Benchmark gsub/sub before and after https://github.com/jruby/jruby/pull/5952

gsub.log

BEFORE:
jruby [master] $ benchmark bench/core/string/bench_gsub.rb
Warming up --------------------------------------
         gsub-string    83.418k i/100ms
          gsub-regex   120.922k i/100ms
    gsub-regex-block    82.905k i/100ms
         gsub-string    96.724k i/100ms
          gsub-regex   128.786k i/100ms
    gsub-regex-block    83.732k i/100ms
         gsub-string   100.446k i/100ms
          gsub-regex   117.749k i/100ms
    gsub-regex-block    81.020k i/100ms
Calculating -------------------------------------
         gsub-string      1.864M (± 5.2%) i/s -      9.341M in   5.028109s
          gsub-regex      2.821M (± 6.4%) i/s -     14.012M in   4.997615s
    gsub-regex-block      1.580M (± 3.9%) i/s -      7.940M in   5.033951s
         gsub-string      1.843M (± 6.2%) i/s -      9.241M in   5.038603s
          gsub-regex      2.867M (± 4.3%) i/s -     14.365M in   5.020753s
    gsub-regex-block      1.573M (± 5.1%) i/s -      7.859M in   5.009079s
         gsub-string      1.901M (± 3.9%) i/s -      9.542M in   5.028879s
          gsub-regex      2.805M (± 7.5%) i/s -     14.012M in   5.027708s
    gsub-regex-block      1.557M (± 5.4%) i/s -      7.778M in   5.012116s

Comparison:
          gsub-regex:  2805333.0 i/s
         gsub-string:  1900607.3 i/s - 1.48x  slower
    gsub-regex-block:  1556662.7 i/s - 1.80x  slower

AFTER:
jruby [use-string-matching-5905] $ benchmark bench/core/string/bench_gsub.rb
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.headius.backport9.modules.Modules to method sun.nio.ch.NativeThread.signal(long)
WARNING: Please consider reporting this to the maintainers of com.headius.backport9.modules.Modules
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Warming up --------------------------------------
         gsub-string   132.304k i/100ms
          gsub-regex   134.161k i/100ms
    gsub-regex-block    98.747k i/100ms
         gsub-string   146.478k i/100ms
          gsub-regex   137.456k i/100ms
    gsub-regex-block    97.131k i/100ms
         gsub-string   143.662k i/100ms
          gsub-regex   140.012k i/100ms
    gsub-regex-block    96.690k i/100ms
Calculating -------------------------------------
         gsub-string      2.899M (± 5.5%) i/s -     14.510M in   5.022088s
          gsub-regex      2.876M (± 8.2%) i/s -     14.281M in   5.012498s
    gsub-regex-block      1.689M (± 5.3%) i/s -      8.412M in   4.998477s
         gsub-string      2.967M (± 5.0%) i/s -     14.797M in   5.001599s
          gsub-regex      2.984M (± 5.0%) i/s -     14.981M in   5.035178s
    gsub-regex-block      1.671M (± 5.6%) i/s -      8.412M in   5.051254s
         gsub-string      3.084M (± 3.8%) i/s -     15.515M in   5.039117s
          gsub-regex      2.894M (± 6.9%) i/s -     14.421M in   5.009674s
    gsub-regex-block      1.738M (± 3.6%) i/s -      8.702M in   5.013762s

Comparison:
         gsub-string:  3083819.2 i/s
          gsub-regex:  2893563.9 i/s - same-ish: difference falls within error
    gsub-regex-block:  1737972.1 i/s - 1.77x  slower

sub.log

BEFORE:
jruby [use-string-matching-5905] $ benchmark bench/core/string/bench_sub.rb
Warming up --------------------------------------
          sub-string    85.531k i/100ms
           sub-regex   115.471k i/100ms
     sub-regex-block    86.421k i/100ms
          sub-string   112.434k i/100ms
           sub-regex   139.722k i/100ms
     sub-regex-block    89.876k i/100ms
          sub-string   101.295k i/100ms
           sub-regex   138.565k i/100ms
     sub-regex-block    87.712k i/100ms
Calculating -------------------------------------
          sub-string      2.190M (± 7.6%) i/s -     10.940M in   5.025020s
           sub-regex      3.122M (± 8.9%) i/s -     15.519M in   5.017819s
     sub-regex-block      1.648M (± 6.9%) i/s -      8.245M in   5.030430s
          sub-string      2.255M (± 5.5%) i/s -     11.244M in   5.002959s
           sub-regex      3.310M (± 3.5%) i/s -     16.628M in   5.029668s
     sub-regex-block      1.654M (± 5.9%) i/s -      8.245M in   5.003373s
          sub-string      2.301M (± 5.5%) i/s -     11.548M in   5.036839s
           sub-regex      3.263M (± 6.5%) i/s -     16.351M in   5.033664s
     sub-regex-block      1.689M (± 3.8%) i/s -      8.508M in   5.044707s

Comparison:
           sub-regex:  3263463.5 i/s
          sub-string:  2300856.5 i/s - 1.42x  slower
     sub-regex-block:  1689094.8 i/s - 1.93x  slower

AFTER:
jruby [use-string-matching-5905] $ benchmark bench/core/string/bench_sub.rb
Warming up --------------------------------------
          sub-string   130.911k i/100ms
           sub-regex   132.331k i/100ms
     sub-regex-block    97.297k i/100ms
          sub-string   142.288k i/100ms
           sub-regex   138.834k i/100ms
     sub-regex-block    93.862k i/100ms
          sub-string   140.333k i/100ms
           sub-regex   134.390k i/100ms
     sub-regex-block    96.066k i/100ms
Calculating -------------------------------------
          sub-string      3.286M (± 6.1%) i/s -     16.419M in   5.016219s
           sub-regex      3.343M (± 5.4%) i/s -     16.664M in   5.000450s
     sub-regex-block      1.894M (± 5.9%) i/s -      9.511M in   5.041052s
          sub-string      2.969M (±16.2%) i/s -     14.454M in   5.039208s
           sub-regex      3.049M (±15.4%) i/s -     14.917M in   5.025439s
     sub-regex-block      1.858M (± 5.2%) i/s -      9.318M in   5.031101s
          sub-string      3.383M (± 5.1%) i/s -     16.980M in   5.033060s
           sub-regex      3.312M (± 6.6%) i/s -     16.530M in   5.015668s
     sub-regex-block      1.891M (± 5.0%) i/s -      9.511M in   5.042478s

Comparison:
          sub-string:  3383455.0 i/s
           sub-regex:  3312195.3 i/s - same-ish: difference falls within error
     sub-regex-block:  1891378.7 i/s - 1.79x  slower