Remove prototype checks for leaf maps in optimized code.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 844 matching lines @@
   V(FreeSpace)                                 \
   V(JSReceiver)                                \
   V(JSObject)                                  \
   V(JSContextExtensionObject)                  \
   V(JSModule)                                  \
   V(Map)                                       \
   V(DescriptorArray)                           \
   V(TransitionArray)                           \
   V(DeoptimizationInputData)                   \
   V(DeoptimizationOutputData)                  \
-  V(DependentCodes)                            \
+  V(DependentCode)                            \
   V(TypeFeedbackCells)                         \
   V(FixedArray)                                \
   V(FixedDoubleArray)                          \
   V(Context)                                   \
   V(NativeContext)                             \
   V(ScopeInfo)                                 \
   V(JSFunction)                                \
   V(Code)                                      \
   V(Oddball)                                   \
   V(SharedFunctionInfo)                        \
@@ skipping 3812 matching lines @@
 // following layout for n dependency groups:
 //
 // +----+----+-----+----+---------+----------+-----+---------+-----------+
 // | C1 | C2 | ... | Cn | group 1 |  group 2 | ... | group n | undefined |
 // +----+----+-----+----+---------+----------+-----+---------+-----------+
 //
 // The first n elements are Smis, each of them specifies the number of codes
 // in the corresponding group. The subsequent elements contain grouped code
 // objects. The suffix of the array can be filled with the undefined value if
 // the number of codes is less than the length of the array.
-// 
+//
 // All code indexes used in the class are counted starting from the first
 // code object of the first group. In other words, code index 0 corresponds
 // to array index n = kCodesStartIndex.
 
-class DependentCodes: public FixedArray {
+class DependentCode: public FixedArray {
  public:
   enum DependencyGroup {
     // Group of codes that weakly embed this map and depend on being

[Toon Verwaest, 2013/02/13 15:18:25]

Group of code

[ulan, 2013/02/14 09:30:46]

Done.

     // deoptimized when the map is garbage collected.
     kWeaklyEmbeddedGroup,
-    kGroupCount = kWeaklyEmbeddedGroup + 1
+    // Group of code that omit run-time prototype checks for prototypes
+    // described by this map. The group is deoptimized whenever an object
+    // described by this map changes shape (and transitions to a new map),
+    // possibly invalidating the assumptions embedded in the code.
+    kPrototypeCheckGroup,
+    kGroupCount = kPrototypeCheckGroup + 1
   };
   // Array for holding the index of the first code object of each group.
   // The last element stores the total number of code objects.
-  typedef int GroupStartIndexes[kGroupCount + 1];
+  class GroupStartIndexes {
+   public:
+    explicit GroupStartIndexes(DependentCode* codes);
+    void Recompute(DependentCode* codes);
+    int at(int i) { return start_indexes_[i]; }
+   private:
+    int start_indexes_[kGroupCount + 1];
+  };
   inline int number_of_codes(DependencyGroup group);
   inline void set_number_of_codes(DependencyGroup group, int value);
   inline Code* code_at(int i);
   inline void set_code_at(int i, Code* value);
   inline Object** code_slot_at(int i);
   inline void clear_code_at(int i);
-  static inline DependentCodes* cast(Object* object);
-  inline void ComputeGroupStartIndexes(GroupStartIndexes starts);
+  static inline DependentCode* cast(Object* object);
   bool Contains(DependencyGroup group, Code* code);
-  static Handle<DependentCodes> Insert(Handle<DependentCodes> codes,
+  static Handle<DependentCode> Insert(Handle<DependentCode> codes,
                                        DependencyGroup group,
                                        Handle<Code> value);
 
  private:
   // Make a room at the end of the given group by moving out the first
   // code objects of the subsequent groups.
   inline void ExtendGroup(DependencyGroup group);
   static const int kCodesStartIndex = kGroupCount;
 };
 
@@ skipping 221 matching lines @@
   inline JSFunction* unchecked_constructor();
 
   // [instance descriptors]: describes the object.
   DECL_ACCESSORS(instance_descriptors, DescriptorArray)
   inline void InitializeDescriptors(DescriptorArray* descriptors);
 
   // [stub cache]: contains stubs compiled for this map.
   DECL_ACCESSORS(code_cache, Object)
 
   // [dependent codes]: list of optimized codes that have this map embedded.
-  DECL_ACCESSORS(dependent_codes, DependentCodes)
+  DECL_ACCESSORS(dependent_code, DependentCode)
 
   // [back pointer]: points back to the parent map from which a transition
   // leads to this map. The field overlaps with prototype transitions and the
   // back pointer will be moved into the prototype transitions array if
   // required.
   inline Object* GetBackPointer();
   inline void SetBackPointer(Object* value,
                              WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
   inline void init_back_pointer(Object* undefined);
 
@@ skipping 196 matching lines @@
   // heap verification is turned on.
   void ZapPrototypeTransitions();
   void ZapTransitions();
 
   bool CanTransition() {
     // Only JSObject and subtypes have map transitions and back pointers.
     STATIC_ASSERT(LAST_TYPE == LAST_JS_OBJECT_TYPE);
     return instance_type() >= FIRST_JS_OBJECT_TYPE;
   }
 
-  inline void AddDependentCode(DependentCodes::DependencyGroup group,
+
+  inline void NotifyObjectLayoutChange();
+
+  inline bool CanOmitPrototypeChecks();
+
+  inline void AddDependentCode(DependentCode::DependencyGroup group,
                                Handle<Code> code);
 
+  void DeoptimizeDependentCode(DependentCode::DependencyGroup group);
+
   // Dispatched behavior.
   DECLARE_PRINTER(Map)
   DECLARE_VERIFIER(Map)
 
 #ifdef VERIFY_HEAP
   void SharedMapVerify();
 #endif
 
   inline int visitor_id();
   inline void set_visitor_id(int visitor_id);
@@ skipping 28 matching lines @@
   static const int kConstructorOffset = kPrototypeOffset + kPointerSize;
   // Storage for the transition array is overloaded to directly contain a back
   // pointer if unused. When the map has transitions, the back pointer is
   // transferred to the transition array and accessed through an extra
   // indirection.
   static const int kTransitionsOrBackPointerOffset =
       kConstructorOffset + kPointerSize;
   static const int kDescriptorsOffset =
       kTransitionsOrBackPointerOffset + kPointerSize;
   static const int kCodeCacheOffset = kDescriptorsOffset + kPointerSize;
-  static const int kDependentCodesOffset = kCodeCacheOffset + kPointerSize;
-  static const int kBitField3Offset = kDependentCodesOffset + kPointerSize;
+  static const int kDependentCodeOffset = kCodeCacheOffset + kPointerSize;
+  static const int kBitField3Offset = kDependentCodeOffset + kPointerSize;
   static const int kSize = kBitField3Offset + kPointerSize;
 
   // Layout of pointer fields. Heap iteration code relies on them
   // being continuously allocated.
   static const int kPointerFieldsBeginOffset = Map::kPrototypeOffset;
   static const int kPointerFieldsEndOffset = kBitField3Offset + kPointerSize;
 
   // Byte offsets within kInstanceSizesOffset.
   static const int kInstanceSizeOffset = kInstanceSizesOffset + 0;
   static const int kInObjectPropertiesByte = 1;
@@ skipping 3669 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_