abm.rs - source
Description: Source of the Rust file `library/core/src/../../stdarch/crates/core_arch/src/x86_64/abm.rs`.

#
core/stdarch/crates/core_arch/src/x86_64/
abm.rs

    1//! Advanced Bit Manipulation (ABM) instructions
    2//!
    3//! The POPCNT and LZCNT have their own CPUID bits to indicate support.
    4//!
    5//! The references are:
    6//!
    7//! - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2:
    8//!   Instruction Set Reference, A-Z][intel64_ref].
    9//! - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and
    10//!   System Instructions][amd64_ref].
    11//!
    12//! [Wikipedia][wikipedia_bmi] provides a quick overview of the instructions
    13//! available.
    14//!
    15//! [intel64_ref]: https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
    16//! [amd64_ref]: https://docs.amd.com/v/u/en-US/24594_3.37
    17//! [wikipedia_bmi]:
    18//! https://en.wikipedia.org/wiki/Bit_Manipulation_Instruction_Sets#ABM_.28Advanced_Bit_Manipulation.29
    19
    20#[cfg(test)]
    21use stdarch_test::assert_instr;
    22
    23/// Counts the leading most significant zero bits.
    24///
    25/// When the operand is zero, it returns its size in bits.
    26///
    27/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_lzcnt_u64)
    28#[inline]
    29#[target_feature(enable = "lzcnt")]
    30#[cfg_attr(test, assert_instr(lzcnt))]
    31#[stable(feature = "simd_x86", since = "1.27.0")]
    32#[rustc_const_unstable(feature = "stdarch_const_x86", issue = "149298")]
    33pub const fn _lzcnt_u64(x: u64) -> u64 {
    34    x.leading_zeros() as u64
    35}
    36
    37/// Counts the bits that are set.
    38///
    39/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_popcnt64)
    40#[inline]
    41#[target_feature(enable = "popcnt")]
    42#[cfg_attr(test, assert_instr(popcnt))]
    43#[stable(feature = "simd_x86", since = "1.27.0")]
    44#[rustc_const_unstable(feature = "stdarch_const_x86", issue = "149298")]
    45pub const fn _popcnt64(x: i64) -> i32 {
    46    x.count_ones() as i32
    47}
    48
    49#[cfg(test)]
    50mod tests {
    51    use crate::core_arch::assert_eq_const as assert_eq;
    52    use stdarch_test::simd_test;
    53
    54    use crate::core_arch::arch::x86_64::*;
    55
    56    #[simd_test(enable = "lzcnt")]
    57    const fn test_lzcnt_u64() {
    58        assert_eq!(_lzcnt_u64(0b0101_1010), 57);
    59    }
    60
    61    #[simd_test(enable = "popcnt")]
    62    const fn test_popcnt64() {
    63        assert_eq!(_popcnt64(0b0101_1010), 4);
    64    }
    65}