RFR: 8370502: C2: segfault while adding node to IGVN worklist [v2]

[Dean Long]

On Thu, 20 Nov 2025 16:40:49 GMT, Kerem Kat <krk at openjdk.org> wrote:

>> Do not try to replace `fallthrough_memproj` when it is null, fixes crash.
>> 
>> Test case is simplified from the ticket. Verified that the case crashes without the fix.
>
> Kerem Kat has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - fix test spacing
>  - Update src/hotspot/share/opto/macro.cpp
>    
>    Co-authored-by: Manuel Hässig <manuel at haessig.org>
>  - Update src/hotspot/share/opto/macro.cpp
>    
>    Co-authored-by: Manuel Hässig <manuel at haessig.org>

Why is fallthrough_memproj null, and why is this an issue only for expand_unlock_node but not expand_lock_node or other code that tries to replace fallthrough_memproj?

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PR Comment: https://git.openjdk.org/jdk/pull/28432#issuecomment-3560735492