On Wed, Mar 20, 2013 at 4:13 PM, Richard Henderson <r...@redhat.com> wrote: > On 03/20/2013 08:00 AM, Marc Glisse wrote: >> Do you at least agree that vector-vector subregs make sense, or is that part >> wrong as well? > > You mean a V4SImode subreg of a V8SImode register, not just same-size casting? > It makes logical sense, but I'm fairly sure you'll need a lot more surgery > throughout the compiler to make that happen. > > I'm curious how a define_expand can fail in LRA, but your define_insn > succeeds? > Is the failure because of ix86_cannot_change_mode_class? Because that hook > fairly well defines what subregs are valid. And if that says it isn't valid, > then even having a define_insn that uses such is wrong.
Don't we have vec_select to get a V4SImode out of a V8SImode? So you only need a define_insn that special-cases the subreg-like ones? Richard. > > r~
