prelude: |
  class A
    def initialize
      @a = nil
      @b = nil
      @c = nil
      @d = nil
      @e = nil
    end
  end
  class B < A; end
  class C < A; end
benchmark:
  vm_ivar_init_subclass: |
    B.new
    C.new
loop_count: 3000000