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 unsafe 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 unsafe fn _bzhi_u32(a: u32, index: u32) -> u32 {
42    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 unsafe fn _pdep_u32(a: u32, mask: u32) -> u32 {
54    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 unsafe fn _pext_u32(a: u32, mask: u32) -> u32 {
66    x86_bmi2_pext_32(a, mask)
67}
68
69extern "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}