Is there a benchmark where this shows a clear improvement? I'm struggling to find one :/

I tried various simple benchmarks locally, such as

python -m timeit -n5 -r10 -s "from pathlib import Path" "list(Path('.').rglob('Lib/**/test_*.py'))"

I've no doubt that (?s:.) is much faster than [\s\S] in general, but here, I wonder if it makes a noticeable difference

You can ask the OP. I guess that you can see some difference in match() for very long path.

Simple example (in debug build):

$ ./python -m timeit -s "from pathlib import Path; p = Path('a/'*1000)" "p.match('**/a')"
5000 loops, best of 5: 42.5 usec per loop

With this PR:

10000 loops, best of 5: 25.5 usec per loop

You can ask the OP. I guess that you can see some difference in match() for very long path.

Using a PGO-optimised build, I had to create an extremely long path for there to be a difference that wasn't just noise. But yeah, I can see a difference with this benchmark:

main:

>python -m timeit -n10 -r20 -s "from pathlib import Path; p = Path('a/'*1000000)" "p.match('**/a')"
Running PGUpdate|x64 interpreter...
10 loops, best of 20: 22.2 msec per loop

This PR:

10 loops, best of 20: 13 msec per loop