Fortran - extend set of substring expressions handled in length simplification

gcc/fortran/ChangeLog:

	PR fortran/100950
	* simplify.c (substring_has_constant_len): Minimize checks for
	substring expressions being allowed.

gcc/testsuite/ChangeLog:

	PR fortran/100950
	* gfortran.dg/pr100950.f90: Extend coverage.

1 files changed, 2 insertions, 29 deletions

diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index 4cb73e8..b46cbfa 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -4533,14 +4533,7 @@ substring_has_constant_len (gfc_expr *e)
       || !ref->u.ss.start
       || ref->u.ss.start->expr_type != EXPR_CONSTANT
       || !ref->u.ss.end
-      || ref->u.ss.end->expr_type != EXPR_CONSTANT
-      || !ref->u.ss.length)
-    return false;
-
-  /* For non-deferred strings the given length shall be constant.  */
-  if (!e->ts.deferred
-      && (!ref->u.ss.length->length
-	  || ref->u.ss.length->length->expr_type != EXPR_CONSTANT))
+      || ref->u.ss.end->expr_type != EXPR_CONSTANT)
     return false;
 
   /* Basic checks on substring starting and ending indices.  */
@@ -4551,27 +4544,7 @@ substring_has_constant_len (gfc_expr *e)
   iend = gfc_mpz_get_hwi (ref->u.ss.end->value.integer);
 
   if (istart <= iend)
-    {
-      if (istart < 1)
-	{
-	  gfc_error ("Substring start index (%wd) at %L below 1",
-		     istart, &ref->u.ss.start->where);
-	  return false;
-	}
-
-      /* For deferred strings use end index as proxy for length.  */
-      if (e->ts.deferred)
-	length = iend;
-      else
-	length = gfc_mpz_get_hwi (ref->u.ss.length->length->value.integer);
-      if (iend > length)
-	{
-	  gfc_error ("Substring end index (%wd) at %L exceeds string length",
-		     iend, &ref->u.ss.end->where);
-	  return false;
-	}
-      length = iend - istart + 1;
-    }
+    length = iend - istart + 1;
   else
     length = 0;