1667258 - Remove RealmCreationOptions::cloneSingletons

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P1)

Description

[Ted Campbell [:tcampbell]]

This is only used for a test configuration of XDR which doesn't not reflect browser behaviour. Instead we should simply disallow using non-incremental XDR on run-once scripts and a lot of complexity can be removed.

Currently only ScriptLoader/JSBC encodes run-once scripts and that uses the incremental XDR encoder which is compatible.

Comment 1

[Ted Campbell [:tcampbell]]

Attachment: Bug 1667258 - Assert that JSOp::Object is only used for run-once scripts. r?jandem

The JSOp::Object opcode is only for "run-once singleton contexts" which
require the run-once CompileOption to be set. We will use this invariant to
eventually remove the cloneSingletons mechanism.

Comment 2

[Ted Campbell [:tcampbell]]

Attachment: Bug 1667258 - Disallow JS::EncodeScript on run-once scripts. r?jandem!,nbp!

Use the same conditions for EncodeScript as we do for CopyScriptImpl. This
involves checking if the top-level script was compiled as run-once. This
check applies regardless of whether the script has been run on not (which is
a stricter test than might otherwise be required). This lets us avoid the
"cloneSingletons" mechanism altogether.

This is more consistent with browser use-cases of EncodeScript which do not
mark scripts as run-once.

We change test behavior to not use the run-once flag for non-incremental
mode. Cases that are testing run-once-only features now use incremental XDR
which is consisten with what the browser actually does.

Depends on D91363

Comment 3

[Ted Campbell [:tcampbell]]

Attachment: Bug 1667258 - Remove support for RealmCreationOptions::cloneSingletons. r?jandem!

Script object-literal singletons are only generated for top-level run-once
scripts which both XDR and cloning no longer need to support. As a result,
the cloneSingletons mechanism is no longer needed and can be removed.

We can simplify the Interpreter and JITs handling of JSOp::Object to no
longer worry about cloneSingletons as a result. They also lets us remove the
setSingletonsAsValues code since we no longer have realm-wide poison bits.

Depends on D91364

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6711f01eb82f
Assert that JSOp::Object is only used for run-once scripts. r=jandem
https://hg.mozilla.org/integration/autoland/rev/a12dfabdb040
Disallow JS::EncodeScript on run-once scripts. r=jandem,nbp
https://hg.mozilla.org/integration/autoland/rev/e0255e7ef9da
Remove support for RealmCreationOptions::cloneSingletons. r=jandem

Comment 5

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/6711f01eb82f
https://hg.mozilla.org/mozilla-central/rev/a12dfabdb040
https://hg.mozilla.org/mozilla-central/rev/e0255e7ef9da