[GOMP4, OpenACC] Fixed-form Fortran code failing to parse

[Tobias Burnus]

Cesar Philippidis wrote:
>>> I couldn't find anything obvious in gcc/fortran/parse.c; is someone
>>> able to have a more in-depth look than I have?
>> First, some minor point, I think one should crosswise reset the
>> {openmp,openacc}_flag, i.e.
>>
>> --- a/gcc/fortran/scanner.c
>> +++ b/gcc/fortran/scanner.c
>> @@ -735,2 +735,3 @@ skip_oacc_attribute (locus start, locus old_loc,
>> bool continue_flag)
>>                openacc_flag = 1;
>> +              openmp_flag = 0;
>>                openacc_locus = old_loc;
>> @@ -775,2 +776,3 @@ skip_omp_attribute (locus start, locus old_loc, bool
>> continue_flag)
>>                openmp_flag = 1;
>> +             openacc_flag = 0;
>>                openmp_locus = old_loc;
> I think openmp and openacc should be able to coexist, so that should be
> left in for now.

Well, -fopenmp and -fopenacc should coexist, which means that both 
gfc_option.gfc_flag_openmp  (or gfc_option.gfc_flag_openmp_simd) and 
gfc_option.gfc_flag_openacc should coexist. However, openacc_flag and 
openmp_flag are used for continuation lines – and the same line cannot 
be simultaneously an OpenMP and an OpenACC statement. Thus, openacc_flag 
and openmp_flag should be mutually exclusive.

I don't know whether it makes a difference in practice; if it doesn't 
one could also change it into a single flag. However, I would simply 
ensure that maximally only one is set at a given time.

>> Secondly, the following looks wrong (also scanner.c). I have the feeling
>> that this could be behind the issue above. But in any case, it looks
>> wrong to me.
>>
>>
>> skip_fixed_comments (void)
>> ...
>>        start = gfc_current_locus;
>>        c = next_char ();
>>        if (c == '!' || c == 'c' || c == 'C' || c == '*')
>> ...
>>            if (gfc_option.gfc_flag_openmp)
>>              {
>>                if (next_char () == '$')
>> ...
>>                gfc_current_locus = start;
>> ...
>>            if (gfc_option.gfc_flag_openacc)
>>              {
>>                if (next_char () == '$')
>>                  {
> Namely: If "omp" or the "!$" continuation lines hasn't been matched, one
> returns to "start". However, start is "!" or "*" in this case and not
> "$". In addition, also in this case, one might want to set the other
> flag to 0.
>

I still think that there is something wrong with the gfc_current_local 
handling above – even if it is not behind the bug we are currently 
seeing. In addition, I wonder whether the inner else branch couldn't be 
merged, i.e. the one which takes care of conditional compilation of the form
   !$ This line is a comment, unless -fopenmp or -fopenacc is enabled

Those checks appear twice for fixed-form source code and the code is 24 lines long in either case.

> The problem was inside skip_fixed_comments. The openacc_flag wasn't
> being set to zero at the end of that function. [...]
> Thomas, is this patch ok for gomp-4_0-branch? If so, please check it in.

Looks good to me. Thanks for the patch.

Tobias