Immediately "optimize as prototype" when setting as prototype of a function.

src/objects.cc

 // Copyright 2013 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 <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
@@ skipping 10015 matching lines @@
   DCHECK(shrink_by % kEntryLength == 0);
   DCHECK(shrink_by <= code_map->length() - kEntriesStart);
   // Always trim even when array is cleared because of heap verifier.
   GetHeap()->RightTrimFixedArray<Heap::FROM_GC>(code_map, shrink_by);
   if (code_map->length() == kEntriesStart) {
     ClearOptimizedCodeMap();
   }
 }
 
 
+static void GetMinInobjectSlack(Map* map, void* data) {
+  int slack = map->unused_property_fields();
+  if (*reinterpret_cast<int*>(data) > slack) {
+    *reinterpret_cast<int*>(data) = slack;
+  }
+}
+
+
+static void ShrinkInstanceSize(Map* map, void* data) {
+  int slack = *reinterpret_cast<int*>(data);
+  map->set_inobject_properties(map->inobject_properties() - slack);
+  map->set_unused_property_fields(map->unused_property_fields() - slack);
+  map->set_instance_size(map->instance_size() - slack * kPointerSize);
+
+  // Visitor id might depend on the instance size, recalculate it.
+  map->set_visitor_id(StaticVisitorBase::GetVisitorId(map));
+}
+
+
+void JSFunction::CompleteInobjectSlackTracking() {
+  DCHECK(has_initial_map());
+  Map* map = initial_map();
+
+  DCHECK(map->counter() >= Map::kSlackTrackingCounterEnd - 1);
+  map->set_counter(Map::kRetainingCounterStart);
+
+  int slack = map->unused_property_fields();
+  map->TraverseTransitionTree(&GetMinInobjectSlack, &slack);
+  if (slack != 0) {
+    // Resize the initial map and all maps in its transition tree.
+    map->TraverseTransitionTree(&ShrinkInstanceSize, &slack);
+  }
+}
+
+
 void JSObject::OptimizeAsPrototype(Handle<JSObject> object,
                                    PrototypeOptimizationMode mode) {
   if (object->IsGlobalObject()) return;
   if (object->IsJSGlobalProxy()) return;
   if (mode == FAST_PROTOTYPE && !object->map()->is_prototype_map()) {
     // First normalize to ensure all JSFunctions are DATA_CONSTANT.
     JSObject::NormalizeProperties(object, KEEP_INOBJECT_PROPERTIES, 0,
                                   "NormalizeAsPrototype");
   }
   bool has_just_copied_map = false;
@@ skipping 171 matching lines @@
     }
 
     // Deoptimize all code that embeds the previous initial map.
     initial_map->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kInitialMapChangedGroup);
   } else {
     // Put the value in the initial map field until an initial map is
     // needed.  At that point, a new initial map is created and the
     // prototype is put into the initial map where it belongs.
     function->set_prototype_or_initial_map(*value);
+    if (value->IsJSObject()) {
+      // Optimize as prototype to detach it from its transition tree.
+      JSObject::OptimizeAsPrototype(Handle<JSObject>::cast(value),
+                                    FAST_PROTOTYPE);
+    }
   }
   isolate->heap()->ClearInstanceofCache();
 }
 
 
 void JSFunction::SetPrototype(Handle<JSFunction> function,
                               Handle<Object> value) {
   DCHECK(function->should_have_prototype());
   Handle<Object> construct_prototype = value;
 
@@ skipping 522 matching lines @@
       // Re-enable optimizations if they were disabled due to opt_count limit.
       set_optimization_disabled(false);
       code()->set_optimizable(true);
     }
     set_opt_count(0);
     set_deopt_count(0);
   }
 }
 
 
-static void GetMinInobjectSlack(Map* map, void* data) {
-  int slack = map->unused_property_fields();
-  if (*reinterpret_cast<int*>(data) > slack) {
-    *reinterpret_cast<int*>(data) = slack;
-  }
-}
-
-
-static void ShrinkInstanceSize(Map* map, void* data) {
-  int slack = *reinterpret_cast<int*>(data);
-  map->set_inobject_properties(map->inobject_properties() - slack);
-  map->set_unused_property_fields(map->unused_property_fields() - slack);
-  map->set_instance_size(map->instance_size() - slack * kPointerSize);
-
-  // Visitor id might depend on the instance size, recalculate it.
-  map->set_visitor_id(StaticVisitorBase::GetVisitorId(map));
-}
-
-
-void JSFunction::CompleteInobjectSlackTracking() {
-  DCHECK(has_initial_map());
-  Map* map = initial_map();
-
-  DCHECK(map->counter() >= Map::kSlackTrackingCounterEnd - 1);
-  map->set_counter(Map::kRetainingCounterStart);
-
-  int slack = map->unused_property_fields();
-  map->TraverseTransitionTree(&GetMinInobjectSlack, &slack);
-  if (slack != 0) {
-    // Resize the initial map and all maps in its transition tree.
-    map->TraverseTransitionTree(&ShrinkInstanceSize, &slack);
-  }
-}
-
-
 int SharedFunctionInfo::SearchOptimizedCodeMap(Context* native_context,
                                                BailoutId osr_ast_id) {
   DisallowHeapAllocation no_gc;
   DCHECK(native_context->IsNativeContext());
   if (!FLAG_cache_optimized_code) return -1;
   Object* value = optimized_code_map();
   if (!value->IsSmi()) {
     FixedArray* optimized_code_map = FixedArray::cast(value);
     int length = optimized_code_map->length();
     Smi* osr_ast_id_smi = Smi::FromInt(osr_ast_id.ToInt());
@@ skipping 6487 matching lines @@
                                                CompilationInfo* info) {
   Handle<DependentCode> codes = DependentCode::InsertCompilationInfo(
       handle(cell->dependent_code(), info->isolate()),
       DependentCode::kPropertyCellChangedGroup, info->object_wrapper());
   if (*codes != cell->dependent_code()) cell->set_dependent_code(*codes);
   info->dependencies(DependentCode::kPropertyCellChangedGroup)->Add(
       cell, info->zone());
 }
 
 } }  // namespace v8::internal