1 // Copyright 2013 the V8 project authors. All rights reserved.
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3 // modification, are permitted provided that the following conditions are
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29 #include "hydrogen-gvn.h"
35 class HValueMap: public ZoneObject {
37 explicit HValueMap(Zone* zone)
44 free_list_head_(kNil) {
45 ResizeLists(kInitialSize, zone);
46 Resize(kInitialSize, zone);
49 void Kill(GVNFlagSet flags);
51 void Add(HValue* value, Zone* zone) {
52 present_flags_.Add(value->gvn_flags());
56 HValue* Lookup(HValue* value) const;
58 HValueMap* Copy(Zone* zone) const {
59 return new(zone) HValueMap(zone, this);
62 bool IsEmpty() const { return count_ == 0; }
65 // A linked list of HValue* values. Stored in arrays.
66 struct HValueMapListElement {
68 int next; // Index in the array of the next list element.
70 static const int kNil = -1; // The end of a linked list
72 // Must be a power of 2.
73 static const int kInitialSize = 16;
75 HValueMap(Zone* zone, const HValueMap* other);
77 void Resize(int new_size, Zone* zone);
78 void ResizeLists(int new_size, Zone* zone);
79 void Insert(HValue* value, Zone* zone);
80 uint32_t Bound(uint32_t value) const { return value & (array_size_ - 1); }
84 int count_; // The number of values stored in the HValueMap.
85 GVNFlagSet present_flags_; // All flags that are in any value in the
87 HValueMapListElement* array_; // Primary store - contains the first value
88 // with a given hash. Colliding elements are stored in linked lists.
89 HValueMapListElement* lists_; // The linked lists containing hash collisions.
90 int free_list_head_; // Unused elements in lists_ are on the free list.
94 class HSideEffectMap BASE_EMBEDDED {
97 explicit HSideEffectMap(HSideEffectMap* other);
98 HSideEffectMap& operator= (const HSideEffectMap& other);
100 void Kill(GVNFlagSet flags);
102 void Store(GVNFlagSet flags, HInstruction* instr);
104 bool IsEmpty() const { return count_ == 0; }
106 inline HInstruction* operator[](int i) const {
108 ASSERT(i < kNumberOfTrackedSideEffects);
111 inline HInstruction* at(int i) const { return operator[](i); }
115 HInstruction* data_[kNumberOfTrackedSideEffects];
119 void TraceGVN(const char* msg, ...) {
121 va_start(arguments, msg);
122 OS::VPrint(msg, arguments);
127 // Wrap TraceGVN in macros to avoid the expense of evaluating its arguments when
128 // --trace-gvn is off.
129 #define TRACE_GVN_1(msg, a1) \
130 if (FLAG_trace_gvn) { \
134 #define TRACE_GVN_2(msg, a1, a2) \
135 if (FLAG_trace_gvn) { \
136 TraceGVN(msg, a1, a2); \
139 #define TRACE_GVN_3(msg, a1, a2, a3) \
140 if (FLAG_trace_gvn) { \
141 TraceGVN(msg, a1, a2, a3); \
144 #define TRACE_GVN_4(msg, a1, a2, a3, a4) \
145 if (FLAG_trace_gvn) { \
146 TraceGVN(msg, a1, a2, a3, a4); \
149 #define TRACE_GVN_5(msg, a1, a2, a3, a4, a5) \
150 if (FLAG_trace_gvn) { \
151 TraceGVN(msg, a1, a2, a3, a4, a5); \
155 HValueMap::HValueMap(Zone* zone, const HValueMap* other)
156 : array_size_(other->array_size_),
157 lists_size_(other->lists_size_),
158 count_(other->count_),
159 present_flags_(other->present_flags_),
160 array_(zone->NewArray<HValueMapListElement>(other->array_size_)),
161 lists_(zone->NewArray<HValueMapListElement>(other->lists_size_)),
162 free_list_head_(other->free_list_head_) {
164 array_, other->array_, array_size_ * sizeof(HValueMapListElement));
166 lists_, other->lists_, lists_size_ * sizeof(HValueMapListElement));
170 void HValueMap::Kill(GVNFlagSet flags) {
171 GVNFlagSet depends_flags = HValue::ConvertChangesToDependsFlags(flags);
172 if (!present_flags_.ContainsAnyOf(depends_flags)) return;
173 present_flags_.RemoveAll();
174 for (int i = 0; i < array_size_; ++i) {
175 HValue* value = array_[i].value;
177 // Clear list of collisions first, so we know if it becomes empty.
