Missing register defn.

Author: dvanhorn

ziggy/src/compile-ops.rkt

@@ -9,6 +9,7 @@
 {:> E0} (define rdi 'rdi) {:> E0} ; arg
 {:> F}  (define r8  'r8)  {:> F}  ; scratch in op2
 {:> D0} (define r9 'r9)   {:> E0} ; scratch
+{:> F}  (define r15 'r15) {:> F}  ; stack pad (non-volatile)
 
 {:> E0} ;; Op0 -> Asm
 {:> E0}