diff --git a/ChangeLog b/ChangeLog
index b0dd1b15e4..c40e751330 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Wed Sep  3 21:31:59 2008  Tanaka Akira  <akr@fsij.org>
+
+	* transcode_data.h (WORDINDEX_SHIFT_BITS): defined.
+	  (WORDINDEX2INFO): defined.
+	  (INFO2WORDINDEX): defined.
+
+	* tool/transcode-tblgen.rb: use WORDINDEX2INFO.
+
+	* transcode.c: use INFO2WORDINDEX.
+
 Wed Sep  3 21:19:51 2008  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* golf_prelude.rb: suppress warning when goruby -v.
diff --git a/tool/transcode-tblgen.rb b/tool/transcode-tblgen.rb
index cbeccc35ec..75b88b0083 100644
--- a/tool/transcode-tblgen.rb
+++ b/tool/transcode-tblgen.rb
@@ -365,13 +365,13 @@ class ActionMap
 
       size = words_code.length
       words_code.insert_at_last(infos.length,
-        "\#define #{infos_name} (sizeof(unsigned int)*#{size})\n" +
+        "\#define #{infos_name} WORDINDEX2INFO(#{size})\n" +
         format_infos(infos) + "\n")
     end
 
     size = words_code.length
     words_code.insert_at_last(NUM_ELEM_BYTELOOKUP,
-      "\#define #{name} (sizeof(unsigned int)*#{size})\n" +
+      "\#define #{name} WORDINDEX2INFO(#{size})\n" +
       <<"End" + "\n")
     #{offsets_name},
     #{infos_name},
diff --git a/transcode.c b/transcode.c
index c404b0de02..aa89f12a8e 100644
--- a/transcode.c
+++ b/transcode.c
@@ -492,7 +492,7 @@ transcode_restartable0(const unsigned char **in_pos, unsigned char **out_pos,
         }
 
 #define BYTE_ADDR(index) (tr->byte_array + (index))
-#define WORD_ADDR(index) (tr->word_array + (index)/sizeof(*tr->word_array))
+#define WORD_ADDR(index) (tr->word_array + INFO2WORDINDEX(index))
 #define BL_BASE(bl) BYTE_ADDR(BYTE_LOOKUP_BASE(WORD_ADDR(bl)))
 #define BL_INFO(bl) WORD_ADDR(BYTE_LOOKUP_INFO(WORD_ADDR(bl)))
 #define BL_MIN_BYTE(bl)     (BL_BASE(bl)[0])
diff --git a/transcode_data.h b/transcode_data.h
index 1ceb0cf473..6081aec81d 100644
--- a/transcode_data.h
+++ b/transcode_data.h
@@ -14,6 +14,9 @@
 #ifndef RUBY_TRANSCODE_DATA_H
 #define RUBY_TRANSCODE_DATA_H 1
 
+#define WORDINDEX_SHIFT_BITS 2
+#define WORDINDEX2INFO(widx)      ((widx) << WORDINDEX_SHIFT_BITS)
+#define INFO2WORDINDEX(info)      ((info) >> WORDINDEX_SHIFT_BITS)
 #define BYTE_LOOKUP_BASE(bl) ((bl)[0])
 #define BYTE_LOOKUP_INFO(bl) ((bl)[1])