178 int kept = kNil; // List of kept elements.
180 for (int current = array_[i].next; current != kNil; current = next) {
181 next = lists_[current].next;
182 HValue* value = lists_[current].value;
183 if (value->gvn_flags().ContainsAnyOf(depends_flags)) {
186 lists_[current].next = free_list_head_;
187 free_list_head_ = current;
190 lists_[current].next = kept;
192 present_flags_.Add(value->gvn_flags());
195 array_[i].next = kept;
197 // Now possibly drop directly indexed element.
198 value = array_[i].value;
199 if (value->gvn_flags().ContainsAnyOf(depends_flags)) { // Drop it.
201 int head = array_[i].next;
203 array_[i].value = NULL;
205 array_[i].value = lists_[head].value;
206 array_[i].next = lists_[head].next;
207 lists_[head].next = free_list_head_;
208 free_list_head_ = head;
211 present_flags_.Add(value->gvn_flags()); // Keep it.
218 HValue* HValueMap::Lookup(HValue* value) const {
219 uint32_t hash = static_cast<uint32_t>(value->Hashcode());
220 uint32_t pos = Bound(hash);
221 if (array_[pos].value != NULL) {
222 if (array_[pos].value->Equals(value)) return array_[pos].value;
223 int next = array_[pos].next;
224 while (next != kNil) {
225 if (lists_[next].value->Equals(value)) return lists_[next].value;
226 next = lists_[next].next;
233 void HValueMap::Resize(int new_size, Zone* zone) {
234 ASSERT(new_size > count_);
235 // Hashing the values into the new array has no more collisions than in the
236 // old hash map, so we can use the existing lists_ array, if we are careful.
238 // Make sure we have at least one free element.
239 if (free_list_head_ == kNil) {
240 ResizeLists(lists_size_ << 1, zone);
243 HValueMapListElement* new_array =
244 zone->NewArray<HValueMapListElement>(new_size);
245 memset(new_array, 0, sizeof(HValueMapListElement) * new_size);
247 HValueMapListElement* old_array = array_;
248 int old_size = array_size_;
250 int old_count = count_;
252 // Do not modify present_flags_. It is currently correct.
253 array_size_ = new_size;
256 if (old_array != NULL) {
257 // Iterate over all the elements in lists, rehashing them.
258 for (int i = 0; i < old_size; ++i) {
259 if (old_array[i].value != NULL) {
260 int current = old_array[i].next;
261 while (current != kNil) {
262 Insert(lists_[current].value, zone);
263 int next = lists_[current].next;
264 lists_[current].next = free_list_head_;
265 free_list_head_ = current;
268 // Rehash the directly stored value.
269 Insert(old_array[i].value, zone);
274 ASSERT(count_ == old_count);
278 void HValueMap::ResizeLists(int new_size, Zone* zone) {
279 ASSERT(new_size > lists_size_);
281 HValueMapListElement* new_lists =
282 zone->NewArray<HValueMapListElement>(new_size);
283 memset(new_lists, 0, sizeof(HValueMapListElement) * new_size);
285 HValueMapListElement* old_lists = lists_;
286 int old_size = lists_size_;
288 lists_size_ = new_size;
291 if (old_lists != NULL) {
292 OS::MemCopy(lists_, old_lists, old_size * sizeof(HValueMapListElement));
294 for (int i = old_size; i < lists_size_; ++i) {
295 lists_[i].next = free_list_head_;
301 void HValueMap::Insert(HValue* value, Zone* zone) {
302 ASSERT(value != NULL);
303 // Resizing when half of the hashtable is filled up.
304 if (count_ >= array_size_ >> 1) Resize(array_size_ << 1, zone);
305 ASSERT(count_ < array_size_);
307 uint32_t pos = Bound(static_cast<uint32_t>(value->Hashcode()));
308 if (array_[pos].value == NULL) {
309 array_[pos].value = value;
310 array_[pos].next = kNil;
312 if (free_list_head_ == kNil) {
313 ResizeLists(lists_size_ << 1, zone);
315 int new_element_pos = free_list_head_;
316 ASSERT(new_element_pos != kNil);
317 free_list_head_ = lists_[free_list_head_].next;
318 lists_[new_element_pos].value = value;
319 lists_[new_element_pos].next = array_[pos].next;
320 ASSERT(array_[pos].next == kNil || lists_[array_[pos].next].value != NULL);
321 array_[pos].next = new_element_pos;
326 HSideEffectMap::HSideEffectMap() : count_(0) {
327 memset(data_, 0, kNumberOfTrackedSideEffects * kPointerSize);
331 HSideEffectMap::HSideEffectMap(HSideEffectMap* other) : count_(other->count_) {
332 *this = *other; // Calls operator=.
