Integrated: 8255534: Shenandoah: Fix CmpP optimization wrt native-LRB

[Roman Kennke]

On Wed, 28 Oct 2020 12:34:52 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> JDK-8254314 introduced the following code:
> 
>     if (in1->bottom_type() == TypePtr::NULL_PTR &&
>         (in1->Opcode() != Op_ShenandoahLoadReferenceBarrier || !((ShenandoahLoadReferenceBarrierNode*)in1)->is_native())) {
>       in2 = step_over_gc_barrier(in2);
>     }
> 
> However, the check for LRB and !native are the wrong way around: they should check if *in2* are not native LRB.
> 
> The bug is currently only observed in the conc-weakrefs branch, but may manifest (rarely) in mainline too. 
> 
> I am also putting in some refactoring to avoid duped code for good measure.
> 
> Testing: hotspot_gc_shenandoah (also in conc-weakrefs-branch where it manifests)

This pull request has now been integrated.

Changeset: faf23de5
Author:    Roman Kennke <rkennke at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/faf23de5
Stats:     7 lines in 1 file changed: 5 ins; 0 del; 2 mod

8255534: Shenandoah: Fix CmpP optimization wrt native-LRB

Reviewed-by: shade

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PR: https://git.openjdk.java.net/jdk/pull/902