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// Copyright 2017 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/compiler/escape-analysis-reducer.h"
#include "src/compiler/all-nodes.h"
#include "src/compiler/simplified-operator.h"
#include "src/compiler/type-cache.h"
#include "src/frame-constants.h"
namespace v8 {
namespace internal {
namespace compiler {
#ifdef DEBUG
#define TRACE(...) \
do { \
if (FLAG_trace_turbo_escape) PrintF(__VA_ARGS__); \
} while (false)
#else
#define TRACE(...)
#endif // DEBUG
EscapeAnalysisReducer::EscapeAnalysisReducer(
Editor* editor, JSGraph* jsgraph, EscapeAnalysisResult analysis_result,
Zone* zone)
: AdvancedReducer(editor),
jsgraph_(jsgraph),
analysis_result_(analysis_result),
object_id_cache_(zone),
node_cache_(jsgraph->graph(), zone),
arguments_elements_(zone),
zone_(zone) {}
Reduction EscapeAnalysisReducer::ReplaceNode(Node* original,
Node* replacement) {
const VirtualObject* vobject =
analysis_result().GetVirtualObject(replacement);
if (replacement->opcode() == IrOpcode::kDead ||
(vobject && !vobject->HasEscaped())) {
RelaxEffectsAndControls(original);
return Replace(replacement);
}
Type const replacement_type = NodeProperties::GetType(replacement);
Type const original_type = NodeProperties::GetType(original);
if (replacement_type.Is(original_type)) {
RelaxEffectsAndControls(original);
return Replace(replacement);
}
// We need to guard the replacement if we would widen the type otherwise.
DCHECK_EQ(1, original->op()->EffectOutputCount());
DCHECK_EQ(1, original->op()->EffectInputCount());
DCHECK_EQ(1, original->op()->ControlInputCount());
Node* effect = NodeProperties::GetEffectInput(original);
Node* control = NodeProperties::GetControlInput(original);
original->TrimInputCount(0);
original->AppendInput(jsgraph()->zone(), replacement);
original->AppendInput(jsgraph()->zone(), effect);
original->AppendInput(jsgraph()->zone(), control);
NodeProperties::SetType(
original,
Type::Intersect(original_type, replacement_type, jsgraph()->zone()));
NodeProperties::ChangeOp(original,
jsgraph()->common()->TypeGuard(original_type));
ReplaceWithValue(original, original, original, control);
return NoChange();
}
namespace {
Node* SkipTypeGuards(Node* node) {
while (node->opcode() == IrOpcode::kTypeGuard) {
node = NodeProperties::GetValueInput(node, 0);
}
return node;
}
} // namespace
Node* EscapeAnalysisReducer::ObjectIdNode(const VirtualObject* vobject) {
VirtualObject::Id id = vobject->id();
if (id >= object_id_cache_.size()) object_id_cache_.resize(id + 1);
if (!object_id_cache_[id]) {
Node* node = jsgraph()->graph()->NewNode(jsgraph()->common()->ObjectId(id));
NodeProperties::SetType(node, Type::Object());
object_id_cache_[id] = node;
}
return object_id_cache_[id];
}
Reduction EscapeAnalysisReducer::Reduce(Node* node) {
if (Node* replacement = analysis_result().GetReplacementOf(node)) {
DCHECK(node->opcode() != IrOpcode::kAllocate &&
node->opcode() != IrOpcode::kFinishRegion);
DCHECK_NE(replacement, node);
return ReplaceNode(node, replacement);
}
switch (node->opcode()) {
case IrOpcode::kAllocate:
case IrOpcode::kTypeGuard: {
const VirtualObject* vobject = analysis_result().GetVirtualObject(node);
if (vobject && !vobject->HasEscaped()) {
RelaxEffectsAndControls(node);
}
return NoChange();
}
case IrOpcode::kFinishRegion: {
Node* effect = NodeProperties::GetEffectInput(node, 0);
if (effect->opcode() == IrOpcode::kBeginRegion) {
RelaxEffectsAndControls(effect);
RelaxEffectsAndControls(node);
}
return NoChange();
}
case IrOpcode::kNewArgumentsElements:
arguments_elements_.insert(node);
return NoChange();
default: {
// TODO(sigurds): Change this to GetFrameStateInputCount once
// it is working. For now we use EffectInputCount > 0 to determine
// whether a node might have a frame state input.
