RFR: 8343689: AArch64: Optimize MulReduction implementation [v8]

[Hao Sun]

On Fri, 11 Jul 2025 01:39:11 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> Mikhail Ablakatov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   remove the strictly-ordered FP implementation as unused
>
> src/hotspot/share/opto/loopopts.cpp line 4715:
> 
>> 4713:     Node* last_accumulator = phi->in(2);
>> 4714:     Node* post_loop_reduction = ReductionNode::make(sopc, nullptr, init, last_accumulator, bt,
>> 4715:                                                     /* requires_strict_order */ false);
> 
> Why do you change this? Before it requires strict order, but now it is false.

IIUC, it's a correction here.

As noted by this function name `move_unordered_reduction_out_of_loop()` and the comment before this function, **unordered reduction** is expected to be generated. Hence, we should specify `/* requires_strict_order */ false`

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PR Review Comment: https://git.openjdk.org/jdk/pull/23181#discussion_r2199274046