Remove prototype checks for leaf maps in optimized code.

src/mark-compact.cc

 // 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 2276 matching lines @@
       // This map is used for inobject slack tracking and has been detached
       // from SharedFunctionInfo during the mark phase.
       // Since it survived the GC, reattach it now.
       map->unchecked_constructor()->unchecked_shared()->AttachInitialMap(map);
     }
 
     ClearNonLivePrototypeTransitions(map);
     ClearNonLiveMapTransitions(map, map_mark);
 
     if (map_mark.Get()) {
-      ClearNonLiveDependentCodes(map);
+      ClearNonLiveDependentCode(map);
     } else {
-      ClearAndDeoptimizeDependentCodes(map);
+      ClearAndDeoptimizeDependentCode(map);
     }
   }
 }
 
 
 void MarkCompactCollector::ClearNonLivePrototypeTransitions(Map* map) {
   int number_of_transitions = map->NumberOfProtoTransitions();
   FixedArray* prototype_transitions = map->GetPrototypeTransitions();
 
   int new_number_of_transitions = 0;
@@ skipping 49 matching lines @@
   // Follow back pointer, check whether we are dealing with a map transition
   // from a live map to a dead path and in case clear transitions of parent.
   bool current_is_alive = map_mark.Get();
   bool parent_is_alive = Marking::MarkBitFrom(parent).Get();
   if (!current_is_alive && parent_is_alive) {
     parent->ClearNonLiveTransitions(heap());
   }
 }
 
 
-void MarkCompactCollector::ClearAndDeoptimizeDependentCodes(Map* map) {
+void MarkCompactCollector::ClearAndDeoptimizeDependentCode(Map* map) {
   AssertNoAllocation no_allocation_scope;
-  DependentCodes* codes = map->dependent_codes();
-  int number_of_codes = codes->number_of_codes();
+  DependentCode* codes = map->dependent_code();
+  DependentCode::GroupStartIndexes starts(codes);
+  int number_of_codes = starts.at(DependentCode::kGroupCount);

[Michael Starzinger, 2013/02/14 12:44:04]

We should definitely add a number_of_codes() helper to GroupStartIndexes instead
of hard-coding the magic constant here.

[ulan, 2013/02/15 09:24:02]

Done.

   if (number_of_codes == 0) return;
   for (int i = 0; i < number_of_codes; i++) {
     Code* code = codes->code_at(i);
     if (IsMarked(code) && !code->marked_for_deoptimization()) {
       code->set_marked_for_deoptimization(true);
     }
     codes->clear_code_at(i);
   }
-  map->set_dependent_codes(DependentCodes::cast(heap()->empty_fixed_array()));
+  map->set_dependent_code(DependentCode::cast(heap()->empty_fixed_array()));
 }
 
 
-void MarkCompactCollector::ClearNonLiveDependentCodes(Map* map) {
+void MarkCompactCollector::ClearNonLiveDependentCode(Map* map) {
   AssertNoAllocation no_allocation_scope;
-  DependentCodes* codes = map->dependent_codes();
-  int number_of_codes = codes->number_of_codes();
+  DependentCode* codes = map->dependent_code();
+  DependentCode::GroupStartIndexes starts(codes);
+  int number_of_codes = starts.at(DependentCode::kGroupCount);

[Michael Starzinger, 2013/02/14 12:44:04]

Likewise.

[ulan, 2013/02/15 09:24:02]

Done.

   if (number_of_codes == 0) return;
   int new_number_of_codes = 0;
-  for (int i = 0; i < number_of_codes; i++) {
-    Code* code = codes->code_at(i);
-    if (IsMarked(code) && !code->marked_for_deoptimization()) {
-      if (new_number_of_codes != i) {
-        codes->set_code_at(new_number_of_codes, code);
+  // Go through all groups, remove dead codes and compact.
+  for (int g = 0; g < DependentCode::kGroupCount; g++) {
+    int group_number_of_codes = 0;
+    for (int i = starts.at(g); i < starts.at(g + 1); i++) {
+      Code* code = codes->code_at(i);
+      if (IsMarked(code) && !code->marked_for_deoptimization()) {
+        if (new_number_of_codes + group_number_of_codes != i) {
+          codes->set_code_at(new_number_of_codes + group_number_of_codes, code);
+        }
+        Object** slot = codes->code_slot_at(new_number_of_codes +
+                                            group_number_of_codes);
+        RecordSlot(slot, slot, code);
+        group_number_of_codes++;
       }
-      Object** slot = codes->code_slot_at(new_number_of_codes);
-      RecordSlot(slot, slot, code);
-      new_number_of_codes++;
     }
+    codes->set_number_of_codes(static_cast<DependentCode::DependencyGroup>(g),
+                               group_number_of_codes);
+    new_number_of_codes += group_number_of_codes;
   }
   for (int i = new_number_of_codes; i < number_of_codes; i++) {
     codes->clear_code_at(i);
   }
-  codes->set_number_of_codes(new_number_of_codes);
 }
 
 
 void MarkCompactCollector::ProcessWeakMaps() {
   Object* weak_map_obj = encountered_weak_maps();
   while (weak_map_obj != Smi::FromInt(0)) {
     ASSERT(MarkCompactCollector::IsMarked(HeapObject::cast(weak_map_obj)));
     JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(weak_map_obj);
     ObjectHashTable* table = ObjectHashTable::cast(weak_map->table());
     Object** anchor = reinterpret_cast<Object**>(table->address());
@@ skipping 1656 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal