>> I am wondering whether we do have some situations that
>> vec_pack/vec_unpack/vec_widen_xxx/dot_prod pattern can be
>> beneficial for RVV ? I have ever met some situation that vec_unpack
>> can be beneficial when working on SELECT_VL but I don't which
>> case....
>
> With fixed size vectors you'll face the situation that the vectorizer
> chooses the "wrong" vector type so yes, I think implementing
> vec_unpack[s]_{lo,hi} might be useful. But I wouldn't prioritize this
> until you have a more clear picture of how useful it would be.
Another thing that comes to mind is that we currently don't do
vectorizable calls with mismatched vector sizes. So even if we detected
e.g. vec_widen_plus early it wouldn't get us much further.
On the other hand, I don't think we perform many optimizations on such
patterns between vect and combine (where we finally generate those).
Regards
Robin
