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//! pext
/// Parallel bits extract
pub trait Pext {
/// Parallel bits extract.
///
/// Gathers the bits of `x` specified by the `mask_` into the contiguous
/// low order bit positions of the result.
///
/// The remaining high-order bits of the result are set to zero.
///
/// **Keywords**: Parallel bits extract, gather bits.
///
/// # Instructionss
///
/// - [`PEXT`](http://www.felixcloutier.com/x86/PEXT.html):
/// - Description: Parallel bits extract.
/// - Architecture: x86.
/// - Instruction set: BMI2.
/// - Registers: 32/64 bit.
///
/// # Example
///
/// ```
/// # use bitintr::*;
/// let n = 0b1011_1110_1001_0011u16;
///
/// let m0 = 0b0110_0011_1000_0101u16;
/// let s0 = 0b0000_0000_0011_0101u16;
///
/// let m1 = 0b1110_1011_1110_1111u16;
/// let s1 = 0b0001_0111_0100_0011u16;
///
/// assert_eq!(n.pext(m0), s0);
/// assert_eq!(n.pext(m1), s1);
/// ```
fn pext(self, mask: Self) -> Self;
}
macro_rules! empty {
($_x:ident, $_y:ident, $_i:ident) => {};
}
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
macro_rules! pext_spec {
($x:ident, $y:ident, $intr:ident) => {
#[cfg(feature = "unstable")]
#[cfg(
all(
any(target_arch = "x86", target_arch = "x86_64"),
target_feature = "bmi2"
)
)]
{
return unsafe {
::mem::transmute(::arch::$intr(
::mem::transmute($x),
::mem::transmute($y),
))
};
}
};
}
macro_rules! impl_pext {
($id:ident, $arch_pext:ident, $intr:ident) => {
impl Pext for $id {
#[inline]
#[allow(unreachable_code)]
fn pext(self, mut mask: Self) -> Self {
$arch_pext!(self, mask, $intr);
let mut res = 0;
let mut bb = 1;
loop {
if mask == 0 {
break;
}
if self & mask & (mask.wrapping_neg()) != 0 {
res = res | bb;
}
mask = mask & (mask - 1);
bb = bb + bb;
}
res
}
}
};
($id:ident) => {
impl_pext!($id, empty, empty);
};
}
impl_all!(impl_pext: u8, u16, i8, i16);
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
impl_pext!(u32, pext_spec, _pext_u32);
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
impl_pext!(i32, pext_spec, _pext_u32);
#[cfg(target_arch = "x86_64")]
impl_pext!(u64, pext_spec, _pext_u64);
#[cfg(target_arch = "x86_64")]
impl_pext!(i64, pext_spec, _pext_u64);
#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
impl_all!(impl_pext: u32, i32);
#[cfg(not(target_arch = "x86_64"))]
impl_all!(impl_pext: i64, u64);