Index: /trunk/source/compiler/ARM/arm-vinsns.lisp
===================================================================
--- /trunk/source/compiler/ARM/arm-vinsns.lisp	(revision 15455)
+++ /trunk/source/compiler/ARM/arm-vinsns.lisp	(revision 15456)
@@ -1290,4 +1290,10 @@
   (uuo-error-reg-not-xtype src (:$ arm::xtype-s8))
   :ok)
+
+(define-arm-vinsn (%unbox-s8 :predicatable)
+    (((dest :s8))
+     ((src :lisp)))
+  (mov dest (:$ #xff))
+  (and dest dest (:asr src (:$ arm::fixnumshift))))
 
 (define-arm-vinsn unbox-base-char (((dest :u32))