core_arch 0.1.4

`core::arch` - Rust's core library architecture-specific intrinsics.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139

//! Bit Manipulation Instruction (BMI) Set 2.0.
//!
//! The reference is [Intel 64 and IA-32 Architectures Software Developer's
//! Manual Volume 2: Instruction Set Reference, A-Z][intel64_ref].
//!
//! [Wikipedia][wikipedia_bmi] provides a quick overview of the instructions
//! available.
//!
//! [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
//! [wikipedia_bmi]:
//! https://en.wikipedia.org/wiki/Bit_Manipulation_Instruction_Sets#ABM_.28Advanced_Bit_Manipulation.29

#[cfg(test)]
use stdsimd_test::assert_instr;

/// Unsigned multiply without affecting flags.
///
/// Unsigned multiplication of `a` with `b` returning a pair `(lo, hi)` with
/// the low half and the high half of the result.
///
/// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mulx_u64)
#[inline]
#[cfg_attr(test, assert_instr(mul))]
#[target_feature(enable = "bmi2")]
#[cfg(not(target_arch = "x86"))] // calls an intrinsic
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _mulx_u64(a: u64, b: u64, hi: &mut u64) -> u64 {
    let result: u128 = (a as u128) * (b as u128);
    *hi = (result >> 64) as u64;
    result as u64
}

/// Zeroes higher bits of `a` >= `index`.
///
/// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_bzhi_u64)
#[inline]
#[target_feature(enable = "bmi2")]
#[cfg_attr(test, assert_instr(bzhi))]
#[cfg(not(target_arch = "x86"))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _bzhi_u64(a: u64, index: u32) -> u64 {
    x86_bmi2_bzhi_64(a, index as u64)
}

/// Scatter contiguous low order bits of `a` to the result at the positions
/// specified by the `mask`.
///
/// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_pdep_u64)
#[inline]
#[target_feature(enable = "bmi2")]
#[cfg_attr(test, assert_instr(pdep))]
#[cfg(not(target_arch = "x86"))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _pdep_u64(a: u64, mask: u64) -> u64 {
    x86_bmi2_pdep_64(a, mask)
}

/// Gathers the bits of `x` specified by the `mask` into the contiguous low
/// order bit positions of the result.
///
/// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_pext_u64)
#[inline]
#[target_feature(enable = "bmi2")]
#[cfg_attr(test, assert_instr(pext))]
#[cfg(not(target_arch = "x86"))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _pext_u64(a: u64, mask: u64) -> u64 {
    x86_bmi2_pext_64(a, mask)
}

extern "C" {
    #[link_name = "llvm.x86.bmi.bzhi.64"]
    fn x86_bmi2_bzhi_64(x: u64, y: u64) -> u64;
    #[link_name = "llvm.x86.bmi.pdep.64"]
    fn x86_bmi2_pdep_64(x: u64, y: u64) -> u64;
    #[link_name = "llvm.x86.bmi.pext.64"]
    fn x86_bmi2_pext_64(x: u64, y: u64) -> u64;
}

#[cfg(test)]
mod tests {
    use stdsimd_test::simd_test;

    use core_arch::x86_64::*;

    #[simd_test(enable = "bmi2")]
    unsafe fn test_pext_u64() {
        let n = 0b1011_1110_1001_0011u64;

        let m0 = 0b0110_0011_1000_0101u64;
        let s0 = 0b0000_0000_0011_0101u64;

        let m1 = 0b1110_1011_1110_1111u64;
        let s1 = 0b0001_0111_0100_0011u64;

        assert_eq!(_pext_u64(n, m0), s0);
        assert_eq!(_pext_u64(n, m1), s1);
    }

    #[simd_test(enable = "bmi2")]
    unsafe fn test_pdep_u64() {
        let n = 0b1011_1110_1001_0011u64;

        let m0 = 0b0110_0011_1000_0101u64;
        let s0 = 0b0000_0010_0000_0101u64;

        let m1 = 0b1110_1011_1110_1111u64;
        let s1 = 0b1110_1001_0010_0011u64;

        assert_eq!(_pdep_u64(n, m0), s0);
        assert_eq!(_pdep_u64(n, m1), s1);
    }

    #[simd_test(enable = "bmi2")]
    unsafe fn test_bzhi_u64() {
        let n = 0b1111_0010u64;
        let s = 0b0001_0010u64;
        assert_eq!(_bzhi_u64(n, 5), s);
    }

    #[simd_test(enable = "bmi2")]
    #[rustfmt::skip]
    unsafe fn test_mulx_u64() {
        let a: u64 = 9_223_372_036_854_775_800;
        let b: u64 = 100;
        let mut hi = 0;
        let lo = _mulx_u64(a, b, &mut hi);
        /*
result = 922337203685477580000 =
0b00110001_1111111111111111_1111111111111111_1111111111111111_1111110011100000
  ^~hi~~~~ ^~lo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        */
        assert_eq!(
            lo,
            0b11111111_11111111_11111111_11111111_11111111_11111111_11111100_11100000u64
        );
        assert_eq!(hi, 0b00110001u64);
    }
}