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simd_bitmask intrinsic: add a non-power-of-2 multi-byte example

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Ralf Jung 2024-06-08 19:24:32 +02:00
parent 164e1297e1
commit 6896fa6619
1 changed files with 13 additions and 6 deletions
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19
library/core/src/intrinsics/simd.rs
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@ -463,7 +463,7 @@
/// `T` must be an integer vector.
///
/// `U` must be either the smallest unsigned integer with at least as many bits as the length
/// of `T`, or the smallest array of `u8` with as many bits as the length of `T`.
/// of `T`, or the smallest array of `u8` with at least as many bits as the length of `T`.
///
/// Each element is truncated to a single bit and packed into the result.
///
@ -475,12 +475,19 @@
/// * On little endian, the least significant bit corresponds to the first vector element.
/// * On big endian, the least significant bit corresponds to the last vector element.
///
/// For example, `[!0, 0, !0, !0]` packs to `0b1101` on little endian and `0b1011` on big
/// endian.
/// For example, `[!0, 0, !0, !0]` packs to
/// - `0b1101u8` or `[0b1101]` on little endian, and
/// - `0b1011u8` or `[0b1011]` on big endian.
///
/// To consider a larger example, `[!0, 0, 0, 0, 0, 0, 0, 0, !0, !0, 0, 0, 0, 0, !0, 0]` packs
/// to `[0b00000001, 0b01000011]` or `0b0100001100000001` on little endian, and `[0b10000000,
/// 0b11000010]` or `0b1000000011000010` on big endian.
/// To consider a larger example,
/// `[!0, 0, 0, 0, 0, 0, 0, 0, !0, !0, 0, 0, 0, 0, !0, 0]` packs to
/// - `0b0100001100000001u16` or `[0b00000001, 0b01000011]` on little endian, and
/// - `0b1000000011000010u16` or `[0b10000000, 0b11000010]` on big endian.
///
/// And finally, a non-power-of-2 example with multiple bytes:
/// `[!0, !0, 0, !0, 0, 0, !0, 0, !0, 0]` packs to
/// - `0b0101001011u16` or `[0b01001011, 0b01]` on little endian, and
/// - `0b1101001010u16` or `[0b11, 0b01001010]` on big endian.
///
/// # Safety
/// `x` must contain only `0` and `!0`.