From c4c53310c23d913c1ff25863f1d9f7332b548f51 Mon Sep 17 00:00:00 2001
From: tenderlove <tenderlove@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Mon, 12 Sep 2016 15:40:09 +0000
Subject: Copy the serial number from the super class to the singleton class

This helps hit inline method caches more frequently.  Before this
commit:

```
[aaron@TC ruby (trunk)]$ time ./ruby -v benchmark/bm_vm2_poly_singleton.rb
ruby 2.4.0dev (2016-09-12 trunk 56141) [x86_64-darwin15]

real  0m3.679s
user  0m3.632s
sys 0m0.022s
```

After this commit:

```
[aaron@TC ruby (trunk)]$ time ./ruby -v benchmark/bm_vm2_poly_singleton.rb
ruby 2.4.0dev (2016-09-12 trunk 56141) [x86_64-darwin15]
last_commit=Copy the serial number from the super class to the singleton class

real  0m2.246s
user  0m2.203s
sys 0m0.020s
```

[Feature #12364]
[ruby-core:75425]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56144 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 class.c | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'class.c')

diff --git a/class.c b/class.c
index 6c7dfa5c17..ce2ede5c2b 100644
--- a/class.c
+++ b/class.c
@@ -1591,7 +1591,9 @@ singleton_class_of(VALUE obj)
     klass = RBASIC(obj)->klass;
     if (!(FL_TEST(klass, FL_SINGLETON) &&
 	  rb_ivar_get(klass, id_attached) == obj)) {
+	rb_serial_t serial = RCLASS_SERIAL(klass);
 	klass = rb_make_metaclass(obj, klass);
+	RCLASS_SERIAL(klass) = serial;
     }
 
     if (OBJ_TAINTED(obj)) {
-- 
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