On Mon, May 25, 2020 at 7:36 PM Richard Biener <rguent...@suse.de> wrote: > > On Mon, 25 May 2020, Uros Bizjak wrote: > > > On Mon, May 25, 2020 at 8:27 AM Richard Biener <rguent...@suse.de> wrote: > > > > > > On May 25, 2020 8:12:12 AM GMT+02:00, Uros Bizjak <ubiz...@gmail.com> > > > wrote: > > > >On Mon, May 25, 2020 at 7:53 AM Hongtao Liu <crazy...@gmail.com> wrote: > > > > > > > >> > We have to introduce a new expander, that will have conforming mode > > > >of > > > >> > output operand (V2SF) and will produce RTX that will match > > > >> > *float<floatunssuffix>v2div2sf2. A paradoxical output subreg from > > > >> > V2SFmode V4SFmode is needed, generated by simplify_gen_subreg as is > > > >> > the case with paradoxical input subreg. > > > >> > > > >> Problem`is simplify_gen_subreg (V4SFmode, operands[0], V2SFmode, 0) > > > >> will return NULL since > > > >> ---- > > > >> 948 /* Subregs involving floating point modes are not allowed to > > > >> 949 change size. Therefore (subreg:DI (reg:DF) 0) is fine, but > > > >> 950 (subreg:SI (reg:DF) 0) isn't. */ > > > > > > > >But, we are not changing size, we are still operating with SFmode. It > > > >looks to me that this limitation is too strict, the intention is to > > > >not expand scalar SFmode to DFmode. > > > > > > I guess so. The test probably wants to tes the component mode. > > > > There is already some fishy x86 specific workaround in place, which I > > took the liberty to extend to vector modes. The attached patch that > > exercises this code works as expected, and produces expected code. > > > > Liu, can you please test the attached patch? > >
Bootstrap is ok, regression test for i386/x86-64 backend is ok. > > Richi, is the middle end part OK? > > + i.e. (subreg:V4SF (reg:SF) 0) or (subreg:V4SF (reg:V2SF) 0). This > + surely isn't the cleanest way to represent this. It's questionable > + if this ought to be represented at all -- why can't this all be > hidden > + in post-reload splitters that make arbitrarily mode changes to the > + registers themselves. */ > + else if (VECTOR_MODE_P (omode) > + && (GET_MODE_INNER (omode) == imode > + || (VECTOR_MODE_P (imode) > + && (GET_MODE_INNER (omode) == GET_MODE_INNER > (imode))))) > ; > > I'd formulate this simpler, as > > else if (VECTOR_MODE_P (omode) > && GET_MODE_INNER (omode) == GET_MODE_INNER (imode)) > I think they are functionally the same, so i won't bother to run another round test. > since GET_MODE_INNER (DFmode) == DFmode. > > We also allow (subreg:V4SF (reg:V2DF) 0) where we effectively > subref DF with SF but the size check covers the whole vector, so > the comment on the code with float modes is a bit misleading IMHO. > > It also leads to the strange situation that both > (subreg:V4SF (reg:V2DF) 0) and (subreg:V8SF (reg:V4SF) 0) is valid > but (subreg:V8SF (reg:V2DF) 0) is not. > > Anyway, I think generalizing the existing exception is obvious enough > thus OK with my suggestion for the simplification if nobody else > has differing comments. > > Thanks, > Richard. -- BR, Hongtao
