Re: [ping][vect-patterns] Refactor widen_plus/widen_minus as internal_fns

["Andre Vieira (lists)" <andre.simoesdiasvieira@arm.com>]

On 25/04/2023 13:30, Richard Biener wrote:
> On Mon, 24 Apr 2023, Richard Sandiford wrote:
> 
>> Richard Biener <richard.guenther@gmail.com> writes:
>>> On Thu, Apr 20, 2023 at 3:24?PM Andre Vieira (lists) via Gcc-patches
>>> <gcc-patches@gcc.gnu.org> wrote:
>>>>
>>>> Rebased all three patches and made some small changes to the second one:
>>>> - removed sub and abd optabs from commutative_optab_p, I suspect this
>>>> was a copy paste mistake,
>>>> - removed what I believe to be a superfluous switch case in vectorizable
>>>> conversion, the one that was here:
>>>> +  if (code.is_fn_code ())
>>>> +     {
>>>> +      internal_fn ifn = as_internal_fn (code.as_fn_code ());
>>>> +      int ecf_flags = internal_fn_flags (ifn);
>>>> +      gcc_assert (ecf_flags & ECF_MULTI);
>>>> +
>>>> +      switch (code.as_fn_code ())
>>>> +       {
>>>> +       case CFN_VEC_WIDEN_PLUS:
>>>> +         break;
>>>> +       case CFN_VEC_WIDEN_MINUS:
>>>> +         break;
>>>> +       case CFN_LAST:
>>>> +       default:
>>>> +         return false;
>>>> +       }
>>>> +
>>>> +      internal_fn lo, hi;
>>>> +      lookup_multi_internal_fn (ifn, &lo, &hi);
>>>> +      *code1 = as_combined_fn (lo);
>>>> +      *code2 = as_combined_fn (hi);
>>>> +      optab1 = lookup_multi_ifn_optab (lo, !TYPE_UNSIGNED (vectype));
>>>> +      optab2 = lookup_multi_ifn_optab (hi, !TYPE_UNSIGNED (vectype));
>>>>        }
>>>>
>>>> I don't think we need to check they are a specfic fn code, as we look-up
>>>> optabs and if they succeed then surely we can vectorize?
>>>>
>>>> OK for trunk?
>>>
>>> In the first patch I see some uses of safe_as_tree_code like
>>>
>>> +  if (ch.is_tree_code ())
>>> +    return op1 == NULL_TREE ? gimple_build_assign (lhs,
>>> ch.safe_as_tree_code (),
>>> +                                                  op0) :
>>> +                             gimple_build_assign (lhs, ch.safe_as_tree_code (),
>>> +                                                  op0, op1);
>>> +  else
>>> +  {
>>> +    internal_fn fn = as_internal_fn (ch.safe_as_fn_code ());
>>> +    gimple* stmt;
>>>
>>> where the context actually requires a valid tree code.  Please change those
>>> to force to tree code / ifn code.  Just use explicit casts here and the other
>>> places that are similar.  Before the as_internal_fn just put a
>>> gcc_assert (ch.is_internal_fn ()).
>>
>> Also, doesn't the above ?: simplify to the "else" arm?  Null trailing
>> arguments would be ignored for unary operators.
>>
>> I wasn't sure what to make of the op0 handling:
>>
>>> +/* Build a GIMPLE_ASSIGN or GIMPLE_CALL with the tree_code,
>>> +   or internal_fn contained in ch, respectively.  */
>>> +gimple *
>>> +vect_gimple_build (tree lhs, code_helper ch, tree op0, tree op1)
>>> +{
>>> +  if (op0 == NULL_TREE)
>>> +    return NULL;
>>
>> Can that happen, and if so, does returning null make sense?
>> Maybe an assert would be safer.
> 
> Yeah, I was hoping to have a look whether the new gimple_build
> overloads could be used to make this all better (but hoped we can
> finally get this series in in some way).
> 
> Richard.

Yeah, in the newest version of the first patch of the series I found 
that most of the time I can get away with only really needing to 
distinguish between tree_code and internal_fn when building gimple, for 
which it currently uses vect_gimple_build, but it does feel like that 
could easily be a gimple function.

Having said that, as I partially mention in the patch, I didn't rewrite 
the optabs-tree supportable_half_widening and supportable_conversion (or 
whatever they are called) because those also at some point need to 
access the stmt and there is a massive difference in how we handle 
gassigns and gcall's from that perspective, but maybe we can generalize 
that too somehow...

Anyway have a look at the new versions (posted just some minutes after 
the email I'm replying too haha! timing :P)