check_process_code/2: Quickly return 'false' if there is no old code

There is no need to suspend the process if the module has no old
code. Measurements show that this change will make
erlang:check_process_code/2 in an SMP emulator about four times
faster if the module has no old code.

1 files changed, 7 insertions, 6 deletions

diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index d76a7d8e9f..7b5781beeb 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -175,6 +175,13 @@ check_process_code_2(BIF_ALIST_2)
 	Eterm res;
 	if (internal_pid_index(BIF_ARG_1) >= erts_max_processes)
 	    goto error;
+	modp = erts_get_module(BIF_ARG_2);
+	if (modp == NULL) {		/* Doesn't exist. */
+	    return am_false;
+	} else if (modp->old_code == NULL) { /* No old code. */
+	    return am_false;
+	}
+	
 #ifdef ERTS_SMP
 	rp = erts_pid2proc_suspend(BIF_P, ERTS_PROC_LOCK_MAIN,
 				   BIF_ARG_1, ERTS_PROC_LOCK_MAIN);
@@ -188,7 +195,6 @@ check_process_code_2(BIF_ALIST_2)
 	    ERTS_BIF_YIELD2(bif_export[BIF_check_process_code_2], BIF_P,
 			    BIF_ARG_1, BIF_ARG_2);
 	}
-	modp = erts_get_module(BIF_ARG_2);
 	res = check_process_code(rp, modp);
 #ifdef ERTS_SMP
 	if (BIF_P != rp) {
@@ -412,11 +418,6 @@ check_process_code(Process* rp, Module* modp)
 #endif
 
 #define INSIDE(a) (start <= (a) && (a) < end)
-    if (modp == NULL) {		/* Doesn't exist. */
-	return am_false;
-    } else if (modp->old_code == NULL) { /* No old code. */
-	return am_false;
-    }
 
     /*
      * Pick up limits for the module.