Rollup merge of #48035 - technicalguy:Early-exit-empty-hashmap-38880, r=arthurprs

Early exit for empty HashMap (issue #38880)

Addresses issue #38880 by checking if the HashMap is empty before computing the value of the hash.

Before (integer keys)
```
running 4 tests
test empty_once ... bench:          13 ns/iter (+/- 0)
test empty_100  ... bench:       1,367 ns/iter (+/- 35)
test exist_once ... bench:          14 ns/iter (+/- 0)
test exist_100  ... bench:       1,518 ns/iter (+/- 40)
```

After
```
running 4 tests
test empty_once ... bench:           2 ns/iter (+/- 0)
test empty_100  ... bench:         221 ns/iter (+/- 0)
test exist_once ... bench:          15 ns/iter (+/- 0)
test exist_100  ... bench:       1,515 ns/iter (+/- 92)
```

When the HashMap is not empty, the performance remains the same, and when it is empty the performance is significantly improved.

0 files changed, 0 insertions, 0 deletions