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liballoc: Partially inline the refcount manipulation in the Arc

destructor.
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pcwalton committed Mar 19, 2015
1 parent 12cb7c6 commit dbd16a5b475606f1131cd41529be830ee89e7221
Showing with 18 additions and 8 deletions.
  1. +18 −8 src/liballoc/arc.rs
@@ -210,6 +210,21 @@ impl<T> Arc<T> {
// contents.
unsafe { &**self._ptr }
}

// Non-inlined part of `drop`.
#[inline(never)]
unsafe fn drop_slow(&mut self) {
let ptr = *self._ptr;

// Destroy the data at this time, even though we may not free the box allocation itself
// (there may still be weak pointers lying around).
drop(ptr::read(&self.inner().data));

if self.inner().weak.fetch_sub(1, Release) == 1 {
atomic::fence(Acquire);
deallocate(ptr as *mut u8, size_of::<ArcInner<T>>(), min_align_of::<ArcInner<T>>())
}
}
}

/// Get the number of weak references to this value.
@@ -325,6 +340,7 @@ impl<T: Sync + Send> Drop for Arc<T> {
///
/// } // implicit drop
/// ```
#[inline]
fn drop(&mut self) {
// This structure has #[unsafe_no_drop_flag], so this drop glue may run more than once (but
// it is guaranteed to be zeroed after the first if it's run more than once)
@@ -353,14 +369,8 @@ impl<T: Sync + Send> Drop for Arc<T> {
// [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
atomic::fence(Acquire);

// Destroy the data at this time, even though we may not free the box allocation itself
// (there may still be weak pointers lying around).
unsafe { drop(ptr::read(&self.inner().data)); }

if self.inner().weak.fetch_sub(1, Release) == 1 {
atomic::fence(Acquire);
unsafe { deallocate(ptr as *mut u8, size_of::<ArcInner<T>>(),
min_align_of::<ArcInner<T>>()) }
unsafe {
self.drop_slow()
}
}
}

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