Lexing optimizations #15132
Open
Lexing optimizations #15132
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
bonzini
force-pushed
the
parser-opt
branch
4 times, most recently
from
bb9ca51 to
17e9e95
Compare
dnicolodi
reviewed
Oct 17, 2025
dcbaker
reviewed
Oct 17, 2025
dcbaker
requested changes
Oct 17, 2025
Match single-character tokens a separate dictionary lookup. As pointed out by dcbaker, this is even faster than str.index and gives the syntax error check for free (via KeyError). It also enables splitting the special-case "if" in two parts, one for long tokens and one for short tokens, thus providing further speedup. This shaves about 2/3rds of the time spent in lex(). Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Identifiers are more common than strings, check against 'id' first. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tuples are inefficient, require the ability to use hash table lookup via either a frozenset or a dictionary. This also allows using accept_any with COMPARISON_MAP.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
…tor names This avoids creating a dictionary every time an arithmetic operator is evaluated. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
dcbaker
approved these changes
Oct 20, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
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Outdated suggestions cannot be applied.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.
Cut about 2/3 of the execution time of the lexer, and a little more elsewhere. Even on a project like QEMU that spends a lot of time in external scripts, this amounts to a 3-5% saving.