[patch, fortran] Fix PR 78021

[Thomas Koenig]

Hello world,

this rather self-explanatory patch fixes a problem where two
function invocations with 'c    ' and 'c' as arguments
were considered equal.

Regression-tested.  OK for trunk and 6 and 5 branches?

Regards

        Thomas

2016-10-22  Thomas Koenig  <tkoe...@gcc.gnu.org>

        PR fortran/78021
        * gfc_compare_functions:  Strings with different lengths in
        argument lists compare unequal.

2016-10-22  Thomas Koenig  <tkoe...@gcc.gnu.org>

        PR fortran/78021
        * gfortran.dg/string_length-3.f90:  New test.

! { dg-do run }
! { dg-options "-ffrontend-optimize -fdump-tree-original" }
! PR 78021 - calls to mylen were folded after shortening the
! argument list.

PROGRAM test_o_char
  implicit none
  integer :: n
  n = mylen('c') + mylen('c   ')
  if (n /= 5) call abort
CONTAINS

  FUNCTION mylen(c)
    CHARACTER(len=*),INTENT(in) :: c
    INTEGER :: mylen
    mylen=LEN(c)
  END FUNCTION mylen
END PROGRAM test_o_char
! { dg-final { scan-tree-dump-times "__var" 0 "original" } }

Index: dependency.c
===================================================================
--- dependency.c	(Revision 240928)
+++ dependency.c	(Arbeitskopie)
@@ -226,10 +226,27 @@ gfc_dep_compare_functions (gfc_expr *e1, gfc_expr
 	  if ((args1->expr == NULL) ^ (args2->expr == NULL))
 	    return -2;
 
-	  if (args1->expr != NULL && args2->expr != NULL
-	      && gfc_dep_compare_expr (args1->expr, args2->expr) != 0)
-	    return -2;
+	  if (args1->expr != NULL && args2->expr != NULL)
+	    {
+	      gfc_expr *e1, *e2;
+	      e1 = args1->expr;
+	      e2 = args2->expr;
 
+	      if (gfc_dep_compare_expr (e1, e2) != 0)
+		return -2;
+
+	      /* Special case: String arguments which compare equal can have
+		 different lengths, which makes them different in calls to
+		 procedures.  */
+	      
+	      if (e1->expr_type == EXPR_CONSTANT
+		  && e1->ts.type == BT_CHARACTER
+		  && e2->expr_type == EXPR_CONSTANT
+		  && e2->ts.type == BT_CHARACTER
+		  && e1->value.character.length != e2->value.character.length)
+		return -2;
+	    }
+
 	  args1 = args1->next;
 	  args2 = args2->next;
 	}