actually use a VOP

the cross-compiler is built knowing that some functions (usually as a
result of code transformations) should never be compiled as calls, but
should instead be /translated/ using one of our Virtual OPerations.
DATA-VECTOR-REF, which the AREF in our scratch.lisp file translates to
because of the type declarations, is one such function, so we need to
define it: and also define it in such a way that it will be used no
matter what the current compiler policy.

src/compiler/rv32/array.lisp

@@ -13,8 +13,11 @@
 
 (macrolet
     ((def-full-data-vector-frobs (type element-type &rest scs)
-       (let ((setname (symbolicate "DATA-VECTOR-SET/" type)))
+       (let ((refname (symbolicate "DATA-VECTOR-REF/" type))
+             (setname (symbolicate "DATA-VECTOR-SET/" type)))
          `(progn
+            (define-full-reffer ,refname ,type
+              vector-data-offset other-pointer-lowtag ,scs ,element-type data-vector-ref)
             (define-full-setter ,setname ,type
               vector-data-offset other-pointer-lowtag ,scs ,element-type data-vector-set))))
      (def-partial-data-vector-frobs (type element-type size signed &rest scs)

src/compiler/rv32/macros.lisp

@@ -15,6 +15,7 @@
   `(progn
      (define-vop (,name)
        ,@(when translate `((:translate ,translate)))
+       (:policy :fast-safe)
        (:args (object :scs (descriptor-reg)) (index :scs (any-reg)))
        (:arg-types ,type tagged-num)
        (:results (value :scs ,scs))