docs(parser): document is_on_new_line and read_bool performance characteristics #13867
Conversation
This file contains hidden or 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
Contributor
How to use the Graphite Merge QueueAdd either label to this PR to merge it via the merge queue:
You must have a Graphite account in order to use the merge queue. Sign up using this link. An organization admin has enabled the Graphite Merge Queue in this repository. Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue. |
github-actions
bot
added
A-parser
Contributor
There was a problem hiding this comment.
Pull Request Overview
This PR adds comprehensive documentation to the is_on_new_line and read_bool methods in the parser's Token implementation, explaining their purpose and performance characteristics. The documentation provides context for design decisions made in PR #13788.
- Documents
is_on_new_line's role in JavaScript ASI and parsing rules - Adds detailed performance analysis to
read_boolwith assembly code comparison - Explains rationale for using unsafe pointer arithmetic over safe bit operations
Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.
CodSpeed Instrumentation Performance ReportMerging #13867 will not alter performanceComparing Summary
|
Member
Author
Merge activity
|
…cteristics (#13867) ## Summary This PR adds comprehensive documentation to the `is_on_new_line` and `read_bool` methods in the lexer's Token implementation, based on the performance analysis from PR #13788. ## Changes - Document `is_on_new_line`'s purpose for ASI and JavaScript parsing rules - Add detailed performance analysis to `read_bool` showing assembly code comparison - Explain why unsafe pointer arithmetic is used (3 instructions vs 4 for bit operations) - Reference PR #13788's benchmarking discussion for historical context ## Context As discussed in #13788, the unsafe pointer arithmetic implementation was retained because it generates one fewer CPU instruction on this hot path. This documentation helps future contributors understand this design decision. ### Assembly Comparison **Unsafe pointer arithmetic (current):** ```asm movzx eax, BYTE PTR [rdi+9] ; 3 instructions total and eax, 1 ret ``` **Safe bit operations (proposed but rejected):** ```asm mov rax, QWORD PTR [rdi+8] ; 4 instructions total shr rax, 8 and eax, 1 ret ``` 🤖 Generated with [Claude Code](https://claude.ai/code)
graphite-app
bot
force-pushed
the
docs/token-is-on-new-line
branch
from
3a03bdf to
5d4e4f0
Compare
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.
Summary
This PR adds comprehensive documentation to the
is_on_new_lineandread_boolmethods in the lexer's Token implementation, based on the performance analysis from PR #13788.Changes
is_on_new_line's purpose for ASI and JavaScript parsing rulesread_boolshowing assembly code comparisonContext
As discussed in #13788, the unsafe pointer arithmetic implementation was retained because it generates one fewer CPU instruction on this hot path. This documentation helps future contributors understand this design decision.
Assembly Comparison
Unsafe pointer arithmetic (current):
Safe bit operations (proposed but rejected):
🤖 Generated with Claude Code