RFR: 8343824: Remove unused InstructionFlags in C1

[Dean Long]

On Fri, 8 Nov 2024 11:09:27 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change that removes unused/unreferenced flags from the `Instruction::InstructionFlag` enum for the C1 compiler.
> 
> Testing: gha, tier1-3
> 
> Thanks,
>   Thomas

SCCS archeology reveals that these 3 were converted from boolean fields by JDK-4649182:

  bool _needs_write_barrier;
  bool _needs_store_check;
  bool  _is_eliminated; // Set by store elimination

InWorkListFlag was later added by JDK-7153771.  As far as I can tell, the only one that was ever used is _is_eliminated/IsEliminatedFlag, which seems to have gone away between jdk5 and jdk6.

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PR Comment: https://git.openjdk.org/jdk/pull/21973#issuecomment-2465880763