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

[Richard Biener <richard.guenther@gmail.com>]

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 ()).

Maybe the need for the (ugly) safe_as_tree_code/fn_code goes away then.

Otherwise patch1 looks OK.

Unfortunately there are no ChangeLog / patch descriptions on the changes.
patch2 has

-  tree_code rhs_code = gimple_assign_rhs_code (assign);
-  if (rhs_code != code && rhs_code != widened_code)
+  code_helper rhs_code;
+  if (is_gimple_assign (stmt))
+    {
+      rhs_code = gimple_assign_rhs_code (stmt);
+      if (rhs_code.safe_as_tree_code () != code
+         && rhs_code.get_rep () != widened_code.get_rep ())
+       return 0;
+    }
+  else if (is_gimple_call (stmt))
+    {
+      rhs_code = gimple_call_combined_fn (stmt);
+      if (rhs_code.get_rep () != widened_code.get_rep ())
+       return 0;
+    }

that looks mightly complicated - esp. the use of get_rep ()
looks dangerous?  What's the intent of this?  Not that I
understand the existing code much.  A comment would
clearly help (also indicating test coverage).



> Kind regards,
> Andre