Undefined behaviour in hotspot

[Volker Simonis]

On Wed, Apr 23, 2014 at 8:21 PM, Omair Majid <omajid at redhat.com> wrote:

> Hi Volker,
>
> * Volker Simonis <volker.simonis at gmail.com> [2014-04-23 13:47]:
> > So to cut a long story short, I've identified '-fdevirtualize' as the
> culprit.
> > '-fdevirtualize' is automatically set if we compile with -O2 but if I
> compile
> > macroAssembler_x86.o only with '-O2 -fno-devirtualize' I get a VM which
> at
> > least starts up and passes some smoke tests.
>
> Aha, Andrew Haley just walked me through similar logic and the same
> flag! Though I don't really understand how (either of) you jumped from
> miscompiled-code to -fno-devirtualize.
>
>
Simple binary search trough the extra optimizations -O2 applies compared to
O1 :)



> > @Omair: could you please verify this. I haven't tried x86_64 until now
> > so I can not say if this fix also helps there.
>
> Confirmed. On i686, Hotspot built with this is good enough to run javac to
> compile small programs. I will test x86_64 now.
>
> Thanks,
> Omair
>
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