Integrated: 8315247: GenShen: Condition calls to post-write barrier code generation by a flag

[Y. Srinivas Ramakrishna]

On Mon, 28 Aug 2023 19:48:58 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

> Protect the card barrier code generation by a new global `ShenandoahCardBarrier`, which is disabled by default and enabled for GenShen (generational mode Shenandoah) only. If the user forces the barrier flag to a value inconsistent with mode, we exit with an appropriate error message.
> 
> The intention of the change is two-fold:
> 1. Make the card-barrier code in support of GenShen more idiomatic along the lines of existing barrier-gen code in Shenandoah
> 2. Reduce and simplify to the extent possible the impact of changes from GenShen on shared/legacy Shenandoah code, so as to make reviews/audits of shared/legacy code a bit easier
> 
> The changes have been made for x86, aarch, and ppc, and tested as follows:
> 1. I have tested on x86 on a cloud host running jtreg1-4 and SPECjbb.
> 3. A round of aarch64 and x86 pipeline tests have run (but ran into existing assertion that William is fixing).
> 4. Many thanks to Martin Doerr (SAP) for putting this through a "quick spin" on PPC
> 5. RISC-V & S390 don't currently support generational mode Shenandoah.

This pull request has now been integrated.

Changeset: ade7796c
Author:    Y. Srinivas Ramakrishna <ysr at openjdk.org>
URL:       https://git.openjdk.org/shenandoah/commit/ade7796c9401c7348ebd771a11c88f31649e7509
Stats:     106 lines in 15 files changed: 48 ins; 21 del; 37 mod

8315247: GenShen: Condition calls to post-write barrier code generation by a flag

Reviewed-by: wkemper, kdnilsen

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PR: https://git.openjdk.org/shenandoah/pull/313