diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 407065b84cc8..22c5b2d1ccc6 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2001-01-30  Franz Sirl  <Franz.Sirl-kernel@lauterbach.com>
+
+	* jump.c (comparison_dominates_p): Don't try to handle UNKNOWN
+	comparison codes.
+
 2001-01-30  Neil Booth  <neil@daikokuya.demon.co.uk>
 
         * c-decl.c (c_expand_body): Check TYPE_SIZE_UNIT (ret_type)
diff --git a/gcc/jump.c b/gcc/jump.c
index ff2ab146d977..6e1601400f6a 100644
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -2087,6 +2087,12 @@ int
 comparison_dominates_p (code1, code2)
      enum rtx_code code1, code2;
 {
+  /* UNKNOWN comparison codes can happen as a result of trying to revert
+     comparison codes.
+     They can't match anything, so we have to reject them here.  */
+  if (code1 == UNKNOWN || code2 == UNKNOWN)
+    return 0;
+
   if (code1 == code2)
     return 1;