Use stability to only conditionally flush information from the map check table.

src/hydrogen-instructions.h

 // Copyright 2012 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.
 
 #ifndef V8_HYDROGEN_INSTRUCTIONS_H_
 #define V8_HYDROGEN_INSTRUCTIONS_H_
 
 #include "v8.h"
 
 #include "allocation.h"
@@ skipping 1552 matching lines @@
 
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
   static const int kNoKnownSuccessorIndex = -1;
   int known_successor_index() const { return known_successor_index_; }
   void set_known_successor_index(int known_successor_index) {
     known_successor_index_ = known_successor_index;
   }
 
   Unique<Map> map() const { return map_; }
+  bool map_is_stable() const { return map_is_stable_; }
 
   virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
     return Representation::Tagged();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CompareMap)
 
  protected:
   virtual int RedefinedOperandIndex() { return 0; }
 
  private:
   HCompareMap(HValue* value,
               Handle<Map> map,
               HBasicBlock* true_target = NULL,
               HBasicBlock* false_target = NULL)
       : HUnaryControlInstruction(value, true_target, false_target),
-        known_successor_index_(kNoKnownSuccessorIndex), map_(Unique<Map>(map)) {
-    ASSERT(!map.is_null());
+        known_successor_index_(kNoKnownSuccessorIndex),
+        map_is_stable_(map->is_stable()),
+        map_(Unique<Map>::CreateImmovable(map)) {
     set_representation(Representation::Tagged());
   }
 
-  int known_successor_index_;
+  int known_successor_index_ : 31;
+  bool map_is_stable_ : 1;
   Unique<Map> map_;
 };
 
 
 class HContext V8_FINAL : public HTemplateInstruction<0> {
  public:
   static HContext* New(Zone* zone) {
     return new(zone) HContext();
   }
 
@@ skipping 1152 matching lines @@
                          HValue* typecheck = NULL) {
     UniqueSet<Map>* maps = new(zone) UniqueSet<Map>(map_list->length(), zone);
     for (int i = 0; i < map_list->length(); ++i) {
       maps->Add(Unique<Map>::CreateImmovable(map_list->at(i)), zone);
     }
     return new(zone) HCheckMaps(value, maps, typecheck);
   }
 
   bool IsStabilityCheck() const { return is_stability_check_; }
   void MarkAsStabilityCheck() {
+    maps_are_stable_ = true;
     has_migration_target_ = false;
     is_stability_check_ = true;
     ClearChangesFlag(kNewSpacePromotion);
     ClearDependsOnFlag(kElementsKind);
     ClearDependsOnFlag(kMaps);
   }
 
   virtual bool HasEscapingOperandAt(int index) V8_OVERRIDE { return false; }
   virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
     return Representation::Tagged();
@@ skipping 10 matching lines @@
 
   bool HasMigrationTarget() const { return has_migration_target_; }
 
   virtual HValue* Canonicalize() V8_OVERRIDE;
 
   static HCheckMaps* CreateAndInsertAfter(Zone* zone,
                                           HValue* value,
                                           Unique<Map> map,
                                           bool map_is_stable,
                                           HInstruction* instr) {
-    return CreateAndInsertAfter(zone, value, new(zone) UniqueSet<Map>(
-            map, zone), map_is_stable, instr);
+    return instr->Append(new(zone) HCheckMaps(
+            value, new(zone) UniqueSet<Map>(map, zone), map_is_stable));
   }
 
-  static HCheckMaps* CreateAndInsertAfter(Zone* zone,
-                                          HValue* value,
-                                          const UniqueSet<Map>* maps,
-                                          bool maps_are_stable,
-                                          HInstruction* instr) {
-    return instr->Append(new(zone) HCheckMaps(value, maps, maps_are_stable));
+  static HCheckMaps* CreateAndInsertBefore(Zone* zone,
+                                           HValue* value,
+                                           const UniqueSet<Map>* maps,
+                                           bool maps_are_stable,
+                                           HInstruction* instr) {
+    return instr->Prepend(new(zone) HCheckMaps(value, maps, maps_are_stable));
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMaps)
 
  protected:
   virtual bool DataEquals(HValue* other) V8_OVERRIDE {
     return this->maps()->Equals(HCheckMaps::cast(other)->maps());
   }
 
   virtual int RedefinedOperandIndex() { return 0; }
@@ skipping 673 matching lines @@
   static HConstant* CreateAndInsertBefore(Zone* zone,
                                           HValue* context,
                                           int32_t value,
                                           Representation representation,
                                           HInstruction* instruction) {
     return instruction->Prepend(HConstant::New(
         zone, context, value, representation));
   }
 
   static HConstant* CreateAndInsertBefore(Zone* zone,
-                                          Unique<Object> object,
-                                          bool is_not_in_new_space,
+                                          Unique<Map> map,
+                                          bool map_is_stable,
                                           HInstruction* instruction) {
     return instruction->Prepend(new(zone) HConstant(
-        object, Unique<Map>(Handle<Map>::null()), false,
-        Representation::Tagged(), HType::Tagged(), is_not_in_new_space,
-        false, false, kUnknownInstanceType));
+        map, Unique<Map>(Handle<Map>::null()), map_is_stable,
+        Representation::Tagged(), HType::Tagged(), true,
+        false, false, MAP_TYPE));
   }
 
   static HConstant* CreateAndInsertAfter(Zone* zone,
                                          Unique<Map> map,
+                                         bool map_is_stable,
                                          HInstruction* instruction) {
     return instruction->Append(new(zone) HConstant(
-            map, Unique<Map>(Handle<Map>::null()), false,
+            map, Unique<Map>(Handle<Map>::null()), map_is_stable,
             Representation::Tagged(), HType::Tagged(), true,
             false, false, MAP_TYPE));
   }
 
   Handle<Object> handle(Isolate* isolate) {
     if (object_.handle().is_null()) {
       // Default arguments to is_not_in_new_space depend on this heap number
       // to be tenured so that it's guaranteed not to be located in new space.
       object_ = Unique<Object>::CreateUninitialized(
           isolate->factory()->NewNumber(double_value_, TENURED));
@@ skipping 4127 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_