Backport: Remove unused scope from Walker #1357
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The updates to the template compiler made in support of strict mode introduced a number of uses of private class fields, some of them in hot paths. Although all supported versions of Node support private class fields, `tsc` transpiles private class fields to `WeakMap`s for all values of `target` lower than `ESNEXT`. As a result, the use of private class fields results in dramatically higher memory usage and garbage collection than in the previous version of the template compiler. This in turn causes at least a large portion of the regression noted in [emberjs/ember.js#19750][1]. [1]: emberjs/ember.js#19750 Here, we replace *all* private class fields with `_` private fields, which substantially (thought not 100%) closed the gap with the original. Co-authored-by: Brenden Palmer <brendenpalmer@gmail.com>
Previously, this field was being assigned twice: once via direct assignment in the constructor, and once via the `copy` (previously) or `Object.assign` (now in this stream of changes) call.
The project already has handling for using `Object.assign` if available and a polyfill if not; use it!
The `scope` info here is entirely unused in the Glimmer codebase. It may be used in some AST transforms, but this is fairly unlikely, since it has only been available since Ember 3.16. Profiling template compilation highlighted the recursive walking of the whole tree for locals in scope during syntax parsing as a major cost in CPU usage, so the hope is that removing this will help.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Backport for #1341. Should land after #1355 and #1356.