[turbofan] Split JSGlobalObjectSpecialization into separate class.

src/compiler/js-global-object-specialization.cc

+// Copyright 2015 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/js-global-object-specialization.h"
+
+#include "src/compilation-dependencies.h"
+#include "src/compiler/access-builder.h"
+#include "src/compiler/common-operator.h"
+#include "src/compiler/js-graph.h"
+#include "src/compiler/js-operator.h"
+#include "src/compiler/node-properties.h"
+#include "src/compiler/simplified-operator.h"
+#include "src/lookup.h"
+#include "src/objects-inl.h"  // TODO(mstarzinger): Temporary cycle breaker!
+#include "src/type-cache.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+struct JSGlobalObjectSpecialization::ScriptContextTableLookupResult {
+  Handle<Context> context;
+  bool immutable;
+  int index;
+};
+
+
+JSGlobalObjectSpecialization::JSGlobalObjectSpecialization(
+    Editor* editor, JSGraph* jsgraph, Flags flags,
+    Handle<JSGlobalObject> global_object, CompilationDependencies* dependencies)
+    : AdvancedReducer(editor),
+      jsgraph_(jsgraph),
+      flags_(flags),
+      global_object_(global_object),
+      script_context_table_(
+          global_object->native_context()->script_context_table(), isolate()),
+      dependencies_(dependencies),
+      type_cache_(TypeCache::Get()) {}
+
+
+Reduction JSGlobalObjectSpecialization::Reduce(Node* node) {
+  switch (node->opcode()) {
+    case IrOpcode::kJSLoadGlobal:
+      return ReduceJSLoadGlobal(node);
+    case IrOpcode::kJSStoreGlobal:
+      return ReduceJSStoreGlobal(node);
+    default:
+      break;
+  }
+  return NoChange();
+}
+
+
+Reduction JSGlobalObjectSpecialization::ReduceJSLoadGlobal(Node* node) {
+  DCHECK_EQ(IrOpcode::kJSLoadGlobal, node->opcode());
+  Handle<Name> name = LoadGlobalParametersOf(node->op()).name();
+  Node* effect = NodeProperties::GetEffectInput(node);
+  Node* control = NodeProperties::GetControlInput(node);
+
+  // Try to lookup the name on the script context table first (lexical scoping).
+  ScriptContextTableLookupResult result;
+  if (LookupInScriptContextTable(name, &result)) {
+    if (result.context->is_the_hole(result.index)) return NoChange();
+    Node* context = jsgraph()->HeapConstant(result.context);
+    Node* value = effect = graph()->NewNode(
+        javascript()->LoadContext(0, result.index, result.immutable), context,
+        context, effect);
+    ReplaceWithValue(node, value, effect);
+    return Replace(value);
+  }
+
+  // Lookup on the global object instead.  We only deal with own data
+  // properties of the global object here (represented as PropertyCell).
+  LookupIterator it(global_object(), name, LookupIterator::OWN);
+  if (it.state() != LookupIterator::DATA) return NoChange();
+  Handle<PropertyCell> property_cell = it.GetPropertyCell();
+  PropertyDetails property_details = property_cell->property_details();
+  Handle<Object> property_cell_value(property_cell->value(), isolate());
+
+  // Load from non-configurable, read-only data property on the global
+  // object can be constant-folded, even without deoptimization support.
+  if (!property_details.IsConfigurable() && property_details.IsReadOnly()) {
+    Node* value = jsgraph()->Constant(property_cell_value);
+    ReplaceWithValue(node, value);
+    return Replace(value);
+  }
+
+  // Load from non-configurable, data property on the global can be lowered to
+  // a field load, even without deoptimization, because the property cannot be
+  // deleted or reconfigured to an accessor/interceptor property.  Yet, if
+  // deoptimization support is available, we can constant-fold certain global
+  // properties or at least lower them to field loads annotated with more
+  // precise type feedback.
+  Type* property_cell_value_type = Type::Tagged();
+  if (flags() & kDeoptimizationEnabled) {
+    // Record a code dependency on the cell if we can benefit from the
+    // additional feedback, or the global property is configurable (i.e.
+    // can be deleted or reconfigured to an accessor property).
