
Value *And = Builder->CreateAnd(A, AndConst, CSrc->getName()+".mask");