Re: [PATCH 2/2] Fortran: add attribute target_clones

[Mikael Morin <morin-mikael@orange.fr>]

Le 21/11/2022 à 23:26, Bernhard Reutner-Fischer a écrit :
> On Mon, 21 Nov 2022 20:13:40 +0100
> Mikael Morin <morin-mikael@orange.fr> wrote:
> 
>> Hello,
>>
>> Le 09/11/2022 à 20:02, Bernhard Reutner-Fischer via Fortran a écrit :
>>> Hi!
>>>
(...)
>>> +  if (allow_multiple && gfc_match_char (')') != MATCH_YES)
>>> +    {
>>> +      gfc_error ("expected ')' at %C");
>>> +      return NULL_TREE;
>>> +    }
>>> +
>>> +  return attr_args;
>>> +}
>> I'm not sure this function need to do all the parsing manually.
>> I would rather use gfc_match_actual_arglist, or maybe implement the
>> function as a wrapper around it.
>> What is allowed here?  Are non-literal constants allowed, for example
>> parameter variables?  Is line continuation supported ?
> 
> Line continuation is supported i think.
> Parameter variables supposedly are or should not be supported. Why would
> you do that in the context of an attribute target decl? > Either way, if the ME does not find such an fndecl, it will complain
> and ignore the attribute.
> I don't understand non-literal constants in this context.
> This very attribute applies to decls, so the existing code supposedly
> matches a comma separated list of identifiers. The usual dollar-ok
> caveats apply.
> 
No, my comment and my questions were about your function, which, as I 
understand it, matches the arguments to the attribute: it matches open 
and closing parenthesis, double quotes, etc.
Matching of decl names comes after that.
I asked the question about non-literal constant (and the other as well), 
because I saw it as a possible reason to not reuse the existing parsing 
functions.

> As to gfc_match_actual_arglist, probably.
> target_clones has
> +  { "target_clones",          1, -1, true, false, false, false,
> +                             dummy, NULL },
> with tree-core.h struct attribute_spec, so
> name, min=1, max=unbounded, decl_required=yes, ...ignore...
> 
> hence applies to functions and subroutines and the like. It does take an
> unbounded list of strings, isa1, isa2, isa4, default. We could add
> "default" unless seen, but i'd rather want it spelled out by the user
> for the user is supposed to know what she's doing, as in c or c++.
> The ME has code to sanity-check the attributes, including conflicting
> (ME) attributes.
> 
> The reason why i contemplated with a separate parser was that for stuff
> like regparm or sseregparm, you would want to require a single number
> for the equivalent of
> 
> __attribute__((regparm(3),stdcall)
> 
> which you would provide in 2 separate !GCC$ attributes i assume.
> 
Well, the check could as easily be enforced after parsing with the 
existing parsing functions.

>>
>> Nothing (bad) to say about the rest, but there is enough to change with
>> the above comments.
> 
> Yes, many thanks for your comments.
> I think there is no other non-intrusive way to pass the data through the
> frontend. So for an acceptable way this means touching quite some spots
> for every single ME attribute anybody would like to add in the future.

I'm not sure I understand.  Please let's just add what is necessary for 
this attribute, not more.