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

[Jeff Law <jeffreyalaw@gmail.com>]

On 11/15/22 07:54, Richard Sandiford via Gcc-patches wrote:
> 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.

It's just a matter of finding that 2X wider mode to make the 
transformation possible.  So I don't see any concerns here.


jeff