+    if (property_details.cell_type() != PropertyCellType::kMutable ||
+        property_details.IsConfigurable()) {
+      dependencies()->AssumePropertyCell(property_cell);
+    }
+
+    // Load from constant/undefined global property can be constant-folded.
+    if ((property_details.cell_type() == PropertyCellType::kConstant ||
+         property_details.cell_type() == PropertyCellType::kUndefined)) {
+      Node* value = jsgraph()->Constant(property_cell_value);
+      ReplaceWithValue(node, value);
+      return Replace(value);
+    }
+
+    // Load from constant type cell can benefit from type feedback.
+    if (property_details.cell_type() == PropertyCellType::kConstantType) {
+      // Compute proper type based on the current value in the cell.
+      if (property_cell_value->IsSmi()) {
+        property_cell_value_type = type_cache_.kSmi;
+      } else if (property_cell_value->IsNumber()) {
+        property_cell_value_type = type_cache_.kHeapNumber;
+      } else {
+        Handle<Map> property_cell_value_map(
+            Handle<HeapObject>::cast(property_cell_value)->map(), isolate());
+        property_cell_value_type =
+            Type::Class(property_cell_value_map, graph()->zone());
+      }
+    }
+  } else if (property_details.IsConfigurable()) {
+    // Access to configurable global properties requires deoptimization support.
+    return NoChange();
+  }
+  Node* value = effect = graph()->NewNode(
+      simplified()->LoadField(
+          AccessBuilder::ForPropertyCellValue(property_cell_value_type)),
+      jsgraph()->HeapConstant(property_cell), effect, control);
+  ReplaceWithValue(node, value, effect, control);
+  return Replace(value);
+}
+
+
+Reduction JSGlobalObjectSpecialization::ReduceJSStoreGlobal(Node* node) {
+  DCHECK_EQ(IrOpcode::kJSStoreGlobal, node->opcode());
+  Handle<Name> name = StoreGlobalParametersOf(node->op()).name();
+  Node* value = NodeProperties::GetValueInput(node, 0);
+  Node* frame_state = NodeProperties::GetFrameStateInput(node, 1);
+  Node* effect = NodeProperties::GetEffectInput(node);
+  Node* control = NodeProperties::GetControlInput(node);
+
+  // Try to lookup the name on the script context table first (lexical scoping).
+  ScriptContextTableLookupResult result;
+  if (LookupInScriptContextTable(name, &result)) {
+    if (result.context->is_the_hole(result.index)) return NoChange();
+    if (result.immutable) return NoChange();
+    Node* context = jsgraph()->HeapConstant(result.context);
+    effect = graph()->NewNode(javascript()->StoreContext(0, result.index),
+                              context, value, context, effect, control);
+    ReplaceWithValue(node, value, effect, control);
+    return Replace(value);
+  }
+
+  // Lookup on the global object instead.  We only deal with own data
+  // properties of the global object here (represented as PropertyCell).
+  LookupIterator it(global_object(), name, LookupIterator::OWN);
+  if (it.state() != LookupIterator::DATA) return NoChange();
+  Handle<PropertyCell> property_cell = it.GetPropertyCell();
+  PropertyDetails property_details = property_cell->property_details();
+  Handle<Object> property_cell_value(property_cell->value(), isolate());
+
+  // Don't even bother trying to lower stores to read-only data properties.
+  if (property_details.IsReadOnly()) return NoChange();
+  switch (property_details.cell_type()) {
+    case PropertyCellType::kUndefined: {
+      return NoChange();
+    }
+    case PropertyCellType::kConstant: {
+      // Store to constant property cell requires deoptimization support,
+      // because we might even need to eager deoptimize for mismatch.
+      if (!(flags() & kDeoptimizationEnabled)) return NoChange();
+      dependencies()->AssumePropertyCell(property_cell);
+      Node* check =
+          graph()->NewNode(simplified()->ReferenceEqual(Type::Tagged()), value,
+                           jsgraph()->Constant(property_cell_value));
+      Node* branch =
+          graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control);
+      Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+      Node* deoptimize = graph()->NewNode(common()->Deoptimize(), frame_state,
+                                          effect, if_false);
+      // TODO(bmeurer): This should be on the AdvancedReducer somehow.
