-
Notifications
You must be signed in to change notification settings - Fork 1.6k
/
flow_graph.cc
3149 lines (2847 loc) · 117 KB
/
flow_graph.cc
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
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/compiler/backend/flow_graph.h"
#include <array>
#include "vm/bit_vector.h"
#include "vm/compiler/backend/dart_calling_conventions.h"
#include "vm/compiler/backend/flow_graph_compiler.h"
#include "vm/compiler/backend/il.h"
#include "vm/compiler/backend/il_printer.h"
#include "vm/compiler/backend/loops.h"
#include "vm/compiler/backend/range_analysis.h"
#include "vm/compiler/cha.h"
#include "vm/compiler/compiler_state.h"
#include "vm/compiler/compiler_timings.h"
#include "vm/compiler/frontend/flow_graph_builder.h"
#include "vm/compiler/frontend/kernel_translation_helper.h"
#include "vm/growable_array.h"
#include "vm/object_store.h"
#include "vm/resolver.h"
namespace dart {
DEFINE_FLAG(bool, prune_dead_locals, true, "optimize dead locals away");
// Quick access to the current zone.
#define Z (zone())
static bool ShouldReorderBlocks(const Function& function,
FlowGraph::CompilationMode mode) {
return (mode == FlowGraph::CompilationMode::kOptimized) &&
FLAG_reorder_basic_blocks && !function.IsFfiCallbackTrampoline();
}
static bool ShouldOmitCheckBoundsIn(const Function& function) {
auto& state = CompilerState::Current();
return state.is_aot() && state.PragmasOf(function).unsafe_no_bounds_checks;
}
FlowGraph::FlowGraph(const ParsedFunction& parsed_function,
GraphEntryInstr* graph_entry,
intptr_t max_block_id,
PrologueInfo prologue_info,
CompilationMode compilation_mode)
: thread_(Thread::Current()),
parent_(),
current_ssa_temp_index_(0),
max_block_id_(max_block_id),
parsed_function_(parsed_function),
num_direct_parameters_(parsed_function.function().MakesCopyOfParameters()
? 0
: parsed_function.function().NumParameters()),
direct_parameter_locations_(
parsed_function.function().num_fixed_parameters()),
graph_entry_(graph_entry),
preorder_(),
postorder_(),
reverse_postorder_(),
optimized_block_order_(),
constant_null_(nullptr),
constant_dead_(nullptr),
licm_allowed_(true),
should_reorder_blocks_(
ShouldReorderBlocks(parsed_function.function(), compilation_mode)),
prologue_info_(prologue_info),
loop_hierarchy_(nullptr),
loop_invariant_loads_(nullptr),
captured_parameters_(new(zone()) BitVector(zone(), variable_count())),
inlining_id_(-1),
should_print_(false),
should_omit_check_bounds_(
dart::ShouldOmitCheckBoundsIn(parsed_function.function())) {
should_print_ = FlowGraphPrinter::ShouldPrint(parsed_function.function(),
&compiler_pass_filters_);
ComputeLocationsOfFixedParameters(
zone(), function(),
/*should_assign_stack_locations=*/
!parsed_function.function().MakesCopyOfParameters(),
&direct_parameter_locations_);
DiscoverBlocks();
}
void FlowGraph::EnsureSSATempIndex(Definition* defn, Definition* replacement) {
if ((replacement->ssa_temp_index() == -1) && (defn->ssa_temp_index() != -1)) {
AllocateSSAIndex(replacement);
}
}
intptr_t FlowGraph::ComputeArgumentsSizeInWords(const Function& function,
intptr_t argument_count) {
ASSERT(function.num_fixed_parameters() <= argument_count);
ASSERT(argument_count <= function.NumParameters());
const intptr_t fixed_parameters_size_in_bytes =
ComputeLocationsOfFixedParameters(Thread::Current()->zone(), function);
// Currently we box all optional parameters.