336 HSideEffectMap& HSideEffectMap::operator= (const HSideEffectMap& other) {
337 if (this != &other) {
338 OS::MemCopy(data_, other.data_, kNumberOfTrackedSideEffects * kPointerSize);
344 void HSideEffectMap::Kill(GVNFlagSet flags) {
345 for (int i = 0; i < kNumberOfTrackedSideEffects; i++) {
346 GVNFlag changes_flag = HValue::ChangesFlagFromInt(i);
347 if (flags.Contains(changes_flag)) {
348 if (data_[i] != NULL) count_--;
355 void HSideEffectMap::Store(GVNFlagSet flags, HInstruction* instr) {
356 for (int i = 0; i < kNumberOfTrackedSideEffects; i++) {
357 GVNFlag changes_flag = HValue::ChangesFlagFromInt(i);
358 if (flags.Contains(changes_flag)) {
359 if (data_[i] == NULL) count_++;
366 HGlobalValueNumberingPhase::HGlobalValueNumberingPhase(HGraph* graph)
367 : HPhase("H_Global value numbering", graph),
368 removed_side_effects_(false),
369 block_side_effects_(graph->blocks()->length(), zone()),
370 loop_side_effects_(graph->blocks()->length(), zone()),
371 visited_on_paths_(graph->blocks()->length(), zone()) {
372 ASSERT(!AllowHandleAllocation::IsAllowed());
373 block_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
375 loop_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
380 void HGlobalValueNumberingPhase::Run() {
381 ASSERT(!removed_side_effects_);
382 for (int i = FLAG_gvn_iterations; i > 0; --i) {
383 // Compute the side effects.
384 ComputeBlockSideEffects();
386 // Perform loop invariant code motion if requested.
387 if (FLAG_loop_invariant_code_motion) LoopInvariantCodeMotion();
389 // Perform the actual value numbering.
392 // Continue GVN if we removed any side effects.
393 if (!removed_side_effects_) break;
394 removed_side_effects_ = false;
396 // Clear all side effects.
397 ASSERT_EQ(block_side_effects_.length(), graph()->blocks()->length());
398 ASSERT_EQ(loop_side_effects_.length(), graph()->blocks()->length());
399 for (int i = 0; i < graph()->blocks()->length(); ++i) {
400 block_side_effects_[i].RemoveAll();
401 loop_side_effects_[i].RemoveAll();
403 visited_on_paths_.Clear();
408 void HGlobalValueNumberingPhase::ComputeBlockSideEffects() {
409 for (int i = graph()->blocks()->length() - 1; i >= 0; --i) {
410 // Compute side effects for the block.
411 HBasicBlock* block = graph()->blocks()->at(i);
412 GVNFlagSet side_effects;
413 if (block->IsReachable() && !block->IsDeoptimizing()) {
414 int id = block->block_id();
415 for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
416 HInstruction* instr = it.Current();
417 side_effects.Add(instr->ChangesFlags());
419 block_side_effects_[id].Add(side_effects);
421 // Loop headers are part of their loop.
422 if (block->IsLoopHeader()) {
423 loop_side_effects_[id].Add(side_effects);
426 // Propagate loop side effects upwards.
