Implement magic references

Magic references are *intentionally* indistinguishable from ordinary
references for the Erlang software. Magic references do not change
the language, and are intended as a pure runtime internal optimization.

An ordinary reference is typically used as a key in some table. A
magic reference has a direct pointer to a reference counted magic
binary. This makes it possible to implement various things without
having to do lookups in a table, but instead access the data directly.
Besides very fast lookups this can also improve scalability by
removing a potentially contended table. A couple of examples of
planned future usage of magic references are ETS table identifiers,
and BIF timer identifiers.

Besides future optimizations using magic references it should also
be possible to replace the exposed magic binary cludge with magic
references. That is, magic binaries that are exposed as empty
binaries to the Erlang software.

1 files changed, 8 insertions, 7 deletions

diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index a2d2433ed8..bda7b9224c 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -199,7 +199,7 @@ BIF_RETTYPE link_1(BIF_ALIST_1)
 		goto res_no_proc;
 	    case ERTS_PORT_OP_SCHEDULED:
 		if (refp) {
-		    ASSERT(is_internal_ref(ref));
+		    ASSERT(is_internal_ordinary_ref(ref));
 		    BIF_TRAP3(await_port_send_result_trap, BIF_P, ref, am_true, am_true);
 		}
 	    default:
@@ -782,7 +782,7 @@ local_name_monitor(Process *self, Eterm type, Eterm target_name)
         case ERTS_PORT_OP_DONE:
             return ret;
         case ERTS_PORT_OP_SCHEDULED: { /* Scheduled a signal */
-            ASSERT(is_internal_ref(ret));
+            ASSERT(is_internal_ordinary_ref(ret));
             BIF_TRAP3(await_port_send_result_trap, self,
                       ret, am_true, ret);
             /* bif_trap returns */
@@ -1180,7 +1180,7 @@ BIF_RETTYPE unlink_1(BIF_ALIST_1)
 		res = erts_port_unlink(BIF_P, prt, BIF_P->common.id, refp);
 
 		if (refp && res == ERTS_PORT_OP_SCHEDULED) {
-		    ASSERT(is_internal_ref(ref));
+		    ASSERT(is_internal_ordinary_ref(ref));
 		    BIF_TRAP3(await_port_send_result_trap, BIF_P, ref, am_true, am_true);
 		}
 	    }
@@ -1586,7 +1586,7 @@ BIF_RETTYPE exit_2(BIF_ALIST_2)
 	     ERTS_BIF_CHK_EXITED(BIF_P);
 
 	     if (refp && res == ERTS_PORT_OP_SCHEDULED) {
-		 ASSERT(is_internal_ref(ref));
+		 ASSERT(is_internal_ordinary_ref(ref));
 		 BIF_TRAP3(await_port_send_result_trap, BIF_P, ref, am_true, am_true);
 	     }
 
@@ -2221,7 +2221,7 @@ do_send(Process *p, Eterm to, Eterm msg, Eterm *refp, ErtsSendContext* ctx)
 		/* Fall through */
 	    case ERTS_PORT_OP_SCHEDULED:
 		if (is_not_nil(*refp)) {
-		    ASSERT(is_internal_ref(*refp));
+		    ASSERT(is_internal_ordinary_ref(*refp));
 		    ret_val = SEND_AWAIT_RESULT;
 		}
 		break;
@@ -2409,7 +2409,7 @@ BIF_RETTYPE send_3(BIF_ALIST_3)
 	ERTS_BIF_PREP_YIELD_RETURN(retval, p, am_ok);
         break;
     case SEND_AWAIT_RESULT:
-	ASSERT(is_internal_ref(ref));
+	ASSERT(is_internal_ordinary_ref(ref));
 	ERTS_BIF_PREP_TRAP3(retval, await_port_send_result_trap, p, ref, am_nosuspend, am_ok);
 	break;
     case SEND_BADARG:
@@ -2526,7 +2526,7 @@ Eterm erl_send(Process *p, Eterm to, Eterm msg)
 	ERTS_BIF_PREP_YIELD_RETURN(retval, p, msg);
         break;
     case SEND_AWAIT_RESULT:
-	ASSERT(is_internal_ref(ref));
+	ASSERT(is_internal_ordinary_ref(ref));
 	ERTS_BIF_PREP_TRAP3(retval,
 			    await_port_send_result_trap, p, ref, msg, msg);
 	break;
@@ -4109,6 +4109,7 @@ BIF_RETTYPE ref_to_list_1(BIF_ALIST_1)
 {
     if (is_not_ref(BIF_ARG_1))
 	BIF_ERROR(BIF_P, BADARG);
+    erts_magic_ref_save_bin(BIF_ARG_1);
     BIF_RET(term2list_dsprintf(BIF_P, BIF_ARG_1));
 }