return fixed_parameters_size_in_bytes +
(argument_count - function.num_fixed_parameters());
}
Representation FlowGraph::ParameterRepresentationAt(const Function& function,
intptr_t index) {
if (function.IsNull()) {
return kTagged;
}
ASSERT(index < function.NumParameters());
if (function.is_unboxed_integer_parameter_at(index)) {
return kUnboxedInt64;
} else if (function.is_unboxed_double_parameter_at(index)) {
return kUnboxedDouble;
} else {
ASSERT(!function.is_unboxed_parameter_at(index));
return kTagged;
}
}
Representation FlowGraph::ReturnRepresentationOf(const Function& function) {
if (function.IsNull()) {
return kTagged;
}
if (function.has_unboxed_integer_return()) {
return kUnboxedInt64;
} else if (function.has_unboxed_double_return()) {
return kUnboxedDouble;
} else if (function.has_unboxed_record_return()) {
return kPairOfTagged;
} else {
ASSERT(!function.has_unboxed_return());
return kTagged;
}
}
void FlowGraph::ReplaceCurrentInstruction(ForwardInstructionIterator* iterator,
Instruction* current,
Instruction* replacement) {
Definition* current_defn = current->AsDefinition();
if ((replacement != nullptr) && (current_defn != nullptr)) {
Definition* replacement_defn = replacement->AsDefinition();
ASSERT(replacement_defn != nullptr);
current_defn->ReplaceUsesWith(replacement_defn);
EnsureSSATempIndex(current_defn, replacement_defn);
if (FLAG_trace_optimization && should_print()) {
THR_Print("Replacing v%" Pd " with v%" Pd "\n",
current_defn->ssa_temp_index(),
replacement_defn->ssa_temp_index());
}
} else if (FLAG_trace_optimization && should_print()) {
if (current_defn == nullptr) {
THR_Print("Removing %s\n", current->DebugName());
} else {
ASSERT(!current_defn->HasUses());
THR_Print("Removing v%" Pd ".\n", current_defn->ssa_temp_index());
}
}
if (current->ArgumentCount() != 0) {
ASSERT(!current->HasMoveArguments());
}
iterator->RemoveCurrentFromGraph();
}
GrowableArray<BlockEntryInstr*>* FlowGraph::CodegenBlockOrder() {
return should_reorder_blocks() ? &optimized_block_order_
: &reverse_postorder_;
}
const GrowableArray<BlockEntryInstr*>* FlowGraph::CodegenBlockOrder() const {
return should_reorder_blocks() ? &optimized_block_order_
: &reverse_postorder_;
}
ConstantInstr* FlowGraph::GetExistingConstant(
const Object& object,
Representation representation) const {
return constant_instr_pool_.LookupValue(
ConstantAndRepresentation{object, representation});
}
ConstantInstr* FlowGraph::GetConstant(const Object& object,
Representation representation) {
ConstantInstr* constant = GetExistingConstant(object, representation);
if (constant == nullptr) {
// Otherwise, allocate and add it to the pool.
const Object& zone_object = Object::ZoneHandle(zone(), object.ptr());
if (representation == kTagged) {
constant = new (zone()) ConstantInstr(zone_object);
} else {
constant = new (zone()) UnboxedConstantInstr(zone_object, representation);
}
AllocateSSAIndex(constant);
AddToGraphInitialDefinitions(constant);
constant_instr_pool_.Insert(constant);
}
return constant;
}
bool FlowGraph::IsConstantRepresentable(const Object& value,
Representation target_rep,
bool tagged_value_must_be_smi) {
switch (target_rep) {
case kTagged:
return !tagged_value_must_be_smi || value.IsSmi();
case kUnboxedInt32:
if (value.IsInteger()) {
return Utils::IsInt(32, Integer::Cast(value).Value());
}
return false;
case kUnboxedUint32:
if (value.IsInteger()) {
return Utils::IsUint(32, Integer::Cast(value).Value());
}
return false;
case kUnboxedInt64:
return value.IsInteger();
case kUnboxedFloat:
case kUnboxedDouble:
return value.IsInteger() || value.IsDouble();
default:
return false;
}
}
Definition* FlowGraph::TryCreateConstantReplacementFor(Definition* op,
const Object& value) {
// Check that representation of the constant matches expected representation.
const auto representation = op->representation();
if (!IsConstantRepresentable(
value, representation,
/*tagged_value_must_be_smi=*/op->Type()->IsNullableSmi())) {
return op;
}
if (((representation == kUnboxedFloat) ||
(representation == kUnboxedDouble)) &&
value.IsInteger()) {
// Convert the boxed constant from int to float/double.
