[9] RFR(XS): 8068505: interpreter profiling incorrect on PPC

[Volker Simonis]

Hi Zoltan,

thanks for this change. I think you're right with your observation
that the code is wrong. It seems this is an old copy and paste error
which has been in the port since the first day. The historical
background is that we implemented tiered compilation with the C2
compiler only but haven't contributed that to the OpenJDK. But even
with our C2-based tiered compilation, the code region fixed by you was
never executed and still isn't executed because we have no C1 in the
ppc64 port (and therefore no tiered compilation).

So the only test I can currently do is to verify that the new code
compiles - which I've just verified. Nevertheless your change is good
since we might start working on C1 later this year.

I can sponsor this change (and push it because it only touches a
ppc-specific file).

Regards,
Volker

PS: just out of curiosity - how did you stumble over this problem
without even having ppc64 hardware? Maybe you just like reading
ppc-assembly:)


On Tue, Jan 6, 2015 at 2:45 PM, Zoltán Majó <zoltan.majo at oracle.com> wrote:
> Hi,
>
>
> I've recently looked at the PPC port in hotspot and I noticed the following
> small problem.
>
> Problem: The method TemplateInterpreterGenerator::generate_counter_incr()
> increments method invocations counters on all supported architectures,
> except on PPC (w/ tiered compilation enabled). As a result, methods might be
> compiled later and OSR happens sooner than specified by compilation
> thresholds.
>
> Solution: Change generate_counter_incr() in templateInterpreter_ppc.cpp to
> use invocation counters instead of backedge counters.
>
> Webrev: http://cr.openjdk.java.net/~zmajo/8068505/webrev.00/
>
> JDK Bug: https://bugs.openjdk.java.net/browse/JDK-8068505
>
> I was not able to test the change as I don't have access to appropriate
> infrastructure.
>
> Maybe this is the wrong list to send this RFR to. If yes, could you please
> tell me where to send it?
>
> Thank you and best regards,
>
>
> Zoltan
>