Eliminate RawObject::class_ field entirely.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
@@ skipping 254 matching lines @@
   Isolate::Current()->object_store()->set_empty_array(Array::Handle());
 
   Class& cls = Class::Handle();
 
   // Allocate and initialize the class class.
   {
     intptr_t size = Class::InstanceSize();
     uword address = heap->Allocate(size, Heap::kOld);
     class_class_ = reinterpret_cast<RawClass*>(address + kHeapObjectTag);
     InitializeObject(address, Class::kInstanceKind, size);
-    // Make the class_ field point to itself.
-    class_class_->ptr()->class_ = class_class_;
 
     Class fake;
     // Initialization from Class::New<Class>.
     // Directly set raw_ to break a circular dependency: SetRaw will attempt
     // to lookup class class in the class table where it is not registered yet.
     cls.raw_ = class_class_;
     cls.set_handle_vtable(fake.vtable());
     cls.set_instance_size(Class::InstanceSize());
     cls.set_next_field_offset(Class::InstanceSize());
     cls.set_instance_kind(Class::kInstanceKind);
     cls.set_id(Class::kInstanceKind);
     cls.raw_ptr()->is_const_ = false;
     cls.raw_ptr()->is_interface_ = false;
     cls.set_is_finalized();
     cls.raw_ptr()->type_arguments_instance_field_offset_ =
         Class::kNoTypeArguments;
     cls.raw_ptr()->num_native_fields_ = 0;
     cls.InitEmptyFields();
     Isolate::Current()->class_table()->Register(cls);
   }
 
   // Allocate and initialize the null class.
   cls = Class::New<Instance>(kNullClassId);
   cls.set_is_finalized();
   null_class_ = cls.raw();
 
-  // Complete initialization of null_ instance, i.e. initialize its class_
-  // field.
-  null_->ptr()->class_ = null_class_;
-
   // Allocate and initialize the sentinel values of Null class.
   {
     cls = null_class_;
     Instance& sentinel = Instance::Handle();
     sentinel ^= Object::Allocate(cls, Instance::InstanceSize(), Heap::kOld);
     sentinel_ = sentinel.raw();
 
     Instance& transition_sentinel = Instance::Handle();
     transition_sentinel ^=
         Object::Allocate(cls, Instance::InstanceSize(), Heap::kOld);
@@ skipping 671 matching lines @@
     // Use the preallocated out of memory exception to avoid calling
     // into dart code or allocating any code.
     const Instance& exception =
         Instance::Handle(isolate->object_store()->out_of_memory());
     Exceptions::Throw(exception);
     UNREACHABLE();
   }
   NoGCScope no_gc;
   InitializeObject(address, cls.id(), size);
   RawObject* raw_obj = reinterpret_cast<RawObject*>(address + kHeapObjectTag);
-  raw_obj->ptr()->class_ = cls.raw();
   ASSERT(cls.id() == RawObject::ClassIdTag::decode(raw_obj->ptr()->tags_));
   return raw_obj;
 }
 
 
 RawString* Class::Name() const {
   if (raw_ptr()->name_ != String::null()) {
     return raw_ptr()->name_;
   }
   ASSERT(class_class() != Class::null());  // class_class_ should be set up.
@@ skipping 8017 matching lines @@
   return result.raw();
 }
 
 
 void Array::MakeImmutable() const {
   Isolate* isolate = Isolate::Current();
   const Class& cls = Class::Handle(
       isolate, isolate->object_store()->immutable_array_class());
   {
     NoGCScope no_gc;
-    raw_ptr()->class_ = cls.raw();
     uword tags = raw_ptr()->tags_;
     tags = RawObject::ClassIdTag::update(cls.id(), tags);
     raw_ptr()->tags_ = tags;
   }
 }
 
 
 const char* Array::ToCString() const {
   return "Array";
 }
@@ skipping 50 matching lines @@
   if (capacity_size != used_size) {
     ASSERT(capacity_len > used_len);
     intptr_t leftover_size = capacity_size - used_size;
 
     uword addr = RawObject::ToAddr(array.raw()) + used_size;
     if (leftover_size >= Array::InstanceSize(0)) {
       // As we have enough space to use an array object, update the leftover
       // space as an Array object.
       RawArray* raw = reinterpret_cast<RawArray*>(RawObject::FromAddr(addr));
       const Class& cls = Class::Handle(isolate->object_store()->array_class());
-      raw->ptr()->class_ = cls.raw();
       tags = 0;
       tags = RawObject::SizeTag::update(leftover_size, tags);
       tags = RawObject::ClassIdTag::update(cls.id(), tags);
       raw->ptr()->tags_ = tags;
       intptr_t leftover_len =
           ((leftover_size - Array::InstanceSize(0)) / kWordSize);
       raw->ptr()->tags_ = tags;
       raw->ptr()->length_ = Smi::New(leftover_len);
     } else {
       // Update the leftover space as a basic object.
       ASSERT(leftover_size == Object::InstanceSize());
       RawObject* raw = reinterpret_cast<RawObject*>(RawObject::FromAddr(addr));
       const Class& cls = Class::Handle(isolate->object_store()->object_class());
-      raw->ptr()->class_ = cls.raw();
       tags = 0;
       tags = RawObject::SizeTag::update(leftover_size, tags);
       tags = RawObject::ClassIdTag::update(cls.id(), tags);
       raw->ptr()->tags_ = tags;
     }
   }
   return array.raw();
 }
 
 
@@ skipping 978 matching lines @@
   const String& str = String::Handle(pattern());
   const char* format = "JSRegExp: pattern=%s flags=%s";
   intptr_t len = OS::SNPrint(NULL, 0, format, str.ToCString(), Flags());
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len + 1));
   OS::SNPrint(chars, (len + 1), format, str.ToCString(), Flags());
   return chars;
 }
 
 }  // namespace dart