return GetConstant(
Double::Handle(Double::NewCanonical(Integer::Cast(value).ToDouble())),
representation);
}
return GetConstant(value, representation);
}
void FlowGraph::AddToGraphInitialDefinitions(Definition* defn) {
defn->set_previous(graph_entry_);
graph_entry_->initial_definitions()->Add(defn);
}
void FlowGraph::AddToInitialDefinitions(BlockEntryWithInitialDefs* entry,
Definition* defn) {
ASSERT(defn->previous() == nullptr);
defn->set_previous(entry);
if (auto par = defn->AsParameter()) {
par->set_block(entry); // set cached block
}
entry->initial_definitions()->Add(defn);
}
void FlowGraph::InsertAfter(Instruction* prev,
Instruction* instr,
Environment* env,
UseKind use_kind) {
if (use_kind == kValue) {
ASSERT(instr->IsDefinition());
AllocateSSAIndex(instr->AsDefinition());
}
instr->InsertAfter(prev);
ASSERT(instr->env() == nullptr);
if (env != nullptr) {
env->DeepCopyTo(zone(), instr);
}
}
void FlowGraph::InsertSpeculativeAfter(Instruction* prev,
Instruction* instr,
Environment* env,
UseKind use_kind) {
InsertAfter(prev, instr, env, use_kind);
if (instr->env() != nullptr) {
instr->env()->MarkAsLazyDeoptToBeforeDeoptId();
}
}
Instruction* FlowGraph::AppendTo(Instruction* prev,
Instruction* instr,
Environment* env,
UseKind use_kind) {
if (use_kind == kValue) {
ASSERT(instr->IsDefinition());
AllocateSSAIndex(instr->AsDefinition());
}
ASSERT(instr->env() == nullptr);
if (env != nullptr) {
env->DeepCopyTo(zone(), instr);
}
return prev->AppendInstruction(instr);
}
Instruction* FlowGraph::AppendSpeculativeTo(Instruction* prev,
Instruction* instr,
Environment* env,
UseKind use_kind) {
auto result = AppendTo(prev, instr, env, use_kind);
if (instr->env() != nullptr) {
instr->env()->MarkAsLazyDeoptToBeforeDeoptId();
}
return result;
}
// A wrapper around block entries including an index of the next successor to
// be read.
class BlockTraversalState {
public:
explicit BlockTraversalState(BlockEntryInstr* block)
: block_(block),
next_successor_ix_(block->last_instruction()->SuccessorCount() - 1) {}
bool HasNextSuccessor() const { return next_successor_ix_ >= 0; }
BlockEntryInstr* NextSuccessor() {
ASSERT(HasNextSuccessor());
return block_->last_instruction()->SuccessorAt(next_successor_ix_--);
}
BlockEntryInstr* block() const { return block_; }
private:
BlockEntryInstr* block_;
intptr_t next_successor_ix_;
DISALLOW_ALLOCATION();
};
void FlowGraph::DiscoverBlocks() {
COMPILER_TIMINGS_TIMER_SCOPE(thread(), DiscoverBlocks);
StackZone zone(thread());
// Initialize state.
preorder_.Clear();
postorder_.Clear();
reverse_postorder_.Clear();
parent_.Clear();
GrowableArray<BlockTraversalState> block_stack;
graph_entry_->DiscoverBlock(nullptr, &preorder_, &parent_);
block_stack.Add(BlockTraversalState(graph_entry_));
while (!block_stack.is_empty()) {
BlockTraversalState& state = block_stack.Last();
BlockEntryInstr* block = state.block();
if (state.HasNextSuccessor()) {
// Process successors one-by-one.
BlockEntryInstr* succ = state.NextSuccessor();
if (succ->DiscoverBlock(block, &preorder_, &parent_)) {
block_stack.Add(BlockTraversalState(succ));
}
} else {
// All successors have been processed, pop the current block entry node
// and add it to the postorder list.
block_stack.RemoveLast();
block->set_postorder_number(postorder_.length());
postorder_.Add(block);
}
}
ASSERT(postorder_.length() == preorder_.length());
// Create an array of blocks in reverse postorder.
intptr_t block_count = postorder_.length();
for (intptr_t i = 0; i < block_count; ++i) {
reverse_postorder_.Add(postorder_[block_count - i - 1]);
}
ResetLoopHierarchy();
}
void FlowGraph::MergeBlocks() {
bool changed = false;
BitVector* merged = new (zone()) BitVector(zone(), postorder().length());
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
BlockEntryInstr* block = block_it.Current();
if (block->IsGraphEntry()) continue;
if (merged->Contains(block->postorder_number())) continue;
Instruction* last = block->last_instruction();
BlockEntryInstr* last_merged_block = nullptr;
while (auto goto_instr = last->AsGoto()) {
JoinEntryInstr* successor = goto_instr->successor();
if (successor->PredecessorCount() > 1) break;
if (block->try_index() != successor->try_index()) break;
// Replace all phis with their arguments prior to removing successor.
