1895628 - Simplify string deduplication code by taking advantage of dependent string sweeping

Status: RESOLVED FIXED

(Core :: JavaScript: GC, enhancement, P2)

Description

[Steve Fink [:sfink] [:s:]]

We no longer have to give up when hitting a tenured string while walking up a dependent string's base chain. All we need is the root of the base chain tree.

Comment 1

[Steve Fink [:sfink] [:s:]]

Attachment: Bug 1895628 - Simplify string deduplication to take advantage of dependent string sweeping during minor GC.

Rather than laboriously walking the chain of dependent strings, unconditionally collapse everything to a single base during a minor GC, force the base to be traced (while recording information about the previous value), and then sweep the dependent string to update the chars pointer in case it moved (using the previous value and the new value). Previously too much information was being destroyed, and in an order-dependent way.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

There is an r+ patch which didn't land and no activity in this bug for 2 weeks.
:sfink, could you have a look please?
If you still have some work to do, you can add an action "Plan Changes" in Phabricator.
For more information, please visit BugBot documentation.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5ca95f23f29f
Simplify string deduplication to take advantage of dependent string sweeping during minor GC. r=jandem,jonco

Comment 4

[Cristian Tuns]

Backed out for causing SM bustages in bug1375074.js

• Backout link
• Push with failures
• Failure Log
• Failure line: TEST-UNEXPECTED-FAIL | js/src/jit-test/tests/bug1375074.js | Unknown (code -11, args "") [0.1 s]

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8fc85f56c3a8
Simplify string deduplication to take advantage of dependent string sweeping during minor GC. r=jandem,jonco

Comment 6

[pstanciu]

https://hg.mozilla.org/mozilla-central/rev/8fc85f56c3a8