RFR: 8376761: ARM32: Constant base assert after JDK-8373266

[Stefan Karlsson]

On Mon, 2 Feb 2026 18:39:50 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Missed the obvious spot in [JDK-8373266](https://bugs.openjdk.org/browse/JDK-8373266). ARM32 uses this cached field for quick loads in CardTableBarrierSet barriers. This does not apply to Shenandoah and G1 barriers. So we only need to make sure card table is properly initialized to nullptr.
> 
> Additional testing:
>  - [x] Linux ARM32 build now passes `java HelloWorld.java`

> > Instead of relying on `bs->is_a`, I wonder whether the intention is more explicit if using `UseXGC`, sth like:
> 
> Maybe, but the current fix follows [88c8a55](https://github.com/openjdk/jdk/commit/88c8a55a4337a857ac17ffff068f730f67cf5763) style.

FWIW, I would have been less confused if the code was using "UseXGC". I didn't know that the FakeRTTI / is_a had support for answering true for multiple tags

-------------

PR Comment: https://git.openjdk.org/jdk/pull/29528#issuecomment-3846081380