Re: [aarch64] PR102376 - Emit better diagnostic for arch extensions in target attr

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

Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
> Hi,
> The attached patch emits a more verbose diagnostic for target attribute that
> is an architecture extension needing a leading '+'.
>
> For the following test,
> void calculate(void) __attribute__ ((__target__ ("sve")));
>
> With patch, the compiler now emits:
> 102376.c:1:1: error: arch extension ‘sve’ should be prepended with ‘+’
>     1 | void calculate(void) __attribute__ ((__target__ ("sve")));
>       | ^~~~
>
> instead of:
> 102376.c:1:1: error: pragma or attribute ‘target("sve")’ is not valid
>     1 | void calculate(void) __attribute__ ((__target__ ("sve")));
>       | ^~~~

Nice :-)

> (This isn't specific to sve though).
> OK to commit after bootstrap+test ?
>
> Thanks,
> Prathamesh
>
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index a9a1800af53..975f7faf968 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -17821,7 +17821,16 @@ aarch64_process_target_attr (tree args)
>        num_attrs++;
>        if (!aarch64_process_one_target_attr (token))
>  	{
> -	  error ("pragma or attribute %<target(\"%s\")%> is not valid", token);
> +	  /* Check if token is possibly an arch extension without
> +	     leading '+'.  */
> +	  char *str = (char *) xmalloc (strlen (token) + 2);
> +	  str[0] = '+';
> +	  strcpy(str + 1, token);

I think std::string would be better here, e.g.:

  auto with_plus = std::string ("+") + token;

> +	  if (aarch64_handle_attr_isa_flags (str))
> +	    error("arch extension %<%s%> should be prepended with %<+%>", token);

Nit: should be a space before the “(”.

In principle, a fixit hint would have been nice here, but I don't think
we have enough information to provide one.  (Just saying for the record.)

Thanks,
Richard

> +	  else
> +	    error ("pragma or attribute %<target(\"%s\")%> is not valid", token);
> +	  free (str);
>  	  return false;
>  	}
>