[PATCH 2/5, OpenACC] Support Fortran optional arguments in the firstprivate clause

[Kwok Cheung Yeung]

On 12/07/2019 12:41 pm, Jakub Jelinek wrote:
> This should be done through a langhook.
> Are really all PARM_DECLs wtih DECL_BY_REFERENCE and pointer type optional
> arguments?  I mean, POINTER_TYPE is used for a lot of cases.

Hmmm... I thought it was the case that if you pass an argument in by reference 
(the default) in Fortran, the PARM_DECL will always be a reference to the 
argument type if non-optional, or a pointer if optional. However, fixed-shape 
arrays are passed in via a pointer whether optional or not...

I also experimented with passing in a pointer by value, but it seems like that 
is not allowed. e.g.

   subroutine foo(x)
     integer, pointer, value :: x
   end subroutine foo

results in:

    11 |     integer, pointer, value :: x
       |                           1
Error: VALUE attribute conflicts with POINTER attribute at (1)

Are there any more examples in Fortran where a PARM_DECL is a pointer type 
without being optional?

In the Fortran FE, optional arguments are indicated by setting attr.optional on 
the gfc_symbol for the parameter, but the OMP lowering works on a tree - is it 
somehow possible to get from the tree back to the gfc_symbol? If so, that would 
be a more reliable method of detecting optional arguments.

Thanks

Kwok