https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91204
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #3)
> --- gcc/optabs.c.jj 2019-07-15 10:53:10.743205405 +0200
> +++ gcc/optabs.c 2019-07-19 00:38:20.271852242 +0200
> @@ -2972,6 +2972,17 @@ expand_unop (machine_mode mode, optab un
> return target;
> }
>
> + /* Emit ~op0 as op0 ^ -1. */
> + if (unoptab == one_cmpl_optab
> + && (SCALAR_INT_MODE_P (mode) || GET_MODE_CLASS (mode) ==
> MODE_VECTOR_INT)
> + && optab_handler (xor_optab, mode) != CODE_FOR_nothing)
> + {
> + temp = expand_binop (mode, xor_optab, op0, CONSTM1_RTX (mode),
> + target, unsignedp, OPTAB_DIRECT);
> + if (temp)
> + return temp;
> + }
> +
> if (optab_to_code (unoptab) == NEG)
> {
> /* Try negating floating point values by flipping the sign bit. */
>
> seems to work for me. Or of course something similar can be done in
> config/i386/mmx.md, basically copy the sse.md one_cmpl<mode>2 pattern to
> mmx.md with TARGET_MMX_WITH_SSE and MMXMODEI iterator.
Doing it in the middle-end is better IMHO. But yeah, we're somewhat sloppy
with vector optabs checks in match.pd where it seems "obvious" targets need
to have support...
