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

[Vladimir Kozlov]

On Fri, 7 Nov 2025 11:16:20 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code, the exception handler stub code used to be patched upon deoptimization, however presumably these comments are outdated as the patching upon deoptimization happens for post-call NOPs only.
>
>> Thanks @ruben-arm. Let's go with this clean back out for now - testing just came back clean. Once you have the REDO ready, I can submit some more sophisticated testing to make sure it addresses the issues we're seeing.
> 
> @TobiHartmann, I would appreciate it if you could initiate the extended testing for this PR.

@ruben-arm what was the issue in the original changes?

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PR Comment: https://git.openjdk.org/jdk/pull/28192#issuecomment-3503214174