https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70721
--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> --- There were already a number of discussions on gcc-patches in 2012 (Oct, Nov, Dec) with title "[i386] scalar ops that preserve the high part of a vector" (see also PR54855). In particular, around this message, rth says he doesn't like the vec_concat approach I had started with and prefers using vec_merge as with v4sf. https://gcc.gnu.org/ml/gcc-patches/2012-12/msg00824.html The latest message AFAICS was https://gcc.gnu.org/ml/gcc-patches/2012-12/msg00824.html which approves one approach, but I never found time to complete the series. (of course we should check that people haven't changed their mind since then)
