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Unified Diff: src/hydrogen-check-elimination.cc

Issue 1405363003: Move Hydrogen and Lithium to src/crankshaft/ (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: rebased Created 5 years, 2 months ago
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Index: src/hydrogen-check-elimination.cc
diff --git a/src/hydrogen-check-elimination.cc b/src/hydrogen-check-elimination.cc
deleted file mode 100644
index 74be2e42f4a1134783be7ddda531a5fea3bd8e87..0000000000000000000000000000000000000000
--- a/src/hydrogen-check-elimination.cc
+++ /dev/null
@@ -1,913 +0,0 @@
-// Copyright 2013 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "src/hydrogen-check-elimination.h"
-
-#include "src/hydrogen-alias-analysis.h"
-#include "src/hydrogen-flow-engine.h"
-
-#define GLOBAL 1
-
-// Only collect stats in debug mode.
-#if DEBUG
-#define INC_STAT(x) phase_->x++
-#else
-#define INC_STAT(x)
-#endif
-
-// For code de-uglification.
-#define TRACE(x) if (FLAG_trace_check_elimination) PrintF x
-
-namespace v8 {
-namespace internal {
-
-typedef const UniqueSet<Map>* MapSet;
-
-struct HCheckTableEntry {
- enum State {
- // We have seen a map check (i.e. an HCheckMaps) for these maps, so we can
- // use this information to eliminate further map checks, elements kind
- // transitions, etc.
- CHECKED,
- // Same as CHECKED, but we also know that these maps are stable.
- CHECKED_STABLE,
- // These maps are stable, but not checked (i.e. we learned this via field
- // type tracking or from a constant, or they were initially CHECKED_STABLE,
- // but became UNCHECKED_STABLE because of an instruction that changes maps
- // or elements kind), and we need a stability check for them in order to use
- // this information for check elimination (which turns them back to
- // CHECKED_STABLE).
- UNCHECKED_STABLE
- };
-
- static const char* State2String(State state) {
- switch (state) {
- case CHECKED: return "checked";
- case CHECKED_STABLE: return "checked stable";
- case UNCHECKED_STABLE: return "unchecked stable";
- }
- UNREACHABLE();
- return NULL;
- }
-
- static State StateMerge(State state1, State state2) {
- if (state1 == state2) return state1;
- if ((state1 == CHECKED && state2 == CHECKED_STABLE) ||
- (state2 == CHECKED && state1 == CHECKED_STABLE)) {
- return CHECKED;
- }
- DCHECK((state1 == CHECKED_STABLE && state2 == UNCHECKED_STABLE) ||
- (state2 == CHECKED_STABLE && state1 == UNCHECKED_STABLE));
- return UNCHECKED_STABLE;
- }
-
- HValue* object_; // The object being approximated. NULL => invalid entry.
- HInstruction* check_; // The last check instruction.
- MapSet maps_; // The set of known maps for the object.
- State state_; // The state of this entry.
-};
-
-
-// The main data structure used during check elimination, which stores a
-// set of known maps for each object.
-class HCheckTable : public ZoneObject {
- public:
- static const int kMaxTrackedObjects = 16;
-
- explicit HCheckTable(HCheckEliminationPhase* phase)
- : phase_(phase),
- cursor_(0),
- size_(0) {
- }
-
- // The main processing of instructions.
- HCheckTable* Process(HInstruction* instr, Zone* zone) {
- switch (instr->opcode()) {
- case HValue::kCheckMaps: {
- ReduceCheckMaps(HCheckMaps::cast(instr));
- break;
- }
- case HValue::kLoadNamedField: {
- ReduceLoadNamedField(HLoadNamedField::cast(instr));
- break;
- }
- case HValue::kStoreNamedField: {
- ReduceStoreNamedField(HStoreNamedField::cast(instr));
- break;
- }
- case HValue::kCompareMap: {
- ReduceCompareMap(HCompareMap::cast(instr));
- break;
- }
- case HValue::kCompareObjectEqAndBranch: {
- ReduceCompareObjectEqAndBranch(HCompareObjectEqAndBranch::cast(instr));
- break;
- }
- case HValue::kIsStringAndBranch: {
- ReduceIsStringAndBranch(HIsStringAndBranch::cast(instr));
- break;
- }
- case HValue::kTransitionElementsKind: {
- ReduceTransitionElementsKind(
- HTransitionElementsKind::cast(instr));
- break;
- }
- case HValue::kCheckHeapObject: {
- ReduceCheckHeapObject(HCheckHeapObject::cast(instr));
- break;
- }
- case HValue::kCheckInstanceType: {
- ReduceCheckInstanceType(HCheckInstanceType::cast(instr));
- break;
- }
- default: {
- // If the instruction changes maps uncontrollably, drop everything.
