[lworld] RFR: 8373567: [lworld] Move array copy excpetion throwing out of GC barriers

[Stefan Karlsson]

On Fri, 12 Dec 2025 09:16:44 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

> The lworld branch has support for null-restricted arrays, and to support this code has been adjacent to the code that perform array copy check casts. The code that performs the check casts used to be located inside the GC access barriers, but the code that finally threw exceptions were located in the runtime code. In the lworld branch the code that throws the check cast exception and the new null pointer exception has been moved into the GC access barriers.
> 
> I propose that we revert back to the old style where the exception throwing was somewhat decoupled from the GC access barriers.

If this is accepted I think we could push the usage of `OopCopyResult` changes into the openjdk/jdk and thereby shrinking the lworld patch.

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PR Comment: https://git.openjdk.org/valhalla/pull/1792#issuecomment-3645623111