| //! Advanced Bit Manipulation (ABM) instructions |
| //! |
| //! The POPCNT and LZCNT have their own CPUID bits to indicate support. |
| //! |
| //! The references are: |
| //! |
| //! - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2: |
| //! Instruction Set Reference, A-Z][intel64_ref]. |
| //! - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and |
| //! System Instructions][amd64_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 |
| //! [amd64_ref]: http://support.amd.com/TechDocs/24594.pdf |
| //! [wikipedia_bmi]: |
| //! https://en.wikipedia.org/wiki/Bit_Manipulation_Instruction_Sets#ABM_.28Advanced_Bit_Manipulation.29 |
| |
| #[cfg(test)] |
| use stdarch_test::assert_instr; |
| |
| /// Counts the leading most significant zero bits. |
| /// |
| /// When the operand is zero, it returns its size in bits. |
| /// |
| /// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_lzcnt_u32) |
| #[inline] |
| #[target_feature(enable = "lzcnt")] |
| #[cfg_attr(test, assert_instr(lzcnt))] |
| #[stable(feature = "simd_x86", since = "1.27.0")] |
| pub unsafe fn _lzcnt_u32(x: u32) -> u32 { |
| x.leading_zeros() |
| } |
| |
| /// Counts the bits that are set. |
| /// |
| /// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_popcnt32) |
| #[inline] |
| #[target_feature(enable = "popcnt")] |
| #[cfg_attr(test, assert_instr(popcnt))] |
| #[stable(feature = "simd_x86", since = "1.27.0")] |
| pub unsafe fn _popcnt32(x: i32) -> i32 { |
| x.count_ones() as i32 |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use stdarch_test::simd_test; |
| |
| use crate::core_arch::x86::*; |
| |
| #[simd_test(enable = "lzcnt")] |
| unsafe fn test_lzcnt_u32() { |
| assert_eq!(_lzcnt_u32(0b0101_1010), 25); |
| } |
| |
| #[simd_test(enable = "popcnt")] |
| unsafe fn test_popcnt32() { |
| assert_eq!(_popcnt32(0b0101_1010), 4); |
| } |
| } |