- if (instr->CheckChangesFlag(kOsrEntries)) {
- Kill();
- break;
- }
- if (instr->CheckChangesFlag(kElementsKind) ||
- instr->CheckChangesFlag(kMaps)) {
- KillUnstableEntries();
- }
- }
- // Improvements possible:
- // - eliminate redundant HCheckSmi instructions
- // - track which values have been HCheckHeapObject'd
- }
-
- return this;
- }
-
- // Support for global analysis with HFlowEngine: Merge given state with
- // the other incoming state.
- static HCheckTable* Merge(HCheckTable* succ_state, HBasicBlock* succ_block,
- HCheckTable* pred_state, HBasicBlock* pred_block,
- Zone* zone) {
- if (pred_state == NULL || pred_block->IsUnreachable()) {
- return succ_state;
- }
- if (succ_state == NULL) {
- return pred_state->Copy(succ_block, pred_block, zone);
- } else {
- return succ_state->Merge(succ_block, pred_state, pred_block, zone);
- }
- }
-
- // Support for global analysis with HFlowEngine: Given state merged with all
- // the other incoming states, prepare it for use.
- static HCheckTable* Finish(HCheckTable* state, HBasicBlock* block,
- Zone* zone) {
- if (state == NULL) {
- block->MarkUnreachable();
- } else if (block->IsUnreachable()) {
- state = NULL;
- }
- if (FLAG_trace_check_elimination) {
- PrintF("Processing B%d, checkmaps-table:\n", block->block_id());
- Print(state);
- }
- return state;
- }
-
- private:
- // Copy state to successor block.
- HCheckTable* Copy(HBasicBlock* succ, HBasicBlock* from_block, Zone* zone) {
- HCheckTable* copy = new(zone) HCheckTable(phase_);
- for (int i = 0; i < size_; i++) {
- HCheckTableEntry* old_entry = &entries_[i];
- DCHECK(old_entry->maps_->size() > 0);
- HCheckTableEntry* new_entry = &copy->entries_[i];
- new_entry->object_ = old_entry->object_;
- new_entry->maps_ = old_entry->maps_;
- new_entry->state_ = old_entry->state_;
- // Keep the check if the existing check's block dominates the successor.
- if (old_entry->check_ != NULL &&
- old_entry->check_->block()->Dominates(succ)) {
- new_entry->check_ = old_entry->check_;
- } else {
- // Leave it NULL till we meet a new check instruction for this object
- // in the control flow.
- new_entry->check_ = NULL;
- }
- }
- copy->cursor_ = cursor_;
- copy->size_ = size_;
-
- // Create entries for succ block's phis.
- if (!succ->IsLoopHeader() && succ->phis()->length() > 0) {
- int pred_index = succ->PredecessorIndexOf(from_block);
- for (int phi_index = 0;
- phi_index < succ->phis()->length();
- ++phi_index) {
- HPhi* phi = succ->phis()->at(phi_index);
- HValue* phi_operand = phi->OperandAt(pred_index);
-
- HCheckTableEntry* pred_entry = copy->Find(phi_operand);
- if (pred_entry != NULL) {
- // Create an entry for a phi in the table.
- copy->Insert(phi, NULL, pred_entry->maps_, pred_entry->state_);
- }
- }
- }
-
- // Branch-sensitive analysis for certain comparisons may add more facts
- // to the state for the successor on the true branch.
- bool learned = false;
- if (succ->predecessors()->length() == 1) {
- HControlInstruction* end = succ->predecessors()->at(0)->end();
- bool is_true_branch = end->SuccessorAt(0) == succ;
- if (end->IsCompareMap()) {
- HCompareMap* cmp = HCompareMap::cast(end);
- HValue* object = cmp->value()->ActualValue();
- HCheckTableEntry* entry = copy->Find(object);
- if (is_true_branch) {
- HCheckTableEntry::State state = cmp->map_is_stable()
- ? HCheckTableEntry::CHECKED_STABLE
- : HCheckTableEntry::CHECKED;
- // Learn on the true branch of if(CompareMap(x)).
