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// Copyright 2014 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/base/adapters.h"
#include "src/compiler/js-graph.h"
#include "src/compiler/liveness-analyzer.h"
#include "src/compiler/node.h"
#include "src/compiler/node-matchers.h"
#include "src/compiler/state-values-utils.h"
namespace v8 {
namespace internal {
namespace compiler {
LivenessAnalyzer::LivenessAnalyzer(size_t local_count, Zone* zone)
: zone_(zone), blocks_(zone), local_count_(local_count), queue_(zone) {}
void LivenessAnalyzer::Print(std::ostream& os) {
for (auto block : blocks_) {
block->Print(os);
os << std::endl;
}
}
LivenessAnalyzerBlock* LivenessAnalyzer::NewBlock() {
LivenessAnalyzerBlock* result =
new (zone()->New(sizeof(LivenessAnalyzerBlock)))
LivenessAnalyzerBlock(blocks_.size(), local_count_, zone());
blocks_.push_back(result);
return result;
}
LivenessAnalyzerBlock* LivenessAnalyzer::NewBlock(
LivenessAnalyzerBlock* predecessor) {
LivenessAnalyzerBlock* result = NewBlock();
result->AddPredecessor(predecessor);
return result;
}
void LivenessAnalyzer::Queue(LivenessAnalyzerBlock* block) {
if (!block->IsQueued()) {
block->SetQueued();
queue_.push(block);
}
}
void LivenessAnalyzer::Run(NonLiveFrameStateSlotReplacer* replacer) {
if (local_count_ == 0) {
// No local variables => nothing to do.
return;
}
// Put all blocks into the queue.
DCHECK(queue_.empty());
for (auto block : blocks_) {
Queue(block);
}
// Compute the fix-point.
BitVector working_area(static_cast<int>(local_count_), zone_);
while (!queue_.empty()) {
LivenessAnalyzerBlock* block = queue_.front();
queue_.pop();
block->Process(&working_area, nullptr);
for (auto i = block->pred_begin(); i != block->pred_end(); i++) {
if ((*i)->UpdateLive(&working_area)) {
Queue(*i);
}
}
}
// Update the frame states according to the liveness.
for (auto block : blocks_) {
block->Process(&working_area, replacer);
}
}
LivenessAnalyzerBlock::LivenessAnalyzerBlock(size_t id, size_t local_count,
Zone* zone)
: entries_(zone),
predecessors_(zone),
live_(local_count == 0 ? 1 : static_cast<int>(local_count), zone),
queued_(false),
id_(id) {}
void LivenessAnalyzerBlock::Process(BitVector* result,
NonLiveFrameStateSlotReplacer* replacer) {
queued_ = false;
// Copy the bitvector to the target bit vector.
result->CopyFrom(live_);
for (auto entry : base::Reversed(entries_)) {
switch (entry.kind()) {
case Entry::kLookup:
result->Add(entry.var());
break;
case Entry::kBind:
result->Remove(entry.var());
break;
case Entry::kCheckpoint:
if (replacer != nullptr) {
replacer->ClearNonLiveFrameStateSlots(entry.node(), result);
}
break;
}
}
}
bool LivenessAnalyzerBlock::UpdateLive(BitVector* working_area) {
return live_.UnionIsChanged(*working_area);
}
void NonLiveFrameStateSlotReplacer::ClearNonLiveFrameStateSlots(
Node* frame_state, BitVector* liveness) {
DCHECK_EQ(frame_state->opcode(), IrOpcode::kFrameState);
Node* locals_state = frame_state->InputAt(1);
DCHECK_EQ(locals_state->opcode(), IrOpcode::kStateValues);
int count = static_cast<int>(StateValuesAccess(locals_state).size());
DCHECK_EQ(count == 0 ? 1 : count, liveness->length());
for (int i = 0; i < count; i++) {
bool live = liveness->Contains(i) || permanently_live_.Contains(i);
if (!live || locals_state->InputAt(i) != replacement_node_) {
Node* new_values = ClearNonLiveStateValues(locals_state, liveness);
frame_state->ReplaceInput(1, new_values);
break;
}
}
}
Node* NonLiveFrameStateSlotReplacer::ClearNonLiveStateValues(
Node* values, BitVector* liveness) {
DCHECK(inputs_buffer_.empty());
for (StateValuesAccess::TypedNode node : StateValuesAccess(values)) {
// Index of the next variable is its furure index in the inputs buffer,
// i.e., the buffer's size.
int var = static_cast<int>(inputs_buffer_.size());
bool live = liveness->Contains(var) || permanently_live_.Contains(var);
inputs_buffer_.push_back(live ? node.node : replacement_node_);
}
Node* result = state_values_cache()->GetNodeForValues(
inputs_buffer_.empty() ? nullptr : &(inputs_buffer_.front()),
inputs_buffer_.size());
inputs_buffer_.clear();
return result;
}
void LivenessAnalyzerBlock::Print(std::ostream& os) {
os << "Block " << id();
bool first = true;
for (LivenessAnalyzerBlock* pred : predecessors_) {
if (!first) {
os << ", ";
} else {
os << "; predecessors: ";
first = false;
}
os << pred->id();
}
os << std::endl;
for (auto entry : entries_) {
os << " ";
switch (entry.kind()) {
case Entry::kLookup:
os << "- Lookup " << entry.var() << std::endl;
break;
case Entry::kBind:
os << "- Bind " << entry.var() << std::endl;
break;
case Entry::kCheckpoint:
os << "- Checkpoint " << entry.node()->id() << std::endl;
break;
}
}
if (live_.length() > 0) {
os << " Live set: ";
for (int i = 0; i < live_.length(); i++) {
os << (live_.Contains(i) ? "L" : ".");
}
os << std::endl;
}
}
} // namespace compiler
} // namespace internal
} // namespace v8
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