Re: [ping][vect-patterns] Refactor widen_plus/widen_minus as internal_fns

[Richard Biener <rguenther@suse.de>]

On Mon, 24 Apr 2023, Richard Sandiford wrote:

> Richard Biener <richard.guenther@gmail.com> writes:
> > On Thu, Apr 20, 2023 at 3:24?PM Andre Vieira (lists) via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> >>
> >> Rebased all three patches and made some small changes to the second one:
> >> - removed sub and abd optabs from commutative_optab_p, I suspect this
> >> was a copy paste mistake,
> >> - removed what I believe to be a superfluous switch case in vectorizable
> >> conversion, the one that was here:
> >> +  if (code.is_fn_code ())
> >> +     {
> >> +      internal_fn ifn = as_internal_fn (code.as_fn_code ());
> >> +      int ecf_flags = internal_fn_flags (ifn);
> >> +      gcc_assert (ecf_flags & ECF_MULTI);
> >> +
> >> +      switch (code.as_fn_code ())
> >> +       {
> >> +       case CFN_VEC_WIDEN_PLUS:
> >> +         break;
> >> +       case CFN_VEC_WIDEN_MINUS:
> >> +         break;
> >> +       case CFN_LAST:
> >> +       default:
> >> +         return false;
> >> +       }
> >> +
> >> +      internal_fn lo, hi;
> >> +      lookup_multi_internal_fn (ifn, &lo, &hi);
> >> +      *code1 = as_combined_fn (lo);
> >> +      *code2 = as_combined_fn (hi);
> >> +      optab1 = lookup_multi_ifn_optab (lo, !TYPE_UNSIGNED (vectype));
> >> +      optab2 = lookup_multi_ifn_optab (hi, !TYPE_UNSIGNED (vectype));
> >>       }
> >>
> >> I don't think we need to check they are a specfic fn code, as we look-up
> >> optabs and if they succeed then surely we can vectorize?
> >>
> >> OK for trunk?
> >
> > In the first patch I see some uses of safe_as_tree_code like
> >
> > +  if (ch.is_tree_code ())
> > +    return op1 == NULL_TREE ? gimple_build_assign (lhs,
> > ch.safe_as_tree_code (),
> > +                                                  op0) :
> > +                             gimple_build_assign (lhs, ch.safe_as_tree_code (),
> > +                                                  op0, op1);
> > +  else
> > +  {
> > +    internal_fn fn = as_internal_fn (ch.safe_as_fn_code ());
> > +    gimple* stmt;
> >
> > where the context actually requires a valid tree code.  Please change those
> > to force to tree code / ifn code.  Just use explicit casts here and the other
> > places that are similar.  Before the as_internal_fn just put a
> > gcc_assert (ch.is_internal_fn ()).
> 
> Also, doesn't the above ?: simplify to the "else" arm?  Null trailing
> arguments would be ignored for unary operators.
> 
> I wasn't sure what to make of the op0 handling:
> 
> > +/* Build a GIMPLE_ASSIGN or GIMPLE_CALL with the tree_code,
> > +   or internal_fn contained in ch, respectively.  */
> > +gimple *
> > +vect_gimple_build (tree lhs, code_helper ch, tree op0, tree op1)
> > +{
> > +  if (op0 == NULL_TREE)
> > +    return NULL;
> 
> Can that happen, and if so, does returning null make sense?
> Maybe an assert would be safer.

Yeah, I was hoping to have a look whether the new gimple_build
overloads could be used to make this all better (but hoped we can
finally get this series in in some way).

Richard.