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Add benchmark for slice is_ascii using align_to

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This commit is contained in:
Thom Chiovoloni 2020-07-05 14:33:27 -07:00
parent 63e2e2e326
commit e1d4db6055
1 changed files with 24 additions and 1 deletions
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25
src/libcore/benches/ascii.rs
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@ -74,8 +74,9 @@ macro_rules! benches {
#[bench]
fn $name(bencher: &mut Bencher) {
bencher.bytes = $input.len() as u64;
let vec = $input.as_bytes().to_vec();
let mut vec = $input.as_bytes().to_vec();
bencher.iter(|| {
black_box(&mut vec);
let $arg = black_box(&vec[..]);
black_box($body)
})
@ -278,6 +279,28 @@ benches! {
fn is_ascii_slice_iter_all(bytes: &[u8]) {
bytes.iter().all(|b| b.is_ascii())
}
fn is_ascii_slice_align_to(bytes: &[u8]) {
is_ascii_align_to_impl(bytes)
}
}
// Separate since it's easier to debug errors if they don't go through macro
// expansion first.
fn is_ascii_align_to_impl(bytes: &[u8]) -> bool {
if bytes.len() < core::mem::size_of::<usize>() {
return bytes.iter().all(|b| b.is_ascii());
}
let (head, body, tail) = unsafe { bytes.align_to::<usize>() };
head.iter().all(|b| b.is_ascii()) &&
body.iter().all(|w| !contains_nonascii(*w)) &&
tail.iter().all(|b| b.is_ascii())
}
#[inline]
fn contains_nonascii(v: usize) -> bool {
const NONASCII_MASK: usize = 0x80808080_80808080u64 as usize;
(NONASCII_MASK & v) != 0
}
macro_rules! repeat {