Scalarization of simplification of constant expressions?

Scalarization of simplification of constant expressions?

[Harald Anlauf]

Dear all,

the restrictions on what can be used in constant expressions have been
greatly reduced in F2018, so one might want to simplify more than what
was possible before.

E.g. the following is currently not simplified at compile time:

  print *, index('abcd',['c'], .true. )
  print *, index('abcd', 'b' ,[.true.])

c.f. PR95979, while the scalar variants do simplify.

Is there something like scalarization also available for simplification
of constant expressions?

Regards,
Harald

Re: Scalarization of simplification of constant expressions?

[Paul Richard Thomas]

Hi Harald,

Yes, there is a scalarizer for elemental calls:
expr.c(scalarize_intrinsic_call) first appears in 2007.

Cheers

Paul


On Mon, 5 Oct 2020 at 20:59, Harald Anlauf <anlauf@gmx.de> wrote:

> Dear all,
>
> the restrictions on what can be used in constant expressions have been
> greatly reduced in F2018, so one might want to simplify more than what
> was possible before.
>
> E.g. the following is currently not simplified at compile time:
>
>   print *, index('abcd',['c'], .true. )
>   print *, index('abcd', 'b' ,[.true.])
>
> c.f. PR95979, while the scalar variants do simplify.
>
> Is there something like scalarization also available for simplification
> of constant expressions?
>
> Regards,
> Harald
>
>

-- 
"If you can't explain it simply, you don't understand it well enough" -
Albert Einstein

Aw: Re: Scalarization of simplification of constant expressions?

[Harald Anlauf]

Hi Paul,
 
> Yes, there is a scalarizer for elemental calls: expr.c(scalarize_intrinsic_call) first appears in 2007.
 
thanks for pointing this out.
 
However, can you elaborate a little bit on how to use it?
 
A grep show just two places where it is used, and only in expr.c:
 
 
In gfc_simplify_expr:
 

      if (p->expr_type == EXPR_FUNCTION)
    {
      if (p->symtree)
        isym = gfc_find_function (p->symtree->n.sym->name);
      if (isym && isym->elemental)
        scalarize_intrinsic_call (p, false);
    }
 
 

In gfc_check_init_expr:
 

    /* Try to scalarize an elemental intrinsic function that has an
       array argument.  */
    isym = gfc_find_function (e->symtree->n.sym->name);
    if (isym && isym->elemental
        && (t = scalarize_intrinsic_call (e, true)))
      break;
 
 
Do you have an example how to apply it?
 
Thanks,
Harald