RFR: 8278874: tighten VerifyStack constraints [v12]

[Dean Long]

On Wed, 13 Aug 2025 19:42:31 GMT, Dean Long <dlong at openjdk.org> wrote:

>> The VerifyStack logic in Deoptimization::unpack_frames() attempts to check the expression stack size of the interpreter frame against what GenerateOopMap computes.  To do this, it needs to know if the state at the current bci represents the "before" state, meaning the bytecode will be reexecuted, or the "after" state, meaning we will advance to the next bytecode.  The old code didn't know how to determine exactly what state we were in, so it checked both.  This PR cleans that up, so we only have to compute the oopmap once.  It also removes old SPARC support.
>
> Dean Long has updated the pull request incrementally with one additional commit since the last revision:
> 
>   cleanup

Our Graal "tier9" testing passed, so I'm optimistically asking for another round of reviews now, while the longer "tier10" keeps running.

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PR Comment: https://git.openjdk.org/jdk/pull/26121#issuecomment-3189817405