1827420 - Optimize AutoSetNewObjectMetadata

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P2)

Description

[Jan de Mooij [:jandem]]

AutoSetNewObjectMetadata often shows up in profiles. We can make this quite a lot faster for the common case when there's no active metadata builder.

I have some patches for this that improve the micro-benchmark below from ~405 ms to ~345 ms.

function f() {
    var obj = {};
    var res;
    var t = new Date;
    for (var i = 0; i < 10_000_000; i++) {
        res = Object.getOwnPropertyNames(obj);
    }
    print(new Date - t);
    return res;
}
f();

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1827420 part 1 - Remove some unnecessary AutoSetNewObjectMetadata uses. r?jonco!

If we're not using JSCLASS_DELAY_METADATA_BUILDER, we won't set pending metadata
so AutoSetNewObjectMetadata will be a no-op.

Also adds an assertion to catch these.

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1827420 part 2 - Optimize AutoSetNewObjectMetadata. r?jonco!

Inline more code and add realm->hasAllocationMetadataBuilder() checks in a
few places.

Removes the prevState_ field beacuse it was always ImmediateMetadata. We now
assert this in the constructor.

This makes a getOwnPropertyNames micro-benchmark about 15% faster.

Depends on D175136

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f3ea7807cf5c
part 1 - Remove some unnecessary AutoSetNewObjectMetadata uses. r=jonco
https://hg.mozilla.org/integration/autoland/rev/8872eb50a6b1
part 2 - Optimize AutoSetNewObjectMetadata. r=jonco

Comment 4

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/f3ea7807cf5c
https://hg.mozilla.org/mozilla-central/rev/8872eb50a6b1