[Bug fortran/93956] Wrong array creation with p => array_dt(1:n)%component

["pault at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93956

--- Comment #16 from Paul Thomas <pault at gcc dot gnu.org> ---
Hi Thomas,

I am sorry that you are having such a hassle with this - perhaps this helps?

> 
> I assume that the span is not used correctly in the
> function.

Yes, that is correct. Within 'foo', we have 

    a.0 = (integer(kind=4)[0:D.3967] * restrict) a->data;

and the sum is inlined as:

        while (1)
          {
            if (S.10 > D.3961) goto L.1;
            val.9 = (*a.0)[S.10 * D.3963 + D.3960] + val.9;
            S.10 = S.10 + 1;
          }
        L.1:;

so that the sum becomes: sum(r(1:500)%u) + sum(r(1:500)%v).

This fixes the problem at the expense of more temporaries but regtests fine:

diff --git a/gcc/fortran/expr.c b/gcc/fortran/expr.c
index a9fa03ad153..8ca2b9bb3cb 100644
--- a/gcc/fortran/expr.c
+++ b/gcc/fortran/expr.c
@@ -1098,10 +1098,14 @@ is_subref_array (gfc_expr * e)
   bool seen_array;
   gfc_symbol *sym;

-  if (e->expr_type != EXPR_VARIABLE)
-    return false;

-  sym = e->symtree->n.sym;
+  if (e->expr_type == EXPR_VARIABLE)
+    sym = e->symtree->n.sym;
+  else if (e->expr_type == EXPR_FUNCTION
+          && gfc_expr_attr (e).subref_array_pointer)
+    return true;
+  else
+    return false;

   if (sym->attr.subref_array_pointer)
     return true;
@@ -4242,7 +4246,7 @@ gfc_check_pointer_assign (gfc_expr *lvalue, gfc_expr
*rvalue,
   if (rvalue->expr_type == EXPR_NULL)
     return true;

-  if (rvalue->expr_type == EXPR_VARIABLE && is_subref_array (rvalue))
+  if (is_subref_array (rvalue))
     lvalue->symtree->n.sym->attr.subref_array_pointer = 1;

   attr = gfc_expr_attr (rvalue);


Paul