Destructuring performace (V8 ToT 2016/11/16)

destructuring-performance-test.js

/////////////////////////////////////////////////////////////////////////////
// Test framework:

// Warmup
for (var i = 0; i < 1000; ++i) test(data);

function time(test, a) {
  let startTime = Date.now();
  // Using F.p.apply here to prevent inlining, so we can really
  // just measure the performance of test stand-alone.
  for (let i = 0; i < 5000000; ++i) test.apply(undefined, [a]);
  let endTime = Date.now();
  print("Time: " + (endTime - startTime) + "ms.");
}

time(test, data);

/////////////////////////////////////////////////////////////////////////////
// Test data (Source: https://fhinkel.github.io/six-speed)

var data = {
  a: 'foo',
  b: {c: 'd'},
  arr: [1, 2, 3]
};

/////////////////////////////////////////////////////////////////////////////
// Naive ES5 version (Source: https://fhinkel.github.io/six-speed)

function test(data) {
  var a = data.a,
      b = data.b.c,
      c = data.arr[1];
  return c;
}

/////////////////////////////////////////////////////////////////////////////
// ES6 destructuring version (Source: https://fhinkel.github.io/six-speed)

function test(data) {
  var {a, b:{c:b}, arr:[, c]} = data;
  return c;
}

/////////////////////////////////////////////////////////////////////////////
// Results (with experimental TurboFan escape analysis):
//
// $ d8 --turbo-escape destructuring.es5
// Time: 275ms.
//
// $ d8 --turbo-escape destructuring.es6
// Time: 344ms.
//
// State: 20% missing for ES6 version to reach parity.