for (PhiIterator it(successor); !it.Done(); it.Advance()) {
PhiInstr* phi = it.Current();
Value* input = phi->InputAt(0);
phi->ReplaceUsesWith(input->definition());
input->RemoveFromUseList();
}
// Remove environment uses and unlink goto and block entry.
successor->UnuseAllInputs();
last->previous()->LinkTo(successor->next());
last->UnuseAllInputs();
last = successor->last_instruction();
merged->Add(successor->postorder_number());
last_merged_block = successor;
changed = true;
if (FLAG_trace_optimization && should_print()) {
THR_Print("Merged blocks B%" Pd " and B%" Pd "\n", block->block_id(),
successor->block_id());
}
}
// The new block inherits the block id of the last successor to maintain
// the order of phi inputs at its successors consistent with block ids.
if (last_merged_block != nullptr) {
block->set_block_id(last_merged_block->block_id());
}
}
// Recompute block order after changes were made.
if (changed) DiscoverBlocks();
}
void FlowGraph::ComputeIsReceiverRecursive(
PhiInstr* phi,
GrowableArray<PhiInstr*>* unmark) const {
if (phi->is_receiver() != PhiInstr::kUnknownReceiver) return;
phi->set_is_receiver(PhiInstr::kReceiver);
for (intptr_t i = 0; i < phi->InputCount(); ++i) {
Definition* def = phi->InputAt(i)->definition();
if (def->IsParameter() && (def->AsParameter()->env_index() == 0)) continue;
if (!def->IsPhi()) {
phi->set_is_receiver(PhiInstr::kNotReceiver);
break;
}
ComputeIsReceiverRecursive(def->AsPhi(), unmark);
if (def->AsPhi()->is_receiver() == PhiInstr::kNotReceiver) {
phi->set_is_receiver(PhiInstr::kNotReceiver);
break;
}
}
if (phi->is_receiver() == PhiInstr::kNotReceiver) {
unmark->Add(phi);
}
}
void FlowGraph::ComputeIsReceiver(PhiInstr* phi) const {
GrowableArray<PhiInstr*> unmark;
ComputeIsReceiverRecursive(phi, &unmark);
// Now drain unmark.
while (!unmark.is_empty()) {
PhiInstr* phi = unmark.RemoveLast();
for (Value::Iterator it(phi->input_use_list()); !it.Done(); it.Advance()) {
PhiInstr* use = it.Current()->instruction()->AsPhi();
if ((use != nullptr) && (use->is_receiver() == PhiInstr::kReceiver)) {
use->set_is_receiver(PhiInstr::kNotReceiver);
unmark.Add(use);
}
}
}
}
bool FlowGraph::IsReceiver(Definition* def) const {
def = def->OriginalDefinition(); // Could be redefined.
if (def->IsParameter()) return (def->AsParameter()->env_index() == 0);
if (!def->IsPhi() || graph_entry()->HasSingleEntryPoint()) {
return false;
}
PhiInstr* phi = def->AsPhi();
if (phi->is_receiver() != PhiInstr::kUnknownReceiver) {
return (phi->is_receiver() == PhiInstr::kReceiver);
}
// Not known if this phi is the receiver yet. Compute it now.
ComputeIsReceiver(phi);
return (phi->is_receiver() == PhiInstr::kReceiver);
}
FlowGraph::ToCheck FlowGraph::CheckForInstanceCall(
InstanceCallInstr* call,
UntaggedFunction::Kind kind) const {
if (!FLAG_use_cha_deopt && !isolate_group()->all_classes_finalized()) {
// Even if class or function are private, lazy class finalization
// may later add overriding methods.
return ToCheck::kCheckCid;
}
// Best effort to get the receiver class.
