[PATCH, fortran] reduce character array parameters (PR fortran/22491)

[David Edelsohn <dje at watson dot ibm dot com>]

	While fixing PR 21730, Feng Wang pointed out that constant
character array parameters produced an error message that they could not
be reduced.  For example,

        character*2 a (1)
        character*4 b (1)
        character*6 c
        parameter (a="12")
        parameter (b = a)
        write (c,'("#",A,"#")') b
        if (c .ne. '#12  #') call abort
        end

The value of the EXPR_VARIABLE is a constant and it is simplified to a
constant in expr.c:simplify_parameter_variable().  The subobject refs from
the original expression also are copied, which gives the impression that
subobjects were not elimintated during simplification, although they are
irrelevant in a constant expression.

	This patch modifies the function simplify_parameter_variable so
that subobject refs are not copied if the value is a constant expression,
allowing the example to succeed.

Okay for mainline?

Thanks, David


	PR fortran/22491
	* expr.c (simplify_parameter_variable): Do not copy the subobject
	references if the expression value is a constant.

Index: expr.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fortran/expr.c,v
retrieving revision 1.27
diff -c -p -r1.27 expr.c
*** expr.c	7 Jul 2005 07:54:41 -0000	1.27
--- expr.c	21 Jul 2005 01:47:32 -0000
*************** simplify_parameter_variable (gfc_expr * 
*** 1068,1074 ****
    try t;
  
    e = gfc_copy_expr (p->symtree->n.sym->value);
!   if (p->ref)
      e->ref = copy_ref (p->ref);
    t = gfc_simplify_expr (e, type);
  
--- 1068,1074 ----
    try t;
  
    e = gfc_copy_expr (p->symtree->n.sym->value);
!   if (e->expr_type != EXPR_CONSTANT && p->ref != NULL)
      e->ref = copy_ref (p->ref);
    t = gfc_simplify_expr (e, type);