RFR: 8365047: Remove exception handler stub code in C2 [v2]

[Dean Long]

On Thu, 14 Aug 2025 08:56:19 GMT, Ruben <duke at openjdk.org> wrote:

>> 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code, the exception handler stub code used to be patched upon deoptimization, however presumably these comments are outdated as the patching upon deoptimization happens for post-call NOPs only.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:
> 
>   Address review comments

If we end up adding a nop or illegal instruction, then we can also undo the work-around that we did in JDK-8172844 for a similar problem.

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PR Comment: https://git.openjdk.org/jdk/pull/26678#issuecomment-3235129423