st.c: use ccan linked-list (try 2)

This improves the bm_vm2_bighash benchmark significantly by
removing branches during insert, but slows down anything
requiring iteration with the more complex loop termination
checking.

Speedup ratio of 1.10 - 1.20 is typical for the vm2_bighash
benchmark.

* include/ruby/st.h (struct st_table): hide struct list_head
* st.c (struct st_table_entry): adjust struct
  (head, tail): remove shortcut macros
  (st_head): new wrapper function
  (st_init_table_with_size): adjust to new struct and API
  (st_clear): ditto
  (add_direct): ditto
  (unpack_entries): ditto
  (rehash): ditto
  (st_copy): ditto
  (remove_entry): ditto
  (st_shift): ditto
  (st_foreach_check): ditto
  (st_foreach): ditto
  (get_keys): ditto
  (get_values): ditto
  (st_values_check): ditto
  (st_reverse_foreach_check): ditto (unused)
  (st_reverse_foreach): ditto (unused)
  [ruby-core:69726] [Misc #10278]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51044 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,26 @@
+Sat Jun 27 06:58:01 2015  Eric Wong  <e@80x24.org>
+
+	* include/ruby/st.h (struct st_table): hide struct list_head
+	* st.c (struct st_table_entry): adjust struct
+	  (head, tail): remove shortcut macros
+	  (st_head): new wrapper function
+	  (st_init_table_with_size): adjust to new struct and API
+	  (st_clear): ditto
+	  (add_direct): ditto
+	  (unpack_entries): ditto
+	  (rehash): ditto
+	  (st_copy): ditto
+	  (remove_entry): ditto
+	  (st_shift): ditto
+	  (st_foreach_check): ditto
+	  (st_foreach): ditto
+	  (get_keys): ditto
+	  (get_values): ditto
+	  (st_values_check): ditto
+	  (st_reverse_foreach_check): ditto (unused)
+	  (st_reverse_foreach): ditto (unused)
+	  [ruby-core:69726] [Misc #10278]
+
 Fri Jun 26 12:48:37 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* transcode.c (load_transcoder_entry): fix transcoder loading race

include/ruby/st.h

@@ -86,7 +86,7 @@ struct st_table {
     union {
 	struct {
 	    struct st_table_entry **bins;
-	    struct st_table_entry *head, *tail;
+	    void *private_list_head[2];
 	} big;
 	struct {
 	    struct st_packed_entry *entries;