Make nqp::encode take a buffer, not create it.

src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java

@@ -2918,9 +2918,8 @@ private static void stashBytes(ThreadContext tc, SixModelObject res, byte[] byte
             }
         }
     }
-    public static SixModelObject encode(String str, String encoding, SixModelObject bufType, ThreadContext tc) {
+    public static SixModelObject encode(String str, String encoding, SixModelObject res, ThreadContext tc) {
         try {
-            SixModelObject res = bufType.st.REPR.allocate(tc, bufType.st);
             if (encoding.equals("utf8")) {
                 stashBytes(tc, res, str.getBytes("UTF-8"));
             }

src/vm/parrot/ops/nqp.ops

@@ -3359,25 +3359,21 @@ inline op nqp_getlexrelcaller(out PMC, in PMC, in STR) :base_core {
 
 =item nqp_encode
 
-Encodes the specified string with the specified encoding into a buffer of
-the provided type.
+Encodes the specified string with the specified encoding into the provided
+empty buffer.
 
 =cut
 
 */
 inline op nqp_encode(out PMC, in STR, in STR, invar PMC) {
-    PMC *res_type = $4;
+    PMC *res = $4;
     STRING *enc;
     STable *res_elem_st;
     storage_spec res_elem_ss;
     const char *buffer_data;
     INTVAL bytes, i;
     NativeValue nv;
 
-    /* Allocate buffer result. */
-    PMC *res = REPR(res_type)->allocate(interp, STABLE(res_type));
-    REPR(res)->initialize(interp, STABLE(res), OBJECT_BODY(res));
-
     /* Transform string to the requested encoding (Parrot considers
      * everything as encoded strings rather than having a Buf/Str
      * split). */