1782953 - Optimize sparse element accesses in more cases

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, task, P3)

Description

[Jan de Mooij [:jandem]]

I noticed a few issues related to sparse elements in bug 1782566:

1. We only optimize getting/setting sparse elements on arrays and not plain objects.
2. We don't optimize getting/setting sparse elements if index < initializedLength (dense element holes).

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1782953 part 1 - Optimize getting/setting sparse elements on plain objects too. r?iain!

We only supported arrays, but plain objects often have sparse elements too.

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1782953 part 2 - Optimize sparse elements with index < initializedLength. r?iain!

Turns GuardIndexGreaterThanDenseInitLength into GuardIndexIsNotDenseElement.

It's not uncommon to have objects with both sparse elements and holes in the dense
elements. We can now optimize dense element holes with the sparse element VM functions
instead of deoptimizing the IC.

Depends on D153600

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/bff0d79f0218
part 1 - Optimize getting/setting sparse elements on plain objects too. r=iain
https://hg.mozilla.org/integration/autoland/rev/27d77030e725
part 2 - Optimize sparse elements with index < initializedLength. r=iain

Comment 4

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/bff0d79f0218
https://hg.mozilla.org/mozilla-central/rev/27d77030e725