Add Iterative scan register allocator.

llvm-svn: 15068
diff --git a/llvm/docs/CommandGuide/llc.pod b/llvm/docs/CommandGuide/llc.pod
index 1f202aa..c1b451c 100644
--- a/llvm/docs/CommandGuide/llc.pod
+++ b/llvm/docs/CommandGuide/llc.pod
@@ -141,6 +141,10 @@
 
 Linear scan global register allocator
 
+=item I<iterativerscan>
+
+Iterative scan global register allocator
+
 =back
 
 =item B<--spiller>=I<spiller>