Reenable map collection.

src/mark-compact.cc

 // Copyright 2011 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 41 matching lines @@
 
 // -------------------------------------------------------------------------
 // MarkCompactCollector
 
 MarkCompactCollector::MarkCompactCollector() :  // NOLINT
 #ifdef DEBUG
       state_(IDLE),
 #endif
       sweep_precisely_(false),
       compacting_(false),
+      collect_maps_(FLAG_collect_maps),
       tracer_(NULL),
       migration_slots_buffer_(NULL),
 #ifdef DEBUG
       live_young_objects_size_(0),
       live_old_pointer_objects_size_(0),
       live_old_data_objects_size_(0),
       live_code_objects_size_(0),
       live_map_objects_size_(0),
       live_cell_objects_size_(0),
       live_lo_objects_size_(0),
@@ skipping 175 matching lines @@
 
 
 void MarkCompactCollector::CollectGarbage() {
   // Make sure that Prepare() has been called. The individual steps below will
   // update the state as they proceed.
   ASSERT(state_ == PREPARE_GC);
 
   MarkLiveObjects();
   ASSERT(heap_->incremental_marking()->IsStopped());
 
-  if (FLAG_collect_maps) ClearNonLiveTransitions();
+  if (collect_maps_) ClearNonLiveTransitions();
 
 #ifdef DEBUG
   if (FLAG_verify_heap) {
     VerifyMarking(heap_);
   }
 #endif
 
   SweepSpaces();
 
+  if (!collect_maps_) ReattachInitialMaps();
+
   heap_->isolate()->pc_to_code_cache()->Flush();
 
   Finish();
 
   tracer_ = NULL;
 }
 
 
 #ifdef DEBUG
 static void VerifyMarkbitsAreClean(PagedSpace* space) {
@@ skipping 118 matching lines @@
 
 
 void MarkCompactCollector::Prepare(GCTracer* tracer) {
   // TODO(gc) re-enable code flushing.
   FLAG_flush_code = false;
   FLAG_always_compact = false;
 
   // Disable collection of maps if incremental marking is enabled.
   // TODO(gc) improve maps collection algorithm to work with incremental
   // marking.
-  if (FLAG_incremental_marking) FLAG_collect_maps = false;
+  // TODO(gc) consider oscillating collect_maps_ on and off when possible.
+  // This will allow map transition tree to die from both root and leaves.

[Lasse Reichstein, 2011/07/15 07:00:14]

"a map transition tree" or "map transition trees"?

+  collect_maps_ = FLAG_collect_maps &&
+      !heap()->incremental_marking()->IsMarking();
 
   // Rather than passing the tracer around we stash it in a static member
   // variable.
   tracer_ = tracer;
 
 #ifdef DEBUG
   ASSERT(state_ == IDLE);
   state_ = PREPARE_GC;
 #endif
   ASSERT(!FLAG_always_compact || !FLAG_never_compact);
 
-  if (FLAG_collect_maps) CreateBackPointers();
+  if (collect_maps_) CreateBackPointers();
 #ifdef ENABLE_GDB_JIT_INTERFACE
   if (FLAG_gdbjit) {
     // If GDBJIT interface is active disable compaction.
     compacting_collection_ = false;
   }
 #endif
 
   if (heap()->incremental_marking()->IsMarking() && PreciseSweepingRequired()) {
     heap()->incremental_marking()->Abort();
   }
@@ skipping 1000 matching lines @@
   if (object->IsMap()) {
     Map* map = Map::cast(object);
     if (FLAG_cleanup_code_caches_at_gc) {
       map->ClearCodeCache(heap());
     }
 
     // When map collection is enabled we have to mark through map's transitions
     // in a special way to make transition links weak.
     // Only maps for subclasses of JSReceiver can have transitions.
     STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE);
-    if (FLAG_collect_maps && map->instance_type() >= FIRST_JS_RECEIVER_TYPE) {
+    if (collect_maps_ && map->instance_type() >= FIRST_JS_RECEIVER_TYPE) {
       MarkMapContents(map);
     } else {
       marking_deque_.PushBlack(map);
     }
   } else {
     marking_deque_.PushBlack(object);
   }
 }
 
 
@@ skipping 581 matching lines @@
     live_code_objects_size_ += obj->Size();
   } else if (heap()->lo_space()->Contains(obj)) {
     live_lo_objects_size_ += obj->Size();
   } else {
     UNREACHABLE();
   }
 }
 #endif  // DEBUG
 
 
+void MarkCompactCollector::ReattachInitialMaps() {
+  HeapObjectIterator map_iterator(heap()->map_space());
+  for (HeapObject* obj = map_iterator.Next();
+       obj != NULL;
+       obj = map_iterator.Next()) {
+    if (obj->IsFreeSpace()) continue;
+    Map* map = Map::cast(obj);
+
+    STATIC_ASSERT(LAST_TYPE == LAST_CALLABLE_SPEC_OBJECT_TYPE);
+    if (map->instance_type() < FIRST_JS_RECEIVER_TYPE) continue;
+
+    if (map->attached_to_shared_function_info()) {
+      JSFunction::cast(map->constructor())->shared()->AttachInitialMap(map);
+    }
+  }
+}
+
+
 void MarkCompactCollector::ClearNonLiveTransitions() {
   HeapObjectIterator map_iterator(heap()->map_space());
   // Iterate over the map space, setting map transitions that go from
   // a marked map to an unmarked map to null transitions.  At the same time,
   // set all the prototype fields of maps back to their original value,
   // dropping the back pointers temporarily stored in the prototype field.
   // Setting the prototype field requires following the linked list of
   // back pointers, reversing them all at once.  This allows us to find
   // those maps with map transitions that need to be nulled, and only
   // scan the descriptor arrays of those maps, not all maps.
@@ skipping 1270 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal