From 1553ea23165fc795b8c7e8188d2782c39c94b922 Mon Sep 17 00:00:00 2001 From: Dmytro Shynkevych Date: Sat, 4 Aug 2018 01:49:36 -0400 Subject: [PATCH] Changed `Rc::inc_{weak,strong}` to better hint optimization to LLVM --- src/liballoc/rc.rs | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs index be049eb6e5e..aec60bc18f9 100644 --- a/src/liballoc/rc.rs +++ b/src/liballoc/rc.rs @@ -1359,7 +1359,14 @@ fn strong(&self) -> usize { #[inline] fn inc_strong(&self) { - self.inner().strong.set(self.strong().checked_add(1).unwrap_or_else(|| unsafe { abort() })); + // We want to abort on overflow instead of dropping the value. + // The reference count will never be zero when this is called; + // nevertheless, we insert an abort here to hint LLVM at + // an otherwise missied optimization. + if self.strong() == 0 || self.strong() == usize::max_value() { + unsafe { abort(); } + } + self.inner().strong.set(self.strong() + 1); } #[inline] @@ -1374,7 +1381,14 @@ fn weak(&self) -> usize { #[inline] fn inc_weak(&self) { - self.inner().weak.set(self.weak().checked_add(1).unwrap_or_else(|| unsafe { abort() })); + // We want to abort on overflow instead of dropping the value. + // The reference count will never be zero when this is called; + // nevertheless, we insert an abort here to hint LLVM at + // an otherwise missied optimization. + if self.weak() == 0 || self.weak() == usize::max_value() { + unsafe { abort(); } + } + self.inner().weak.set(self.weak() + 1); } #[inline] -- 2.44.0