cs: add missing unsafe-struct*-cas!

racket/src/cs/primitive/unsafe.ss

@@ -153,6 +153,7 @@
   [unsafe-string-length (known-procedure/pure 2)]
   [unsafe-string-ref (known-procedure/pure 4)]
   [unsafe-string-set! (known-procedure/pure 8)]
+  [unsafe-struct*-cas! (known-procedure 16)]
   [unsafe-struct*-ref (known-procedure/pure 4)]
   [unsafe-struct*-set! (known-procedure/pure 8)]
   [unsafe-struct-ref (known-procedure/pure 4)]

racket/src/cs/rumble.sls

@@ -650,6 +650,7 @@
           unsafe-struct-set!
           unsafe-struct*-ref
           unsafe-struct*-set!
+          unsafe-struct*-cas!
           unsafe-struct? ; not exported to racket
 
           unsafe-s16vector-ref

racket/src/cs/rumble/unsafe.ss

@@ -78,6 +78,9 @@
 (define unsafe-vector*-set! (unsafe-primitive vector-set!))
 (define unsafe-vector*-cas! (unsafe-primitive vector-cas!))
 
+(define (unsafe-struct*-cas! s k old new)
+  (#%vector-cas! s k old new))
+
 (define unsafe-unbox* (unsafe-primitive unbox))
 (define unsafe-set-box*! (unsafe-primitive set-box!))
 (define unsafe-box*-cas! (unsafe-primitive box-cas!))