[Bug rtl-optimization/56766] Fails to combine (vec_select (vec_concat ...)) to (vec_merge ...)

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56766



--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2013-04-02 
08:08:34 UTC ---

Btw, vec_merge is a special-case of a non-existing vec_shuffle2.

vec_merge (and a vec_suffle2) as opposed to a vec_select (vec_concat (...))

combination has the advantage that we don't need intermediate vector

modes of double size.



So in the long run it might be most profitable to remove vec_merge

and instead introduce vec_shuffle to catch almost all vec_select (vec_concat

())

cases.