re PR fortran/78021 (Wrong result with optimization on character constant)

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

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

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

	PR fortran/78021
	* gfortran.dg/string_length_3.f90:  New test.

From-SVN: r241440

gcc/fortran/ChangeLog

+2016-10-22  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/78021
+	* gfc_compare_functions:  Strings with different lengths in
+	argument lists compare unequal.
+
 2016-10-22  Andre Vehreschild  <vehre@gcc.gnu.org>
 
 	PR fortran/43366

gcc/fortran/dependency.c

@@ -226,9 +226,26 @@ gfc_dep_compare_functions (gfc_expr *e1, gfc_expr *e2, bool impure_ok)
 	  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;

gcc/testsuite/ChangeLog

+2016-10-22  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/78021
+	* gfortran.dg/string_length_3.f90:  New test.
+
 2016-10-22  Andre Vehreschild  <vehre@gcc.gnu.org>
 
 	Forgot to add on original commit.

gcc/testsuite/gfortran.dg/string_length_3.f90

+! { 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" } }