hash.c: optimize Hash#compare_by_identity

hash.c (rb_hash_compare_by_id): avoid unnecessary allocation of st_table.
formerly, st_table created in rb_hash_modify() was not used and replaced immediately.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60337 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 9 insertions, 3 deletions

diff --git a/hash.c b/hash.c
index ecc9110d58..25ab9959a4 100644
--- a/hash.c
+++ b/hash.c
@@ -2899,10 +2899,16 @@ rb_hash_compact_bang(VALUE hash)
 static VALUE
 rb_hash_compare_by_id(VALUE hash)
 {
+    st_table *identtable;
     if (rb_hash_compare_by_id_p(hash)) return hash;
-    rb_hash_modify(hash);
-    RHASH(hash)->ntbl->type = &identhash;
-    rb_hash_rehash(hash);
+    rb_hash_modify_check(hash);
+
+    identtable = rb_init_identtable_with_size(RHASH_SIZE(hash));
+    rb_hash_foreach(hash, rb_hash_rehash_i, (VALUE)identtable);
+    if (RHASH(hash)->ntbl)
+	st_free_table(RHASH(hash)->ntbl);
+    RHASH(hash)->ntbl = identtable;
+
     return hash;
 }