RFR: 8304450: [vectorapi] Refactor VectorShuffle implementation [v4]

[Quan Anh Mai]

On Wed, 22 Mar 2023 07:59:40 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   reviews
>
> src/hotspot/share/opto/vectorIntrinsics.cpp line 2059:
> 
>> 2057:   if (need_load_shuffle) {
>> 2058:     shuffle = gvn().transform(new VectorLoadShuffleNode(shuffle, vt));
>> 2059:   }
> 
> How about generating `VectorLoadShuffleNode` for all platforms that support Vector API, and remove the helper method `vector_needs_load_shuffle()` ? For those platforms that do not need this shuffle preparation, we can emit nothing  in codegen.

I think not emitting `VectorLoadShuffleNode` is more common so it is better to emit them only when needed, as it will simplify the graph and may allow better inspections of the indices in the future. Additionally, a do-nothing node does not alias with its input and therefore kills the input, which leads to an additional spill if they both need to live.

> src/hotspot/share/opto/vectorIntrinsics.cpp line 2426:
> 
>> 2424:   if (is_vector_shuffle(vbox_klass_from)) {
>> 2425:     return false; // vector shuffles aren't supported
>> 2426:   }
> 
> Is it better to change this as an "assertion" or print the log details?

The change indifferentiates a vector shuffle from a normal vector in C2, so this should be removed, as vector shuffles are converted to/from normal vector using this routine

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PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1144748489
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1144744663