1986983 - Support baking in constant property values for builtin JS prototypes and constructors

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, task, P1)

Description

[Jan de Mooij [:jandem]]

After the global object and global lexical environment, we can also enable object fuses for builtin prototypes and constructors. This lets us get rid of more guards for cases such as Math.abs(x), array.join(), or number.toString().

This won't cover prototype objects created by the DOM or JS code yet, but it's a start.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Bug 1986983 part 1 - Use object fuses for builtin JS constructors and prototypes. r?iain!

This lets us eliminate guards for calls to builtins such as Math.abs(x) or
array.join().

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1986983 part 2 - Optimize GetProp for objects with an object fuse. r?iain!

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/b8e3fb41fc38
https://hg.mozilla.org/integration/autoland/rev/859aa9f31374
part 1 - Use object fuses for builtin JS constructors and prototypes. r=iain
https://github.com/mozilla-firefox/firefox/commit/18da8fdd9602
https://hg.mozilla.org/integration/autoland/rev/6a272cfe39b5
part 2 - Optimize GetProp for objects with an object fuse. r=iain

Comment 4

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/859aa9f31374
https://hg.mozilla.org/mozilla-central/rev/6a272cfe39b5

Comment 5

[Acasandrei Beatrice (needinfo me)]

(In reply to Pulsebot from comment #3)

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/b8e3fb41fc38
https://hg.mozilla.org/integration/autoland/rev/859aa9f31374
part 1 - Use object fuses for builtin JS constructors and prototypes. r=iain
https://github.com/mozilla-firefox/firefox/commit/18da8fdd9602
https://hg.mozilla.org/integration/autoland/rev/6a272cfe39b5
part 2 - Optimize GetProp for objects with an object fuse. r=iain

Perfherder has detected a talos performance change from push 6a272cfe39b51dec0b2ffb95c1b7d419f38c6584.

If you have any questions, please reach out to a performance sheriff. Alternatively, you can find help on Slack by joining #perf-help, and on Matrix you can find help by joining #perftest.

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
6%	perf_reftest_singletons id-getter-4.html	windows11-64-24h2-shippable	e10s fission stylo webrender	145.58 -> 137.03
6%	perf_reftest_singletons id-getter-3.html	windows11-64-24h2-shippable	e10s fission stylo webrender	145.63 -> 137.10
6%	perf_reftest_singletons id-getter-5.html	windows11-64-24h2-shippable	e10s fission stylo webrender	145.71 -> 137.18
6%	perf_reftest_singletons id-getter-6.html	windows11-64-24h2-shippable	e10s fission stylo webrender	145.84 -> 137.35
6%	perf_reftest_singletons id-getter-7.html	windows11-64-24h2-shippable	e10s fission stylo webrender	145.99 -> 137.57

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask a performance sheriff to do that for you.

You can run all of these tests on try with ./mach try perf --alert 46834

The following documentation link provides more information about this command.