Ruby dup optimization

ruby_dup_optimization

⋊> ~/c/ruby on getlocal-of-same-object-becomes-dup ⨯ ./ruby --version                                                                                                                                                                                 15:27:30
ruby 3.1.0dev (2021-03-17T21:17:37Z getlocal-of-same-o.. 383292776f) [x86_64-darwin19]
⋊> ~/c/ruby on getlocal-of-same-object-becomes-dup ⨯ /Users/hparker/.rbenv/shims/ruby --version                                                                                                                                                       15:27:53
ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin19]
⋊> ~/c/ruby on getlocal-of-same-object-becomes-dup ⨯ benchmark-driver benchmark/repeated_local.rb -e ./ruby -e /Users/hparker/.rbenv/shims/ruby                                                                                                       15:27:55
Calculating -------------------------------------
                         ./ruby  /Users/hparker/.rbenv/shims/ruby 
      repeated_local   142.861k                          166.678k i/s -       1.000 times in 0.000007s 0.000006s

Comparison:
                   repeated_local
/Users/hparker/.rbenv/shims/ruby:    166678.3 i/s 
              ./ruby:    142860.8 i/s - 1.17x  slower

⋊> ~/c/ruby on getlocal-of-same-object-becomes-dup ⨯ /Users/hparker/.rbenv/shims/ruby --dump=insns benchmark/repeated_local.rb                                                                                                                        15:29:10
== disasm: #<ISeq:<main>@benchmark/repeated_local.rb:1 (1,0)-(6,15)> (catch: FALSE)
local table (size: 1, argc: 0 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] x@0
0000 definemethod                           :square, square           (   1)[Li]
0003 putself                                                          (   6)[Li]
0004 putobject                              100
0006 opt_send_without_block                 <calldata!mid:square, argc:1, FCALL|ARGS_SIMPLE>
0008 dup
0009 setlocal_WC_0                          x@0
0011 leave

== disasm: #<ISeq:square@benchmark/repeated_local.rb:1 (1,0)-(5,3)> (catch: FALSE)
== catch table
| catch type: break  st: 0000 ed: 0004 sp: 0000 cont: 0004
| == disasm: #<ISeq:block in square@benchmark/repeated_local.rb:2 (2,10)-(4,5)> (catch: FALSE)
| == catch table
| | catch type: redo   st: 0001 ed: 0007 sp: 0000 cont: 0001
| | catch type: next   st: 0001 ed: 0007 sp: 0000 cont: 0007
| |------------------------------------------------------------------------
| 0000 nop                                                              (   2)[Bc]
| 0001 getlocal_WC_1                          x@0                       (   3)[Li]
| 0003 getlocal_WC_1                          x@0
| 0005 opt_mult                               <calldata!mid:*, argc:1, ARGS_SIMPLE>
| 0007 nop
| 0008 leave                                                            (   4)[Br]
|------------------------------------------------------------------------
local table (size: 1, argc: 1 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] x@0<Arg>
0000 putobject_INT2FIX_1_                                             (   2)[LiCa]
0001 send                                   <calldata!mid:times, argc:0>, block in square
0004 nop
0005 leave                                                            (   5)[Re]
⋊> ~/c/ruby on getlocal-of-same-object-becomes-dup ⨯ ./ruby --dump=insns benchmark/repeated_local.rb                                                                                                                                                  15:29:17
== disasm: #<ISeq:<main>@benchmark/repeated_local.rb:1 (1,0)-(6,15)> (catch: FALSE)
local table (size: 1, argc: 0 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] x@0
0000 definemethod                           :square, square           (   1)[Li]
0003 putself                                                          (   6)[Li]
0004 putobject                              100
0006 opt_send_without_block                 <calldata!mid:square, argc:1, FCALL|ARGS_SIMPLE>
0008 dup
0009 setlocal_WC_0                          x@0
0011 leave

== disasm: #<ISeq:square@benchmark/repeated_local.rb:1 (1,0)-(5,3)> (catch: FALSE)
local table (size: 1, argc: 1 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] x@0<Arg>
0000 putobject_INT2FIX_1_                                             (   2)[LiCa]
0001 send                                   <calldata!mid:times, argc:0>, block in square
0004 leave                                                            (   5)[Re]

== disasm: #<ISeq:block in square@benchmark/repeated_local.rb:2 (2,10)-(4,5)> (catch: FALSE)
0000 getlocal_WC_1                          x@0                       (   3)[LiBc]
0002 dup
0003 opt_mult                               <calldata!mid:*, argc:1, ARGS_SIMPLE>
0005 leave                                                            (   4)[Br]