diff --git a/ChangeLog b/ChangeLog
index 90f81752a6..8a9cabdb04 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun Sep 28 12:36:09 2008  Koichi Sasada  <ko1@atdot.net>
+
+	* vm_exec.c (vm_exec_core): add an UNLIKELY() hint.
+
+	* vm_insnhelper.h (BASIC_OP_UNREDEFINED_P): add a LIKELY() hint.
+
 Sun Sep 28 12:04:18 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* string.c (str_new): sets empty string to coderange 7bit.
diff --git a/vm_exec.c b/vm_exec.c
index 392fde0cf7..fc04fc6a1d 100644
--- a/vm_exec.c
+++ b/vm_exec.c
@@ -83,7 +83,7 @@ vm_exec_core(rb_thread_t *th, VALUE initial)
 
 #if OPT_TOKEN_THREADED_CODE || OPT_DIRECT_THREADED_CODE
 #include "vmtc.inc"
-    if (th == 0) {
+    if (UNLIKELY(th == 0)) {
 #if OPT_STACK_CACHING
 	finish_insn_seq[0] = (VALUE)&&LABEL (finish_SC_ax_ax);
 #else
diff --git a/vm_insnhelper.h b/vm_insnhelper.h
index 6e931e1622..1d2bdafdad 100644
--- a/vm_insnhelper.h
+++ b/vm_insnhelper.h
@@ -180,7 +180,7 @@ extern VALUE ruby_vm_redefined_flag;
 
 /* optimize insn */
 #define FIXNUM_2_P(a, b) ((a) & (b) & 1)
-#define BASIC_OP_UNREDEFINED_P(op) ((ruby_vm_redefined_flag & (op)) == 0)
+#define BASIC_OP_UNREDEFINED_P(op) (LIKELY((ruby_vm_redefined_flag & (op)) == 0))
 #define HEAP_CLASS_OF(obj) RBASIC(obj)->klass
 
 #define CALL_SIMPLE_METHOD(num, id, recv) do { \