Loads and stores to global vars are now made via property cell shortcuts installed into parent scri…

src/runtime/runtime-object.cc

 // Copyright 2014 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/v8.h"
 
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/debug.h"
 #include "src/messages.h"
@@ skipping 430 matching lines @@
   // %ObjectSeal is a fast path and these cases are handled elsewhere.
   RUNTIME_ASSERT(!object->HasSloppyArgumentsElements() &&
                  !object->map()->is_observed() && !object->IsJSProxy());
 
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result, JSObject::Seal(object));
   return *result;
 }
 
 
+RUNTIME_FUNCTION(Runtime_LoadGlobalViaContext) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 3);
+  CONVERT_ARG_HANDLE_CHECKED(Context, script_context, 0);
+  CONVERT_SMI_ARG_CHECKED(index, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Name, name, 2);
+  DCHECK(script_context->IsScriptContext());
+  DCHECK(script_context->get(index)->IsPropertyCell());
+
+  Handle<GlobalObject> global(script_context->global_object());
+
+  LookupIterator it(global, name, LookupIterator::OWN);
+
+  Handle<Object> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result, Object::GetProperty(&it));
+
+  if (LookupIterator::DATA == it.state()) {

[Toon Verwaest, 2015/07/10 16:46:11]

You should probably do this check before GetProperty since otherwise it'll walk
beyond an interceptor for example. If there's an interceptor, we can essentially
never cache, since it can decide on a whim to make a property appear that wasn't
there before.

[Igor Sheludko, 2015/07/13 08:34:51]

Done.

+    // Now update cell in the script context.
+    Handle<PropertyCell> cell = it.GetPropertyCell();
+    script_context->set(index, *cell);
+  } else {
+    // This is not a fast case, so keep this access in a slow mode.

[Toon Verwaest, 2015/07/10 16:46:11]

Add comment that you're doing this just to release the property cell containing
the hole, replacing it by the single global empty one.

[Igor Sheludko, 2015/07/13 08:34:51]

Done.

+    script_context->set(index, isolate->heap()->empty_property_cell());
+  }
+  return *result;
+}
+
+
+RUNTIME_FUNCTION(Runtime_StoreGlobalViaContext) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 5);
+  CONVERT_ARG_HANDLE_CHECKED(Context, script_context, 0);
+  CONVERT_SMI_ARG_CHECKED(index, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Name, name, 2);
+  CONVERT_ARG_HANDLE_CHECKED(Object, value, 3);
+  CONVERT_LANGUAGE_MODE_ARG_CHECKED(language_mode_arg, 4);
+  DCHECK(script_context->IsScriptContext());
+  DCHECK(script_context->get(index)->IsPropertyCell());
+  LanguageMode language_mode = language_mode_arg;
+
+  Handle<GlobalObject> global(script_context->global_object());
+
+  LookupIterator it(global, name, LookupIterator::OWN);
+
+  Handle<Object> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result,
+      Object::SetProperty(&it, value, language_mode,
+                          Object::CERTAINLY_NOT_STORE_FROM_KEYED));
+
+  if (LookupIterator::DATA == it.state()) {

[Toon Verwaest, 2015/07/10 16:46:11]

Same as above.

[Igor Sheludko, 2015/07/13 08:34:51]

Done.

+    // Now update cell in the script context.
+    Handle<PropertyCell> cell = it.GetPropertyCell();
+    script_context->set(index, *cell);
+  } else {
+    // This is not a fast case, so keep this access in a slow mode.
+    script_context->set(index, isolate->heap()->empty_property_cell());
+  }
+  return *result;
+}
+
+
 RUNTIME_FUNCTION(Runtime_GetProperty) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
 
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, key, 1);
 
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
@@ skipping 969 matching lines @@
   CONVERT_PROPERTY_ATTRIBUTES_CHECKED(attrs, 3);
 
   RETURN_FAILURE_ON_EXCEPTION(
       isolate,
       JSObject::DefineAccessor(object, name, isolate->factory()->null_value(),
                                setter, attrs));
   return isolate->heap()->undefined_value();
 }
 }  // namespace internal
 }  // namespace v8