Re: [PATCH] vect: Missed opportunity to use [SU]ABD

[<oluwatamilore.adebayo@arm.com>]

> Yeah.  Like Tami says, this is what the instruction does.
> 
> I think all three definitions are equivalent: the extend/operate/truncate
> one, the ?: one above, and the "max - min" one.  Probably just personal
> preference as to which seems more natural.

Decided to switch to using the ?: one as it makes more sense
for unsigned types.

> It would be good to document what the parameters mean (except VINFO,
> which is obvious).

Documentation added for vect_recog_absolute_difference.

> I think this should instead be:
> 
>   if (TYPE_PRECISION (unprom_diff.type) != TYPE_PRECISION (abs_type)
>       && TYPE_UNSIGNED (unprom_diff.type)
>       && TYPE_UNSIGNED (abs_type))
>     return false;
> 
> ....
> 
> I think the code would be easier to follow if it used vect_widened_op_tree
> first, and only considered the unextended case on failure.

Implemented Richard's suggested changes to vect_recog_absolute_difference.

> Minor formatting nit: GCC style is to indent braces by two spaces
> further than an "if":
> 
>   if (...)
>     {
>       ...
>     }

Adopted this style.

New patch will be in the reply.