Cache the match object in the compiled re pattern

Feature or enhancement

Proposal:

re allocates a new match object for every successful match. Matches of one pattern all have the same size, and in a typical loop the previous match dies just before the next one is created.

Keep one dead match object in the compiled pattern and reuse it for the next match instead of allocating. This saves 15-18 ns per successful match (e.g. p.match('42') goes 89 ns → 71 ns, and the string-to-Fraction constructor gains ~6%), with no behavior change. The cache slot is accessed with atomic operations; validated with the test suite, refleak runs, and a concurrent stress test on the free-threaded build.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Linked PRs

• gh-153162

Inizia con l’implementazione del pattern re compilato ed esamina come vengono allocate le corrispondenze riuscite. Usa la suite di test esistente per confermare che il comportamento rimanga invariato, quindi esegui i controlli refleak e lo stress test concorrente su una build free-threaded. Il lavoro è completo quando l’oggetto match morto viene riutilizzato in modo sicuro e il miglioramento delle prestazioni riportato viene mantenuto.