gh-152033: Optimize category escapes outside character sets#152035
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serhiy-storchaka wants to merge 2 commits into
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gh-152033: Optimize category escapes outside character sets#152035serhiy-storchaka wants to merge 2 commits into
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Character class escapes (``\d``, ``\D``, ``\s``, ``\S``, ``\w`` and ``\W``) that occur outside a character set are now compiled directly to a single CATEGORY opcode instead of being wrapped in an IN block. This removes the IN wrapper (three code words) and an indirect charset() call, and makes such an escape a simple repeatable unit so that, for example, ``\d+`` uses the REPEAT_ONE fast path; a CATEGORY case is added to SRE(count). The transformation preserves behaviour exactly. For category-heavy patterns the compiled byte code is about 20% smaller and matching is up to ~2x faster, with no effect on patterns that do not use bare category escapes. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Documentation build overview
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_get_charset_prefix() did not recognize a leading bare CATEGORY opcode, so a pattern starting with a category escape (such as ``\d``) lost its SRE_INFO_CHARSET prefix and search() could no longer skip non-matching start positions -- a regression relative to the IN-wrapped form. Handle CATEGORY there too, which restores the charset-prefix optimization and makes search() of category-prefixed patterns up to ~1.9x faster. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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The character class escapes
\d,\D,\s,\S,\wand\Ware currently always compiled to anINblock containing a singleCATEGORYitem, even when they occur outside a character set.This PR compiles such an escape directly to a bare
CATEGORYopcode, removing theINwrapper (three code words) and the indirectSRE(charset)call. It also makes a category escape a "simple" repeatable unit, so\d+now uses theREPEAT_ONEfast path instead of the genericREPEAT/MAX_UNTILloop; aCATEGORYcase is added toSRE(count)accordingly.The transformation preserves behaviour exactly (the engine already matched the same category); only the compiled byte code changes.
In a release build I measure ~1.3x geometric-mean speedup across a range of category-heavy patterns — roughly 1.7–2.0x on scans like
\d+,\s+and\S+, and ~1.1–1.2x on realistic tokenizing, date and IP-address patterns — together with ~20% smaller compiled byte code for those patterns. Patterns that do not use bare category escapes are unaffected.Verified with the full
test_resuite, a broad sweep of regex-dependent stdlib modules, and ~80k differential fuzz cases compared against the unmodified engine (0 mismatches).🤖 Generated with Claude Code