Fix a bug in the handling of moves in register allocator.

Change-Id: Iaf1f34b0bece4f252290a97c3b73cc06e365985a
diff --git a/test/408-move-bug/info.txt b/test/408-move-bug/info.txt
new file mode 100644
index 0000000..27a3dbc
--- /dev/null
+++ b/test/408-move-bug/info.txt
@@ -0,0 +1,2 @@
+Regression test for the register allocator in the optimizing
+compiler. Input moves where being overridden by sibling moves.