Review Request: Zero and Shark fixes

[Dr Andrew John Hughes]

On 19:20 Thu 31 Mar     , Dr Andrew John Hughes wrote:
> Errr... what ARM interpreter rewrite?
> 
> On 31/03/2011, Gary Benson <gbenson at redhat.com> wrote:
> > Dr Andrew John Hughes wrote:
> >> On 31/03/2011, Gary Benson <gbenson at redhat.com> wrote:
> >> > Ok, I looked a little further into 3.  The root cause was this:
> >> >
> >> >   changeset: 1611:136b78722a08
> >> >   user:      jrose
> >> >   date:      Wed Jun 09 18:50:45 2010 -0700
> >> >   summary:   6939203: JSR 292 needs method handle constants
> >> >
> >> > It two new internal instructions, _fast_aldc and _fast_aldc_w, but
> >> > it added them *before* _return_register_finalizer, which broke the
> >> > instructions table in bytecodeInterpreter.cpp.  It meant that when
> >> > the C++ interpreter saw _return_register_finalizer it would
> >> > execute opc_default, which should have thrown an error but for the
> >> > piece of the ARM interpreter which hid the error by rewriting the
> >> > instruction to a plain _return.  I didn't see it before because I
> >> > was doing debug builds, and the C++ interpreter only uses the
> >> > instructions table for product builds.
> >> >
> >> > The bottom line is, if you see _fast_aldc in bytecodes.hpp then
> >> > Zero won't work correctly without this patch.
> >>
> >> Ok, that change is in hs19 and thus OpenJDK6 already:
> >>
> >> $ hg log -R ../../jdk6/hotspot -k 6939203
> >> changeset:   1805:136b78722a08
> >> parent:      1795:49fac4acd688
> >> user:        jrose
> >> date:        Wed Jun 09 18:50:45 2010 -0700
> >> summary:     6939203: JSR 292 needs method handle constants
> >>
> >> I'm still wary that the fix is untested, but my main worry (that
> >> it fixed a newer change that wasn't in hs20) is alleviated.
> >>
> >> If Zero is broken without this, it needs to go in the 1.9 (hs19
> >> non-default), 1.10 (hs19 default, hs20 non-default) and HEAD (hs20
> >> default, hs19 non-default) branches of IcedTea6.
> >
> > If it really is in there (ie bytecodes.hpp contains _fast_aldc) then
> > removing the ARM interpreter rewrite will cause the VM to instantly
> > abort.
> >
> > Removal of the ARM interpreter rewrite is not necessary for this fix
> > to work, but it'd be nice if it doesn't break other stuff.  The fact
> > this bug has persisted for so long is because the ARM interpreter
> > code has hidden it.
> >
> > Cheers,
> > Gary
> >
> > --
> > http://gbenson.net/
> >

Sorry for the top-post; stupid broken Gmail client... Didn't realise I had
this mail in my RH inbox too.
-- 
Andrew :)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

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