Cleanup allocation site pretenuring tracing, added new flag --trace-pretenuring-statistics.

Cleanup allocation site pretenuring tracing, added new flag --trace-pretenuring-statistics.

BUG=
R=bmeurer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=19141

[Benedikt Meurer, 2014-02-06 10:28:41]

LGTM

[Hannes Payer (out of office), 2014-02-06 10:30:20]

Committed patchset #1 manually as r19141 (presubmit successful).

[mvstanton, 2014-02-06 10:30:42]

Very nice, two comments in objects-inl. Have a look at that and send back my
weg.

https://codereview.chromium.org/153273003/diff/1/src/objects-inl.h
File src/objects-inl.h (right):

https://codereview.chromium.org/153273003/diff/1/src/objects-inl.h#newcode1555
src/objects-inl.h:1555: PretenureFlag current_mode = GetPretenureMode();
This is a little more expensive, because we are only computing ratio for
printing purposes if we didn't meet kPretenureMinimumCreated.

Can it be organized such that we don't compute ratio if there is no audience for
the computation?

https://codereview.chromium.org/153273003/diff/1/src/objects-inl.h#newcode1577
src/objects-inl.h:1577: 
Why drive a VW when you can have a Cadillac? Can the printing tell us about the
decision making above, like: did we decide, or did we "change our mind" and mark
for deopt?

[mvstanton, 2014-02-06 10:30:59]

Oh.

[Hannes Payer (out of office), 2014-02-06 10:47:26]

https://codereview.chromium.org/153273003/diff/1/src/objects-inl.h
File src/objects-inl.h (right):

https://codereview.chromium.org/153273003/diff/1/src/objects-inl.h#newcode1555
src/objects-inl.h:1555: PretenureFlag current_mode = GetPretenureMode();
On 2014/02/06 10:30:42, mvstanton wrote:
> This is a little more expensive, because we are only computing ratio for
> printing purposes if we didn't meet kPretenureMinimumCreated.
> 
> Can it be organized such that we don't compute ratio if there is no audience
for
> the computation?

I do not think that this is an issue, but we can do that.

https://codereview.chromium.org/153273003/diff/1/src/objects-inl.h#newcode1577
src/objects-inl.h:1577: 
On 2014/02/06 10:30:42, mvstanton wrote:
> Why drive a VW when you can have a Cadillac? Can the printing tell us about
the
> decision making above, like: did we decide, or did we "change our mind" and
mark
> for deopt?

We do exactly that in old state => new state.