if (node->op()->EffectInputCount() > 0) {
ReduceFrameStateInputs(node);
}
return NoChange();
}
}
}
// While doing DFS on the FrameState tree, we have to recognize duplicate
// occurrences of virtual objects.
class Deduplicator {
public:
explicit Deduplicator(Zone* zone) : is_duplicate_(zone) {}
bool SeenBefore(const VirtualObject* vobject) {
VirtualObject::Id id = vobject->id();
if (id >= is_duplicate_.size()) {
is_duplicate_.resize(id + 1);
}
bool is_duplicate = is_duplicate_[id];
is_duplicate_[id] = true;
return is_duplicate;
}
private:
ZoneVector<bool> is_duplicate_;
};
void EscapeAnalysisReducer::ReduceFrameStateInputs(Node* node) {
DCHECK_GE(node->op()->EffectInputCount(), 1);
for (int i = 0; i < node->InputCount(); ++i) {
Node* input = node->InputAt(i);
if (input->opcode() == IrOpcode::kFrameState) {
Deduplicator deduplicator(zone());
if (Node* ret = ReduceDeoptState(input, node, &deduplicator)) {
node->ReplaceInput(i, ret);
}
}
}
}
Node* EscapeAnalysisReducer::ReduceDeoptState(Node* node, Node* effect,
Deduplicator* deduplicator) {
if (node->opcode() == IrOpcode::kFrameState) {
NodeHashCache::Constructor new_node(&node_cache_, node);
// This input order is important to match the DFS traversal used in the
// instruction selector. Otherwise, the instruction selector might find a
// duplicate node before the original one.
for (int input_id : {kFrameStateOuterStateInput, kFrameStateFunctionInput,
kFrameStateParametersInput, kFrameStateContextInput,
kFrameStateLocalsInput, kFrameStateStackInput}) {
Node* input = node->InputAt(input_id);
new_node.ReplaceInput(ReduceDeoptState(input, effect, deduplicator),
input_id);
}
return new_node.Get();
} else if (node->opcode() == IrOpcode::kStateValues) {
NodeHashCache::Constructor new_node(&node_cache_, node);
for (int i = 0; i < node->op()->ValueInputCount(); ++i) {
Node* input = NodeProperties::GetValueInput(node, i);
new_node.ReplaceValueInput(ReduceDeoptState(input, effect, deduplicator),
i);
}
return new_node.Get();
} else if (const VirtualObject* vobject =
analysis_result().GetVirtualObject(SkipTypeGuards(node))) {
if (vobject->HasEscaped()) return node;
if (deduplicator->SeenBefore(vobject)) {
return ObjectIdNode(vobject);
} else {
std::vector<Node*> inputs;
for (int offset = 0; offset < vobject->size(); offset += kPointerSize) {
Node* field =
analysis_result().GetVirtualObjectField(vobject, offset, effect);
CHECK_NOT_NULL(field);
if (field != jsgraph()->Dead()) {
inputs.push_back(ReduceDeoptState(field, effect, deduplicator));
}
}
int num_inputs = static_cast<int>(inputs.size());
NodeHashCache::Constructor new_node(
&node_cache_,
jsgraph()->common()->ObjectState(vobject->id(), num_inputs),
num_inputs, &inputs.front(), NodeProperties::GetType(node));
return new_node.Get();
}
} else {
return node;
}
}
void EscapeAnalysisReducer::VerifyReplacement() const {
AllNodes all(zone(), jsgraph()->graph());
for (Node* node : all.reachable) {
if (node->opcode() == IrOpcode::kAllocate) {
if (const VirtualObject* vobject =
analysis_result().GetVirtualObject(node)) {
if (!vobject->HasEscaped()) {
FATAL("Escape analysis failed to remove node %s#%d\n",
node->op()->mnemonic(), node->id());
}
}
}
}
}
void EscapeAnalysisReducer::Finalize() {
for (Node* node : arguments_elements_) {
int mapped_count = NewArgumentsElementsMappedCountOf(node->op());
Node* arguments_frame = NodeProperties::GetValueInput(node, 0);
if (arguments_frame->opcode() != IrOpcode::kArgumentsFrame) continue;
Node* arguments_length = NodeProperties::GetValueInput(node, 1);
if (arguments_length->opcode() != IrOpcode::kArgumentsLength) continue;
// If mapped arguments are specified, then their number is always equal to
// the number of formal parameters. This allows to use just the three-value
// {ArgumentsStateType} enum because the deoptimizer can reconstruct the
// value of {mapped_count} from the number of formal parameters.
