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Make char::is_ascii_whitespace branchless on 32 and 64-bit targets #77021

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Make char::is_ascii_whitespace branchless on 32 and 64-bit targets #77021

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82ff02b
Make char::is_ascii_whitespace branchless on 64-bit
lnicola Sep 21, 2020
960c039
Update mailmap
lnicola Sep 21, 2020
f1e7495
Use a 32-bit implementation
lnicola Sep 22, 2020
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3 changes: 2 additions & 1 deletion .mailmap
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Original file line number Diff line number Diff line change
Expand Up @@ -160,7 +160,8 @@ Kyle J Strand <batmanaod@gmail.com> <BatmanAoD@users.noreply.github.com>
Kyle J Strand <batmanaod@gmail.com> <kyle.j.strand@gmail.com>
Kyle J Strand <batmanaod@gmail.com> <kyle.strand@pieinsurance.com>
Kyle J Strand <batmanaod@gmail.com> <kyle.strand@rms.com>
Laurențiu Nicola <lnicola@dend.ro>
Laurențiu Nicola <lnicola@dend.ro> Laurentiu Nicola <lnicola@dend.ro>
Laurențiu Nicola <lnicola@dend.ro> <lnicola@users.noreply.github.com>
Lee Jeffery <leejeffery@gmail.com> Lee Jeffery <lee@leejeffery.co.uk>
Lee Wondong <wdlee91@gmail.com>
Lennart Kudling <github@kudling.de>
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20 changes: 17 additions & 3 deletions library/core/src/char/methods.rs
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Expand Up @@ -1544,9 +1544,23 @@ impl char {
#[rustc_const_stable(feature = "const_ascii_ctype_on_intrinsics", since = "1.47.0")]
#[inline]
pub const fn is_ascii_whitespace(&self) -> bool {
match *self {
'\t' | '\n' | '\x0C' | '\r' | ' ' => true,
_ => false,
#[cfg(not(target_pointer_width = "16"))]
{
// Inspired from https://pdimov.github.io/blog/2020/07/19/llvm-and-memchr/
const MASK: u32 = 1 << (b'\t' - 1)
| 1 << (b'\n' - 1)
| 1 << (b'\x0C' - 1)
| 1 << (b'\r' - 1)
| 1 << (b' ' - 1);
let ch = (*self as u32).wrapping_sub(1);
ch < (' ' as u32) && 1 << (ch as u8) & MASK != 0
}
#[cfg(target_pointer_width = "16")]
{
match *self {
'\t' | '\n' | '\x0C' | '\r' | ' ' => true,
_ => false,
}
}
}

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