- if (entry == NULL) {
- copy->Insert(object, cmp, cmp->map(), state);
- } else {
- entry->maps_ = new(zone) UniqueSet<Map>(cmp->map(), zone);
- entry->check_ = cmp;
- entry->state_ = state;
- }
- } else {
- // Learn on the false branch of if(CompareMap(x)).
- if (entry != NULL) {
- EnsureChecked(entry, object, cmp);
- UniqueSet<Map>* maps = entry->maps_->Copy(zone);
- maps->Remove(cmp->map());
- entry->maps_ = maps;
- DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
- }
- }
- learned = true;
- } else if (is_true_branch && end->IsCompareObjectEqAndBranch()) {
- // Learn on the true branch of if(CmpObjectEq(x, y)).
- HCompareObjectEqAndBranch* cmp =
- HCompareObjectEqAndBranch::cast(end);
- HValue* left = cmp->left()->ActualValue();
- HValue* right = cmp->right()->ActualValue();
- HCheckTableEntry* le = copy->Find(left);
- HCheckTableEntry* re = copy->Find(right);
- if (le == NULL) {
- if (re != NULL) {
- copy->Insert(left, NULL, re->maps_, re->state_);
- }
- } else if (re == NULL) {
- copy->Insert(right, NULL, le->maps_, le->state_);
- } else {
- EnsureChecked(le, cmp->left(), cmp);
- EnsureChecked(re, cmp->right(), cmp);
- le->maps_ = re->maps_ = le->maps_->Intersect(re->maps_, zone);
- le->state_ = re->state_ = HCheckTableEntry::StateMerge(
- le->state_, re->state_);
- DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, le->state_);
- DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, re->state_);
- }
- learned = true;
- } else if (end->IsIsStringAndBranch()) {
- HIsStringAndBranch* cmp = HIsStringAndBranch::cast(end);
- HValue* object = cmp->value()->ActualValue();
- HCheckTableEntry* entry = copy->Find(object);
- if (is_true_branch) {
- // Learn on the true branch of if(IsString(x)).
- if (entry == NULL) {
- copy->Insert(object, NULL, string_maps(),
- HCheckTableEntry::CHECKED);
- } else {
- EnsureChecked(entry, object, cmp);
- entry->maps_ = entry->maps_->Intersect(string_maps(), zone);
- DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
- }
- } else {
- // Learn on the false branch of if(IsString(x)).
- if (entry != NULL) {
- EnsureChecked(entry, object, cmp);
- entry->maps_ = entry->maps_->Subtract(string_maps(), zone);
- DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
- }
- }
- }
- // Learning on false branches requires storing negative facts.
- }
-
- if (FLAG_trace_check_elimination) {
- PrintF("B%d checkmaps-table %s from B%d:\n",
- succ->block_id(),
- learned ? "learned" : "copied",
- from_block->block_id());
- Print(copy);
- }
-
- return copy;
- }
-
- // Merge this state with the other incoming state.
- HCheckTable* Merge(HBasicBlock* succ, HCheckTable* that,
- HBasicBlock* pred_block, Zone* zone) {
- if (that->size_ == 0) {
- // If the other state is empty, simply reset.
- size_ = 0;
- cursor_ = 0;
- } else {
- int pred_index = succ->PredecessorIndexOf(pred_block);
- bool compact = false;
- for (int i = 0; i < size_; i++) {
- HCheckTableEntry* this_entry = &entries_[i];
- HCheckTableEntry* that_entry;
- if (this_entry->object_->IsPhi() &&
- this_entry->object_->block() == succ) {
- HPhi* phi = HPhi::cast(this_entry->object_);
- HValue* phi_operand = phi->OperandAt(pred_index);
- that_entry = that->Find(phi_operand);
-
- } else {
- that_entry = that->Find(this_entry->object_);
- }
-
- if (that_entry == NULL ||
- (that_entry->state_ == HCheckTableEntry::CHECKED &&
- this_entry->state_ == HCheckTableEntry::UNCHECKED_STABLE) ||
- (this_entry->state_ == HCheckTableEntry::CHECKED &&
- that_entry->state_ == HCheckTableEntry::UNCHECKED_STABLE)) {
- this_entry->object_ = NULL;
- compact = true;
- } else {
- this_entry->maps_ =
- this_entry->maps_->Union(that_entry->maps_, zone);
- this_entry->state_ = HCheckTableEntry::StateMerge(
- this_entry->state_, that_entry->state_);
- if (this_entry->check_ != that_entry->check_) {
- this_entry->check_ = NULL;
- }
- DCHECK(this_entry->maps_->size() > 0);
- }
- }
- if (compact) Compact();
- }
-
- if (FLAG_trace_check_elimination) {
- PrintF("B%d checkmaps-table merged with B%d table:\n",
- succ->block_id(), pred_block->block_id());
- Print(this);
- }
- return this;
- }
-
- void ReduceCheckMaps(HCheckMaps* instr) {
- HValue* object = instr->value()->ActualValue();
- HCheckTableEntry* entry = Find(object);
- if (entry != NULL) {
- // entry found;
- HGraph* graph = instr->block()->graph();
- if (entry->maps_->IsSubset(instr->maps())) {
- // The first check is more strict; the second is redundant.
