apply_binary_op.rs

// https://godbolt.org/z/KoMfsEszq
// https://godbolt.org/z/18PKTE6Ej
// https://godbolt.org/z/vGs9Eeoo5

// Base on Hacker's Delight section 2.3 THE 16 BINARY LOGICAL OPERATIONS

#![feature(portable_simd)]

extern crate core;
#[repr(u8)]
pub enum Op {
    ConstZero = 0b0000,
    And =       0b1000,
    AndNot =    0b0100,
    First =     0b1100,
    NotAnd =    0b0010,
    Second =    0b1010,
    Xor =       0b0110,
    Or =        0b1110,
    NOr =       0b0001,
    Eq =        0b1001,
    NotSecond = 0b0101,
    OrNot =     0b1101,
    NotFirst =  0b0011,
    NotOr =     0b1011,
    NAnd =      0b0111,
    ConstOne =  0b1111,
}

pub fn apply_binary_op(x: u32, y: u32, op: Op) -> u32 {
    let op = op as u8;

    let select_00 = (((op >> 0) & 1) as u32).wrapping_neg();
    let bit_00 = !x & !y;

    let select_01 = (((op >> 1) & 1) as u32).wrapping_neg();
    let bit_01 = !x & y;

    let select_10 = (((op >> 2) & 1) as u32).wrapping_neg();
    let bit_10 = x & !y;

    let select_11 = (((op >> 3) & 1) as u32).wrapping_neg();
    let bit_11 = x & y;

    (bit_00 & select_00)
        | (bit_01 & select_01)
        | (bit_10 & select_10)
        | (bit_11 & select_11)
}

pub fn apply_binary_op_simd(x: u32, y: u32, op: Op) -> u32 {
    use core::simd::Simd;
    let select = (Simd::splat(op as u32) >> Simd::from_array([0, 1, 2, 3])) & Simd::splat(1);
    let select = Simd::splat(0) - select;
    let even = Simd::from_array([!0, 0, !0, 0]);
    let half = Simd::from_array([!0, !0, 0, 0]);
    let x = Simd::splat(x) ^ half;
    let y = Simd::splat(y) ^ even;
    let bits = (x & y) & select;
    IntoIterator::into_iter(bits.to_array()).fold(0, |a, b| a | b)
}

fn main() {
    let x = 0x1337;
    let y = 0x3713; 
    assert_eq!(x ^ y, apply_binary_op(x, y, Op::Xor));
    assert_eq!(x ^ y, apply_binary_op_simd(x, y, Op::Xor));
}