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

[Richard Sandiford]

Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
> On Wed, 20 Oct 2021 at 15:05, Richard Sandiford
> <richard.sandiford@arm.com> wrote:
>>
>> Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
>> > On Tue, 19 Oct 2021 at 19:58, Richard Sandiford
>> > <richard.sandiford@arm.com> wrote:
>> >>
>> >> 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 for the suggestions.
>> > Does the attached patch look OK ?
>>
>> Looks good apart from a couple of formatting nits.
>> >
>> > Thanks,
>> > Prathamesh
>> >>
>> >> Thanks,
>> >> Richard
>> >>
>> >> > +       else
>> >> > +         error ("pragma or attribute %<target(\"%s\")%> is not valid", token);
>> >> > +       free (str);
>> >> >         return false;
>> >> >       }
>> >> >
>> >
>> > [aarch64] PR102376 - Emit better diagnostics for arch extension in target attribute.
>> >
>> > gcc/ChangeLog:
>> >       PR target/102376
>> >       * config/aarch64/aarch64.c (aarch64_handle_attr_isa_flags): Change str's
>> >       type to const char *.
>> >       (aarch64_process_target_attr): Check if token is possibly an arch extension
>> >       without leading '+' and emit diagnostic accordingly.
>> >
>> > gcc/testsuite/ChangeLog:
>> >       PR target/102376
>> >       * gcc.target/aarch64/pr102376.c: New test.
>> > diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
>> > index a9a1800af53..b72079bc466 100644
>> > --- a/gcc/config/aarch64/aarch64.c
>> > +++ b/gcc/config/aarch64/aarch64.c
>> > @@ -17548,7 +17548,7 @@ aarch64_handle_attr_tune (const char *str)
>> >     modified.  */
>> >
>> >  static bool
>> > -aarch64_handle_attr_isa_flags (char *str)
>> > +aarch64_handle_attr_isa_flags (const char *str)
>> >  {
>> >    enum aarch64_parse_opt_result parse_res;
>> >    uint64_t isa_flags = aarch64_isa_flags;
>> > @@ -17821,7 +17821,13 @@ 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 '+'.  */
>> > +       auto with_plus = std::string("+") + token;
>>
>> Should be a space before “(”.
>>
>> > +       if (aarch64_handle_attr_isa_flags (with_plus.c_str ()))
>> > +         error ("arch extension %<%s%> should be prepended with %<+%>", token);
>>
>> Long line, should be:
>>
>>             error ("arch extension %<%s%> should be prepended with %<+%>",
>>                    token);
>>
>> OK with those changes, thanks.
> Thanks, the patch regressed some target attr tests because it emitted
> diagnostics twice from
> aarch64_handle_attr_isa_flags.
> So for eg, spellcheck_1.c:
> __attribute__((target ("arch=armv8-a-typo"))) void foo () {}
>
> results in:
> spellcheck_1.c:5:1: error: invalid name ("armv8-a-typo") in
> ‘target("arch=")’ pragma or attribute
>     5 | {
>       | ^
> spellcheck_1.c:5:1: note: valid arguments are: armv8-a armv8.1-a
> armv8.2-a armv8.3-a armv8.4-a armv8.5-a armv8.6-a armv8.7-a armv8-r
> armv9-a
> spellcheck_1.c:5:1: error: invalid feature modifier arch=armv8-a-typo
> of value ("+arch=armv8-a-typo") in ‘target()’ pragma or attribute
> spellcheck_1.c:5:1: error: pragma or attribute
> ‘target("arch=armv8-a-typo")’ is not valid
>
> The patch adds an additional argument to the
> aarch64_handle_attr_isa_flags, to optionally not emit an error, which
> works to fix the issue.
> Does it look OK ?

I think we should instead call aarch64_parse_arch directly, passing
temporary ISA flags instead of &aarch64_isa_flags.  That should ensure
that the call has no side effects.

I agree the new wording (in the later patch) is better, thanks.

Richard