From: "Marcin Mielżyński" <lopx@...>
Date: 2008-04-02T02:20:14+09:00
Subject: Re: Why Ruby do not optimize code at all?

ts pisze:
> Marcin Mielżyński wrote:
>> Well, that's why I'd rather call it temporary breakage since the sources
>> say the author's been aware of it from very beginning (chance the TODO:
>> comment). Just, opt_case_dispatch impl is not complete _yet_, still
>> being faster by default by not using funcall dispatch.
> 
>  The TODO has nothing to do with this problem. It has worked one day
>  on early version of 1.9, then matz has modified the class Symbol
>  and brutally ruby failed because the optimisation was not removed

This case ?

ruby -ve "puts :a === 'a'"
ruby 1.8.6 (2008-02-02 patchlevel 5000) [i686-linux]
false

./ruby -ve "puts :a === 'a'"
ruby 1.9.0 (2008-04-01 revision 15368) [i686-linux]
true

I still claim opt_case_dispatch will be responsible for the fallback 
like any other opt_* opcode and no optimization will be removed.

> 
> vgs% cat b.rb
> #!/usr/bin/ruby
> class Symbol
>    def === other
>       puts "foo"
>    end
> end
> case :s
> when :s
>    puts "s"
> end
> vgs%
> 
> vgs% /usr/bin/ruby -v b.rb
> ruby 1.8.6 (2007-06-07 patchlevel 36) [i486-linux]
> b.rb:3: warning: method redefined; discarding old ===
> foo
> vgs%
> 
> vgs% ./ruby -v b.rb
> ruby 1.9.0 (2008-04-01 revision 15881) [i686-linux]
> b.rb:3: warning: method redefined; discarding old ===
> foo
> vgs%
> 
That's a bit surprising for me:
ruby -v a.rb
ruby 1.8.6 (2008-02-02 patchlevel 5000) [i686-linux]
a.rb:2: warning: method redefined; discarding old ===
foo


./ruby -v a.rb
ruby 1.9.0 (2008-04-01 revision 15368) [i686-linux]
a.rb:2: warning: method redefined; discarding old ===
s

Since opt_case_dispatch doesn't fallback yet.

lopex