[Bug tree-optimization/54939] Very poor vectorization of loops with complex arithmetic

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54939

--- Comment #11 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to rguenther@suse.de from comment #10)
> even if that means introducing of "fake" larger vector modes.

That would be a good reason to not do this, except many targets already
do need double-length modes to describe their permute instructions?