RFR: 8365047: Remove exception handler stub code in C2 [v10]

[Dean Long]

On Tue, 4 Nov 2025 09:48:20 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code, the exception handler stub code used to be patched upon deoptimization, however presumably these comments are outdated as the patching upon deoptimization happens for post-call NOPs only.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 with a new target base due to a merge or a rebase. The pull request now contains 15 commits:
> 
>  - Rename deoptHandlerOffsetField -> deoptHandlerEntryOffsetField
>  - Merge from the main branch
>  - Address review comments and fix a mistype
>  - Check for NOP and MOVK separately in NativePostCallNop
>  - Test for deoptimization in virtual threads
>    
>    Change-Id: I9ef51b426d34e9b44a3891f6a45307232f900e5a
>  - Merge from the main branch
>  - Address review comments
>  - Address review comments
>  - Address review comments
>  - The patch is contributed by @TheRealMDoerr
>  - ... and 5 more: https://git.openjdk.org/jdk/compare/1922c4fd...359c2f18

We are seeing some new crashes ([JDK-8371388](https://bugs.openjdk.org/browse/JDK-8371388)) trying to access a PC that is just past the end of the nmethod and the page is unmapped because it also happens to be the last page of the CodeHeap.  Could it be related to the changes in this PR?

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PR Comment: https://git.openjdk.org/jdk/pull/26678#issuecomment-3499890263