diff -r 93b6525e3b82 -r a761c2d3b76a src/share/vm/opto/loopUnswitch.cpp
--- a/src/share/vm/opto/loopUnswitch.cpp	Tue Apr 08 12:23:15 2008 -0400
+++ b/src/share/vm/opto/loopUnswitch.cpp	Wed Apr 09 09:25:45 2008 -0700
@@ -51,6 +51,9 @@
   if( !LoopUnswitching ) {
     return false;
   }
+  if (!_head->is_Loop()) {
+    return false;
+  }
   uint nodes_left = MaxNodeLimit - phase->C->unique();
   if (2 * _body.size() > nodes_left) {
     return false; // Too speculative if running low on nodes.