Value* receiver = call->Receiver();
Class& receiver_class = Class::Handle(zone());
bool receiver_maybe_null = false;
if (function().IsDynamicFunction() && IsReceiver(receiver->definition())) {
// Call receiver is callee receiver: calling "this.g()" in f().
receiver_class = function().Owner();
} else {
// Get the receiver's compile type. Note that
// we allow nullable types, which may result in just generating
// a null check rather than the more elaborate class check
CompileType* type = receiver->Type();
const intptr_t receiver_cid = type->ToNullableCid();
if (receiver_cid != kDynamicCid) {
receiver_class = isolate_group()->class_table()->At(receiver_cid);
receiver_maybe_null = type->is_nullable();
} else {
const AbstractType* atype = type->ToAbstractType();
if (atype->IsInstantiated() && atype->HasTypeClass() &&
!atype->IsDynamicType()) {
if (type->is_nullable()) {
receiver_maybe_null = true;
}
receiver_class = atype->type_class();
if (receiver_class.is_implemented()) {
receiver_class = Class::null();
}
}
}
}
// Useful receiver class information?
if (receiver_class.IsNull() ||
receiver_class.has_dynamically_extendable_subtypes()) {
return ToCheck::kCheckCid;
} else if (call->HasICData()) {
// If the static class type does not match information found in ICData
// (which may be "guessed"), then bail, since subsequent code generation
// (AOT and JIT) for inlining uses the latter.
// TODO(ajcbik): improve this by using the static class.
const intptr_t cid = receiver_class.id();
const ICData* data = call->ic_data();
bool match = false;
Class& cls = Class::Handle(zone());
Function& fun = Function::Handle(zone());
for (intptr_t i = 0, len = data->NumberOfChecks(); i < len; i++) {
if (!data->IsUsedAt(i)) {
continue; // do not consider
}
fun = data->GetTargetAt(i);
cls = fun.Owner();
if (data->GetReceiverClassIdAt(i) == cid || cls.id() == cid) {
match = true;
break;
}
}
if (!match) {
return ToCheck::kCheckCid;
}
}
const String& method_name =
(kind == UntaggedFunction::kMethodExtractor)
? String::Handle(zone(), Field::NameFromGetter(call->function_name()))
: call->function_name();
// If the receiver can have the null value, exclude any method
// that is actually valid on a null receiver.
if (receiver_maybe_null) {
const Class& null_class =
Class::Handle(zone(), isolate_group()->object_store()->null_class());
Function& target = Function::Handle(zone());
if (null_class.EnsureIsFinalized(thread()) == Error::null()) {
target = Resolver::ResolveDynamicAnyArgs(zone(), null_class, method_name,
/*allow_add=*/true);
}
if (!target.IsNull()) {
return ToCheck::kCheckCid;
}
}
// Use CHA to determine if the method is not overridden by any subclass
// of the receiver class. Any methods that are valid when the receiver
// has a null value are excluded above (to avoid throwing an exception
// on something valid, like null.hashCode).
intptr_t subclass_count = 0;
CHA& cha = thread()->compiler_state().cha();
if (!cha.HasOverride(receiver_class, method_name, &subclass_count)) {
if (FLAG_trace_cha) {
THR_Print(
" **(CHA) Instance call needs no class check since there "
"are no overrides of method '%s' on '%s'\n",
method_name.ToCString(), receiver_class.ToCString());
}
if (FLAG_use_cha_deopt) {
cha.AddToGuardedClassesForSubclassCount(receiver_class, subclass_count);
}
return receiver_maybe_null ? ToCheck::kCheckNull : ToCheck::kNoCheck;
}
return ToCheck::kCheckCid;
}
Instruction* FlowGraph::CreateCheckClass(Definition* to_check,
const Cids& cids,
intptr_t deopt_id,
const InstructionSource& source) {
if (cids.IsMonomorphic() && cids.MonomorphicReceiverCid() == kSmiCid) {
return new (zone())
CheckSmiInstr(new (zone()) Value(to_check), deopt_id, source);
}
return new (zone())
CheckClassInstr(new (zone()) Value(to_check), deopt_id, cids, source);
}
bool FlowGraph::ShouldOmitCheckBoundsIn(const Function& caller) {
if (caller.ptr() == function().ptr()) {
return should_omit_check_bounds();
}
return dart::ShouldOmitCheckBoundsIn(caller);