427 if (block->HasParentLoopHeader()) {
428 HBasicBlock* with_parent = block;
429 if (block->IsLoopHeader()) side_effects = loop_side_effects_[id];
431 HBasicBlock* parent_block = with_parent->parent_loop_header();
432 loop_side_effects_[parent_block->block_id()].Add(side_effects);
433 with_parent = parent_block;
434 } while (with_parent->HasParentLoopHeader());
441 SmartArrayPointer<char> GetGVNFlagsString(GVNFlagSet flags) {
442 char underlying_buffer[kNumberOfFlags * 128];
443 Vector<char> buffer(underlying_buffer, sizeof(underlying_buffer));
446 const char* separator = "";
447 const char* comma = ", ";
449 uint32_t set_depends_on = 0;
450 uint32_t set_changes = 0;
451 for (int bit = 0; bit < kNumberOfFlags; ++bit) {
452 if (flags.Contains(static_cast<GVNFlag>(bit))) {
460 bool positive_changes = set_changes < (kNumberOfFlags / 2);
461 bool positive_depends_on = set_depends_on < (kNumberOfFlags / 2);
462 if (set_changes > 0) {
463 if (positive_changes) {
464 offset += OS::SNPrintF(buffer + offset, "changes [");
466 offset += OS::SNPrintF(buffer + offset, "changes all except [");
468 for (int bit = 0; bit < kNumberOfFlags; ++bit) {
469 if (flags.Contains(static_cast<GVNFlag>(bit)) == positive_changes) {
470 switch (static_cast<GVNFlag>(bit)) {
471 #define DECLARE_FLAG(type) \
472 case kChanges##type: \
473 offset += OS::SNPrintF(buffer + offset, separator); \
474 offset += OS::SNPrintF(buffer + offset, #type); \
477 GVN_TRACKED_FLAG_LIST(DECLARE_FLAG)
478 GVN_UNTRACKED_FLAG_LIST(DECLARE_FLAG)
485 offset += OS::SNPrintF(buffer + offset, "]");
487 if (set_depends_on > 0) {
489 if (set_changes > 0) {
490 offset += OS::SNPrintF(buffer + offset, ", ");
492 if (positive_depends_on) {
493 offset += OS::SNPrintF(buffer + offset, "depends on [");
495 offset += OS::SNPrintF(buffer + offset, "depends on all except [");
497 for (int bit = 0; bit < kNumberOfFlags; ++bit) {
498 if (flags.Contains(static_cast<GVNFlag>(bit)) == positive_depends_on) {
499 switch (static_cast<GVNFlag>(bit)) {
500 #define DECLARE_FLAG(type) \
501 case kDependsOn##type: \
502 offset += OS::SNPrintF(buffer + offset, separator); \
503 offset += OS::SNPrintF(buffer + offset, #type); \
506 GVN_TRACKED_FLAG_LIST(DECLARE_FLAG)
507 GVN_UNTRACKED_FLAG_LIST(DECLARE_FLAG)
514 offset += OS::SNPrintF(buffer + offset, "]");
517 OS::SNPrintF(buffer, "0x%08X", flags.ToIntegral());
519 size_t string_len = strlen(underlying_buffer) + 1;
520 ASSERT(string_len <= sizeof(underlying_buffer));
521 char* result = new char[strlen(underlying_buffer) + 1];
522 OS::MemCopy(result, underlying_buffer, string_len);
523 return SmartArrayPointer<char>(result);
527 void HGlobalValueNumberingPhase::LoopInvariantCodeMotion() {
528 TRACE_GVN_1("Using optimistic loop invariant code motion: %s\n",
529 graph()->use_optimistic_licm() ? "yes" : "no");
530 for (int i = graph()->blocks()->length() - 1; i >= 0; --i) {
531 HBasicBlock* block = graph()->blocks()->at(i);
532 if (block->IsLoopHeader()) {
533 GVNFlagSet side_effects = loop_side_effects_[block->block_id()];
534 TRACE_GVN_2("Try loop invariant motion for block B%d %s\n",
536 GetGVNFlagsString(side_effects).get());
538 HBasicBlock* last = block->loop_information()->GetLastBackEdge();
539 for (int j = block->block_id(); j <= last->block_id(); ++j) {
540 ProcessLoopBlock(graph()->blocks()->at(j), block, side_effects);
547 void HGlobalValueNumberingPhase::ProcessLoopBlock(
549 HBasicBlock* loop_header,
550 GVNFlagSet loop_kills) {
551 HBasicBlock* pre_header = loop_header->predecessors()->at(0);
552 GVNFlagSet depends_flags = HValue::ConvertChangesToDependsFlags(loop_kills);
553 TRACE_GVN_2("Loop invariant motion for B%d %s\n",
555 GetGVNFlagsString(depends_flags).get());
556 HInstruction* instr = block->first();
557 while (instr != NULL) {
558 HInstruction* next = instr->next();
559 if (instr->CheckFlag(HValue::kUseGVN)) {
560 TRACE_GVN_4("Checking instruction %d (%s) %s. Loop %s\n",
563 GetGVNFlagsString(instr->gvn_flags()).get(),
564 GetGVNFlagsString(loop_kills).get());
565 bool can_hoist = !instr->gvn_flags().ContainsAnyOf(depends_flags);
566 if (can_hoist && !graph()->use_optimistic_licm()) {
567 can_hoist = block->IsLoopSuccessorDominator();
571 bool inputs_loop_invariant = true;
572 for (int i = 0; i < instr->OperandCount(); ++i) {
573 if (instr->OperandAt(i)->IsDefinedAfter(pre_header)) {
574 inputs_loop_invariant = false;
578 if (inputs_loop_invariant && ShouldMove(instr, loop_header)) {
579 TRACE_GVN_2("Hoisting loop invariant instruction i%d to block B%d\n",
580 instr->id(), pre_header->block_id());
581 // Move the instruction out of the loop.
