GC interface update

[Roman Kennke]

Am 12.04.2017 um 21:54 schrieb Kirk Pepperdine:
>> On Apr 12, 2017, at 9:10 PM, Roman Kennke <rkennke at redhat.com> wrote:
>>
>> Am 12.04.2017 um 21:02 schrieb Christian Thalinger:
>>> Two or three JavaOnes ago Jon Masa (where is he anyway? ;-)
>> I think he retired?
> He retired just after JavaONE.
>
>>> and I discussed JVMCI and a possible GC interface.  One issue with compilers is that they need to emit different barrier code for different garbage collectors.  You mention this in the JEP.
>>>
>>> Where are you with your thinking on this?
>> That's a tricky one.
> You could inject the barrier rules into the compiler? The compiler would also need an interface for this to work.
I'm currently mostly thinking about C1 and C2. I think JVMCI would be
similar though. We need some smallish code between the compiler and the
GC that knows about both, and generates the IR for the corresponding
compiler and GC. (It becomes even more complicated in the case of the
interpreter, which requires arch-specific barriers too..)

There's other issues to think about, like GC/barrier specific class
definitions, e.g. GC specific Node sub-classes in C2, and GC specific
compiler optimizations. I have some ideas how to do that, but it's not
very useful to to think about it on a theoretical basis that much. We'll
see when we get there I think.

Roman

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