[serializer] encode recent long-encoded root list items as hot objects.

src/snapshot/partial-serializer.cc

 // Copyright 2016 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.
 
 #include "src/snapshot/partial-serializer.h"
 #include "src/snapshot/startup-serializer.h"
 
 #include "src/objects-inl.h"
 
 namespace v8 {
@@ skipping 33 matching lines @@
                                         WhereToPoint where_to_point, int skip) {
   if (obj->IsMap()) {
     // The code-caches link to context-specific code objects, which
     // the startup and context serializes cannot currently handle.
     DCHECK(Map::cast(obj)->code_cache() == obj->GetHeap()->empty_fixed_array());
   }
 
   // Replace typed arrays by undefined.
   if (obj->IsJSTypedArray()) obj = isolate_->heap()->undefined_value();
 
+  if (SerializeHotObject(obj, how_to_code, where_to_point, skip)) return;
+
   int root_index = root_index_map_.Lookup(obj);
   if (root_index != RootIndexMap::kInvalidRootIndex) {
     PutRoot(root_index, obj, how_to_code, where_to_point, skip);
     return;
   }
 
+  if (SerializeBackReference(obj, how_to_code, where_to_point, skip)) return;
+
   if (ShouldBeInThePartialSnapshotCache(obj)) {
     FlushSkip(skip);
 
     int cache_index = startup_serializer_->PartialSnapshotCacheIndex(obj);
     sink_.Put(kPartialSnapshotCache + how_to_code + where_to_point,
               "PartialSnapshotCache");
     sink_.PutInt(cache_index, "partial_snapshot_cache_index");
     return;
   }
 
   // Pointers from the partial snapshot to the objects in the startup snapshot
   // should go through the root array or through the partial snapshot cache.
   // If this is not the case you may have to add something to the root array.
   DCHECK(!startup_serializer_->reference_map()->Lookup(obj).is_valid());
   // All the internalized strings that the partial snapshot needs should be
   // either in the root table or in the partial snapshot cache.
   DCHECK(!obj->IsInternalizedString());
   // Function and object templates are not context specific.
   DCHECK(!obj->IsTemplateInfo());
 
-  if (SerializeKnownObject(obj, how_to_code, where_to_point, skip)) return;
-
   FlushSkip(skip);
 
   // Clear literal boilerplates.
   if (obj->IsJSFunction()) {
-    LiteralsArray* literals = JSFunction::cast(obj)->literals();
+    JSFunction* function = JSFunction::cast(obj);
+    LiteralsArray* literals = function->literals();
     for (int i = 0; i < literals->literals_count(); i++) {
       literals->set_literal_undefined(i);
     }
+    function->ClearTypeFeedbackInfo();
   }
 
   // Object has not yet been serialized.  Serialize it here.
   ObjectSerializer serializer(this, obj, &sink_, how_to_code, where_to_point);
   serializer.Serialize();
 }
 
 bool PartialSerializer::ShouldBeInThePartialSnapshotCache(HeapObject* o) {
   // Scripts should be referred only through shared function infos.  We can't
   // allow them to be part of the partial snapshot because they contain a
   // unique ID, and deserializing several partial snapshots containing script
   // would cause dupes.
   DCHECK(!o->IsScript());
   return o->IsName() || o->IsSharedFunctionInfo() || o->IsHeapNumber() ||
          o->IsCode() || o->IsScopeInfo() || o->IsAccessorInfo() ||
          o->map() ==
              startup_serializer_->isolate()->heap()->fixed_cow_array_map();
 }
 
 }  // namespace internal
 }  // namespace v8