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Auto merge of #114339 - ttsugriy:unsafe-utf8, r=davidtwco
[rustc_data_structures][base_n][perf] Remove unnecessary utf8 check. Since all output characters taken from `BASE_64` are valid UTF8 chars there is no need to waste cycles on validation. Even though it's obviously a perf win, I've also used a [benchmark](https://gist.github.com/ttsugriy/e1e63c07927d8f31e71695a9c617bbf3) on M1 MacBook Air with following results: ``` Running benches/base_n_benchmark.rs (target/release/deps/base_n_benchmark-825fe5895b5c2693) push_str/old time: [14.670 µs 14.852 µs 15.074 µs] Found 11 outliers among 100 measurements (11.00%) 4 (4.00%) high mild 7 (7.00%) high severe push_str/new time: [12.573 µs 12.674 µs 12.801 µs] Found 11 outliers among 100 measurements (11.00%) 7 (7.00%) high mild 4 (4.00%) high severe ```
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commit
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@ -30,7 +30,10 @@ pub fn push_str(mut n: u128, base: usize, output: &mut String) {
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}
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}
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output.push_str(str::from_utf8(&s[index..]).unwrap());
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output.push_str(unsafe {
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// SAFETY: `s` is populated using only valid utf8 characters from `BASE_64`
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str::from_utf8_unchecked(&s[index..])
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});
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}
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#[inline]
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