583 instr->InsertBefore(pre_header->end());
584 if (instr->HasSideEffects()) removed_side_effects_ = true;
593 bool HGlobalValueNumberingPhase::AllowCodeMotion() {
594 return info()->IsStub() || info()->opt_count() + 1 < FLAG_max_opt_count;
598 bool HGlobalValueNumberingPhase::ShouldMove(HInstruction* instr,
599 HBasicBlock* loop_header) {
600 // If we've disabled code motion or we're in a block that unconditionally
601 // deoptimizes, don't move any instructions.
602 return AllowCodeMotion() && !instr->block()->IsDeoptimizing() &&
603 instr->block()->IsReachable();
608 HGlobalValueNumberingPhase::CollectSideEffectsOnPathsToDominatedBlock(
609 HBasicBlock* dominator, HBasicBlock* dominated) {
610 GVNFlagSet side_effects;
611 for (int i = 0; i < dominated->predecessors()->length(); ++i) {
612 HBasicBlock* block = dominated->predecessors()->at(i);
613 if (dominator->block_id() < block->block_id() &&
614 block->block_id() < dominated->block_id() &&
615 !visited_on_paths_.Contains(block->block_id())) {
616 visited_on_paths_.Add(block->block_id());
617 side_effects.Add(block_side_effects_[block->block_id()]);
618 if (block->IsLoopHeader()) {
619 side_effects.Add(loop_side_effects_[block->block_id()]);
621 side_effects.Add(CollectSideEffectsOnPathsToDominatedBlock(
629 // Each instance of this class is like a "stack frame" for the recursive
630 // traversal of the dominator tree done during GVN (the stack is handled
631 // as a double linked list).
632 // We reuse frames when possible so the list length is limited by the depth
633 // of the dominator tree but this forces us to initialize each frame calling
634 // an explicit "Initialize" method instead of a using constructor.
635 class GvnBasicBlockState: public ZoneObject {
637 static GvnBasicBlockState* CreateEntry(Zone* zone,
638 HBasicBlock* entry_block,
639 HValueMap* entry_map) {
641 GvnBasicBlockState(NULL, entry_block, entry_map, NULL, zone);
644 HBasicBlock* block() { return block_; }
645 HValueMap* map() { return map_; }
646 HSideEffectMap* dominators() { return &dominators_; }
648 GvnBasicBlockState* next_in_dominator_tree_traversal(
650 HBasicBlock** dominator) {
651 // This assignment needs to happen before calling next_dominated() because
652 // that call can reuse "this" if we are at the last dominated block.
653 *dominator = block();
654 GvnBasicBlockState* result = next_dominated(zone);
655 if (result == NULL) {
656 GvnBasicBlockState* dominator_state = pop();
657 if (dominator_state != NULL) {
658 // This branch is guaranteed not to return NULL because pop() never
659 // returns a state where "is_done() == true".
660 *dominator = dominator_state->block();
661 result = dominator_state->next_dominated(zone);
663 // Unnecessary (we are returning NULL) but done for cleanness.
671 void Initialize(HBasicBlock* block,
673 HSideEffectMap* dominators,
677 map_ = copy_map ? map->Copy(zone) : map;
678 dominated_index_ = -1;
679 length_ = block->dominated_blocks()->length();
680 if (dominators != NULL) {
681 dominators_ = *dominators;
684 bool is_done() { return dominated_index_ >= length_; }
686 GvnBasicBlockState(GvnBasicBlockState* previous,
689 HSideEffectMap* dominators,
691 : previous_(previous), next_(NULL) {
692 Initialize(block, map, dominators, true, zone);
695 GvnBasicBlockState* next_dominated(Zone* zone) {
697 if (dominated_index_ == length_ - 1) {
698 // No need to copy the map for the last child in the dominator tree.
