1687400 - Reduce size of XDR FunctionKey

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P3)

Description

[Ted Campbell [:tcampbell]]

The FunctionKey is currently 64-bits and is composed of a start,end pair. Is the second value even needed or is the start offset sufficiently unique? We should be able to use a 32-bit value here.

This would reduce overhead of delazification stencils.

Comment 1

[Ted Campbell [:tcampbell]]

This should work. The sourceEnd doesn't provide any further information.

The script-source-extent test shows a number of the potentially issues, and it looks fine. The one particularly tricky one is lazy arrow functions in default argument expressions, but only one of these is ever delazified.

Edit: One edge case will be () => {}; where the function starts at 0 which is currently the null key. This is easy to fix though.

Comment 2

[Ted Campbell [:tcampbell]]

Attachment: Bug 1687400 - Use uint32_t for Stencil FunctionKey. r?arai!

The sourceEnd doesn't help with uniqueness so don't include in the key in
order to save space. A function may start in beginning of script, so add 1 to
the sourceStart to generate the key.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/14a41aec9db8
Use uint32_t for Stencil FunctionKey. r=arai

Comment 4

[Dorel Luca [:dluca]]

Backed out changeset 14a41aec9db8 (bug 1687400) for Valgrind failure. CLOSED TREE

Log:
https://treeherder.mozilla.org/logviewer?job_id=327167769&repo=autoland&lineNumber=58738

Backout:
https://hg.mozilla.org/integration/autoland/rev/0ac6c7e669a83788a44d08cb255383bd83621a38

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0478698744b1
Use uint32_t for Stencil FunctionKey. r=arai CLOSED TREE

Comment 6

[Ted Campbell [:tcampbell]]

False alarm. We should be able to reland now :)

Comment 7

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/0478698744b1