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]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
16//! [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf
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")]
32pub unsafe fn _lzcnt_u64(x: u64) -> u64 {
33 x.leading_zeros() as u64
34}
35
36/// Counts the bits that are set.
37///
38/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_popcnt64)
39#[inline]
40#[target_feature(enable = "popcnt")]
41#[cfg_attr(test, assert_instr(popcnt))]
42#[stable(feature = "simd_x86", since = "1.27.0")]
43pub unsafe fn _popcnt64(x: i64) -> i32 {
44 x.count_ones() as i32
45}
46
47#[cfg(test)]
48mod tests {
49 use stdarch_test::simd_test;
50
51 use crate::core_arch::arch::x86_64::*;
52
53 #[simd_test(enable = "lzcnt")]
54 unsafe fn test_lzcnt_u64() {
55 assert_eq!(_lzcnt_u64(0b0101_1010), 57);
56 }
57
58 #[simd_test(enable = "popcnt")]
59 unsafe fn test_popcnt64() {
60 assert_eq!(_popcnt64(0b0101_1010), 4);
61 }
62}
63