}
static Definition* CreateCheckBound(Zone* zone,
Definition* length,
Definition* index,
intptr_t deopt_id) {
Value* val1 = new (zone) Value(length);
Value* val2 = new (zone) Value(index);
if (CompilerState::Current().is_aot()) {
return new (zone) GenericCheckBoundInstr(val1, val2, deopt_id);
}
return new (zone) CheckArrayBoundInstr(val1, val2, deopt_id);
}
Instruction* FlowGraph::AppendCheckBound(Instruction* cursor,
Definition* length,
Definition** index,
intptr_t deopt_id,
Environment* env) {
if (!ShouldOmitCheckBoundsIn(env->function())) {
*index = CreateCheckBound(zone(), length, *index, deopt_id);
cursor = AppendTo(cursor, *index, env, FlowGraph::kValue);
}
return cursor;
}
void FlowGraph::AddExactnessGuard(InstanceCallInstr* call,
intptr_t receiver_cid) {
const Class& cls =
Class::Handle(zone(), isolate_group()->class_table()->At(receiver_cid));
Definition* load_type_args = new (zone()) LoadFieldInstr(
call->Receiver()->CopyWithType(),
Slot::GetTypeArgumentsSlotFor(thread(), cls), call->source());
InsertBefore(call, load_type_args, call->env(), FlowGraph::kValue);
const AbstractType& type =
AbstractType::Handle(zone(), call->ic_data()->receivers_static_type());
ASSERT(!type.IsNull());
const TypeArguments& args = TypeArguments::Handle(
zone(), Type::Cast(type).GetInstanceTypeArguments(thread()));
Instruction* guard = new (zone()) CheckConditionInstr(
new StrictCompareInstr(call->source(), Token::kEQ_STRICT,
new (zone()) Value(load_type_args),
new (zone()) Value(GetConstant(args)),
/*needs_number_check=*/false, call->deopt_id()),
call->deopt_id());
InsertBefore(call, guard, call->env(), FlowGraph::kEffect);
}
// Verify that a redefinition dominates all uses of the redefined value.
bool FlowGraph::VerifyRedefinitions() {
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
for (ForwardInstructionIterator instr_it(block_it.Current());
!instr_it.Done(); instr_it.Advance()) {
RedefinitionInstr* redefinition = instr_it.Current()->AsRedefinition();
if (redefinition != nullptr) {
Definition* original = redefinition->value()->definition();
for (Value::Iterator it(original->input_use_list()); !it.Done();
it.Advance()) {
Value* original_use = it.Current();
if (original_use->instruction() == redefinition) {
continue;
}
if (original_use->instruction()->IsDominatedBy(redefinition)) {
FlowGraphPrinter::PrintGraph("VerifyRedefinitions", this);
THR_Print("%s\n", redefinition->ToCString());
THR_Print("use=%s\n", original_use->instruction()->ToCString());
return false;
}
}
}
}
}
return true;
}
LivenessAnalysis::LivenessAnalysis(
intptr_t variable_count,
const GrowableArray<BlockEntryInstr*>& postorder)
: zone_(Thread::Current()->zone()),
variable_count_(variable_count),
postorder_(postorder),
live_out_(postorder.length()),
kill_(postorder.length()),
live_in_(postorder.length()) {}
bool LivenessAnalysis::UpdateLiveOut(const BlockEntryInstr& block) {
BitVector* live_out = live_out_[block.postorder_number()];
bool changed = false;
Instruction* last = block.last_instruction();
ASSERT(last != nullptr);
for (intptr_t i = 0; i < last->SuccessorCount(); i++) {
BlockEntryInstr* succ = last->SuccessorAt(i);
ASSERT(succ != nullptr);
if (live_out->AddAll(live_in_[succ->postorder_number()])) {
changed = true;
}
}
return changed;
}
bool LivenessAnalysis::UpdateLiveIn(const BlockEntryInstr& block) {
BitVector* live_out = live_out_[block.postorder_number()];
BitVector* kill = kill_[block.postorder_number()];
BitVector* live_in = live_in_[block.postorder_number()];
return live_in->KillAndAdd(kill, live_out);
}
void LivenessAnalysis::ComputeLiveInAndLiveOutSets() {
const intptr_t block_count = postorder_.length();
bool changed;
do {
changed = false;
for (intptr_t i = 0; i < block_count; i++) {
const BlockEntryInstr& block = *postorder_[i];
// Live-in set depends only on kill set which does not
// change in this loop and live-out set. If live-out
// set does not change there is no need to recompute
// live-in set.
