Issue #11203 has been reported by Koichi Sasada.

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Bug #11203: Change method entries into VALUE
https://bugs.ruby-lang.org/issues/11203

* Author: Koichi Sasada
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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Now, rb_method_entry_t is an allocated data pointed from method tables (class/module has) and from control frame stacks.

I will change this data structure to make VALUE (T_IMEMO/ment).
And I put them onto value frames instead of control frame stacks.

This change has several advantages.

* Solve these issues.
  * [Bug #11200] Memory leak of method entries
  * [Bug #11046] __callee__ returns incorrect method name in orphan proc
* Simplify sweeping process of method entry
* We can remove rb_control_frame_t::me
* No need to push CREF for every method invocation. Method entries know required CREF.
* We can share per method CREF only for make them public visibility scope.
* We can introduce other optimization techniques.
  * We can remove rb_control_frame_t::klass field because method entries can manipulate this information.
  * We can introduce new method cache mechanism (maybe).

The following pictures show how SVAR/CREF/MENT are located at value stacks.

![before-value-stack](1.PNG)
![after-value-stack](2.PNG)

The following picture shows how alias was implemented.

![alias-relation](3.PNG)



---Files--------------------------------
1.PNG (46.6 KB)
2.PNG (43.4 KB)
3.png (31.8 KB)


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