+      NodeProperties::MergeControlToEnd(graph(), common(), deoptimize);
+      control = graph()->NewNode(common()->IfTrue(), branch);
+      break;
+    }
+    case PropertyCellType::kConstantType: {
+      // Store to constant-type property cell requires deoptimization support,
+      // because we might even need to eager deoptimize for mismatch.
+      if (!(flags() & kDeoptimizationEnabled)) return NoChange();
+      dependencies()->AssumePropertyCell(property_cell);
+      Node* check = graph()->NewNode(simplified()->ObjectIsSmi(), value);
+      if (property_cell_value->IsHeapObject()) {
+        Node* branch = graph()->NewNode(common()->Branch(BranchHint::kFalse),
+                                        check, control);
+        Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+        Node* deoptimize = graph()->NewNode(common()->Deoptimize(), frame_state,
+                                            effect, if_true);
+        // TODO(bmeurer): This should be on the AdvancedReducer somehow.
+        NodeProperties::MergeControlToEnd(graph(), common(), deoptimize);
+        control = graph()->NewNode(common()->IfFalse(), branch);
+        Node* value_map =
+            graph()->NewNode(simplified()->LoadField(AccessBuilder::ForMap()),
+                             value, effect, control);
+        Handle<Map> property_cell_value_map(
+            Handle<HeapObject>::cast(property_cell_value)->map(), isolate());
+        check = graph()->NewNode(
+            simplified()->ReferenceEqual(Type::Any()), value_map,
+            jsgraph()->HeapConstant(property_cell_value_map));
+      }
+      Node* branch =
+          graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control);
+      Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+      Node* deoptimize = graph()->NewNode(common()->Deoptimize(), frame_state,
+                                          effect, if_false);
+      // TODO(bmeurer): This should be on the AdvancedReducer somehow.
+      NodeProperties::MergeControlToEnd(graph(), common(), deoptimize);
+      control = graph()->NewNode(common()->IfTrue(), branch);
+      effect = graph()->NewNode(
+          simplified()->StoreField(AccessBuilder::ForPropertyCellValue()),
+          jsgraph()->HeapConstant(property_cell), value, effect, control);
+      break;
+    }
+    case PropertyCellType::kMutable: {
+      // Store to non-configurable, data property on the global can be lowered
+      // to a field store, even without deoptimization, because the property
+      // cannot be deleted or reconfigured to an accessor/interceptor property.
+      if (property_details.IsConfigurable()) {
+        // With deoptimization support, we can lower stores even to configurable
+        // data properties on the global object, by adding a code dependency on
+        // the cell.
+        if (!(flags() & kDeoptimizationEnabled)) return NoChange();
+        dependencies()->AssumePropertyCell(property_cell);
+      }
+      effect = graph()->NewNode(
+          simplified()->StoreField(AccessBuilder::ForPropertyCellValue()),
+          jsgraph()->HeapConstant(property_cell), value, effect, control);
+      break;
+    }
+  }
+  ReplaceWithValue(node, value, effect, control);
+  return Replace(value);
+}
+
+
+bool JSGlobalObjectSpecialization::LookupInScriptContextTable(
+    Handle<Name> name, ScriptContextTableLookupResult* result) {
+  if (!name->IsString()) return false;
+  ScriptContextTable::LookupResult lookup_result;
+  if (!ScriptContextTable::Lookup(script_context_table(),
+                                  Handle<String>::cast(name), &lookup_result)) {
+    return false;
+  }
+  Handle<Context> script_context = ScriptContextTable::GetContext(
+      script_context_table(), lookup_result.context_index);
+  result->context = script_context;
+  result->immutable = IsImmutableVariableMode(lookup_result.mode);
+  result->index = lookup_result.slot_index;
+  return true;
+}
+
+
+Graph* JSGlobalObjectSpecialization::graph() const {
+  return jsgraph()->graph();
+}
+
+
+Isolate* JSGlobalObjectSpecialization::isolate() const {
+  return jsgraph()->isolate();
+}
+
+
+CommonOperatorBuilder* JSGlobalObjectSpecialization::common() const {
+  return jsgraph()->common();
+}
+
+
+JSOperatorBuilder* JSGlobalObjectSpecialization::javascript() const {
+  return jsgraph()->javascript();
+}
+
+
+SimplifiedOperatorBuilder* JSGlobalObjectSpecialization::simplified() const {
+  return jsgraph()->simplified();
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8