RFR: 8354215: Clean up Loom support after 32-bit x86 removal

[Coleen Phillimore]

On Fri, 11 Apr 2025 08:31:06 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Small cleanup, we do not need this code anymore. This effectively reverts [JDK-8288040](https://bugs.openjdk.org/browse/JDK-8288040).
> 
> Additional testing:
>  - [ ] GHA

@pchilano Can you review too?

src/hotspot/cpu/x86/macroAssembler_x86.cpp line 2996:

> 2994: 
> 2995:   Label done;
> 2996:   cmpptr(rrealsp, Address(rthread, JavaThread::cont_fastpath_offset()));

While you're here, can you change rthread to r15_thread?

src/hotspot/cpu/x86/macroAssembler_x86.cpp line 3011:

> 3009:   cmpptr(rrealsp, Address(rthread, JavaThread::cont_fastpath_offset()));
> 3010:   jccb(Assembler::below, done);
> 3011:   movptr(Address(rthread, JavaThread::cont_fastpath_offset()), 0);

same here?  I think realsp might be useful to keep.  Or not, either way.  Since these are small functions it might be better to just use rsp.

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PR Review: https://git.openjdk.org/jdk/pull/24591#pullrequestreview-2760070293
PR Review Comment: https://git.openjdk.org/jdk/pull/24591#discussion_r2039370053
PR Review Comment: https://git.openjdk.org/jdk/pull/24591#discussion_r2039375247