1653567 - Redesign Private Fields implementation to reduce complexity

Status: RESOLVED FIXED

(Core :: JavaScript Engine, enhancement, P2)

Description

[Matthew Gaudet (he/him) [:mgaudet]]

After looking at implementing the existing Private Fields support for Ion, I came to the conclusion that what I'd built was too complex and didn't share enough functionality with our pre-existing codebase.

Given my increasing level of comfort with the front end, I was able to find a new design that's appreciably simpler, while also easing the (upcoming) implementation of both private methods and ergnomic brand checks.

Comment 1

[Matthew Gaudet (he/him) [:mgaudet]]

Attachment: Bug 1653567 - Redesign Private Fields implementation to reduce complexity r?jorendorff

Adds CheckPrivateField, and uses it to guard private field access before
calling regular element ops, rather than having custom element ops

CheckPrivateField takes two arguments: A ThrowCondition, a message, then using
the top two elements of the stack determines if a throw is required, and if it
is not, places on top of the stack whether or not the field exists.

This design is nice because it means that we'll be able to easily use this
opcode for implementing private methods and ergonomic brand checks for private
fields.

This patch implements the new opcode, deletes the old PrivateElem ops,
and provides Baseline callVM support. It's future work to provide IC, Ion and
Warp support.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/aa11e196e0c7
Redesign Private Fields implementation to reduce complexity r=jorendorff

Comment 3

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/aa11e196e0c7

Comment 4

[Jan de Mooij [:jandem]]

A non-unified build warns about CanAttachPrivateInitIC being unused. Also \o/