[Isolates] Speed up Context::Lookup by avoiding implicit TLS reads.

src/contexts.cc

 // Copyright 2006-2008 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 58 matching lines @@
   return global_context()->global_proxy_object();
 }
 
 void Context::set_global_proxy(JSObject* object) {
   global_context()->set_global_proxy_object(object);
 }
 
 
 Handle<Object> Context::Lookup(Handle<String> name, ContextLookupFlags flags,
                                int* index_, PropertyAttributes* attributes) {
-  Heap* heap = GetHeap();
-  Handle<Context> context(this);
+  Isolate* isolate = GetIsolate();
+  Handle<Context> context(this, isolate);
 
   bool follow_context_chain = (flags & FOLLOW_CONTEXT_CHAIN) != 0;
   *index_ = -1;
   *attributes = ABSENT;
 
   if (FLAG_trace_contexts) {
     PrintF("Context::Lookup(");
     name->ShortPrint();
     PrintF(")\n");
   }
 
   do {
     if (FLAG_trace_contexts) {
       PrintF(" - looking in context %p", reinterpret_cast<void*>(*context));
       if (context->IsGlobalContext()) PrintF(" (global context)");
       PrintF("\n");
     }
 
     // check extension/with object
     if (context->has_extension()) {
-      Handle<JSObject> extension = Handle<JSObject>(context->extension());
+      Handle<JSObject> extension = Handle<JSObject>(context->extension(),
+                                                    isolate);
       // Context extension objects needs to behave as if they have no
       // prototype.  So even if we want to follow prototype chains, we
       // need to only do a local lookup for context extension objects.
       if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
           extension->IsJSContextExtensionObject()) {
         *attributes = extension->GetLocalPropertyAttribute(*name);
       } else {
         *attributes = extension->GetPropertyAttribute(*name);
       }
       if (*attributes != ABSENT) {
         // property found
         if (FLAG_trace_contexts) {
           PrintF("=> found property in context object %p\n",
                  reinterpret_cast<void*>(*extension));
         }
         return extension;
       }
     }
 
     if (context->is_function_context()) {
       // we have context-local slots
 
       // check non-parameter locals in context
       Handle<SerializedScopeInfo> scope_info(
-          context->closure()->shared()->scope_info());
+          context->closure()->shared()->scope_info(), isolate);
       Variable::Mode mode;
       int index = scope_info->ContextSlotIndex(*name, &mode);
       ASSERT(index < 0 || index >= MIN_CONTEXT_SLOTS);
       if (index >= 0) {
         // slot found
         if (FLAG_trace_contexts) {
           PrintF("=> found local in context slot %d (mode = %d)\n",
                  index, mode);
         }
         *index_ = index;
@@ skipping 12 matching lines @@
           case Variable::DYNAMIC_LOCAL: UNREACHABLE(); break;
           case Variable::TEMPORARY: UNREACHABLE(); break;
         }
         return context;
       }
 
       // check parameter locals in context
       int param_index = scope_info->ParameterIndex(*name);
       if (param_index >= 0) {
         // slot found.
-        int index =
-            scope_info->ContextSlotIndex(heap->arguments_shadow_symbol(), NULL);
+        int index = scope_info->ContextSlotIndex(
+            isolate->heap()->arguments_shadow_symbol(), NULL);
         ASSERT(index >= 0);  // arguments must exist and be in the heap context
-        Handle<JSObject> arguments(JSObject::cast(context->get(index)));
-        ASSERT(arguments->HasLocalProperty(heap->length_symbol()));
+        Handle<JSObject> arguments(JSObject::cast(context->get(index)),
+                                   isolate);
+        ASSERT(arguments->HasLocalProperty(isolate->heap()->length_symbol()));
         if (FLAG_trace_contexts) {
           PrintF("=> found parameter %d in arguments object\n", param_index);
         }
         *index_ = param_index;
         *attributes = NONE;
         return arguments;
       }
 
       // check intermediate context (holding only the function name variable)
       if (follow_context_chain) {
         int index = scope_info->FunctionContextSlotIndex(*name);
         if (index >= 0) {
           // slot found
           if (FLAG_trace_contexts) {
             PrintF("=> found intermediate function in context slot %d\n",
                    index);
           }
           *index_ = index;
           *attributes = READ_ONLY;
           return context;
         }
       }
     }
 
     // proceed with enclosing context
     if (context->IsGlobalContext()) {
       follow_context_chain = false;
     } else if (context->is_function_context()) {
-      context = Handle<Context>(Context::cast(context->closure()->context()));
+      context = Handle<Context>(Context::cast(context->closure()->context()),
+                                isolate);
     } else {
-      context = Handle<Context>(context->previous());
+      context = Handle<Context>(context->previous(), isolate);
     }
   } while (follow_context_chain);
 
   // slot not found
   if (FLAG_trace_contexts) {
     PrintF("=> no property/slot found\n");
   }
   return Handle<Object>::null();
 }
 
@@ skipping 110 matching lines @@
   // During bootstrapping we allow all objects to pass as global
   // objects. This is necessary to fix circular dependencies.
   Isolate* isolate = Isolate::Current();
   return isolate->heap()->gc_state() != Heap::NOT_IN_GC ||
       isolate->bootstrapper()->IsActive() ||
       object->IsGlobalObject();
 }
 #endif
 
 } }  // namespace v8::internal