This came about from conversations with Iain, and it might need a better name. Basically, the idea is we don't need to go through trial inlining if we observe that a function is monomorphic, because we're not going to be able to specialize it any further on a per-caller basis. So, we can just skip the trial inlining phase and use the function's own ICScript. This should save us a little on mprotects, and also if the function has lots of callers, this helps prevent it from staying in Baseline for a long time as the warmup count would be spread across all the callers.

Initial performance numbers are very encouraging: https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=17569aaafe2cc7e9bd41bef9d2cd0367d6ee6297&originalSignature=3451139&newSignature=3451139&framework=13&originalRevision=c1f84d9c4c398160f5a0c46d079b967d472cd3c3&page=1&showOnlyImportant=1

As an added bonus this should fix bug 1818830 - but I'm keeping that around for now as a reminder to verify.

(In reply to Doug Thayer [:dthayer] (he/him) from comment #0)

This should save us a little on mprotects

Baseline IC code is shared and an extra ICScript for trial inlining doesn't require mprotects because we reuse the script's Baseline JIT code. Am I missing something?

https://hg.mozilla.org/mozilla-central/rev/1c6df7a4bef8

crash signatures which were likely regressions from this change

• js::jit::MConstant::toJSValue
• js::jit::MDefinition::type

(In reply to Pulsebot from comment #3)

Pushed by dothayer@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/1c6df7a4bef8
Monomorphic inlining r=iain

== Change summary for alert #37889 (as of Thu, 30 Mar 2023 07:23:38 GMT) ==

Improvements:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=37889

(In reply to Pulsebot from comment #5)

Backout by sstanca@mozilla.com:
https://hg.mozilla.org/mozilla-central/rev/45fc9bb4de9c
Backed out changeset 1c6df7a4bef8 for likely causing jit crashes.

== Change summary for alert #37901 (as of Thu, 30 Mar 2023 13:18:19 GMT) ==

Regressions:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=37901

When this landed, it appears to have regressed the following (and the backout 'fixed' the regression):

All Jetstream2-Crypto-* tests on AWFY
Example : https://treeherder.mozilla.org/perfherder/graphs?highlightAlerts=1&highlightChangelogData=1&highlightCommonAlerts=0&series=mozilla-central,3737973,1,13&series=mozilla-central,3737973,1,13&series=autoland,3911360,1,13&timerange=5184000&zoom=1679857713861,1680169328503,130.16712013598493,322.94543073509533

JEtstream2-lebab-*
https://treeherder.mozilla.org/perfherder/graphs?highlightAlerts=1&highlightChangelogData=1&highlightCommonAlerts=0&series=mozilla-central,3738029,1,13&series=mozilla-central,3738029,1,13&series=autoland,3911416,1,13&timerange=5184000&zoom=1679821649367,1680195253835,22.966431480119773,51.535760491540714

Mandreel:
https://treeherder.mozilla.org/perfherder/graphs?highlightAlerts=1&highlightChangelogData=1&highlightCommonAlerts=0&series=mozilla-central,3738034,1,13&series=mozilla-central,3738034,1,13&series=autoland,3911421,1,13&timerange=5184000&zoom=1679836443679,1680165808797,29.224623091897424,38.32988492963711

(In reply to Pulsebot from comment #5)

Backout by sstanca@mozilla.com:
https://hg.mozilla.org/mozilla-central/rev/45fc9bb4de9c
Backed out changeset 1c6df7a4bef8 for likely causing jit crashes.

== Change summary for alert #37976 (as of Mon, 03 Apr 2023 17:13:54 GMT) ==

Improvements:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=37976

(In reply to Alexandru Ionescu (needinfo me) [:alexandrui] from comment #8)

(In reply to Pulsebot from comment #5)

Backout by sstanca@mozilla.com:
https://hg.mozilla.org/mozilla-central/rev/45fc9bb4de9c
Backed out changeset 1c6df7a4bef8 for likely causing jit crashes.

== Change summary for alert #37901 (as of Thu, 30 Mar 2023 13:18:19 GMT) ==

Regressions:

