[aarch64-port-dev ] RFR: RFR: Bulk integration shenandoah/jdk8u -> aarch64-port/jdk8u-shenandoah 2018-12-13

[Andrew Hughes]

On Sat, 22 Dec 2018 at 16:19, Aleksey Shipilev <shade at redhat.com> wrote:
>
> On 12/22/18 4:53 PM, Andrew Hughes wrote:
> >>> Mostly ok, but for:
> >>>
> >>> changeset:   10742:c935e0b6b4b2
> >>> user:        shade
> >>> date:        Thu Oct 25 20:38:21 2018 +0200
> >>> summary:     [backport] Cherry-pick JDK-8212673, fix for Node::eqv_uncast
> >>>
> >>> This doesn't seem to have been requested for OpenJDK 11 upstream, never mind 8u.
> >>> Why is it being backported only to shenandoah?
> >>
> >>
> >> Because the orginal issue has been made more or less specifically for
> >> Shenandoah:
> >>
> >> https://bugs.openjdk.java.net/browse/JDK-8212603
> >>
> >> and JDK-8212673 fixes an issue with the change. IOW, it's Shenandoah
> >> specific.
> >>
> >> Roman
> >>
> >
> > Ok, but is it harmful to other collectors to have it upstream? I'm trying to
> > minimise our divergence where possible.
> >
> > 8212603 is not in 8u or shenandoah-8u. Is 8212673 still applicable in its
> > absence as a standalone fix?
>
> Yes. 8212673 reverts parts of 8212603, and does the fix more narrowly.
>
> The final code in 11+ is calling to BarrierSet at callnode.cpp, and particular GC choose what to do
> with it. In 8u, there is no good GC interface, so we "just" call through Shenandoah-specific
> ShenandoahBarrierNode::skip_through_barrier, which is no-op when Shenandoah is disabled. I think
> there are other existing places in 8u where the same thing happens.
>
> The final code for 8u does not diverge from upstream much:
>
> https://builds.shipilev.net/patch-openjdk-shenandoah-jdk8-only-shared/latest/src/share/vm/opto/callnode.cpp.sdiff.html
>
> ...and there are no changes in node.{c|h}pp from 8212603 left:
>
> https://builds.shipilev.net/patch-openjdk-shenandoah-jdk8-only-shared/latest/src/share/vm/opto/node.cpp.sdiff.html
>
> https://builds.shipilev.net/patch-openjdk-shenandoah-jdk8-only-shared/latest/src/share/vm/opto/node.hpp.sdiff.html
>
> HTHS,
> -Aleksey
>

Thanks. It's still not clear to me why this couldn't go into upstream
8u & 11u though.
-- 
Andrew :)

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

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