RFR: 8371458: [REDO] Remove exception handler stub code in C2 [v4]

[Ruben]

On Thu, 20 Nov 2025 23:56:48 GMT, Ruben <duke at openjdk.org> wrote:

>> The original fix [JDK-8365047](https://bugs.openjdk.org/browse/JDK-8365047) was backed out by [JDK-8371388](https://bugs.openjdk.org/browse/JDK-8371388), this is the REDO.
>> 
>> The C2 exception handler stub code is only a trampoline to the generated exception handler blob. This change removes the extra step on the way to the generated blob.
>> 
>> According to some comments in the source code, the exception handler stub code used to be patched upon deoptimization, however presumably these comments are outdated as the patching upon deoptimization happens for post-call NOPs only.
>
> Ruben has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Refine `first_check_size` definitions

Thank you both. I am planning to submit the `/integrate` request in a few hours.

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PR Comment: https://git.openjdk.org/jdk/pull/28192#issuecomment-3569791332