DCHECK_IMPLIES(
mapped_count != 0,
mapped_count == FormalParameterCountOf(arguments_length->op()));
ArgumentsStateType type = IsRestLengthOf(arguments_length->op())
? ArgumentsStateType::kRestParameter
: (mapped_count == 0)
? ArgumentsStateType::kUnmappedArguments
: ArgumentsStateType::kMappedArguments;
Node* arguments_length_state = nullptr;
for (Edge edge : arguments_length->use_edges()) {
Node* use = edge.from();
switch (use->opcode()) {
case IrOpcode::kObjectState:
case IrOpcode::kTypedObjectState:
case IrOpcode::kStateValues:
case IrOpcode::kTypedStateValues:
if (!arguments_length_state) {
arguments_length_state = jsgraph()->graph()->NewNode(
jsgraph()->common()->ArgumentsLengthState(type));
NodeProperties::SetType(arguments_length_state,
Type::OtherInternal());
}
edge.UpdateTo(arguments_length_state);
break;
default:
break;
}
}
bool escaping_use = false;
ZoneVector<Node*> loads(zone());
for (Edge edge : node->use_edges()) {
Node* use = edge.from();
if (!NodeProperties::IsValueEdge(edge)) continue;
if (use->use_edges().empty()) {
// A node without uses is dead, so we don't have to care about it.
continue;
}
switch (use->opcode()) {
case IrOpcode::kStateValues:
case IrOpcode::kTypedStateValues:
case IrOpcode::kObjectState:
case IrOpcode::kTypedObjectState:
break;
case IrOpcode::kLoadElement:
if (mapped_count == 0) {
loads.push_back(use);
} else {
escaping_use = true;
}
break;
case IrOpcode::kLoadField:
if (FieldAccessOf(use->op()).offset == FixedArray::kLengthOffset) {
loads.push_back(use);
} else {
escaping_use = true;
}
break;
default:
// If the arguments elements node node is used by an unhandled node,
// then we cannot remove this allocation.
escaping_use = true;
break;
}
if (escaping_use) break;
}
if (!escaping_use) {
Node* arguments_elements_state = jsgraph()->graph()->NewNode(
jsgraph()->common()->ArgumentsElementsState(type));
NodeProperties::SetType(arguments_elements_state, Type::OtherInternal());
ReplaceWithValue(node, arguments_elements_state);
ElementAccess stack_access;
stack_access.base_is_tagged = BaseTaggedness::kUntaggedBase;
// Reduce base address by {kPointerSize} such that (length - index)
// resolves to the right position.
stack_access.header_size =
CommonFrameConstants::kFixedFrameSizeAboveFp - kPointerSize;
stack_access.type = Type::NonInternal();
stack_access.machine_type = MachineType::AnyTagged();
stack_access.write_barrier_kind = WriteBarrierKind::kNoWriteBarrier;
const Operator* load_stack_op =
jsgraph()->simplified()->LoadElement(stack_access);
for (Node* load : loads) {
switch (load->opcode()) {
case IrOpcode::kLoadElement: {
Node* index = NodeProperties::GetValueInput(load, 1);
// {offset} is a reverted index starting from 1. The base address is
// adapted to allow offsets starting from 1.
