Improve long_hash

[eendebakpt]

Feature or enhancement

Proposal:

• There is a corner case in the C code that not tested in long_hash, the final check

    if (x == (Py_uhash_t)-1)
        x = (Py_uhash_t)-2;

• We can improve performance of long_hash by unrolling the first two digits

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-136599: Improve long_hash #136600
• gh-136599: Add tests for long_hash #138335
• [3.14] gh-136599: Add tests for long_hash (GH-138335) #138390
• [3.13] gh-136599: Add tests for long_hash (GH-138335) #138391

[eendebakpt]

PRs for main have been merged, so closing the issue.