Performance regression in ActiveRecord model accessing generated property method

benchmark.rb

require 'benchmark/ips'

begin
  class CreateModels < ActiveRecord::Migration
    def change
      create_table :users do |t|
        t.string :attribute1
        t.string :attribute2
        t.string :attribute3
        t.string :attribute4
        t.string :attribute5
        t.string :attribute6
        t.string :attribute7

        t.timestamps null: false
      end
    end
  end

  CreateModels.new.change


  unless User.count >= 1000
    # insert 1000 records via seeds
    1000.times do
      User.create! attribute1: 'foo', attribute2: 'foo', attribute3: 'foo', attribute4: 'foo', attribute5: 'foo', attribute6: 'foo', attribute7: 'foo'
    end
  end

rescue => e
  # Tables already exist
  # puts e.message
ensure

  users1 = User.all.to_a
  users2 = User.all.to_a
  Benchmark.ips do |x|

    x.report('generated method') do
      users1.each do |user|
        user.attribute1
        user.attribute2
        user.attribute3
        user.attribute4
        user.attribute5
        user.attribute6
        user.attribute7
      end
    end

    x.report('read_attribute') do
      users2.each do |user|
        user.read_attribute(:attribute1)
        user.read_attribute(:attribute2)
        user.read_attribute(:attribute3)
        user.read_attribute(:attribute4)
        user.read_attribute(:attribute5)
        user.read_attribute(:attribute6)
        user.read_attribute(:attribute7)
      end
    end
  end
end

result

---  Rails 3.2
Calculating -------------------------------------
    generated method    33.000  i/100ms
      read_attribute    12.000  i/100ms
-------------------------------------------------
    generated method    346.685  (± 1.7%) i/s -      1.749k
      read_attribute    124.214  (± 0.8%) i/s -    624.000

---  Rails 4.2 edge
-- create_table(:users)
Calculating -------------------------------------
    generated method    19.000  i/100ms
      read_attribute    16.000  i/100ms
-------------------------------------------------
    generated method    200.527  (± 2.0%) i/s -      1.007k
      read_attribute    160.680  (± 2.5%) i/s -    816.000