1465472 - Remove the atoms realm/compartment

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement)

Description

[Jan de Mooij [:jandem]]

A while ago Jon suggested we could remove the atoms realm and compartment and just keep the atoms zone. AutoAtomsRealm could be renamed to AutoAtomsZone.

I tried this and it's pretty nice, for instance the CompartmentsIter and RealmsIter classes no longer need a ZoneSelector argument. It also saves some memory because we no longer allocate a mostly-unused realm and compartment for each runtime.

Comment 1

[Jan de Mooij [:jandem]]

Attachment: Patch

Some of the less trivial changes:

* When we allocated a symbol, we used the atom realm's RNG to create a hash code [0]. Instead of this I added a RNG for this to the runtime.

* IsCompilingWasm returned true if the JitContext's realm is nullptr, but that's now also true when we initialize the trampolines stored in the atoms zone. To fix that I added a CompileZone* to JitContext, in addition to the CompileRuntime and CompileRealm, and we now check the zone instead of the realm in IsCompilingWasm.

* JSContext::hasEnteredRealm is only called in DEBUG builds so I made hasEnteredRealm and enterRealmDepth_ #ifdef DEBUG.

[0] https://searchfox.org/mozilla-central/rev/5a744713370ec47969595e369fd5125f123e6d24/js/src/vm/SymbolType.cpp#52

Comment 2

[Jon Coppeard (:jonco)]

Comment on attachment 8981894 [details] [diff] [review]
Patch

Review of attachment 8981894 [details] [diff] [review]:
-----------------------------------------------------------------

Nice.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/b671b92bea18
Remove the atoms realm/compartment. r=jonco

Comment 4

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/mozilla-central/rev/b671b92bea18

Comment 5

[Jan de Mooij [:jandem]]

Attachment: Followup - Remove (now always-false) check for atoms compartment

Just a GCRuntime::markCompartments one-liner to remove the |comp->zone()->isAtomsZone()| check. The atoms zone no longer contains any compartments.

Comment 6

[Jon Coppeard (:jonco)]

Comment on attachment 8982991 [details] [diff] [review]
Followup - Remove (now always-false) check for atoms compartment

Review of attachment 8982991 [details] [diff] [review]:
-----------------------------------------------------------------

Thanks.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/52c23f361adb
followup - Remove (now always-false) check for atoms compartment. r=jonco

Comment 8

[Andrei Ciure[:aciure]]

https://hg.mozilla.org/mozilla-central/rev/52c23f361adb