From: "Marcin Mielżyński" <lopx@...>
Date: 2008-04-01T02:45:09+09:00
Subject: Re: Why Ruby do not optimize code at all?

ts pisze:
> Park Heesob wrote:
>> So ruby is never fast but flexible language :)
> 
>  Well I can give you another example of "premature" optimisation, but
>  for 1.9
> 
>  [ruby-bugs:16163]
> 
> 
> http://rubyforge.org/tracker/index.php?func=detail&aid=16163&group_id=426&atid=1698
> 
>  it worked but a modification was made to ruby and the optimisation
>  break the code now
> 
> 

It's not a premature optimisation, just unimplemented yet fallback with 
/* TODO: if some === method is overrided */ comment in the source 
(insns.def) for opt_case_dispatch specialized instruction (very easy to 
accomplish having vm_opt_method_table and ruby_vm_redefined_flag).

For some time there's been similar issue though for case:

a = 0
10.times do |i|
     class Fixnum
         private :+
     end
     a+=i
end

Where private didn't record redefined bit in ruby_vm_redefined_flag 
(vm.c). Now it's fixed and checked against in rb_export_method 
(eval_method.c) and rb_vm_check_redefinition_opt_method (vm.c).

So all standard ruby semantics is still obeyed without sacrificing 1.9 
performance.

lopex