RFR: 8372285: G1: Micro-optimize x86 barrier code [v2]

[Aleksey Shipilev]

On Fri, 21 Nov 2025 09:46:59 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Comment
>>  - Shorten a few more branches
>
> src/hotspot/cpu/x86/gc/g1/g1BarrierSetAssembler_x86.cpp line 209:
> 
>> 207:   // Jump out if done, or fall-through to runtime
>> 208:   __ bind(L_null);
>> 209:   __ jmp(L_done);
> 
> Maybe add a comment that we do not know the distance of `L_done` we use the long form or something (I assume that's the reason for not using `jmpb` here).

I don't see significant value in a comment like that, but why not, added.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28446#discussion_r2549197438