- if (entry->check_ != NULL) {
- DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
- TRACE(("Replacing redundant CheckMaps #%d at B%d with #%d\n",
- instr->id(), instr->block()->block_id(), entry->check_->id()));
- instr->DeleteAndReplaceWith(entry->check_);
- INC_STAT(redundant_);
- } else if (entry->state_ == HCheckTableEntry::UNCHECKED_STABLE) {
- DCHECK_NULL(entry->check_);
- TRACE(("Marking redundant CheckMaps #%d at B%d as stability check\n",
- instr->id(), instr->block()->block_id()));
- instr->set_maps(entry->maps_->Copy(graph->zone()));
- instr->MarkAsStabilityCheck();
- entry->state_ = HCheckTableEntry::CHECKED_STABLE;
- } else if (!instr->IsStabilityCheck()) {
- TRACE(("Marking redundant CheckMaps #%d at B%d as dead\n",
- instr->id(), instr->block()->block_id()));
- // Mark check as dead but leave it in the graph as a checkpoint for
- // subsequent checks.
- instr->SetFlag(HValue::kIsDead);
- entry->check_ = instr;
- INC_STAT(removed_);
- }
- return;
- }
- MapSet intersection = instr->maps()->Intersect(
- entry->maps_, graph->zone());
- if (intersection->size() == 0) {
- // Intersection is empty; probably megamorphic.
- INC_STAT(empty_);
- entry->object_ = NULL;
- Compact();
- } else {
- // Update set of maps in the entry.
- entry->maps_ = intersection;
- // Update state of the entry.
- if (instr->maps_are_stable() ||
- entry->state_ == HCheckTableEntry::UNCHECKED_STABLE) {
- entry->state_ = HCheckTableEntry::CHECKED_STABLE;
- }
- if (intersection->size() != instr->maps()->size()) {
- // Narrow set of maps in the second check maps instruction.
- if (entry->check_ != NULL &&
- entry->check_->block() == instr->block() &&
- entry->check_->IsCheckMaps()) {
- // There is a check in the same block so replace it with a more
- // strict check and eliminate the second check entirely.
- HCheckMaps* check = HCheckMaps::cast(entry->check_);
- DCHECK(!check->IsStabilityCheck());
- TRACE(("CheckMaps #%d at B%d narrowed\n", check->id(),
- check->block()->block_id()));
- // Update map set and ensure that the check is alive.
- check->set_maps(intersection);
- check->ClearFlag(HValue::kIsDead);
- TRACE(("Replacing redundant CheckMaps #%d at B%d with #%d\n",
- instr->id(), instr->block()->block_id(), entry->check_->id()));
- instr->DeleteAndReplaceWith(entry->check_);
- } else {
- TRACE(("CheckMaps #%d at B%d narrowed\n", instr->id(),
- instr->block()->block_id()));
- instr->set_maps(intersection);
- entry->check_ = instr->IsStabilityCheck() ? NULL : instr;
- }
-
- if (FLAG_trace_check_elimination) {
- Print(this);
- }
- INC_STAT(narrowed_);
- }
- }
- } else {
- // No entry; insert a new one.
