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912 lines
32 KiB
912 lines
32 KiB
// Copyright 2013 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "src/hydrogen-check-elimination.h"
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#include "src/hydrogen-alias-analysis.h"
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#include "src/hydrogen-flow-engine.h"
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#define GLOBAL 1
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// Only collect stats in debug mode.
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#if DEBUG
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#define INC_STAT(x) phase_->x++
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#else
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#define INC_STAT(x)
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#endif
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// For code de-uglification.
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#define TRACE(x) if (FLAG_trace_check_elimination) PrintF x
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namespace v8 {
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namespace internal {
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typedef const UniqueSet<Map>* MapSet;
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struct HCheckTableEntry {
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enum State {
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// We have seen a map check (i.e. an HCheckMaps) for these maps, so we can
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// use this information to eliminate further map checks, elements kind
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// transitions, etc.
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CHECKED,
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// Same as CHECKED, but we also know that these maps are stable.
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CHECKED_STABLE,
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// These maps are stable, but not checked (i.e. we learned this via field
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// type tracking or from a constant, or they were initially CHECKED_STABLE,
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// but became UNCHECKED_STABLE because of an instruction that changes maps
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// or elements kind), and we need a stability check for them in order to use
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// this information for check elimination (which turns them back to
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// CHECKED_STABLE).
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UNCHECKED_STABLE
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};
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static const char* State2String(State state) {
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switch (state) {
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case CHECKED: return "checked";
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case CHECKED_STABLE: return "checked stable";
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case UNCHECKED_STABLE: return "unchecked stable";
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}
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UNREACHABLE();
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return NULL;
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}
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static State StateMerge(State state1, State state2) {
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if (state1 == state2) return state1;
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if ((state1 == CHECKED && state2 == CHECKED_STABLE) ||
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(state2 == CHECKED && state1 == CHECKED_STABLE)) {
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return CHECKED;
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}
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DCHECK((state1 == CHECKED_STABLE && state2 == UNCHECKED_STABLE) ||
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(state2 == CHECKED_STABLE && state1 == UNCHECKED_STABLE));
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return UNCHECKED_STABLE;
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}
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HValue* object_; // The object being approximated. NULL => invalid entry.
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HInstruction* check_; // The last check instruction.
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MapSet maps_; // The set of known maps for the object.
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State state_; // The state of this entry.
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};
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// The main data structure used during check elimination, which stores a
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// set of known maps for each object.
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class HCheckTable : public ZoneObject {
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public:
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static const int kMaxTrackedObjects = 16;
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explicit HCheckTable(HCheckEliminationPhase* phase)
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: phase_(phase),
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cursor_(0),
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size_(0) {
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}
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// The main processing of instructions.
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HCheckTable* Process(HInstruction* instr, Zone* zone) {
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switch (instr->opcode()) {
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case HValue::kCheckMaps: {
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ReduceCheckMaps(HCheckMaps::cast(instr));
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break;
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}
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case HValue::kLoadNamedField: {
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ReduceLoadNamedField(HLoadNamedField::cast(instr));
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break;
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}
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case HValue::kStoreNamedField: {
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ReduceStoreNamedField(HStoreNamedField::cast(instr));
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break;
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}
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case HValue::kCompareMap: {
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ReduceCompareMap(HCompareMap::cast(instr));
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break;
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}
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case HValue::kCompareObjectEqAndBranch: {
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ReduceCompareObjectEqAndBranch(HCompareObjectEqAndBranch::cast(instr));
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break;
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}
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case HValue::kIsStringAndBranch: {
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ReduceIsStringAndBranch(HIsStringAndBranch::cast(instr));
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break;
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}
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case HValue::kTransitionElementsKind: {
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ReduceTransitionElementsKind(
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HTransitionElementsKind::cast(instr));
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break;
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}
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case HValue::kCheckHeapObject: {
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ReduceCheckHeapObject(HCheckHeapObject::cast(instr));
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break;
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}
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case HValue::kCheckInstanceType: {
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ReduceCheckInstanceType(HCheckInstanceType::cast(instr));
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break;
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}
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default: {
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// If the instruction changes maps uncontrollably, drop everything.
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if (instr->CheckChangesFlag(kOsrEntries)) {
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Kill();
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break;
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}
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if (instr->CheckChangesFlag(kElementsKind) ||
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instr->CheckChangesFlag(kMaps)) {
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KillUnstableEntries();
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}
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}
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// Improvements possible:
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// - eliminate redundant HCheckSmi instructions
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// - track which values have been HCheckHeapObject'd
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}
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return this;
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}
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// Support for global analysis with HFlowEngine: Merge given state with
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// the other incoming state.
