diff --git a/src/libcore/hint.rs b/src/libcore/hint.rs index 9e57a4ebc99..ad5a2071a73 100644 --- a/src/libcore/hint.rs +++ b/src/libcore/hint.rs @@ -49,3 +49,26 @@ use intrinsics; pub unsafe fn unreachable_unchecked() -> ! { intrinsics::unreachable() } + +/// Save power or switch hyperthreads in a busy-wait spin-loop. +/// +/// This function is deliberately more primitive than +/// [`std::thread::yield_now`](../../std/thread/fn.yield_now.html) and +/// does not directly yield to the system's scheduler. +/// In some cases it might be useful to use a combination of both functions. +/// Careful benchmarking is advised. +/// +/// On some platforms this function may not do anything at all. +#[inline] +#[unstable(feature = "renamed_spin_loop", issue = "55002")] +pub fn spin_loop() { + #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] + unsafe { + asm!("pause" ::: "memory" : "volatile"); + } + + #[cfg(target_arch = "aarch64")] + unsafe { + asm!("yield" ::: "memory" : "volatile"); + } +} diff --git a/src/libcore/sync/atomic.rs b/src/libcore/sync/atomic.rs index 99e6365d15e..8992e513e83 100644 --- a/src/libcore/sync/atomic.rs +++ b/src/libcore/sync/atomic.rs @@ -84,6 +84,8 @@ use intrinsics; use cell::UnsafeCell; use fmt; +use hint::spin_loop; + /// Save power or switch hyperthreads in a busy-wait spin-loop. /// /// This function is deliberately more primitive than @@ -96,15 +98,7 @@ use fmt; #[inline] #[stable(feature = "spin_loop_hint", since = "1.24.0")] pub fn spin_loop_hint() { - #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] - unsafe { - asm!("pause" ::: "memory" : "volatile"); - } - - #[cfg(target_arch = "aarch64")] - unsafe { - asm!("yield" ::: "memory" : "volatile"); - } + spin_loop() } /// A boolean type which can be safely shared between threads. diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index 41f1ac867ed..83db3f347a7 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -286,6 +286,7 @@ #![feature(staged_api)] #![feature(stmt_expr_attributes)] #![feature(str_internals)] +#![feature(renamed_spin_loop)] #![feature(rustc_private)] #![feature(thread_local)] #![feature(toowned_clone_into)]