diff --git a/ChangeLog b/ChangeLog
index 15a6f6881b..4584cb39c2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Sep 10 01:57:23 2008  Tanaka Akira  <akr@fsij.org>
+
+	* tool/transcode-tblgen.rb (StrSet#hash): cache hash value.
+	  (ActionMap#hash): ditto.
+
 Wed Sep 10 01:26:01 2008  Tanaka Akira  <akr@fsij.org>
 
 	* include/ruby/encoding.h (econv_after_output): renamed from
diff --git a/tool/transcode-tblgen.rb b/tool/transcode-tblgen.rb
index 5395460ee5..05ee5d314e 100644
--- a/tool/transcode-tblgen.rb
+++ b/tool/transcode-tblgen.rb
@@ -62,7 +62,8 @@ class StrSet
   end
 
   def hash
-    @pat.hash
+    return @hash if defined? @hash
+    @hash = @pat.hash
   end
 
   def eql?(other)
@@ -196,11 +197,12 @@ class ActionMap
   end
 
   def hash
+    return @hash if defined? @hash
     hash = 0
     @map.each {|k,v|
       hash ^= k.hash ^ v.hash
     }
-    hash
+    @hash = hash
   end
 
   def eql?(other)