Re: [PATCH]middle-end: replace GET_MODE_WIDER_MODE with GET_MODE_NEXT_MODE

[Richard Sandiford <richard.sandiford@arm.com>]

Tamar Christina <Tamar.Christina@arm.com> writes:
>> -----Original Message-----
>> From: Richard Sandiford <richard.sandiford@arm.com>
>> Sent: Tuesday, November 15, 2022 11:59 AM
>> To: Tamar Christina via Gcc-patches <gcc-patches@gcc.gnu.org>
>> Cc: Tamar Christina <Tamar.Christina@arm.com>; nd <nd@arm.com>;
>> rguenther@suse.de; jlaw@ventanamicro.com
>> Subject: Re: [PATCH]middle-end: replace GET_MODE_WIDER_MODE with
>> GET_MODE_NEXT_MODE
>> 
>> Tamar Christina via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
>> > Hi All,
>> >
>> > After the fix to the addsub patch yesterday for bootstrap I had only
>> regtested on x86.
>> > While looking today it seemed the new tests were failing, this was
>> > caused by a change in the behavior of the GET_MODE_WIDER_MODE
>> macro on trunk.
>> >
>> > This patch fixes that issue. Sorry for the mess, have rebased all branches
>> now.
>> >
>> > Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
>> >
>> > Ok for master?
>> >
>> > Thanks,
>> > Tamar
>> >
>> > gcc/ChangeLog:
>> >
>> > 	* match.pd: Replace GET_MODE_WIDER_MODE with
>> > 	GET_MODE_NEXT_MODE.
>> >
>> > --- inline copy of patch --
>> > diff --git a/gcc/match.pd b/gcc/match.pd index
>> >
>> 1b0ab7cf60fa4772fbe8304c622b0b8fab1bdefa..28191a992039c6f3a1dab5f7c0
>> e3
>> > 5dd58dc47092 100644
>> > --- a/gcc/match.pd
>> > +++ b/gcc/match.pd
>> > @@ -7997,7 +7997,7 @@ and,
>> >         machine_mode wide_mode;
>> >       }
>> >       (if (sel.series_p (0, 2, 0, 2)
>> > -          && GET_MODE_WIDER_MODE (vec_mode).exists (&wide_mode)
>> > +          && GET_MODE_NEXT_MODE (vec_mode).exists (&wide_mode)
>> >  	  && VECTOR_MODE_P (wide_mode)
>> >  	  && (GET_MODE_UNIT_BITSIZE (vec_mode) * 2
>> >  	      == GET_MODE_UNIT_BITSIZE (wide_mode)))
>> 
>> Does anything guarantee that the next mode will be the right one?
>> It think it would be safer to replace the last three && conditions with:
>> 
>>    && GET_MODE_2XWIDER_MODE (GET_MODE_INNER (vec_mode)).exists
>> (&wide_elt_mode)
>>    && multiple_p (GET_MODE_NUNITS (vec_mode), 2, &wide_nunits)
>>    && related_vector_mode (vec_mode, wide_elt_mode,
>> 			   wide_nunits).exists (&wide_mode)
>
> I see, respun patch accordingly.

LGTM, but I'm nervous when it comes to match.pd stuff so I'd prefer
Richi or Jeff to have the final say.

Thanks,
Richard

>
> Ok for master?
>
> --- inline copy of patch ---
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 1b0ab7cf60fa4772fbe8304c622b0b8fab1bdefa..82f05bbc912e4f80f3984d930c4a8dcb010136e1 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -7995,12 +7995,15 @@ and,
>         vec_perm_indices sel (builder, 2, nelts);
>         machine_mode vec_mode = TYPE_MODE (type);
>         machine_mode wide_mode;
> +       scalar_mode wide_elt_mode;
> +       poly_uint64 wide_nunits;
> +       scalar_mode inner_mode = GET_MODE_INNER (vec_mode);
>       }
>       (if (sel.series_p (0, 2, 0, 2)
> -          && GET_MODE_WIDER_MODE (vec_mode).exists (&wide_mode)
> -	  && VECTOR_MODE_P (wide_mode)
> -	  && (GET_MODE_UNIT_BITSIZE (vec_mode) * 2
> -	      == GET_MODE_UNIT_BITSIZE (wide_mode)))
> +	  && GET_MODE_2XWIDER_MODE (inner_mode).exists (&wide_elt_mode)
> +	  && multiple_p (GET_MODE_NUNITS (vec_mode), 2, &wide_nunits)
> +	  && related_vector_mode (vec_mode, wide_elt_mode,
> +				  wide_nunits).exists (&wide_mode))
>  	(with
>  	 {
>  	   tree stype