[master] Integrated: Simplify stable_mark() routine

[Roman Kennke]

On Wed, 30 Mar 2022 14:36:19 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> The code in ObjectSynchronizer::stable_mark() is a bit over-complicated: it has a 'fast' path (which really isn't a fast-path, because the really-fast path is already in the various oopDesc::klass() methods), and for the slow-path loop dives into ObjectSynchronizer::safe_load_mark(). This change proposes to remove the stable_mark() method, and rename safe_load_mark() to stable_mark() instead.
> 
> I also propose a small improvement: we can use read_stable_mark() to deal with INFLATING mark properly, and handle the remaining cases in the loop: monitor and stack-locked are the most common - deal with them first. Stack-locked can safely access the mark when current thread is owning thread of the lock - avoid CASing INFLATING into the header in this case. Neutral and Marked cases go last, because they should not be very common (neutral is already caught in oopDesc::klass() variants, marked should only happen during full GCs by GC internal code).
> 
> Testing:
>  - [x] tier1
>  - [x] tier2
>  - [x] tier3
>  - [x] tier4

This pull request has now been integrated.

Changeset: b6c888bf
Author:    Roman Kennke <rkennke at openjdk.org>
URL:       https://git.openjdk.java.net/lilliput/commit/b6c888bf303c846ff5c3f690a7b5ade42eadb094
Stats:     62 lines in 3 files changed: 12 ins; 42 del; 8 mod

Simplify stable_mark() routine

Reviewed-by: zgu, stuefe

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PR: https://git.openjdk.java.net/lilliput/pull/46