gh-148762: speed up SRE_AT_BEGINNING_LINE regexes#148778
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haampie wants to merge 1 commit intopython:mainfrom
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gh-148762: speed up SRE_AT_BEGINNING_LINE regexes#148778haampie wants to merge 1 commit intopython:mainfrom
haampie wants to merge 1 commit intopython:mainfrom
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`SRE(search)` has an early exit for `SRE_AT_BEGINNING` and
`SRE_AT_BEGINNING_STRING`, but lacks fast-forward for
`SRE_AT_BEGINNING_LINE`. This means that a regex of the following form
is slow:
```
re.compile("^foo", re.MULTILINE)
```
The current implementation does a character-by-character loop that calls
`SRE(match)` each time. This is rather expensive function call.
This commit
* ensures `SRE(match)` is only called right after a newline
* optimizes fast-forwarding to the next newline by calling `memchr` in
the UCS1 case
This can lead to 10x or even 100x speedups in the no-match case with
long lines, while not causing overhead in the case of short lines.
Signed-off-by: Harmen Stoppels <[email protected]>
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SRE(search)has an early exit for SRE_AT_BEGINNING andSRE_AT_BEGINNING_STRING, but lacks a similar fast-forward for
SRE_AT_BEGINNING_LINE. This means that a regex of the following form
is slow:
The current implementation does a character-by-character loop that calls
SRE(match)each iteration, leading to a lot of overhead.This commit
SRE(match)is only called right after a newlinememchrinthe UCS-1 case
This can lead to 10x or even 100x speedups in the no-match case with
long lines, while not causing overhead in the case of short lines.
^. #148762