RFR: 8300865: C2: product reduction in ProdRed_Double is not vectorized [v3]

[Sandhya Viswanathan]

On Tue, 23 May 2023 02:59:41 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> Sandhya Viswanathan has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   change to superword_max_vector_size
>
> src/hotspot/share/opto/superword.cpp line 3724:
> 
>> 3722:             // For vector reduction implemented check we need atleast two elements.
>> 3723:             int min_vec_size = MAX2(Matcher::min_vector_size(bt), 2);
>> 3724:             if (ReductionNode::implemented(use->Opcode(), min_vec_size, bt)) {
> 
> Hi @sviswa7, can we use `superword_max_vector_size()` as the input here? `MAX2(Matcher::min_vector_size(bt), 2);` may not tally with the actual situation on other 64-bit platforms. WDYT?

@fg1417 Thanks a lot for the review. Yes, we could use superword_max_vector_size here. I have made the change.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14065#discussion_r1203099854