Node* offset = jsgraph()->graph()->NewNode(
jsgraph()->simplified()->NumberSubtract(), arguments_length,
index);
NodeProperties::SetType(offset,
TypeCache::Get().kArgumentsLengthType);
NodeProperties::ReplaceValueInput(load, arguments_frame, 0);
NodeProperties::ReplaceValueInput(load, offset, 1);
NodeProperties::ChangeOp(load, load_stack_op);
break;
}
case IrOpcode::kLoadField: {
DCHECK_EQ(FieldAccessOf(load->op()).offset,
FixedArray::kLengthOffset);
Node* length = NodeProperties::GetValueInput(node, 1);
ReplaceWithValue(load, length);
break;
}
default:
UNREACHABLE();
}
}
}
}
}
Node* NodeHashCache::Query(Node* node) {
auto it = cache_.find(node);
if (it != cache_.end()) {
return *it;
} else {
return nullptr;
}
}
NodeHashCache::Constructor::Constructor(NodeHashCache* cache,
const Operator* op, int input_count,
Node** inputs, Type type)
: node_cache_(cache), from_(nullptr) {
if (node_cache_->temp_nodes_.size() > 0) {
tmp_ = node_cache_->temp_nodes_.back();
node_cache_->temp_nodes_.pop_back();
int tmp_input_count = tmp_->InputCount();
if (input_count <= tmp_input_count) {
tmp_->TrimInputCount(input_count);
}
for (int i = 0; i < input_count; ++i) {
if (i < tmp_input_count) {
tmp_->ReplaceInput(i, inputs[i]);
} else {
tmp_->AppendInput(node_cache_->graph_->zone(), inputs[i]);
}
}
NodeProperties::ChangeOp(tmp_, op);
} else {
tmp_ = node_cache_->graph_->NewNode(op, input_count, inputs);
}
NodeProperties::SetType(tmp_, type);
}
Node* NodeHashCache::Constructor::Get() {
DCHECK(tmp_ || from_);
Node* node;
if (!tmp_) {
node = node_cache_->Query(from_);
if (!node) node = from_;
} else {
node = node_cache_->Query(tmp_);
if (node) {
node_cache_->temp_nodes_.push_back(tmp_);
} else {
node = tmp_;
node_cache_->Insert(node);
}
}
tmp_ = from_ = nullptr;
return node;
}
Node* NodeHashCache::Constructor::MutableNode() {
DCHECK(tmp_ || from_);
if (!tmp_) {
if (node_cache_->temp_nodes_.empty()) {
tmp_ = node_cache_->graph_->CloneNode(from_);
} else {
tmp_ = node_cache_->temp_nodes_.back();
node_cache_->temp_nodes_.pop_back();
int from_input_count = from_->InputCount();
int tmp_input_count = tmp_->InputCount();
if (from_input_count <= tmp_input_count) {
tmp_->TrimInputCount(from_input_count);
}
for (int i = 0; i < from_input_count; ++i) {
if (i < tmp_input_count) {
tmp_->ReplaceInput(i, from_->InputAt(i));
} else {
tmp_->AppendInput(node_cache_->graph_->zone(), from_->InputAt(i));
}
}
NodeProperties::SetType(tmp_, NodeProperties::GetType(from_));
NodeProperties::ChangeOp(tmp_, from_->op());
}
}
return tmp_;
}
#undef TRACE
} // namespace compiler
} // namespace internal
} // namespace v8
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