immediate-hash, '#&box constants serialized

i.c

@@ -3426,6 +3426,15 @@ define_instruction(igco) {
   gonexti(); 
 }
 
+define_instruction(hshim) {
+  unsigned long long v = (unsigned long long)ac, base = 0; obj b = spop(); 
+  if (v && isaptr(v)) failtype(v, "immediate value");
+  if (b) { ckk(b); base = get_fixnum(b); } 
+  if (!base) base = 1 + (unsigned long long)FIXNUM_MAX;
+  ac = fixnum_obj((fixnum_t)(v % base));
+  gonexti();
+}
+
 define_instruction(rdsx) {
   cks(ac); 
   unload_ac(); /* ac->ra (string) */
@@ -3448,6 +3457,7 @@ define_instruction(rdsc) {
   gonexti(); 
 }
 
+
 define_instruction(litf) { ac = bool_obj(0); gonexti(); }  
 define_instruction(litt) { ac = bool_obj(1); gonexti(); }  
 define_instruction(litn) { ac = null_obj(); gonexti(); }  
@@ -4097,7 +4107,16 @@ static obj *rds_sexp(obj *r, obj *sp, obj *hp)
       }
       ra = hpushu8v(sp-r, newbytevector((unsigned char *)cbdata(pcb), (int)cblen(pcb)));
       freecb(pcb);
-    }
+    } break;
+    case 'z': {
+      spush(port);
+      ra = sref(0); hp = rds_elt(r, sp, hp); 
+      if (iseof(ra)) { sdrop(1); return hp; } else spush(ra);
+      hreserve(boxbsz(), sp-r);
+      *--hp = sref(0);  
+      ra = hend_box();
+      sdrop(2);      
+    } break;
   }  
   return hp;
 }

i.h

@@ -523,7 +523,7 @@ declare_instruction(panic,      "Z7",           0,  "%panic",
 declare_instruction(abort,      "Z8\0t",        0,  "%abort",                   'u', AUTOGL)
 declare_instruction(exit,       "Z9\0t",        0,  "%exit",                    'u', AUTOGL)
 
-/* serialization and deserialization instructions */             
+/* serialization, deserialization, compilation-related instructions */             
 declare_instruction(igp,        "U0",           0,  "integrable?",              '1', AUTOGL)
 declare_instruction(itrs,       "U1",           0,  "initial-transformers",     '0', AUTOGL)
 declare_instruction(rdsx,       "U3",           0,  "deserialize-sexp",         '1', AUTOGL)
@@ -532,6 +532,7 @@ declare_instruction(iglk,       "U5",           0,  "lookup-integrable",
 declare_instruction(igty,       "U6",           0,  "integrable-type",          '1', AUTOGL)
 declare_instruction(iggl,       "U7",           0,  "integrable-global",        '1', AUTOGL)
 declare_instruction(igco,       "U8",           0,  "integrable-code",          '2', AUTOGL)
+declare_instruction(hshim,      "H2\0f",        0,  "immediate-hash",           'b', AUTOGL)
 
 /* inlined integrables (no custom instructions) */               
 declare_integrable(NULL,        "N0",           0,  "complex?",                 '1', AUTOGL)

src/k.sf

@@ -793,6 +793,9 @@
            (write-serialized-size (string-length x) port)
            (do ([i 0 (fx+ i 1)]) [(fx=? i (string-length x))]
              (write-serialized-char (string-ref x i) port)))]
+        [(box? x)
+         (write-char #\z port)
+         (write-serialized-element (unbox x) port)]
         [else (c-error "cannot encode literal" x)]))
 
 (define (write-serialized-arg arg port)