RFR: 8283726: x86_64 intrinsics for compareUnsigned method in Integer and Long [v3]

[Quan Anh Mai]

On Tue, 28 Jun 2022 05:20:03 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add comparison for direct value of compare
>
> src/hotspot/cpu/x86/x86_64.ad line 13043:
> 
>> 13041:     __ cmpl($src1$$Register, $src2$$Register);
>> 13042:     __ movl($dst$$Register, -1);
>> 13043:     __ jccb(Assembler::below, done);
> 
> By placing compare adjacent to conditional jump in-order frontend can trigger macro-fusion. 
> Kindly refer section 3.4.2.2 of Intel's optimization manual.

I realised that by swapping the `mov` and the `cmp` instruction, the rule needs to have `dst` different from `src1` and `src2`, which increases register pressure.

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PR: https://git.openjdk.org/jdk/pull/9068