bench.rb

#!/usr/bin/env ruby
require 'benchmark'

def bitmask
  2 ** 32 - 1
end

def bitmask_with_assignment
  overshoot = 2 ** 32
  overshoot - 1
end

iterations = 10_000_000

Benchmark.bmbm do |x|
  x.report('without') { iterations.times { bitmask } }
  x.report('with') { iterations.times { bitmask_with_assignment } }
end