Make object groups and implicit references a bit more lightweight.

Make object groups and implicit references a bit more lightweight.

We can only call malloc/free once per group and we can avoid scanning
through a list of NULLs if we keep unprocessed groups in the beginning.

I also changed the internal representation of implicit references to
hold a handle to the parent (instead of a direct pointer). The
prologue callback must not trigger a GC, but it's better to be safe.

[antonm, 2011-04-06 11:01:47]

LGTM

http://codereview.chromium.org/6800003/diff/1/src/allocation.h
File src/allocation.h (right):

http://codereview.chromium.org/6800003/diff/1/src/allocation.h#newcode55
src/allocation.h:55: class CustomlyAllocated {
I don't like the name, but I cannot come up with anything better.

However, apparently the best way to make class really custom allocated is by
making its ctor/dtor private (so it cannot be stack allocated).

Maybe just declare a macro for it and forget about special base class?

http://codereview.chromium.org/6800003/diff/1/src/global-handles.h
File src/global-handles.h (right):

http://codereview.chromium.org/6800003/diff/1/src/global-handles.h#newcode64
src/global-handles.h:64: Object** objects_[1];
maybe add a comment that it's a placeholder for variable size object.

http://codereview.chromium.org/6800003/diff/1/src/global-handles.h#newcode94
src/global-handles.h:94: Object** children_[1];
ditto

http://codereview.chromium.org/6800003/diff/1/src/mark-compact.cc
File src/mark-compact.cc (right):

http://codereview.chromium.org/6800003/diff/1/src/mark-compact.cc#newcode1249
src/mark-compact.cc:1249: // be processed again.
nit: comment appears to be slightly incorrect: disposing won't prevent a group
for being processed again, it's just not needed anymore.

http://codereview.chromium.org/6800003/diff/1/src/mark-compact.cc#newcode1279
src/mark-compact.cc:1279: // be processed again.
Ditto

[Vitaly Repeshko, 2011-04-06 19:11:01]

Anton, thanks for the review!

Comments addressed. I also added a test for empty groups. (It doesn't make sense
to allocate them.)


-- Vitaly

http://codereview.chromium.org/6800003/diff/1/src/allocation.h
File src/allocation.h (right):

http://codereview.chromium.org/6800003/diff/1/src/allocation.h#newcode55
src/allocation.h:55: class CustomlyAllocated {
On 2011/04/06 11:01:48, antonm wrote:
> I don't like the name, but I cannot come up with anything better.
> 
> However, apparently the best way to make class really custom allocated is by
> making its ctor/dtor private (so it cannot be stack allocated).
> 
> Maybe just declare a macro for it and forget about special base class?

Yeah, since it requires hiding both new/delete and ctor/dtor, we need a macro.
But given that we'd only have two usages, I removed this base class and made
new/delete private explicitly in the global handle classes.

http://codereview.chromium.org/6800003/diff/1/src/global-handles.h
File src/global-handles.h (right):

http://codereview.chromium.org/6800003/diff/1/src/global-handles.h#newcode64
src/global-handles.h:64: Object** objects_[1];
On 2011/04/06 11:01:48, antonm wrote:
> maybe add a comment that it's a placeholder for variable size object.

Done.

http://codereview.chromium.org/6800003/diff/1/src/global-handles.h#newcode94
src/global-handles.h:94: Object** children_[1];
On 2011/04/06 11:01:48, antonm wrote:
> ditto

Done.

http://codereview.chromium.org/6800003/diff/1/src/mark-compact.cc
File src/mark-compact.cc (right):

http://codereview.chromium.org/6800003/diff/1/src/mark-compact.cc#newcode1249
src/mark-compact.cc:1249: // be processed again.
On 2011/04/06 11:01:48, antonm wrote:
> nit: comment appears to be slightly incorrect: disposing won't prevent a group
> for being processed again, it's just not needed anymore.

Done.

http://codereview.chromium.org/6800003/diff/1/src/mark-compact.cc#newcode1279
src/mark-compact.cc:1279: // be processed again.
On 2011/04/06 11:01:48, antonm wrote:
> Ditto

Done.