699 Initialize(block_->dominated_blocks()->at(dominated_index_),
705 } else if (dominated_index_ < length_) {
706 return push(zone, block_->dominated_blocks()->at(dominated_index_));
712 GvnBasicBlockState* push(Zone* zone, HBasicBlock* block) {
715 new(zone) GvnBasicBlockState(this, block, map(), dominators(), zone);
717 next_->Initialize(block, map(), dominators(), true, zone);
721 GvnBasicBlockState* pop() {
722 GvnBasicBlockState* result = previous_;
723 while (result != NULL && result->is_done()) {
724 TRACE_GVN_2("Backtracking from block B%d to block b%d\n",
726 previous_->block()->block_id())
727 result = result->previous_;
732 GvnBasicBlockState* previous_;
733 GvnBasicBlockState* next_;
736 HSideEffectMap dominators_;
737 int dominated_index_;
742 // This is a recursive traversal of the dominator tree but it has been turned
743 // into a loop to avoid stack overflows.
744 // The logical "stack frames" of the recursion are kept in a list of
745 // GvnBasicBlockState instances.
746 void HGlobalValueNumberingPhase::AnalyzeGraph() {
747 HBasicBlock* entry_block = graph()->entry_block();
748 HValueMap* entry_map = new(zone()) HValueMap(zone());
749 GvnBasicBlockState* current =
750 GvnBasicBlockState::CreateEntry(zone(), entry_block, entry_map);
752 while (current != NULL) {
753 HBasicBlock* block = current->block();
754 HValueMap* map = current->map();
755 HSideEffectMap* dominators = current->dominators();
757 TRACE_GVN_2("Analyzing block B%d%s\n",
759 block->IsLoopHeader() ? " (loop header)" : "");
761 // If this is a loop header kill everything killed by the loop.
762 if (block->IsLoopHeader()) {
763 map->Kill(loop_side_effects_[block->block_id()]);
764 dominators->Kill(loop_side_effects_[block->block_id()]);
767 // Go through all instructions of the current block.
768 for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
769 HInstruction* instr = it.Current();
770 if (instr->CheckFlag(HValue::kTrackSideEffectDominators)) {
771 for (int i = 0; i < kNumberOfTrackedSideEffects; i++) {
772 HValue* other = dominators->at(i);
773 GVNFlag changes_flag = HValue::ChangesFlagFromInt(i);
774 GVNFlag depends_on_flag = HValue::DependsOnFlagFromInt(i);
775 if (instr->DependsOnFlags().Contains(depends_on_flag) &&
777 TRACE_GVN_5("Side-effect #%d in %d (%s) is dominated by %d (%s)\n",
783 if (instr->HandleSideEffectDominator(changes_flag, other)) {
784 removed_side_effects_ = true;
789 // Instruction was unlinked during graph traversal.
790 if (!instr->IsLinked()) continue;
792 GVNFlagSet flags = instr->ChangesFlags();
793 if (!flags.IsEmpty()) {
794 // Clear all instructions in the map that are affected by side effects.
795 // Store instruction as the dominating one for tracked side effects.
797 dominators->Store(flags, instr);
798 TRACE_GVN_2("Instruction %d %s\n", instr->id(),
799 GetGVNFlagsString(flags).get());
801 if (instr->CheckFlag(HValue::kUseGVN)) {
802 ASSERT(!instr->HasObservableSideEffects());
803 HValue* other = map->Lookup(instr);
805 ASSERT(instr->Equals(other) && other->Equals(instr));
806 TRACE_GVN_4("Replacing value %d (%s) with value %d (%s)\n",
811 if (instr->HasSideEffects()) removed_side_effects_ = true;
812 instr->DeleteAndReplaceWith(other);
814 map->Add(instr, zone());
819 HBasicBlock* dominator_block;
820 GvnBasicBlockState* next =
821 current->next_in_dominator_tree_traversal(zone(),
825 HBasicBlock* dominated = next->block();
826 HValueMap* successor_map = next->map();
827 HSideEffectMap* successor_dominators = next->dominators();
829 // Kill everything killed on any path between this block and the
830 // dominated block. We don't have to traverse these paths if the
831 // value map and the dominators list is already empty. If the range
832 // of block ids (block_id, dominated_id) is empty there are no such
834 if ((!successor_map->IsEmpty() || !successor_dominators->IsEmpty()) &&
835 dominator_block->block_id() + 1 < dominated->block_id()) {
836 visited_on_paths_.Clear();
837 GVNFlagSet side_effects_on_all_paths =
838 CollectSideEffectsOnPathsToDominatedBlock(dominator_block,
840 successor_map->Kill(side_effects_on_all_paths);
841 successor_dominators->Kill(side_effects_on_all_paths);
848 } } // namespace v8::internal