Special case division by small constants

Do the standard reciprocal multiply trick for small division
by small constants.

Change-Id: Iad1060ccdc6ffeb7b47d45c29ba741683ad01ab9
diff --git a/src/compiler/codegen/arm/ArmLIR.h b/src/compiler/codegen/arm/ArmLIR.h
index da39713..484892a 100644
--- a/src/compiler/codegen/arm/ArmLIR.h
+++ b/src/compiler/codegen/arm/ArmLIR.h
@@ -617,6 +617,10 @@
                                    [0000] rm[3..0] */
     kThumb2Push1,        /* t3 encoding of push */
     kThumb2Pop1,         /* t3 encoding of pop */
+    kThumb2RsubRRR,      /* rsb [111010111101] rn[19..16] [0000] rd[11..8]
+                                [0000] rm[3..0] */
+    kThumb2Smull,        /* smull [111110111000] rn[19-16], rdlo[15-12]
+                                  rdhi[11-8] [0000] rm[3-0] */
     kArmLast,
 };