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Add is_ascii function optimized for LoongArch64 for [u8] #146699

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Add is_ascii function optimized for LoongArch64 for [u8] #146699

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19 changes: 14 additions & 5 deletions library/core/src/slice/ascii.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,10 @@
use core::ascii::EscapeDefault;

use crate::fmt::{self, Write};
#[cfg(not(all(target_arch = "x86_64", target_feature = "sse2")))]
#[cfg(not(any(
all(target_arch = "x86_64", target_feature = "sse2"),
all(target_arch = "loongarch64", target_feature = "lsx")
)))]
use crate::intrinsics::const_eval_select;
use crate::{ascii, iter, ops};

Expand Down Expand Up @@ -357,7 +360,10 @@ pub const fn is_ascii_simple(mut bytes: &[u8]) -> bool {
///
/// If any of these loads produces something for which `contains_nonascii`
/// (above) returns true, then we know the answer is false.
#[cfg(not(all(target_arch = "x86_64", target_feature = "sse2")))]
#[cfg(not(any(
all(target_arch = "x86_64", target_feature = "sse2"),
all(target_arch = "loongarch64", target_feature = "lsx")
)))]
#[inline]
#[rustc_allow_const_fn_unstable(const_eval_select)] // fallback impl has same behavior
const fn is_ascii(s: &[u8]) -> bool {
Expand Down Expand Up @@ -455,12 +461,15 @@ const fn is_ascii(s: &[u8]) -> bool {
)
}

/// ASCII test optimized to use the `pmovmskb` instruction available on `x86-64`
/// platforms.
/// ASCII test optimized to use the `pmovmskb` instruction on `x86-64` and the
/// `vmskltz.b` instruction on `loongarch64`.
///
/// Other platforms are not likely to benefit from this code structure, so they
/// use SWAR techniques to test for ASCII in `usize`-sized chunks.
#[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
#[cfg(any(
all(target_arch = "x86_64", target_feature = "sse2"),
all(target_arch = "loongarch64", target_feature = "lsx")
))]
#[inline]
const fn is_ascii(bytes: &[u8]) -> bool {
// Process chunks of 32 bytes at a time in the fast path to enable
Expand Down
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