RFR: 8345169: Implement JEP 503: Remove the 32-bit x86 Port

[Magnus Ihse Bursie]

On Tue, 4 Mar 2025 16:52:16 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This PR implements JEP 503: Remove the 32-bit x86 Port.
> 
> The JEP is proposed to target 25, we would not integrate until JEP is ready. Reviews are appreciated meanwhile.
> 
> This is only the removal of obvious 32-bit x86 parts, mostly files with `x86_32` in their name.  Those are only built when build system knows we are compiling for x86_32. There is therefore no impact on x86_64. The approach for removing x86_32 files only also makes this PR borderline trivial, and requires no additional testing beyond normal pre-integration checks.
> 
> The rest of the code is quite heavily intertwined with x86_64 and/or Zero, and would require accurate untangling. It would be much easier to review and test once we purge the free-standing parts of 32-bit x86 port, which is also a bulk of the port. The tangling with 32-bit x86 Zero is also why I did not touch most of the build system paths that handle x86. There is [JDK-8351148](https://bugs.openjdk.org/browse/JDK-8351148) umbrella that tracks further cleanup work. One can peek the final state that can be reached with all the cleanups in my earlier exploratory https://github.com/openjdk/jdk/pull/22567.
> 
> Additional testing:
>  - [x] Linux x86_32 Server fastdebug, `make bootcycle-images` (now fails configure)
>  - [x] Linux x86_64 Server fastdebug, `make bootcycle-images` (still works)
>  - [x] Linux x86_32 Zero fastdebug, `make bootcycle-images` (still works)
>  - [x] Linux x86_64 Zero fastdebug, `make bootcycle-images` (still works)

I agree with David here. Yes, implementing this multiple PRs is the correct approach (I think we all agree on this). However, it seems strange to mark just this single PR as implementing the JEP. Instead, that honor should fall on an umbrella JBS issue, which is dependent on this PR, but also the other planned updates. Before these are done, we can't really say that the JEP is implemented. In practical terms it does not mean much, but the bookkeeping seems better aligned with reality in that way.

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PR Comment: https://git.openjdk.org/jdk/pull/23906#issuecomment-2706212136