From: Joseph Jones <joeyi5216@...>
Date: 2015-12-17T21:06:00-07:00
Subject: [ruby-core:72251] [Ruby trunk - Feature #11769] [Open] optimize case / when for `nil`

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Joseph Jones liked your message with Boxer. On December 3, 2015 at 14:43:=
24 MST, tenderlove=40ruby-lang.org wrote:Issue =2311769 has been reported=
 by Aaron Patterson.----------------------------------------=46eature =23=
11769: optimize case / when for =60nil=60https://bugs.ruby-lang.org/issue=
s/11769* Author: Aaron Patterson* Status: Open* Priority: Normal* Assigne=
e: ----------------------------------------Hi,I've noticed that when ther=
e are certain values in a case / when statement it gets optimized to a ha=
sh lookup. =46or example, code like this:=7E=7E=7Edef foo socket case str=
 =3D socket.read=5Fnonblock(10, exception: false) when :wait=5Freadable =23=
 do something else str endendputs RubyVM::InstructionSequence.of(method(:=
foo)).disasm=7E=7E=7EThe above code will use =60opt=5Fcase=5Fdispatch=60 =
instruction with a hash. However, if I use =60nil=60 in the case statemen=
t like this:=7E=7E=7Edef foo socket case str =3D socket.read=5Fnonblock(1=
0, exception: false) when :wait=5Freadable =23 do something when nil =23 =
got an EO=46 else str endendputs RubyVM::InstructionSequence.of(method(:f=
oo)).disasm=7E=7E=7EThen the optimization is lost.I've attached a patch t=
hat adds =60nil=60 to the optimized case such that the above code will us=
e =60opt=5Fcase=5Fdispatch=60. My patch defines =60=3D=3D=3D=60 on =60nil=
=60, then adds nil to the list of =22optimizable literals=22.---=46iles--=
------------------------------0001-optimize-case-when-for-nil.patch (3.4 =
KB)-- https://bugs.ruby-lang.org/     
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<html><body><div>Joseph Jones liked your message with <a href=3D=22http:/=
/bxr.io/PBIqo=22>Boxer</a>.</div><br/><br/><div><div class=3D=22quote=22>=
On December 3, 2015 at 14:43:24 MST, tenderlove=40ruby-lang.org wrote:<br=
/><blockquote type=3D=22cite=22 style=3D=22border-left-style:solid;border=
-width:1px;margin-left:0px;padding-left:10px;=22>Issue =2311769 has been =
reported by Aaron Patterson.<br /><br />---------------------------------=
-------<br />=46eature =2311769: optimize case / when for =60nil=60<br />=
https://bugs.ruby-lang.org/issues/11769<br /><br />* Author: Aaron Patter=
son<br />* Status: Open<br />* Priority: Normal<br />* Assignee: <br />--=
--------------------------------------<br />Hi,<br /><br />I've noticed t=
hat when there are certain values in a case / when statement it gets opti=
mized to a hash lookup.  =46or example, code like this:<br /><br />=7E=7E=
=7E<br />def foo socket<br />  case str =3D socket.read=5Fnonblock(10, ex=
ception: false)<br />  when :wait=5Freadable<br />    =23 do something<br=
 />  else<br />    str<br />  end<br />end<br /><br />puts RubyVM::Instru=
ctionSequence.of(method(:foo)).disasm<br />=7E=7E=7E<br /><br />The above=
 code will use =60opt=5Fcase=5Fdispatch=60 instruction with a hash.  Howe=
ver, if I use =60nil=60 in the case statement like this:<br /><br />=7E=7E=
=7E<br />def foo socket<br />  case str =3D socket.read=5Fnonblock(10, ex=
ception: false)<br />  when :wait=5Freadable<br />    =23 do something<br=
 />  when nil<br />    =23 got an EO=46<br />  else<br />    str<br />  e=
nd<br />end<br /><br />puts RubyVM::InstructionSequence.of(method(:foo)).=
disasm<br />=7E=7E=7E<br /><br />Then the optimization is lost.<br /><br =
/>I've attached a patch that adds =60nil=60 to the optimized case such th=
at the above code will use =60opt=5Fcase=5Fdispatch=60.  My patch defines=
 =60=3D=3D=3D=60 on =60nil=60, then adds nil to the list of =22optimizabl=
e literals=22.<br /><br />---=46iles--------------------------------<br /=
>0001-optimize-case-when-for-nil.patch (3.4 KB)<br /><br /><br />-- <br /=
>https://bugs.ruby-lang.org/<br /></blockquote></div></div></body></html>
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