1457125 - Use interpreter fast path for calls also for calls to non-constructors

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement)

Description

[Jan de Mooij [:jandem]]

Attachment: Patch

Noticed this while investigating bug 1449950 in the debugger on Windows.

The interpreter has an inline-call path that's guarded by:

    /* Don't bother trying to fast-path calls to scripted non-constructors. */
    if (!isFunction || !maybeFun->isInterpreted() || !maybeFun->isConstructor() ||
        (!construct && maybeFun->isClassConstructor()))

We were not using this path for calls to some self-hosted function because isConstructor() returns false, but we only care about that if we're actually constructing.

Comment 1

[Jan de Mooij [:jandem]]

Note that bug 667824 added this "Don't bother trying to fast-path calls to scripted non-constructors." comment, but back then I think the only non-constructor function was probably Function.prototype -- nowadays we have a lot more of them.

Comment 2

[Jan de Mooij [:jandem]]

FWIW this improves the micro-benchmark below from 210 ms to 151 ms with --no-baseline

function f() {
    var g = () => 1;
    var t = new Date;
    for (var i = 0; i < 1000000; i++)
        g();
    print(new Date - t);
}
f();

Comment 3

[Ted Campbell [:tcampbell]]

Comment on attachment 8971207 [details] [diff] [review]
Patch

Review of attachment 8971207 [details] [diff] [review]:
-----------------------------------------------------------------

Good find. This is going to move a huge amount of normal calls to the "fast-path". Probably worth getting some talos/AWFY results before landing, especially if aiming for FF61.

While you are here, do you mind changing the definition of |construct| to use |IsConstructorCallPC|?

Comment 4

[Ted Campbell [:tcampbell]]

Ah, I was missing that functions by default are constructors, even if code doesn't use them as constructors. This looks reasonable then. :)

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/314f5e5e4502
Use interpreter fast path for calls also for calls to non-constructors. r=tcampbell

Comment 6

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/314f5e5e4502