#
core/stdarch/crates/core_arch/src/x86/
bmi2.rs

    1//! Bit Manipulation Instruction (BMI) Set 2.0.
    2//!
    3//! The reference is [Intel 64 and IA-32 Architectures Software Developer's
    4//! Manual Volume 2: Instruction Set Reference, A-Z][intel64_ref].
    5//!
    6//! [Wikipedia][wikipedia_bmi] provides a quick overview of the instructions
    7//! available.
    8//!
    9//! [intel64_ref]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
    10//! [wikipedia_bmi]:
    11//! https://en.wikipedia.org/wiki/Bit_Manipulation_Instruction_Sets#ABM_.28Advanced_Bit_Manipulation.29
    12
    13#[cfg(test)]
    14use stdarch_test::assert_instr;
    15
    16/// Unsigned multiply without affecting flags.
    17///
    18/// Unsigned multiplication of `a` with `b` returning a pair `(lo, hi)` with
    19/// the low half and the high half of the result.
    20///
    21/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mulx_u32)
    22#[inline]
    23// LLVM BUG (should be mulxl): https://bugs.llvm.org/show_bug.cgi?id=34232
    24#[cfg_attr(all(test, target_arch = "x86_64"), assert_instr(imul))]
    25#[cfg_attr(all(test, target_arch = "x86"), assert_instr(mul))]
    26#[target_feature(enable = "bmi2")]
    27#[stable(feature = "simd_x86", since = "1.27.0")]
    28pub fn _mulx_u32(a: u32, b: u32, hi: &mut u32) -> u32 {
    29    let result: u64 = (a as u64) * (b as u64);
    30    *hi = (result >> 32) as u32;
    31    result as u32
    32}
    33
    34/// Zeroes higher bits of `a` >= `index`.
    35///
    36/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_bzhi_u32)
    37#[inline]
    38#[target_feature(enable = "bmi2")]
    39#[cfg_attr(test, assert_instr(bzhi))]
    40#[stable(feature = "simd_x86", since = "1.27.0")]
    41pub fn _bzhi_u32(a: u32, index: u32) -> u32 {
    42    unsafe { x86_bmi2_bzhi_32(a, index) }
    43}
    44
    45/// Scatter contiguous low order bits of `a` to the result at the positions
    46/// specified by the `mask`.
    47///
    48/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_pdep_u32)
    49#[inline]
    50#[target_feature(enable = "bmi2")]
    51#[cfg_attr(test, assert_instr(pdep))]
    52#[stable(feature = "simd_x86", since = "1.27.0")]
    53pub fn _pdep_u32(a: u32, mask: u32) -> u32 {
    54    unsafe { x86_bmi2_pdep_32(a, mask) }
    55}
    56
    57/// Gathers the bits of `x` specified by the `mask` into the contiguous low
    58/// order bit positions of the result.
    59///
    60/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_pext_u32)
    61#[inline]
    62#[target_feature(enable = "bmi2")]
    63#[cfg_attr(test, assert_instr(pext))]
    64#[stable(feature = "simd_x86", since = "1.27.0")]
    65pub fn _pext_u32(a: u32, mask: u32) -> u32 {
    66    unsafe { x86_bmi2_pext_32(a, mask) }
    67}
    68
    69unsafe extern "C" {
    70    #[link_name = "llvm.x86.bmi.bzhi.32"]
    71    fn x86_bmi2_bzhi_32(x: u32, y: u32) -> u32;
    72    #[link_name = "llvm.x86.bmi.pdep.32"]
    73    fn x86_bmi2_pdep_32(x: u32, y: u32) -> u32;
    74    #[link_name = "llvm.x86.bmi.pext.32"]
    75    fn x86_bmi2_pext_32(x: u32, y: u32) -> u32;
    76}
    77
    78#[cfg(test)]
    79mod tests {
    80    use stdarch_test::simd_test;
    81
    82    use crate::core_arch::x86::*;
    83
    84    #[simd_test(enable = "bmi2")]
    85    unsafe fn test_pext_u32() {
    86        let n = 0b1011_1110_1001_0011u32;
    87
    88        let m0 = 0b0110_0011_1000_0101u32;
    89        let s0 = 0b0000_0000_0011_0101u32;
    90
    91        let m1 = 0b1110_1011_1110_1111u32;
    92        let s1 = 0b0001_0111_0100_0011u32;
    93
    94        assert_eq!(_pext_u32(n, m0), s0);
    95        assert_eq!(_pext_u32(n, m1), s1);
    96    }
    97
    98    #[simd_test(enable = "bmi2")]
    99    unsafe fn test_pdep_u32() {
    100        let n = 0b1011_1110_1001_0011u32;
    101
    102        let m0 = 0b0110_0011_1000_0101u32;
    103        let s0 = 0b0000_0010_0000_0101u32;
    104
    105        let m1 = 0b1110_1011_1110_1111u32;
    106        let s1 = 0b1110_1001_0010_0011u32;
    107
    108        assert_eq!(_pdep_u32(n, m0), s0);
    109        assert_eq!(_pdep_u32(n, m1), s1);
    110    }
    111
    112    #[simd_test(enable = "bmi2")]
    113    unsafe fn test_bzhi_u32() {
    114        let n = 0b1111_0010u32;
    115        let s = 0b0001_0010u32;
    116        assert_eq!(_bzhi_u32(n, 5), s);
    117    }
    118
    119    #[simd_test(enable = "bmi2")]
    120    unsafe fn test_mulx_u32() {
    121        let a: u32 = 4_294_967_200;
    122        let b: u32 = 2;
    123        let mut hi = 0;
    124        let lo = _mulx_u32(a, b, &mut hi);
    125        /*
    126        result = 8589934400
    127               = 0b0001_1111_1111_1111_1111_1111_1111_0100_0000u64
    128                   ^~hi ^~lo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    129                */
    130        assert_eq!(lo, 0b1111_1111_1111_1111_1111_1111_0100_0000u32);
    131        assert_eq!(hi, 0b0001u32);
    132    }
    133}