     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

    //! 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 stdsimd_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://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_lzcnt_u64)
    #[inline]
    #[target_feature(enable = "lzcnt")]
    #[cfg_attr(test, assert_instr(lzcnt))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _lzcnt_u64(x: u64) -> u64 {
        x.leading_zeros() as u64
    }

    /// Counts the bits that are set.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_popcnt64)
    #[inline]
    #[target_feature(enable = "popcnt")]
    #[cfg_attr(test, assert_instr(popcnt))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _popcnt64(x: i64) -> i32 {
        x.count_ones() as i32
    }

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

        use coresimd::arch::x86_64::*;

        #[simd_test(enable = "lzcnt")]
        unsafe fn test_lzcnt_u64() {
            assert_eq!(_lzcnt_u64(0b0101_1010), 57);
        }

        #[simd_test(enable = "popcnt")]
        unsafe fn test_popcnt64() {
            assert_eq!(_popcnt64(0b0101_1010), 4);
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g. `str,u8` or `String,struct:Vec,test`)