a micro benchmark for https://bugs.ruby-lang.org/issues/9508

cov.rb

require "coverage.so"
Coverage.start
at_exit { p Coverage.result }

test.rb

30000000.times do
  true ? false ? 1 : 2 : 3
end

transcript

# without the patch applied
$ time ./ruby -r./cov.rb -e 'require "./test"' 
{"/home/mame/work/ruby/test.rb"=>[1, 30000000, nil]}

real    0m1.792s
user    0m1.784s
sys     0m0.008s

# with the patch applied
$ time ./ruby -r./cov.rb -e 'require "./test"' 
{"/home/mame/work/ruby/test.rb"=>{:lines=>[1, 30000000, nil], :methods=>{}, :decisions=>{2=>[30000000, 30000000]}}}

real    0m4.066s
user    0m4.057s
sys     0m0.008s