Pack GlobalHandles::Node::state_ and three flags into uint8_t

Pack GlobalHandles::Node::state_ and three flags into uint8_t

TEST=test-api.cc (ApiObjectGroupsCycle, ApiObjectGroupsCycleForScavenger, IndependentWeakHandle)

Committed: http://code.google.com/p/v8/source/detail?r=13383

[haraken, 2013-01-14 15:46:10]

As discussed offline with michael and dan, in preparation for inlining
GlobalHandles' APIs, I packed state_ and three flags into a uint8_t.

Would you review it?

[Michael Starzinger, 2013-01-15 09:06:41]

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles.cc
File src/global-handles.cc (right):

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles....
src/global-handles.cc:135: class_id_ = static_cast<uint8_t>(class_id);
The class_id is a full 16 bit, we can drop this cast.

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles....
src/global-handles.cc:141: return static_cast<State>(flags_and_state_ &
NodeStateMask);
Instead of using all of this hand-written magic, consider using our BitField
class, see objects.h for some examples. This allows you to encode arbitrary
types (i.e. bool and State) inside a word.

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles....
src/global-handles.cc:309: uint8_t flags_and_state_;
Let's just call this field "flags_".

[haraken, 2013-01-15 09:40:39]

Thanks for reviewing! Updated the patch.

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles.cc
File src/global-handles.cc (right):

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles....
src/global-handles.cc:135: class_id_ = static_cast<uint8_t>(class_id);
On 2013/01/15 09:06:41, Michael Starzinger wrote:
> The class_id is a full 16 bit, we can drop this cast.

Done.

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles....
src/global-handles.cc:141: return static_cast<State>(flags_and_state_ &
NodeStateMask);
On 2013/01/15 09:06:41, Michael Starzinger wrote:
> Instead of using all of this hand-written magic, consider using our BitField
> class, see objects.h for some examples. This allows you to encode arbitrary
> types (i.e. bool and State) inside a word.

Done.

https://chromiumcodereview.appspot.com/11875015/diff/2001/src/global-handles....
src/global-handles.cc:309: uint8_t flags_and_state_;
On 2013/01/15 09:06:41, Michael Starzinger wrote:
> Let's just call this field "flags_".

Done.

[Michael Starzinger, 2013-01-15 09:49:07]

LGTM, I'll land this for you.

[Michael Starzinger, 2013-01-15 10:27:13]

Landed.

https://chromiumcodereview.appspot.com/11875015/diff/6002/src/global-handles.cc
File src/global-handles.cc (right):

https://chromiumcodereview.appspot.com/11875015/diff/6002/src/global-handles....
src/global-handles.cc:73: set_in_new_space_list_(false);
Two small typos at the trailing underscore. Fixed while landing.