diff options
Diffstat (limited to 'library/alloc/src/task.rs')
| -rw-r--r-- | library/alloc/src/task.rs | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/library/alloc/src/task.rs b/library/alloc/src/task.rs index b214f4946b1..b40768a52b6 100644 --- a/library/alloc/src/task.rs +++ b/library/alloc/src/task.rs @@ -136,6 +136,15 @@ impl<W: Wake + Send + Sync + 'static> From<Arc<W>> for RawWaker { #[inline(always)] fn raw_waker<W: Wake + Send + Sync + 'static>(waker: Arc<W>) -> RawWaker { // Increment the reference count of the arc to clone it. + // + // The #[inline(always)] is to ensure that raw_waker and clone_waker are + // always generated in the same code generation unit as one another, and + // therefore that the structurally identical const-promoted RawWakerVTable + // within both functions is deduplicated at LLVM IR code generation time. + // This allows optimizing Waker::will_wake to a single pointer comparison of + // the vtable pointers, rather than comparing all four function pointers + // within the vtables. + #[inline(always)] unsafe fn clone_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) -> RawWaker { unsafe { Arc::increment_strong_count(waker as *const W) }; RawWaker::new( @@ -304,6 +313,10 @@ impl<W: LocalWake + 'static> From<Rc<W>> for RawWaker { #[inline(always)] fn local_raw_waker<W: LocalWake + 'static>(waker: Rc<W>) -> RawWaker { // Increment the reference count of the Rc to clone it. + // + // Refer to the comment on raw_waker's clone_waker regarding why this is + // always inline. + #[inline(always)] unsafe fn clone_waker<W: LocalWake + 'static>(waker: *const ()) -> RawWaker { unsafe { Rc::increment_strong_count(waker as *const W) }; RawWaker::new( |