- HCheckTableEntry::State state = instr->maps_are_stable()
- ? HCheckTableEntry::CHECKED_STABLE
- : HCheckTableEntry::CHECKED;
- HCheckMaps* check = instr->IsStabilityCheck() ? NULL : instr;
- Insert(object, check, instr->maps(), state);
- }
- }
-
- void ReduceCheckInstanceType(HCheckInstanceType* instr) {
- HValue* value = instr->value()->ActualValue();
- HCheckTableEntry* entry = Find(value);
- if (entry == NULL) {
- if (instr->check() == HCheckInstanceType::IS_STRING) {
- Insert(value, NULL, string_maps(), HCheckTableEntry::CHECKED);
- }
- return;
- }
- UniqueSet<Map>* maps = new(zone()) UniqueSet<Map>(
- entry->maps_->size(), zone());
- for (int i = 0; i < entry->maps_->size(); ++i) {
- InstanceType type;
- Unique<Map> map = entry->maps_->at(i);
- {
- // This is safe, because maps don't move and their instance type does
- // not change.
- AllowHandleDereference allow_deref;
- type = map.handle()->instance_type();
- }
- if (instr->is_interval_check()) {
- InstanceType first_type, last_type;
- instr->GetCheckInterval(&first_type, &last_type);
- if (first_type <= type && type <= last_type) maps->Add(map, zone());
- } else {
- uint8_t mask, tag;
- instr->GetCheckMaskAndTag(&mask, &tag);
- if ((type & mask) == tag) maps->Add(map, zone());
- }
- }
- if (maps->size() == entry->maps_->size()) {
- TRACE(("Removing redundant CheckInstanceType #%d at B%d\n",
- instr->id(), instr->block()->block_id()));
- EnsureChecked(entry, value, instr);
- instr->DeleteAndReplaceWith(value);
- INC_STAT(removed_cit_);
- } else if (maps->size() != 0) {
- entry->maps_ = maps;
- if (entry->state_ == HCheckTableEntry::UNCHECKED_STABLE) {
- entry->state_ = HCheckTableEntry::CHECKED_STABLE;
- }
- }
- }
-
- void ReduceLoadNamedField(HLoadNamedField* instr) {
- // Reduce a load of the map field when it is known to be a constant.
- if (!instr->access().IsMap()) {
- // Check if we introduce field maps here.
- MapSet maps = instr->maps();
- if (maps != NULL) {
- DCHECK_NE(0, maps->size());
- Insert(instr, NULL, maps, HCheckTableEntry::UNCHECKED_STABLE);
- }
- return;
- }
-
- HValue* object = instr->object()->ActualValue();
- HCheckTableEntry* entry = Find(object);
- if (entry == NULL || entry->maps_->size() != 1) return; // Not a constant.
-
- EnsureChecked(entry, object, instr);
- Unique<Map> map = entry->maps_->at(0);
- bool map_is_stable = (entry->state_ != HCheckTableEntry::CHECKED);
- HConstant* constant = HConstant::CreateAndInsertBefore(
- instr->block()->graph()->zone(), map, map_is_stable, instr);
- instr->DeleteAndReplaceWith(constant);
- INC_STAT(loads_);
- }
-
- void ReduceCheckHeapObject(HCheckHeapObject* instr) {
- HValue* value = instr->value()->ActualValue();
- if (Find(value) != NULL) {
- // If the object has known maps, it's definitely a heap object.
- instr->DeleteAndReplaceWith(value);
- INC_STAT(removed_cho_);
- }
- }
-
- void ReduceStoreNamedField(HStoreNamedField* instr) {
- HValue* object = instr->object()->ActualValue();
- if (instr->has_transition()) {
- // This store transitions the object to a new map.
- Kill(object);
- HConstant* c_transition = HConstant::cast(instr->transition());
- HCheckTableEntry::State state = c_transition->HasStableMapValue()
- ? HCheckTableEntry::CHECKED_STABLE
- : HCheckTableEntry::CHECKED;
- Insert(object, NULL, c_transition->MapValue(), state);
- } else if (instr->access().IsMap()) {
- // This is a store directly to the map field of the object.
- Kill(object);
- if (!instr->value()->IsConstant()) return;
- HConstant* c_value = HConstant::cast(instr->value());
- HCheckTableEntry::State state = c_value->HasStableMapValue()
- ? HCheckTableEntry::CHECKED_STABLE
- : HCheckTableEntry::CHECKED;
- Insert(object, NULL, c_value->MapValue(), state);
- } else {
- // If the instruction changes maps, it should be handled above.
