Integrated: 8260106: Shenandoah: refactor reference updating closures and related code

[Aleksey Shipilev]

On Wed, 20 Jan 2021 15:06:20 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> We have a block in `ShenandoahHeap::maybe_update_with_forwarded` that is irrelevant after JDK-8231086. Additionally, "resolve and update" paths are really only used by STW GCs, and thus do not require atomic updates. This leads to considerable simplifications in the code, and improves performance on the common paths (especially in fastdebug builds that drop many irrelevant asserts).
> 
> Additional testing:
>  - [x] `hotspot_gc_shenandoah`
>  - [x] `tier1` with Shenandoah
>  - [x] `tier2` with Shenandoah

This pull request has now been integrated.

Changeset: bd2744dd
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/bd2744dd
Stats:     279 lines in 15 files changed: 86 ins; 116 del; 77 mod

8260106: Shenandoah: refactor reference updating closures and related code

Reviewed-by: zgu, rkennke

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PR: https://git.openjdk.java.net/jdk/pull/2166