Ratio	Test	Platform	Options	Absolute values (old vs new)	Performance Profiles
13%	google-docs LastVisualChange	windows10-64-shippable-qr	fission warm webrender	4,241.58 -> 4,799.83	Before/After
10%	google-docs SpeedIndex	windows10-64-shippable-qr	fission warm webrender	1,157.58 -> 1,270.08	Before/After
7%	google-docs ContentfulSpeedIndex	windows10-64-shippable-qr	fission warm webrender	905.00 -> 968.67	Before/After
7%	google-docs SpeedIndex	linux1804-64-shippable-qr	cold fission webrender	1,695.42 -> 1,810.58	Before/After
7%	google-docs PerceptualSpeedIndex	windows10-64-shippable-qr	fission warm webrender	916.67 -> 978.67	Before/After
7%	google-docs ContentfulSpeedIndex	linux1804-64-shippable-qr	cold fission webrender	1,514.50 -> 1,615.17	Before/After
6%	google-docs LastVisualChange	linux1804-64-shippable-qr	cold fission webrender	6,113.33 -> 6,493.33	Before/After
6%	yahoo-mail LastVisualChange	linux1804-64-shippable-qr	bytecode-cached fission warm webrender	641.67 -> 680.00	Before/After
5%	google-docs PerceptualSpeedIndex	linux1804-64-shippable-qr	cold fission webrender	1,429.67 -> 1,504.08	Before/After
4%	google-docs SpeedIndex	macosx1015-64-shippable-qr	cold fission webrender	1,520.81 -> 1,588.25	Before/After
4%	google-docs SpeedIndex	windows10-64-shippable-qr	cold fission webrender	1,367.00 -> 1,427.25	Before/After
4%	ares6	windows10-64-shippable-qr	fission webrender	37.34 -> 38.83
3%	linkedin SpeedIndex	macosx1015-64-shippable-qr	fission warm webrender	686.12 -> 705.08	Before/After
3%	linkedin LastVisualChange	windows10-64-shippable-qr	fission warm webrender	2,052.75 -> 2,108.25
2%	linkedin ContentfulSpeedIndex	windows10-64-shippable-qr	fission warm webrender	1,364.25 -> 1,393.08

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=37901

We seem to have lost more on the way out than we gained on the way in here. Feels like something else landed at the same time this did which regressed things, just less than this improved them. Is this tracked?

https://hg.mozilla.org/mozilla-central/rev/bd4da5d6dfe0

(In reply to Andrej Glavic (:andrej) from comment #10)

(In reply to Pulsebot from comment #5)

Backout by sstanca@mozilla.com:
https://hg.mozilla.org/mozilla-central/rev/45fc9bb4de9c
Backed out changeset 1c6df7a4bef8 for likely causing jit crashes.

== Change summary for alert #37976 (as of Mon, 03 Apr 2023 17:13:54 GMT) ==

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
3%	kraken	windows10-64-shippable-qr	e10s fission stylo webrender	1,149.99 -> 1,110.25
3%	kraken	macosx1015-64-shippable-qr	e10s fission stylo webrender	1,365.11 -> 1,327.82
2%	kraken	windows10-64-shippable-qr	e10s fission stylo webrender	1,142.58 -> 1,114.39

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=37976

Regarding the kraken differences, I investigated this and it's just a quirk of how this interacts with our inlining entry threshold heuristic. It feels like this is not representative of the real world, but I will in a separate bug take a look at various values for that threshold to see if we can move our numbers around in a beneficial way.

https://hg.mozilla.org/mozilla-central/rev/345c8acf3c32

A patch has been attached on this bug, which was already closed. Filing a separate bug will ensure better tracking. If this was not by mistake and further action is needed, please alert the appropriate party. (Or: if the patch doesn't change behavior -- e.g. landing a test case, or fixing a typo -- then feel free to disregard this message)

(In reply to Pulsebot from comment #12)

Pushed by dothayer@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/bd4da5d6dfe0
Monomorphic inlining r=iain

== Change summary for alert #38015 (as of Fri, 07 Apr 2023 01:29:07 GMT) ==

Regressions:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=38015

(In reply to Pulsebot from comment #3)

Pushed by dothayer@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/1c6df7a4bef8
Monomorphic inlining r=iain

== Change summary for alert #38020 (as of Fri, 07 Apr 2023 06:42:56 GMT) ==

Improvements:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=38020

(In reply to Pulsebot from comment #5)

Backout by sstanca@mozilla.com:
https://hg.mozilla.org/mozilla-central/rev/45fc9bb4de9c
Backed out changeset 1c6df7a4bef8 for likely causing jit crashes.

== Change summary for alert #38022 (as of Fri, 07 Apr 2023 07:04:54 GMT) ==

Regressions:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=38022

(In reply to Doug Thayer [:dthayer] (he/him) from comment #11)

(In reply to Alexandru Ionescu (needinfo me) [:alexandrui] from comment #8)
We seem to have lost more on the way out than we gained on the way in here. Feels like something else landed at the same time this did which regressed things, just less than this improved them. Is this tracked?

In updated the summary, thanks!

(In reply to Pulsebot from comment #12)

Pushed by dothayer@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/bd4da5d6dfe0
Monomorphic inlining r=iain

== Change summary for alert #38030 (as of Fri, 07 Apr 2023 13:32:12 GMT) ==

Improvements:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=38030