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static HCheckTable* Merge(HCheckTable* succ_state, HBasicBlock* succ_block,
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HCheckTable* pred_state, HBasicBlock* pred_block,
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Zone* zone) {
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if (pred_state == NULL || pred_block->IsUnreachable()) {
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return succ_state;
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}
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if (succ_state == NULL) {
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return pred_state->Copy(succ_block, pred_block, zone);
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} else {
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return succ_state->Merge(succ_block, pred_state, pred_block, zone);
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}
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}
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// Support for global analysis with HFlowEngine: Given state merged with all
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// the other incoming states, prepare it for use.
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static HCheckTable* Finish(HCheckTable* state, HBasicBlock* block,
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Zone* zone) {
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if (state == NULL) {
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block->MarkUnreachable();
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} else if (block->IsUnreachable()) {
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state = NULL;
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}
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if (FLAG_trace_check_elimination) {
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PrintF("Processing B%d, checkmaps-table:\n", block->block_id());
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Print(state);
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}
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return state;
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}
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private:
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// Copy state to successor block.
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HCheckTable* Copy(HBasicBlock* succ, HBasicBlock* from_block, Zone* zone) {
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HCheckTable* copy = new(zone) HCheckTable(phase_);
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for (int i = 0; i < size_; i++) {
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HCheckTableEntry* old_entry = &entries_[i];
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DCHECK(old_entry->maps_->size() > 0);
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HCheckTableEntry* new_entry = ©->entries_[i];
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new_entry->object_ = old_entry->object_;
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new_entry->maps_ = old_entry->maps_;
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new_entry->state_ = old_entry->state_;
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// Keep the check if the existing check's block dominates the successor.
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if (old_entry->check_ != NULL &&
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old_entry->check_->block()->Dominates(succ)) {
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new_entry->check_ = old_entry->check_;
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} else {
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// Leave it NULL till we meet a new check instruction for this object
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// in the control flow.
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new_entry->check_ = NULL;
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}
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}
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copy->cursor_ = cursor_;
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copy->size_ = size_;
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// Create entries for succ block's phis.
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if (!succ->IsLoopHeader() && succ->phis()->length() > 0) {
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int pred_index = succ->PredecessorIndexOf(from_block);
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for (int phi_index = 0;
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phi_index < succ->phis()->length();
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++phi_index) {
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HPhi* phi = succ->phis()->at(phi_index);
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HValue* phi_operand = phi->OperandAt(pred_index);
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HCheckTableEntry* pred_entry = copy->Find(phi_operand);
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if (pred_entry != NULL) {
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// Create an entry for a phi in the table.
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copy->Insert(phi, NULL, pred_entry->maps_, pred_entry->state_);
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}
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}
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}
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// Branch-sensitive analysis for certain comparisons may add more facts
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// to the state for the successor on the true branch.
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bool learned = false;
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if (succ->predecessors()->length() == 1) {
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HControlInstruction* end = succ->predecessors()->at(0)->end();
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bool is_true_branch = end->SuccessorAt(0) == succ;
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if (end->IsCompareMap()) {
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HCompareMap* cmp = HCompareMap::cast(end);
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HValue* object = cmp->value()->ActualValue();
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HCheckTableEntry* entry = copy->Find(object);
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if (is_true_branch) {
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HCheckTableEntry::State state = cmp->map_is_stable()
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? HCheckTableEntry::CHECKED_STABLE
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: HCheckTableEntry::CHECKED;
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// Learn on the true branch of if(CompareMap(x)).
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if (entry == NULL) {
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copy->Insert(object, cmp, cmp->map(), state);
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} else {
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entry->maps_ = new(zone) UniqueSet<Map>(cmp->map(), zone);
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entry->check_ = cmp;
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entry->state_ = state;
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}
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} else {
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// Learn on the false branch of if(CompareMap(x)).
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if (entry != NULL) {
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EnsureChecked(entry, object, cmp);
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UniqueSet<Map>* maps = entry->maps_->Copy(zone);
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maps->Remove(cmp->map());
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entry->maps_ = maps;
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DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
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}
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}
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learned = true;
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} else if (is_true_branch && end->IsCompareObjectEqAndBranch()) {
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// Learn on the true branch of if(CmpObjectEq(x, y)).
