Further improve old space allocation write barrier elimination.

Further improve old space allocation write barrier elimination.

Stores to old space allocations require no write barriers if the
object is the new space dominator and the value is not in new space.

R=hpayer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21360

[Benedikt Meurer, 2014-05-18 05:47:28]

PTAL

[Hannes Payer (out of office), 2014-05-18 18:54:58]

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instructions.h
File src/hydrogen-instructions.h (right):

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instruction...
src/hydrogen-instructions.h:5725: // is the new space dominator and the value is
not in new space.
new_space_dominator should be called dominator, otherwise the code does not fit
the description. Moreover the part about  the new space dominator should be
mentioned earlier.

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instruction...
src/hydrogen-instructions.h:5730: // allocated in old space.
broken comment.

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instruction...
src/hydrogen-instructions.h:5737: }
Why not
if (value->IsAllocate() &&
    (HAllocate::cast(value)->IsOldDataSpaceAllocation() ||
        HAllocate::cast(value)->IsOldPointerSpaceAllocation())

[Benedikt Meurer, 2014-05-19 06:17:51]

PTAL

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instructions.h
File src/hydrogen-instructions.h (right):

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instruction...
src/hydrogen-instructions.h:5725: // is the new space dominator and the value is
not in new space.
On 2014/05/18 18:54:58, Hannes Payer wrote:
> new_space_dominator should be called dominator, otherwise the code does not
fit
> the description. Moreover the part about  the new space dominator should be
> mentioned earlier.

Done.

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instruction...
src/hydrogen-instructions.h:5730: // allocated in old space.
On 2014/05/18 18:54:58, Hannes Payer wrote:
> broken comment.

Done.

https://codereview.chromium.org/290173003/diff/20001/src/hydrogen-instruction...
src/hydrogen-instructions.h:5737: }
On 2014/05/18 18:54:58, Hannes Payer wrote:
> Why not
> if (value->IsAllocate() &&
>     (HAllocate::cast(value)->IsOldDataSpaceAllocation() ||
>         HAllocate::cast(value)->IsOldPointerSpaceAllocation())

Done.

[Hannes Payer (out of office), 2014-05-19 09:43:44]

lgtm, one nit

https://codereview.chromium.org/290173003/diff/60001/src/hydrogen-instructions.h
File src/hydrogen-instructions.h (right):

https://codereview.chromium.org/290173003/diff/60001/src/hydrogen-instruction...
src/hydrogen-instructions.h:5729: while (value->IsInnerAllocatedObject()) {
Please add a comment what is going on here.

[Benedikt Meurer, 2014-05-19 09:48:41]

Committed patchset #3 manually as r21360 (presubmit successful).