Virtual dispatch bug in 292 impl

[Charles Oliver Nutter]

Sorry I lost track of this thread going into the holidays...I talked
to Christian a moment ago but I reply here for the record...

Christian Thalinger <christian.thalinger at oracle.com> wrote:
>> I filed:
>>
>> https://jbs.oracle.com/bugs/browse/JDK-8005418
>>
>> But it seems to be C2, not C1:

Does look that way in your output. I'll leave it in your hands. I will
say I am almost positive that when I ran with tier=1 it failed, and
-tiered worked ok, but I don't have the output in front of me.

> What's the name of the [] implementation of ENV?  Is it StringOnlyRubyHash.op_aref?

Yes, that's the one. The handle points at the superclass impl,
RubyHash.op_aref, and that's the one that gets hit instead of the
override.

> Could this be the compile that goes wrong?
>
>   12903  956             java.lang.invoke.LambdaForm$MH/847376::convert (52 bytes)
>                             @ 15   java.lang.invoke.LambdaForm$BMH/23638730::reinvoke (26 bytes)   inline (hot)
>                               @ 12   java.lang.invoke.BoundMethodHandle$Species_LL::reinvokerTarget (8 bytes)   inline (hot)
>                               @ 22   java.lang.invoke.LambdaForm$DMH/20340225::invokeStatic_LL_L (15 bytes)   inline (hot)
>                                 @ 1   java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)   inline (hot)
>                                 @ 11   sun.invoke.util.ValueConversions::castReference (6 bytes)   inline (hot)
>                                   @ 2   java.lang.Class::cast (27 bytes)   inline (hot)
>                                     @ 6   java.lang.Class::isInstance (0 bytes)   (intrinsic)
>                             @ 33   java.lang.Class::cast (27 bytes)   inline (hot)
>                               @ 6   java.lang.Class::isInstance (0 bytes)   (intrinsic)
>                             @ 43   java.lang.Class::cast (27 bytes)   inline (hot)
>                               @ 6   java.lang.Class::isInstance (0 bytes)   (intrinsic)
>                             @ 48   java.lang.invoke.LambdaForm$DMH/32367447::invokeVirtual_LLL_L (18 bytes)   inline (hot)
>                               @ 1   java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)   inline (hot)
>                               @ 14   org.jruby.RubyHash::op_aref (23 bytes)   inline (hot)

This looks like what I saw while debugging, yes. Not sure if this
exact output is right because there's not much context, but I did see
the call that *should* have been going to StringOnlyRubyHash.op_aref
going to RubyHash.op_aref.

There aren't many such cases in JRuby...most overrides are accompanied
by an override in the Ruby class structures, so the child class has
its own handle pointing at the override. That's probably why we don't
see it in more places.

I have not retested with any of the recent work on partial inlining,
etc. Since it looks like you're able to reproduce it ok, I'll leave it
in your hands. Let me know what else I can do.

- Charlie