- CHECK(!instr->CheckChangesFlag(kMaps));
- }
- }
-
- void ReduceCompareMap(HCompareMap* instr) {
- HCheckTableEntry* entry = Find(instr->value()->ActualValue());
- if (entry == NULL) return;
-
- EnsureChecked(entry, instr->value(), instr);
-
- int succ;
- if (entry->maps_->Contains(instr->map())) {
- if (entry->maps_->size() != 1) {
- TRACE(("CompareMap #%d for #%d at B%d can't be eliminated: "
- "ambiguous set of maps\n", instr->id(), instr->value()->id(),
- instr->block()->block_id()));
- return;
- }
- succ = 0;
- INC_STAT(compares_true_);
- } else {
- succ = 1;
- INC_STAT(compares_false_);
- }
-
- TRACE(("Marking redundant CompareMap #%d for #%d at B%d as %s\n",
- instr->id(), instr->value()->id(), instr->block()->block_id(),
- succ == 0 ? "true" : "false"));
- instr->set_known_successor_index(succ);
-
- int unreachable_succ = 1 - succ;
- instr->block()->MarkSuccEdgeUnreachable(unreachable_succ);
- }
-
- void ReduceCompareObjectEqAndBranch(HCompareObjectEqAndBranch* instr) {
- HValue* left = instr->left()->ActualValue();
- HCheckTableEntry* le = Find(left);
- if (le == NULL) return;
- HValue* right = instr->right()->ActualValue();
- HCheckTableEntry* re = Find(right);
- if (re == NULL) return;
-
- EnsureChecked(le, left, instr);
- EnsureChecked(re, right, instr);
-
- // TODO(bmeurer): Add a predicate here instead of computing the intersection
- MapSet intersection = le->maps_->Intersect(re->maps_, zone());
- if (intersection->size() > 0) return;
-
- TRACE(("Marking redundant CompareObjectEqAndBranch #%d at B%d as false\n",
- instr->id(), instr->block()->block_id()));
- int succ = 1;
- instr->set_known_successor_index(succ);
-
- int unreachable_succ = 1 - succ;
- instr->block()->MarkSuccEdgeUnreachable(unreachable_succ);
- }
-
- void ReduceIsStringAndBranch(HIsStringAndBranch* instr) {
- HValue* value = instr->value()->ActualValue();
- HCheckTableEntry* entry = Find(value);
- if (entry == NULL) return;
- EnsureChecked(entry, value, instr);
- int succ;
- if (entry->maps_->IsSubset(string_maps())) {
- TRACE(("Marking redundant IsStringAndBranch #%d at B%d as true\n",
- instr->id(), instr->block()->block_id()));
- succ = 0;
- } else {
- MapSet intersection = entry->maps_->Intersect(string_maps(), zone());
- if (intersection->size() > 0) return;
- TRACE(("Marking redundant IsStringAndBranch #%d at B%d as false\n",
- instr->id(), instr->block()->block_id()));
- succ = 1;
- }
- instr->set_known_successor_index(succ);
- int unreachable_succ = 1 - succ;
- instr->block()->MarkSuccEdgeUnreachable(unreachable_succ);
- }
-
- void ReduceTransitionElementsKind(HTransitionElementsKind* instr) {
- HValue* object = instr->object()->ActualValue();
- HCheckTableEntry* entry = Find(object);
- // Can only learn more about an object that already has a known set of maps.
- if (entry == NULL) {
- Kill(object);
- return;
- }
- EnsureChecked(entry, object, instr);
- if (entry->maps_->Contains(instr->original_map())) {
- // If the object has the original map, it will be transitioned.
- UniqueSet<Map>* maps = entry->maps_->Copy(zone());
- maps->Remove(instr->original_map());
- maps->Add(instr->transitioned_map(), zone());
- HCheckTableEntry::State state =
- (entry->state_ == HCheckTableEntry::CHECKED_STABLE &&
- instr->map_is_stable())
- ? HCheckTableEntry::CHECKED_STABLE
- : HCheckTableEntry::CHECKED;
- Kill(object);
- Insert(object, NULL, maps, state);
- } else {
- // Object does not have the given map, thus the transition is redundant.
- instr->DeleteAndReplaceWith(object);
- INC_STAT(transitions_);
- }
- }
-
- void EnsureChecked(HCheckTableEntry* entry,
- HValue* value,
- HInstruction* instr) {
- if (entry->state_ != HCheckTableEntry::UNCHECKED_STABLE) return;
- HGraph* graph = instr->block()->graph();
- HCheckMaps* check = HCheckMaps::CreateAndInsertBefore(
- graph->zone(), value, entry->maps_->Copy(graph->zone()), true, instr);
- check->MarkAsStabilityCheck();
- entry->state_ = HCheckTableEntry::CHECKED_STABLE;
- entry->check_ = NULL;
- }
-
- // Kill everything in the table.