if (UpdateLiveOut(block) && UpdateLiveIn(block)) {
changed = true;
}
}
} while (changed);
}
void LivenessAnalysis::Analyze() {
const intptr_t block_count = postorder_.length();
for (intptr_t i = 0; i < block_count; i++) {
live_out_.Add(new (zone()) BitVector(zone(), variable_count_));
kill_.Add(new (zone()) BitVector(zone(), variable_count_));
live_in_.Add(new (zone()) BitVector(zone(), variable_count_));
}
ComputeInitialSets();
ComputeLiveInAndLiveOutSets();
}
static void PrintBitVector(const char* tag, BitVector* v) {
THR_Print("%s:", tag);
for (BitVector::Iterator it(v); !it.Done(); it.Advance()) {
THR_Print(" %" Pd "", it.Current());
}
THR_Print("\n");
}
void LivenessAnalysis::Dump() {
const intptr_t block_count = postorder_.length();
for (intptr_t i = 0; i < block_count; i++) {
BlockEntryInstr* block = postorder_[i];
THR_Print("block @%" Pd " -> ", block->block_id());
Instruction* last = block->last_instruction();
for (intptr_t j = 0; j < last->SuccessorCount(); j++) {
BlockEntryInstr* succ = last->SuccessorAt(j);
THR_Print(" @%" Pd "", succ->block_id());
}
THR_Print("\n");
PrintBitVector(" live out", live_out_[i]);
PrintBitVector(" kill", kill_[i]);
PrintBitVector(" live in", live_in_[i]);
}
}
// Computes liveness information for local variables.
class VariableLivenessAnalysis : public LivenessAnalysis {
public:
explicit VariableLivenessAnalysis(FlowGraph* flow_graph)
: LivenessAnalysis(flow_graph->variable_count(), flow_graph->postorder()),
flow_graph_(flow_graph),
assigned_vars_() {}
// For every block (in preorder) compute and return set of variables that
// have new assigned values flowing out of that block.
const GrowableArray<BitVector*>& ComputeAssignedVars() {
// We can't directly return kill_ because it uses postorder numbering while
// SSA construction uses preorder numbering internally.
// We have to permute postorder into preorder.
assigned_vars_.Clear();
const intptr_t block_count = flow_graph_->preorder().length();
for (intptr_t i = 0; i < block_count; i++) {
BlockEntryInstr* block = flow_graph_->preorder()[i];
// All locals are assigned inside a try{} block.
// This is a safe approximation and workaround to force insertion of
// phis for stores that appear non-live because of the way catch-blocks
// are connected to the graph: They normally are dominated by the
// try-entry, but are direct successors of the graph entry in our flow
// graph.
// TODO(fschneider): Improve this approximation by better modeling the
// actual data flow to reduce the number of redundant phis.
BitVector* kill = GetKillSet(block);
if (block->InsideTryBlock()) {
kill->SetAll();
} else {
kill->Intersect(GetLiveOutSet(block));
}
assigned_vars_.Add(kill);
}
return assigned_vars_;
}
// Returns true if the value set by the given store reaches any load from the
// same local variable.
bool IsStoreAlive(BlockEntryInstr* block, StoreLocalInstr* store) {
if (store->local().Equals(*flow_graph_->CurrentContextVar())) {
return true;
}
if (store->is_dead()) {
return false;
}
if (store->is_last()) {
const intptr_t index = flow_graph_->EnvIndex(&store->local());
return GetLiveOutSet(block)->Contains(index);
}
return true;
}
// Returns true if the given load is the last for the local and the value
// of the local will not flow into another one.
bool IsLastLoad(BlockEntryInstr* block, LoadLocalInstr* load) {
if (load->local().Equals(*flow_graph_->CurrentContextVar())) {
return false;
}
const intptr_t index = flow_graph_->EnvIndex(&load->local());
return load->is_last() && !GetLiveOutSet(block)->Contains(index);
}
private:
virtual void ComputeInitialSets();
const FlowGraph* flow_graph_;
GrowableArray<BitVector*> assigned_vars_;
};
void VariableLivenessAnalysis::ComputeInitialSets() {
const intptr_t block_count = postorder_.length();
BitVector* last_loads = new (zone()) BitVector(zone(), variable_count_);
for (intptr_t i = 0; i < block_count; i++) {
BlockEntryInstr* block = postorder_[i];
BitVector* kill = kill_[i];
BitVector* live_in = live_in_[i];
last_loads->Clear();
// There is an implicit use (load-local) of every local variable at each
// call inside a try{} block and every call has an implicit control-flow
// to the catch entry. As an approximation we mark all locals as live
// inside try{}.
