gh-153568: Skip newline translation for source without carriage returns#153584
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pablogsal wants to merge 1 commit into
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gh-153568: Skip newline translation for source without carriage returns#153584pablogsal wants to merge 1 commit into
pablogsal wants to merge 1 commit into
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… returns The tokenizer copied every input byte by byte to normalize newlines, but source without a carriage return needs no translation and can be copied verbatim.
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The tokenizer normalizes newlines by copying the whole input one byte at a time through a state machine, but virtually all source today has no carriage returns at all, in which case the translation is the identity. A single memchr decides that up front and replaces the byte loop with one memcpy; inputs containing carriage returns keep the existing path, including lone-CR and CRLF handling.
Benchmark (parsing 8 of the largest stdlib files, 1.3 MB, 20 times per run with
_PyParser_ASTFromString— parser only, no AST-to-Python conversion; turbo disabled, performance governor, FIFO-pinned to a dedicated core, interleaved runs):About a 1% wall-clock win: small, but stable across runs and the diff is eight lines.