[Bug target/102483] Reduction of 4 chars can be improved

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102483

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |12.0
             Blocks|                            |53947

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's an interesting sub-case which we could eventually handle generally as a
mechanism for the final reduction.  Note we need to constrain vector [us]sad
as to which lanes are summed, otherwise we might get them to spread to
4 integer lanes.

Of course the target could simply provide reduc_plus_scal_v4qi ...


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations