/* Optimize statements on expressions, using gfc.
   Copyright (C) 2010 Free Software Foundation, Inc.
   Contributed by Thomas König

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

/* This contains files for a front end optimizer.  */

#include "config.h"
#include "system.h"
#include "gfortran.h"
#include "arith.h"

/* Forward declarations.  */

static void strip_function_call (gfc_expr *);
static void optimize_assignment (gfc_code *);

/* Go through all executable statements of a namespace, invoking
   specific optimizations along the way.  */

void gfc_optimize_namespace (gfc_namespace * ns)
{
  gfc_code * c;

  for (c = ns->code; c; c = c->next)
    {
      switch (c->op)
	{
	case EXEC_ASSIGN:
	  optimize_assignment (c);
	default:
	  break;
	}
    }
}

/* Do the optimizations for assignments.  This function calls itself
   recursively for any successes.  */

static void
optimize_assignment (gfc_code * c)
{
  gfc_expr *lhs, *rhs;

  lhs = c->expr1;
  rhs = c->expr2;

  /* Optimize away a = trim(b), where a is a character variable.  */

  if (lhs->ts.type == BT_CHARACTER)
    {
      if (rhs->expr_type == EXPR_FUNCTION &&
	  rhs->value.function.isym &&
	  rhs->value.function.isym->id == GFC_ISYM_TRIM)
	{
	  strip_function_call (rhs);
	  optimize_assignment (c);
	}
    }
}

/* Remove an unneeded function call, modifying the expression.
   This replaces the function call with the value of its
   first argument.  The rest of the argument list is freed.  */

static void
strip_function_call (gfc_expr *e)
{
  gfc_expr *e1;
  gfc_actual_arglist *a;

  a = e->value.function.actual;

  /* We should have at least one argument.  */
  gcc_assert (a->expr != NULL);

  e1 = a->expr;

  /* Free the remaining arglist, if any.  */
  if (a->next)
    gfc_free_actual_arglist (a->next);

  /* Graft the argument expression onto the original function.  */
  *e = *e1;
  gfc_free (e1);

}