- void Kill() {
- size_ = 0;
- cursor_ = 0;
- }
-
- // Kill all unstable entries in the table.
- void KillUnstableEntries() {
- bool compact = false;
- for (int i = 0; i < size_; ++i) {
- HCheckTableEntry* entry = &entries_[i];
- DCHECK_NOT_NULL(entry->object_);
- if (entry->state_ == HCheckTableEntry::CHECKED) {
- entry->object_ = NULL;
- compact = true;
- } else {
- // All checked stable entries become unchecked stable.
- entry->state_ = HCheckTableEntry::UNCHECKED_STABLE;
- entry->check_ = NULL;
- }
- }
- if (compact) Compact();
- }
-
- // Kill everything in the table that may alias {object}.
- void Kill(HValue* object) {
- bool compact = false;
- for (int i = 0; i < size_; i++) {
- HCheckTableEntry* entry = &entries_[i];
- DCHECK_NOT_NULL(entry->object_);
- if (phase_->aliasing_->MayAlias(entry->object_, object)) {
- entry->object_ = NULL;
- compact = true;
- }
- }
- if (compact) Compact();
- DCHECK_NULL(Find(object));
- }
-
- void Compact() {
- // First, compact the array in place.
- int max = size_, dest = 0, old_cursor = cursor_;
- for (int i = 0; i < max; i++) {
- if (entries_[i].object_ != NULL) {
- if (dest != i) entries_[dest] = entries_[i];
- dest++;
- } else {
- if (i < old_cursor) cursor_--;
- size_--;
- }
- }
- DCHECK(size_ == dest);
- DCHECK(cursor_ <= size_);
-
- // Preserve the age of the entries by moving the older entries to the end.
- if (cursor_ == size_) return; // Cursor already points at end.
- if (cursor_ != 0) {
- // | L = oldest | R = newest | |
- // ^ cursor ^ size ^ MAX
- HCheckTableEntry tmp_entries[kMaxTrackedObjects];
- int L = cursor_;
- int R = size_ - cursor_;
-
- MemMove(&tmp_entries[0], &entries_[0], L * sizeof(HCheckTableEntry));
- MemMove(&entries_[0], &entries_[L], R * sizeof(HCheckTableEntry));
- MemMove(&entries_[R], &tmp_entries[0], L * sizeof(HCheckTableEntry));
- }
-
- cursor_ = size_; // Move cursor to end.
- }
-
- static void Print(HCheckTable* table) {
- if (table == NULL) {
- PrintF(" unreachable\n");
- return;
- }
-
- for (int i = 0; i < table->size_; i++) {
- HCheckTableEntry* entry = &table->entries_[i];
- DCHECK(entry->object_ != NULL);
- PrintF(" checkmaps-table @%d: %s #%d ", i,
- entry->object_->IsPhi() ? "phi" : "object", entry->object_->id());
- if (entry->check_ != NULL) {
- PrintF("check #%d ", entry->check_->id());
- }
- MapSet list = entry->maps_;
- PrintF("%d %s maps { ", list->size(),
- HCheckTableEntry::State2String(entry->state_));
- for (int j = 0; j < list->size(); j++) {
- if (j > 0) PrintF(", ");
- PrintF("%" V8PRIxPTR, list->at(j).Hashcode());
- }
- PrintF(" }\n");
- }
- }
-
- HCheckTableEntry* Find(HValue* object) {
- for (int i = size_ - 1; i >= 0; i--) {
- // Search from most-recently-inserted to least-recently-inserted.
- HCheckTableEntry* entry = &entries_[i];
- DCHECK(entry->object_ != NULL);
- if (phase_->aliasing_->MustAlias(entry->object_, object)) return entry;
- }
- return NULL;
- }
-
- void Insert(HValue* object,
- HInstruction* check,
- Unique<Map> map,
- HCheckTableEntry::State state) {
- Insert(object, check, new(zone()) UniqueSet<Map>(map, zone()), state);
- }
-
- void Insert(HValue* object,
- HInstruction* check,
- MapSet maps,
- HCheckTableEntry::State state) {
- DCHECK(state != HCheckTableEntry::UNCHECKED_STABLE || check == NULL);
- HCheckTableEntry* entry = &entries_[cursor_++];
- entry->object_ = object;
- entry->check_ = check;
- entry->maps_ = maps;
- entry->state_ = state;
- // If the table becomes full, wrap around and overwrite older entries.
