Nonvirtual pointer visitor in GCs

Method to visit pointers in objects using non-virtual calls to the ObjectPointerVisitor (for user-defined objects).

Used for the visitors in the scavenger and marker. Each of these seems to give a few percent speed improvement for new and old space collections, respectively.

Around 0.1% total VM size increase (on ARM64).

R=erikcorry@google.com
BUG=

Committed: https://github.com/dart-lang/sdk/commit/443033cc3864b0675dcad5a6ba34802a25aeaade

[Aske Simon Christensen, 2017-05-30 12:38:32]

Description was changed from

==========
Nonvirtual pointer visitor in GCs

R=erikcorry@google.com
BUG=
==========

to

==========
Method to visit pointers in objects using non-virtual calls to the
ObjectPointerVisitor (for user-defined objects).

Used for the visitors in the scavenger and marker. Each of these seems to give a
few percent speed improvement for new and old space collections, respectively.

Around 0.1% total VM size increase (on ARM64).

R=erikcorry@google.com
BUG=
==========

[erikcorry, 2017-05-31 10:40:42]

LGTM.

We should do this for the built-in classes too, which may well be a bigger win.

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/gc_marker.cc
File runtime/vm/gc_marker.cc (right):

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/gc_marker.cc...
runtime/vm/gc_marker.cc:275: return raw_weak->VisitPointersNonvirtual(this);
I don't think this is worth it.  Normally there are a lot more non-weak pointers
on the heap than weak pointers. ALso another place in this file.

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/raw_object.h
File runtime/vm/raw_object.h (right):

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/raw_object.h...
runtime/vm/raw_object.h:458: intptr_t VisitPointers(ObjectPointerVisitor*
visitor) {
I think instead of duplicating the code you can just call
VisitPointersNonvirtual(visitor) here.  In that case perhaps you should move
this to a .cc file to stop the inliner getting overly eager for things where it
does not matter.

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/raw_object.h...
runtime/vm/raw_object.h:478: template <class V>
template <class V, bool call_virtually = false>

This way you can avoid the code duplication.

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/raw_object.h...
runtime/vm/raw_object.h:479: intptr_t VisitPointersNonvirtual(V* visitor) {
Perhaps it should be called VisitPointersTemplatized if it is also used for the
virtual version.

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/scavenger.cc
File runtime/vm/scavenger.cc (right):

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/scavenger.cc...
runtime/vm/scavenger.cc:596: cur_weak->VisitPointersNonvirtual(visitor);
Probably not worth it.

https://codereview.chromium.org/2908353002/diff/20001/runtime/vm/scavenger.cc...
runtime/vm/scavenger.cc:664: return raw_weak->VisitPointersNonvirtual(visitor);
Probably not worth it.

[Aske Simon Christensen, 2017-05-31 11:01:16]

Description was changed from

==========
Method to visit pointers in objects using non-virtual calls to the
ObjectPointerVisitor (for user-defined objects).

Used for the visitors in the scavenger and marker. Each of these seems to give a
few percent speed improvement for new and old space collections, respectively.

Around 0.1% total VM size increase (on ARM64).

R=erikcorry@google.com
BUG=
==========

to

==========
Method to visit pointers in objects using non-virtual calls to the
ObjectPointerVisitor (for user-defined objects).

Used for the visitors in the scavenger and marker. Each of these seems to give a
few percent speed improvement for new and old space collections, respectively.

Around 0.1% total VM size increase (on ARM64).

R=erikcorry@google.com
BUG=

Committed:
https://github.com/dart-lang/sdk/commit/443033cc3864b0675dcad5a6ba34802a25aeaade
==========

[Aske Simon Christensen, 2017-05-31 11:01:18]

Committed patchset #2 (id:20001) manually as
443033cc3864b0675dcad5a6ba34802a25aeaade (presubmit successful).