RFR: 8302652: [SuperWord] Reduction should happen after loop, when possible [v2]

[Pengfei Li]

On Mon, 8 May 2023 07:10:23 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> src/hotspot/share/opto/loopopts.cpp line 4318:
>> 
>>> 4316: 
>>> 4317: #ifdef ASSERT
>>> 4318:     if (TraceNewVectors) {
>> 
>> Not sure if this is required. But I haven't seen the creation of vector phi is traced in other places.
>
> Do we even have any other Vector Phi's? SuperWord never does it. Maybe in the Vector API?

My colleague working on VectorAPI just told me yes. A scalar phi may eventually become a vector phi after several transformations in vector intrinsics and vector box/unbox optimizations.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13056#discussion_r1187139644