RFR: 8321003: RISC-V: C2 MulReductionVI [v5]

[Hamlin Li]

On Tue, 18 Feb 2025 11:35:43 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   copyright
>
> src/hotspot/cpu/riscv/riscv_v.ad line 2494:
> 
>> 2492: 
>> 2493: instruct reduce_mulF(fRegF dst, fRegF fsrc, vReg vsrc,
>> 2494:                      vReg tmp1, vReg tmp2) %{
> 
> Seems to me that we need a `predicate(!n->as_Reduction()->requires_strict_order())` for all these newly-added floating-point reduce multiply matched rules. The reason is that your `reduce_mul_fp_v` doesn't respect the order of the operands. And we should better rename the name of the match rules to something like `unordered_reduce_mulF`.
> 
> Reference: https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/x86.ad#L5281

Yes, you're right, fixed. Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/23580#discussion_r1959866663