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HCompareObjectEqAndBranch* cmp =
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HCompareObjectEqAndBranch::cast(end);
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HValue* left = cmp->left()->ActualValue();
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HValue* right = cmp->right()->ActualValue();
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HCheckTableEntry* le = copy->Find(left);
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HCheckTableEntry* re = copy->Find(right);
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if (le == NULL) {
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if (re != NULL) {
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copy->Insert(left, NULL, re->maps_, re->state_);
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}
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} else if (re == NULL) {
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copy->Insert(right, NULL, le->maps_, le->state_);
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} else {
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EnsureChecked(le, cmp->left(), cmp);
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EnsureChecked(re, cmp->right(), cmp);
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le->maps_ = re->maps_ = le->maps_->Intersect(re->maps_, zone);
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le->state_ = re->state_ = HCheckTableEntry::StateMerge(
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le->state_, re->state_);
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DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, le->state_);
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DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, re->state_);
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}
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learned = true;
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} else if (end->IsIsStringAndBranch()) {
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HIsStringAndBranch* cmp = HIsStringAndBranch::cast(end);
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HValue* object = cmp->value()->ActualValue();
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HCheckTableEntry* entry = copy->Find(object);
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if (is_true_branch) {
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// Learn on the true branch of if(IsString(x)).
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if (entry == NULL) {
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copy->Insert(object, NULL, string_maps(),
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HCheckTableEntry::CHECKED);
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} else {
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EnsureChecked(entry, object, cmp);
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entry->maps_ = entry->maps_->Intersect(string_maps(), zone);
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DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
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}
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} else {
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// Learn on the false branch of if(IsString(x)).
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if (entry != NULL) {
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EnsureChecked(entry, object, cmp);
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entry->maps_ = entry->maps_->Subtract(string_maps(), zone);
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DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
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}
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}
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}
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// Learning on false branches requires storing negative facts.
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}
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if (FLAG_trace_check_elimination) {
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PrintF("B%d checkmaps-table %s from B%d:\n",
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succ->block_id(),
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learned ? "learned" : "copied",
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from_block->block_id());
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Print(copy);
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}
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return copy;
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}
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// Merge this state with the other incoming state.
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HCheckTable* Merge(HBasicBlock* succ, HCheckTable* that,
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HBasicBlock* pred_block, Zone* zone) {
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if (that->size_ == 0) {
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// If the other state is empty, simply reset.
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size_ = 0;
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cursor_ = 0;
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} else {
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int pred_index = succ->PredecessorIndexOf(pred_block);
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bool compact = false;
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for (int i = 0; i < size_; i++) {
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HCheckTableEntry* this_entry = &entries_[i];
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HCheckTableEntry* that_entry;
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if (this_entry->object_->IsPhi() &&
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this_entry->object_->block() == succ) {
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HPhi* phi = HPhi::cast(this_entry->object_);
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HValue* phi_operand = phi->OperandAt(pred_index);
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that_entry = that->Find(phi_operand);
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} else {
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that_entry = that->Find(this_entry->object_);
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}
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if (that_entry == NULL ||
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(that_entry->state_ == HCheckTableEntry::CHECKED &&
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this_entry->state_ == HCheckTableEntry::UNCHECKED_STABLE) ||
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(this_entry->state_ == HCheckTableEntry::CHECKED &&
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that_entry->state_ == HCheckTableEntry::UNCHECKED_STABLE)) {
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this_entry->object_ = NULL;
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compact = true;
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} else {
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this_entry->maps_ =
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this_entry->maps_->Union(that_entry->maps_, zone);
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this_entry->state_ = HCheckTableEntry::StateMerge(
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this_entry->state_, that_entry->state_);
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if (this_entry->check_ != that_entry->check_) {
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this_entry->check_ = NULL;
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}
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DCHECK(this_entry->maps_->size() > 0);
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}
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}
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if (compact) Compact();
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}
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if (FLAG_trace_check_elimination) {
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PrintF("B%d checkmaps-table merged with B%d table:\n",
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succ->block_id(), pred_block->block_id());
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Print(this);
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}
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return this;
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}
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void ReduceCheckMaps(HCheckMaps* instr) {
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HValue* object = instr->value()->ActualValue();
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HCheckTableEntry* entry = Find(object);
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if (entry != NULL) {
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// entry found;
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HGraph* graph = instr->block()->graph();
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if (entry->maps_->IsSubset(instr->maps())) {
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// The first check is more strict; the second is redundant.