// TODO(fschneider): Improve this approximation, since not all local
// variable stores actually reach a call.
if (block->InsideTryBlock()) {
live_in->SetAll();
continue;
}
// Iterate backwards starting at the last instruction.
for (BackwardInstructionIterator it(block); !it.Done(); it.Advance()) {
Instruction* current = it.Current();
LoadLocalInstr* load = current->AsLoadLocal();
if (load != nullptr) {
const intptr_t index = flow_graph_->EnvIndex(&load->local());
if (index >= live_in->length()) continue; // Skip tmp_locals.
live_in->Add(index);
if (!last_loads->Contains(index)) {
last_loads->Add(index);
load->mark_last();
}
continue;
}
StoreLocalInstr* store = current->AsStoreLocal();
if (store != nullptr) {
const intptr_t index = flow_graph_->EnvIndex(&store->local());
if (index >= live_in->length()) continue; // Skip tmp_locals.
if (kill->Contains(index)) {
if (!live_in->Contains(index)) {
store->mark_dead();
}
} else {
if (!live_in->Contains(index)) {
store->mark_last();
}
kill->Add(index);
}
live_in->Remove(index);
continue;
}
}
// For blocks with parameter or special parameter instructions we add them
// to the kill set.
const bool is_function_entry = block->IsFunctionEntry();
const bool is_osr_entry = block->IsOsrEntry();
const bool is_catch_block_entry = block->IsCatchBlockEntry();
if (is_function_entry || is_osr_entry || is_catch_block_entry) {
const intptr_t parameter_count =
(is_osr_entry || is_catch_block_entry)
? flow_graph_->variable_count()
: flow_graph_->num_direct_parameters();
for (intptr_t i = 0; i < parameter_count; ++i) {
live_in->Remove(i);
kill->Add(i);
}
}
if (is_function_entry) {
if (flow_graph_->parsed_function().has_arg_desc_var()) {
const auto index = flow_graph_->ArgumentDescriptorEnvIndex();
live_in->Remove(index);
kill->Add(index);
}
}
}
}
void FlowGraph::ComputeSSA(
ZoneGrowableArray<Definition*>* inlining_parameters) {
GrowableArray<BitVector*> dominance_frontier;
GrowableArray<intptr_t> idom;
#ifdef DEBUG
if (inlining_parameters != nullptr) {
for (intptr_t i = 0, n = inlining_parameters->length(); i < n; ++i) {
Definition* defn = (*inlining_parameters)[i];
if (defn->IsConstant()) {
ASSERT(defn->previous() == graph_entry_);
ASSERT(defn->HasSSATemp());
ASSERT(defn->ssa_temp_index() < current_ssa_temp_index());
} else {
ASSERT(defn->previous() == nullptr);
ASSERT(!defn->HasSSATemp());
}
}
} else {
ASSERT(current_ssa_temp_index() == 0);
}
#endif
ComputeDominators(&dominance_frontier);
VariableLivenessAnalysis variable_liveness(this);
variable_liveness.Analyze();
GrowableArray<PhiInstr*> live_phis;
InsertPhis(preorder_, variable_liveness.ComputeAssignedVars(),
dominance_frontier, &live_phis);
// Rename uses to reference inserted phis where appropriate.
// Collect phis that reach a non-environment use.
Rename(&live_phis, &variable_liveness, inlining_parameters);
// Propagate alive mark transitively from alive phis and then remove
// non-live ones.
RemoveDeadPhis(&live_phis);
}
// Compute immediate dominators and the dominance frontier for each basic
// block. As a side effect of the algorithm, sets the immediate dominator
// of each basic block.
//
// dominance_frontier: an output parameter encoding the dominance frontier.
// The array maps the preorder block number of a block to the set of
// (preorder block numbers of) blocks in the dominance frontier.
void FlowGraph::ComputeDominators(
GrowableArray<BitVector*>* dominance_frontier) {
// Use the SEMI-NCA algorithm to compute dominators. This is a two-pass
// version of the Lengauer-Tarjan algorithm (LT is normally three passes)
// that eliminates a pass by using nearest-common ancestor (NCA) to
// compute immediate dominators from semidominators. It also removes a
// level of indirection in the link-eval forest data structure.
//
// The algorithm is described in Georgiadis, Tarjan, and Werneck's