Implement aging of maps embedded in optimized code.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 9c57ea3bdb2a0ad16d97d0595c954aa37d20a097..6591deadebd814ce129d3f8c7d36c64f50b81c46 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -1237,6 +1237,14 @@ void Heap::MarkCompactPrologue() {
   }
 
   ClearNormalizedMapCaches();
+
+  if (mark_compact_collector_.reduce_memory_footprint()) {
+    embedded_map_cache_ = undefined_value();
+  } else {
+    if (embedded_map_cache_->IsEmbeddedMapCache()) {
+      EmbeddedMapCache::cast(embedded_map_cache_)->Age();
+    }
+  }

[Hannes Payer (out of office), 2014/11/17 17:34:33]

Factor that code out into a function to keep the prologue simple, e.g.
AgeEmbeddedMapCache.

 }
 
 
@@ -4909,6 +4917,11 @@ void Heap::IterateStrongRoots(ObjectVisitor* v, VisitMode mode) {
 }
 
 
+void Heap::IterateEmbeddedMapCache(ObjectVisitor* visitor) {
+  visitor->VisitPointer(&embedded_map_cache_);
+}
+
+
 // TODO(1236194): Since the heap size is configurable on the command line
 // and through the API, we should gracefully handle the case that the heap
 // size is not big enough to fit all the initial objects.
@@ -5279,6 +5292,7 @@ bool Heap::CreateHeapObjects() {
   set_array_buffers_list(undefined_value());
   set_allocation_sites_list(undefined_value());
   weak_object_to_code_table_ = undefined_value();
+  embedded_map_cache_ = undefined_value();
   return true;
 }
 
@@ -5489,6 +5503,19 @@ void Heap::EnsureWeakObjectToCodeTable() {
 }
 
 
+void Heap::CacheEmbeddedMap(Handle<Map> map) {
+  HandleScope scope(isolate());
+  if (!embedded_map_cache_->IsHashTable()) {
+    embedded_map_cache_ =
+        *EmbeddedMapCache::New(isolate(), 512, USE_DEFAULT_MINIMUM_CAPACITY,
+                               TENURED);
+  }
+  Handle<EmbeddedMapCache> cache(EmbeddedMapCache::cast(embedded_map_cache_),
+                                 isolate());
+  embedded_map_cache_ = *EmbeddedMapCache::Put(cache, map);
+}
+
+
 void Heap::FatalProcessOutOfMemory(const char* location, bool take_snapshot) {
   v8::internal::V8::FatalProcessOutOfMemory(location, take_snapshot);
 }