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if (entry->check_ != NULL) {
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DCHECK_NE(HCheckTableEntry::UNCHECKED_STABLE, entry->state_);
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TRACE(("Replacing redundant CheckMaps #%d at B%d with #%d\n",
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instr->id(), instr->block()->block_id(), entry->check_->id()));
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instr->DeleteAndReplaceWith(entry->check_);
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INC_STAT(redundant_);
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} else if (entry->state_ == HCheckTableEntry::UNCHECKED_STABLE) {
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DCHECK_NULL(entry->check_);
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TRACE(("Marking redundant CheckMaps #%d at B%d as stability check\n",
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instr->id(), instr->block()->block_id()));
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instr->set_maps(entry->maps_->Copy(graph->zone()));
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instr->MarkAsStabilityCheck();
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entry->state_ = HCheckTableEntry::CHECKED_STABLE;
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} else if (!instr->IsStabilityCheck()) {
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TRACE(("Marking redundant CheckMaps #%d at B%d as dead\n",
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instr->id(), instr->block()->block_id()));
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// Mark check as dead but leave it in the graph as a checkpoint for
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// subsequent checks.
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instr->SetFlag(HValue::kIsDead);
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entry->check_ = instr;
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INC_STAT(removed_);
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}
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return;
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}
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MapSet intersection = instr->maps()->Intersect(
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entry->maps_, graph->zone());
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if (intersection->size() == 0) {
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// Intersection is empty; probably megamorphic.
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INC_STAT(empty_);
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entry->object_ = NULL;
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Compact();
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} else {
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// Update set of maps in the entry.
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entry->maps_ = intersection;
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// Update state of the entry.
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if (instr->maps_are_stable() ||
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entry->state_ == HCheckTableEntry::UNCHECKED_STABLE) {
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entry->state_ = HCheckTableEntry::CHECKED_STABLE;
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}
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if (intersection->size() != instr->maps()->size()) {
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// Narrow set of maps in the second check maps instruction.
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if (entry->check_ != NULL &&
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entry->check_->block() == instr->block() &&
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entry->check_->IsCheckMaps()) {
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// There is a check in the same block so replace it with a more
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// strict check and eliminate the second check entirely.
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HCheckMaps* check = HCheckMaps::cast(entry->check_);
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DCHECK(!check->IsStabilityCheck());
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TRACE(("CheckMaps #%d at B%d narrowed\n", check->id(),
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check->block()->block_id()));
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// Update map set and ensure that the check is alive.
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check->set_maps(intersection);
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check->ClearFlag(HValue::kIsDead);
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TRACE(("Replacing redundant CheckMaps #%d at B%d with #%d\n",
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instr->id(), instr->block()->block_id(), entry->check_->id()));
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instr->DeleteAndReplaceWith(entry->check_);
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} else {
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TRACE(("CheckMaps #%d at B%d narrowed\n", instr->id(),
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instr->block()->block_id()));
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instr->set_maps(intersection);
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entry->check_ = instr->IsStabilityCheck() ? NULL : instr;
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}
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if (FLAG_trace_check_elimination) {
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Print(this);
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}
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INC_STAT(narrowed_);
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}
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}
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} else {
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// No entry; insert a new one.
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HCheckTableEntry::State state = instr->maps_are_stable()
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? HCheckTableEntry::CHECKED_STABLE
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: HCheckTableEntry::CHECKED;
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HCheckMaps* check = instr->IsStabilityCheck() ? NULL : instr;
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Insert(object, check, instr->maps(), state);
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}
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}
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void ReduceCheckInstanceType(HCheckInstanceType* instr) {
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HValue* value = instr->value()->ActualValue();
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HCheckTableEntry* entry = Find(value);
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if (entry == NULL) {
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if (instr->check() == HCheckInstanceType::IS_STRING) {
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Insert(value, NULL, string_maps(), HCheckTableEntry::CHECKED);
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}
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return;
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}
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UniqueSet<Map>* maps = new(zone()) UniqueSet<Map>(
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entry->maps_->size(), zone());
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for (int i = 0; i < entry->maps_->size(); ++i) {
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InstanceType type;
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Unique<Map> map = entry->maps_->at(i);
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{
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// This is safe, because maps don't move and their instance type does
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// not change.
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AllowHandleDereference allow_deref;
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type = map.handle()->instance_type();
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}
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if (instr->is_interval_check()) {
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InstanceType first_type, last_type;
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instr->GetCheckInterval(&first_type, &last_type);
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if (first_type <= type && type <= last_type) maps->Add(map, zone());
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} else {
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uint8_t mask, tag;
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instr->GetCheckMaskAndTag(&mask, &tag);
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if ((type & mask) == tag) maps->Add(map, zone());
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}
|
|
}
|
|
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 v8::internal
|
|
|