- if (cursor_ == kMaxTrackedObjects) cursor_ = 0;
- if (size_ < kMaxTrackedObjects) size_++;
- }
-
- Zone* zone() const { return phase_->zone(); }
- MapSet string_maps() const { return phase_->string_maps(); }
-
- friend class HCheckMapsEffects;
- friend class HCheckEliminationPhase;
-
- HCheckEliminationPhase* phase_;
- HCheckTableEntry entries_[kMaxTrackedObjects];
- int16_t cursor_; // Must be <= kMaxTrackedObjects
- int16_t size_; // Must be <= kMaxTrackedObjects
- STATIC_ASSERT(kMaxTrackedObjects < (1 << 15));
-};
-
-
-// Collects instructions that can cause effects that invalidate information
-// needed for check elimination.
-class HCheckMapsEffects : public ZoneObject {
- public:
- explicit HCheckMapsEffects(Zone* zone) : objects_(0, zone) { }
-
- // Effects are _not_ disabled.
- inline bool Disabled() const { return false; }
-
- // Process a possibly side-effecting instruction.
- void Process(HInstruction* instr, Zone* zone) {
- switch (instr->opcode()) {
- case HValue::kStoreNamedField: {
- HStoreNamedField* store = HStoreNamedField::cast(instr);
- if (store->access().IsMap() || store->has_transition()) {
- objects_.Add(store->object(), zone);
- }
- break;
- }
- case HValue::kTransitionElementsKind: {
- objects_.Add(HTransitionElementsKind::cast(instr)->object(), zone);
- break;
- }
- default: {
- flags_.Add(instr->ChangesFlags());
- break;
- }
- }
- }
-
- // Apply these effects to the given check elimination table.
- void Apply(HCheckTable* table) {
- if (flags_.Contains(kOsrEntries)) {
- // Uncontrollable map modifications; kill everything.
- table->Kill();
- return;
- }
-
- // Kill all unstable entries.
- if (flags_.Contains(kElementsKind) || flags_.Contains(kMaps)) {
- table->KillUnstableEntries();
- }
-
- // Kill maps for each object contained in these effects.
- for (int i = 0; i < objects_.length(); ++i) {
- table->Kill(objects_[i]->ActualValue());
- }
- }
-
- // Union these effects with the other effects.
- void Union(HCheckMapsEffects* that, Zone* zone) {
- flags_.Add(that->flags_);
- for (int i = 0; i < that->objects_.length(); ++i) {
- objects_.Add(that->objects_[i], zone);
- }
- }
-
- private:
- ZoneList<HValue*> objects_;
- GVNFlagSet flags_;
-};
-
-
-// The main routine of the analysis phase. Use the HFlowEngine for either a
-// local or a global analysis.
-void HCheckEliminationPhase::Run() {
- HFlowEngine<HCheckTable, HCheckMapsEffects> engine(graph(), zone());
- HCheckTable* table = new(zone()) HCheckTable(this);
-
- if (GLOBAL) {
- // Perform a global analysis.
- engine.AnalyzeDominatedBlocks(graph()->blocks()->at(0), table);
- } else {
- // Perform only local analysis.
- for (int i = 0; i < graph()->blocks()->length(); i++) {
- table->Kill();
- engine.AnalyzeOneBlock(graph()->blocks()->at(i), table);
- }
- }
-
- if (FLAG_trace_check_elimination) PrintStats();
-}
-
-
-// Are we eliminated yet?
-void HCheckEliminationPhase::PrintStats() {
-#if DEBUG
- #define PRINT_STAT(x) if (x##_ > 0) PrintF(" %-16s = %2d\n", #x, x##_)
-#else
- #define PRINT_STAT(x)
-#endif
- PRINT_STAT(redundant);
- PRINT_STAT(removed);
- PRINT_STAT(removed_cho);
- PRINT_STAT(removed_cit);
- PRINT_STAT(narrowed);
- PRINT_STAT(loads);
- PRINT_STAT(empty);
- PRINT_STAT(compares_true);
- PRINT_STAT(compares_false);
- PRINT_STAT(transitions);
-}
-
-} // namespace internal
-} // namespace v8
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