Use V8 internal methods to test if a JS function can be optimized

optimization-test.js

/**
 * Based on code from <https://github.com/petkaantonov/bluebird/wiki/Optimization-killers>
 * Run this script using:
 *   `node --allow-natives-syntax optimization-test.js`
 * For more diagnostic output use:
 *   `node --trace_opt --trace_deopt --allow-natives-syntax optimization-test.js`
 */

function myFunction() {
  return 'hello world';
}

function printStatus(fn) {
  fn();
  fn();

  %OptimizeFunctionOnNextCall(fn);
  fn();

  switch (%GetOptimizationStatus(fn)) {
    case 1: success('Function is optimized'); break;
    case 2: fail('Function is not optimized'); break;
    case 3: success('Function is always optimized'); break;
    case 4: fail('Function is never optimized'); break;
    case 6: fail('Function is maybe deoptimized'); break;
    case 7: success('Function is optimized by TurboFan'); break;
    default: fail('Unknown optimization status'); break;
  }
}

function success(msg) {
  console.log('\033[32m' + msg + '\033[0m');
}

function fail(msg) {
  console.warn('\033[31m' + msg + '\033[0m');
}

printStatus(myFunction);