RFR (sh/jdk8): Backport 2020-02-27, batch 2

[Roman Kennke]

Hi Aleksey,

>> http://cr.openjdk.java.net/~rkennke/backport-shjdk8-2020-02-27-2/webrev.01/
> 
> Frankly, I suspect C1 rewiring (which also diverged from upstream) runs into the risk of
> destabilizing sh/jdk8 before April CPU release. Can we delay it until July CPU opens?

Ok, I'm cutting it out. It makes sense, the next batch will have more C1
rewirings esp the SFX stuff, which has a bit of a bug trail (I believe
we had one recent bug with C1 register types that stems from the SFX
work), so let's prepare them and then push them together once July CPU
opens.

> I believe we should push the src/cpu/aarch64/vm/c1_LIRGenerator_aarch64.cpp change as the aarch64
> addendum to this one: http://hg.openjdk.java.net/shenandoah/jdk8/hotspot/rev/cf0f69f962d9 -- ahead
> of this backport batch.

Ok.

> Other things:
> 
> *) src/cpu/aarch64/vm/shenandoahBarrierSetAssembler_aarch64.cpp:
>  Do you really need SBSC1 here?
> 
>  252   ShenandoahBarrierSetC1* bs = ShenandoahBarrierSetC1::bsc1();

Apparently not. It comes from 11+ though, and is part of the C1
rewirings that is gone now:

Changesets:
http://cr.openjdk.java.net/~rkennke/backport-shjdk8-2020-02-27-2/changesets-2.txt
Webrev:
http://cr.openjdk.java.net/~rkennke/backport-shjdk8-2020-02-27-2/webrev.02/

ok?

Roman