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

[Vladimir Kozlov]

On Fri, 10 Jan 2025 18:30:04 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Right. Now that I am thinking more deeply about it, maybe that would be a first step here: lift UseSSE >= 2 for x86_32 ahead of this JEP, eliminate all UseSSE < 2 parts. I can see how intrusive this gets.
>
> [not reviewing, just a drive-by comment] Does UseSSE < 2 provide a way to _avoid_ using relevant parts of
> SSE on x86_64, perhaps for debugging?  Or does x86_64 effectively hard-wire UseSSE >= 2?

By default all 64-bits x86 CPU (starting from AMD64) supports all instructions up to SSE2. 32-bit x86 CPU may not support SSE2.

We can generated sse1 or use FPU instructions in 64-bit VM but we decided not to do that -  SSE2 instructions version were much easier to use. We purged all uses of FPU in JDK 15: [JDK-7175279](https://bugs.openjdk.org/browse/JDK-7175279) by using SSE set of instructions because we did not want to mess (save/restore state) with FPU anymore in 64-bit VM.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22567#discussion_r1911258635