Re: [PATCH] ifcvt/vect: Emit COND_ADD for conditional scalar reduction.

[Robin Dapp <rdapp.gcc@gmail.com>]

> So if you think you got everything correct the patch is OK as-is,
> I just wasn't sure - maybe the neutral_element change deserves
> a comment as to how MINUS_EXPR is handled.

Heh, I never think I got everything correct ;)

Added this now:

 static bool
 fold_left_reduction_fn (code_helper code, internal_fn *reduc_fn)
 {
+  /* We support MINUS_EXPR by negating the operand.  This also preserves an
+     initial -0.0 since -0.0 - 0.0 (neutral op for MINUS_EXPR) == -0.0 +
+     (-0.0) = -0.0.  */

What I still found is that aarch64 ICEs at the assertion you added
with -frounding-math.  Therefore I changed it to:

-         gcc_assert (!HONOR_SIGN_DEPENDENT_ROUNDING (vectype_out));
+         if (HONOR_SIGN_DEPENDENT_ROUNDING (vectype_out))
+           {
+             if (dump_enabled_p ())
+               dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                                "cannot vectorize fold-left reduction because"
+                                " signed zeros cannot be preserved.\n");
+             return false;
+           }

No code changes apart from that.  Will leave it until Monday and push then
barring any objections.

Thanks for the pointers.

Regards
 Robin