Review Request: Zero and Shark fixes

[Gary Benson]

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/