diff --git a/ChangeLog b/ChangeLog
index a3ac4c5df1..10bfe629eb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Wed Jun 16 16:01:17 2004  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* gc.c (stack_grow_direction): memoize the direction.
+
+	* gc.c (Init_stack): should always move to end of VALUE.
+
 Tue Jun 15 12:10:04 2004  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
 
 	* ext/tk/lib/tk.rb: bug fix (TkWindow#grab)
@@ -59,7 +65,7 @@ Wed Jun  9 16:09:01 2004  akira yamada  <akira@ruby-lang.org>
 	* lib/uri/generic.rb (URI::Generic::merge,
 	  URI::Generic::route_from): accepts non-hierarchical URI.
 	  [ruby-dev:23631]
-	
+
 	* test/uri/test_generic.rb (TestGeneric::test_route,
 	  TestGeneric::test_merge): added tests for above changes.
 
diff --git a/gc.c b/gc.c
index def4acb3bb..a364b33268 100644
--- a/gc.c
+++ b/gc.c
@@ -447,15 +447,17 @@ static unsigned int STACK_LEVEL_MAX = 655300;
 #elif STACK_GROW_DIRECTION < 0
 # define STACK_UPPER(x, a, b) b
 #else
+static int grow_direction;
 static int
-stack_growup_p(addr)
+stack_grow_direction(addr)
     VALUE *addr;
 {
     SET_STACK_END;
 
-    if (STACK_END > addr) return Qtrue;
-    return Qfalse;
+    if (STACK_END > addr) return grow_direction = 1;
+    return grow_direction = -1;
 }
+# define stack_growup_p(x) ((grow_direction ? grow_direction : stack_grow_direction(x)) > 0)
 # define STACK_UPPER(x, a, b) (stack_growup_p(x) ? a : b)
 #endif
 
@@ -1410,10 +1412,11 @@ Init_stack(addr)
     rb_gc_stack_start = _SEND;
 #else
     if (!addr) addr = (VALUE *)&addr;
+    STACK_UPPER(&addr, addr, ++addr);
     if (rb_gc_stack_start) {
 	if (STACK_UPPER(&addr,
 			rb_gc_stack_start > addr,
-			rb_gc_stack_start < ++addr))
+			rb_gc_stack_start < addr))
 	    rb_gc_stack_start = addr;
 	return;
     }