[PR fortran/89077, patch, part 2] - ICE using * as len specifier for character parameter

[Harald Anlauf]

The attached patch attempts a substring length simplification
so that more complex expressions are handled in initialization
expressions.  Thanks to Thomas König for the suggestion.

Regtested on x86_64-pc-linux-gnu.

(The PR still has other wrong-code issue to be addressed separately.)

OK for trunk?  And for backports to 8/7?

Thanks,
Harald


2019-02-08  Harald Anlauf  <anl...@gmx.de>

        PR fortran/89077
        * resolve.c (gfc_resolve_substring_charlen): Check substring
        length for constantness prior to general calculation of length.

2019-02-08  Harald Anlauf  <anl...@gmx.de>

        PR fortran/89077
        * gfortran.dg/substr_simplify.f90: New test.


Index: gcc/fortran/resolve.c
===================================================================
--- gcc/fortran/resolve.c       (revision 268658)
+++ gcc/fortran/resolve.c       (working copy)
@@ -4965,6 +4965,7 @@
   gfc_ref *char_ref;
   gfc_expr *start, *end;
   gfc_typespec *ts = NULL;
+  mpz_t diff;
 
   for (char_ref = e->ref; char_ref; char_ref = char_ref->next)
     {
@@ -5016,12 +5017,25 @@
       return;
     }
 
-  /* Length = (end - start + 1).  */
-  e->ts.u.cl->length = gfc_subtract (end, start);
-  e->ts.u.cl->length = gfc_add (e->ts.u.cl->length,
-                               gfc_get_int_expr (gfc_charlen_int_kind,
-                                                 NULL, 1));
+  /* Length = (end - start + 1).
+     Check first whether it has a constant length.  */
+  if (gfc_dep_difference (end, start, &diff))
+    {
+      gfc_expr *len = gfc_get_constant_expr (BT_INTEGER, gfc_charlen_int_kind,
+                                            &e->where);
 
+      mpz_add_ui (len->value.integer, diff, 1);
+      mpz_clear (diff);
+      e->ts.u.cl->length = len;
+    }
+  else
+    {
+      e->ts.u.cl->length = gfc_subtract (end, start);
+      e->ts.u.cl->length = gfc_add (e->ts.u.cl->length,
+                                   gfc_get_int_expr (gfc_charlen_int_kind,
+                                                     NULL, 1));
+    }
+
   /* F2008, 6.4.1:  Both the starting point and the ending point shall
      be within the range 1, 2, ..., n unless the starting point exceeds
      the ending point, in which case the substring has length zero.  */

Index: gcc/testsuite/gfortran.dg/substr_simplify.f90
===================================================================
--- gcc/testsuite/gfortran.dg/substr_simplify.f90       (nonexistent)
+++ gcc/testsuite/gfortran.dg/substr_simplify.f90       (working copy)
@@ -0,0 +1,20 @@
+! { dg-do run }
+!
+! Test fixes for substring simplications derived from
+! PR fortran/89077 - ICE using * as len specifier for character parameter
+
+program test
+  implicit none
+  integer :: i
+  character(*), parameter :: s = 'abcdef', y = 'efcdab'
+  character(6), save      :: t = transfer ([(s(i:i),  i=1,len(s)  )], s)
+  character(*), parameter :: u = transfer ([(s(i:i+2),i=1,len(s),3)], s)
+  character(6), save      :: v = transfer ([(s(i:i+2),i=1,len(s),3)], s)
+  character(*), parameter :: w = transfer ([(y(i:i+1),i=len(s)-1,1,-2)], s)
+  character(6), save      :: x = transfer ([(y(i:i+1),i=len(s)-1,1,-2)], s)
+  if (len (t) /= len (s) .or. t /= s) stop 1
+  if (len (u) /= len (s) .or. u /= s) stop 2
+  if (len (v) /= len (s) .or. v /= s) stop 3
+  if (len (w) /= len (s) .or. w /= s) stop 4
+  if (len (x) /= len (s) .or. x /= s) stop 5
+end