#[cfg(feature = "nightly")]
use std::sync::atomic::AtomicUsize;
#[cfg(not(feature = "nightly"))]
use stable::AtomicUsize;
pub trait AtomicElisionExt {
type IntType;
fn elision_acquire(&self, current: Self::IntType, new: Self::IntType) -> bool;
fn elision_release(&self, current: Self::IntType, new: Self::IntType) -> bool;
}
#[inline]
pub fn have_elision() -> bool {
cfg!(all(feature = "nightly",
any(target_arch = "x86", target_arch = "x86_64")))
}
#[cfg(not(all(feature = "nightly", any(target_arch = "x86", target_arch = "x86_64"))))]
impl AtomicElisionExt for AtomicUsize {
type IntType = usize;
#[inline]
fn elision_acquire(&self, _: usize, _: usize) -> bool {
unreachable!();
}
#[inline]
fn elision_release(&self, _: usize, _: usize) -> bool {
unreachable!();
}
}
#[cfg(all(feature = "nightly", target_arch = "x86"))]
impl AtomicElisionExt for AtomicUsize {
type IntType = usize;
#[inline]
fn elision_acquire(&self, current: usize, new: usize) -> bool {
unsafe {
let prev: usize;
asm!("xacquire; lock; cmpxchgl $2, $1"
: "={eax}" (prev), "+*m" (self)
: "r" (new), "{eax}" (current)
: "memory"
: "volatile");
prev == current
}
}
#[inline]
fn elision_release(&self, current: usize, new: usize) -> bool {
unsafe {
let prev: usize;
asm!("xrelease; lock; cmpxchgl $2, $1"
: "={eax}" (prev), "+*m" (self)
: "r" (new), "{eax}" (current)
: "memory"
: "volatile");
prev == current
}
}
}
#[cfg(all(feature = "nightly", target_arch = "x86_64"))]
impl AtomicElisionExt for AtomicUsize {
type IntType = usize;
#[inline]
fn elision_acquire(&self, current: usize, new: usize) -> bool {
unsafe {
let prev: usize;
asm!("xacquire; lock; cmpxchgq $2, $1"
: "={rax}" (prev), "+*m" (self)
: "r" (new), "{rax}" (current)
: "memory"
: "volatile");
prev == current
}
}
#[inline]
fn elision_release(&self, current: usize, new: usize) -> bool {
unsafe {
let prev: usize;
asm!("xrelease; lock; cmpxchgq $2, $1"
: "={rax}" (prev), "+*m" (self)
: "r" (new), "{rax}" (current)
: "memory"
: "volatile");
prev == current
}
}
}