prelude: |
  IVARS = 60
  class Record
    def initialize(offset = false)
      @offset = 1 if offset
      @first = 0
      IVARS.times do |i|
        instance_variable_set("@ivar_#{i}", i)
      end
    end

    def first
      @first
    end

    def lazy_set
      @lazy_set ||= 123
    end

    def undef
      @undef
    end
  end

  Record.new # Need one alloc to right size

  BASE = Record.new
  LAZY = Record.new
  LAZY.lazy_set

  class Miss < Record
    @first = 0
    IVARS.times do |i|
      instance_variable_set("@i_#{i}", i)
    end
  end

  Miss.new # Need one alloc to right size
  MISS = Miss.new

  DIVERGENT = Record.new(true)

benchmark:
  vm_ivar_stable_shape: |
    BASE.first
    BASE.first
    BASE.first
    BASE.first
    BASE.first
    BASE.first
  vm_ivar_memoize_unstable_shape: |
    BASE.first
    LAZY.first
    BASE.first
    LAZY.first
    BASE.first
    LAZY.first
  vm_ivar_memoize_unstable_shape_miss: |
    BASE.first
    MISS.first
    BASE.first
    MISS.first
    BASE.first
    MISS.first
  vm_ivar_unstable_undef: |
    BASE.undef
    LAZY.undef
    BASE.undef
    LAZY.undef
    BASE.undef
    LAZY.undef
  vm_ivar_divergent_shape: |
    BASE.first
    DIVERGENT.first
    BASE.first
    DIVERGENT.first
    BASE.first
    DIVERGENT.first
  vm_ivar_divergent_shape_imbalanced: |
    BASE.first
    DIVERGENT.first
    DIVERGENT.first
    DIVERGENT.first
    DIVERGENT.first
    DIVERGENT.first