1937570 - Optimize JSOp::Lambda in Baseline

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, task, P2)

Description

[Jan de Mooij [:jandem]]

js::Lambda will be the most-called VMFunction on Speedometer 3 after bug 1935632. Baseline IC code is likely responsible for most of these calls.

This is a very common operation (arrow functions likely contributed) that should be fast in Baseline too. The simplest option is probably to implement this with an IC similar to what we do for the NewObject and NewArray ops.

Comment 1

[Jan de Mooij [:jandem]]

A Baseline IC for JSOp::Lambda gets rid of pretty much all of these VM calls. For the micro-benchmark below I get:

--no-ion before: 268 ms
--no-ion after:   94 ms
no flags:         55 ms

function f() {
    var res;
    var t = new Date;
    for (var i = 0; i < 10_000_000; i++) {
        res = x => x + 1;
    }
    print(new Date - t);
    return res;
}
f();

Comment 2

[Jan de Mooij [:jandem]]

Attachment: Bug 1937570 part 1 - Assert canonical function has not resolved length/name. r?iain!

The code for LLambda already relied on this because it copies the flags from
the canonical function to the new function.

Comment 3

[Jan de Mooij [:jandem]]

Attachment: Bug 1937570 part 2 - Add a Baseline IC for JSOp::Lambda. r?iain!

Comment 4

[Jan de Mooij [:jandem]]

Attachment: Bug 1937570 part 3 - Add Baseline CacheIR stub for JSOp::Lambda. r?iain!

This is similar to the NewObject and NewArray IC stubs. We allocate a new
function object in JIT code and copy the shape and most slots from the canonical
function.

js::Lambda is one of our hottest VMFunctions on Speedometer 3 and this gets
rid of most of these calls. On Baseline-only micro-benchmarks this is almost 3x faster.

Comment 5

[Jan de Mooij [:jandem]]

This improves JetStream's date-format-tofte test by about 8%. This test has a function that uses eval (so no Ion) and this function has a number of inner functions that we now clone more efficiently.

Speedometer 3 shows some medium/high confidence 1-2% improvements on various subtests on Windows 11. Pretty nice for a change like this.

https://treeherder.mozilla.org/perfherder/compare?originalProject=try&newProject=try&newRevision=9a26de7a25c562e8eb3ffc9ff32f91085c2dc7be&framework=13&originalRevision=557eeb4584cde4ababf93bc7fc8f85261f226517&page=1

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3ebb07224094
part 1 - Assert canonical function has not resolved length/name. r=iain
https://hg.mozilla.org/integration/autoland/rev/21a62d3a0144
part 2 - Add a Baseline IC for JSOp::Lambda. r=iain
https://hg.mozilla.org/integration/autoland/rev/1dbbfc3b5ee2
part 3 - Add Baseline CacheIR stub for JSOp::Lambda. r=iain

Comment 7

[agoloman]

https://hg.mozilla.org/mozilla-central/rev/3ebb07224094
https://hg.mozilla.org/mozilla-central/rev/21a62d3a0144
https://hg.mozilla.org/mozilla-central/rev/1dbbfc3b5ee2

Comment 8

[Mayank Bansal]

11% improvement on Jetstream2-date-format-tofte-SP