spreadnew-optimization.js

Enable keyboard shortcuts

// Test case adapted from "apply-optimization.js" to test SpreadNew instead of FunApply.

// Uses fewer iterations than "apply-optimization.js" to keep the overall runtime reasonable.

const iterations = 40;

function make(k) {

    var a = new Array(k);

    for ( let i=0 ; i < k ; i++ )

        a[i] = {}

    return a;

function g() {

    // Ensure |new.target| and |this| are correct.

    assertEq(new.target, g);

    assertEq(typeof this, "object");

    assertEq(Object.getPrototypeOf(this), g.prototype);

    // Returns a Number object, because constructor calls need to return an object!

    return new Number(arguments.length);

function f(a) {

    var sum = 0;

    for ( let i=0 ; i < iterations ; i++ )

        sum += new g(...a);

    return sum;

function time(k, t) {

    var then = Date.now();

    assertEq(t(), iterations*k);

    var now = Date.now();

    return now - then;

function p(v) {

    // Uncomment to see timings

    // print(v);

f(make(200));

// There is currently a cutoff after 375 where we bailout in order to avoid

// handling very large stack frames.  This slows the operation down by a factor

// of 100 or so.

p(time(374, () => f(make(374))));

p(time(375, () => f(make(375))));

p(time(376, () => f(make(376))));

p(time(377, () => f(make(377))));