Fix a threaded LLVM bug due the need for operator= on reference counted AttrListImpl's. It might

be possible to implement this very carefully to allow a lock-free implementation while still
avoiding illegal interleavings, but I haven't been able to figure one out.

llvm-svn: 114046

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/VMCore/Attributes.cpp b/llvm/lib/VMCore/Attributes.cpp
index a000aee2ab4..3422faf2730 100644
--- a/llvm/lib/VMCore/Attributes.cpp
+++ b/llvm/lib/VMCore/Attributes.cpp
@@ -195,6 +195,7 @@ AttrListPtr::AttrListPtr(const AttrListPtr &P) : AttrList(P.AttrList) {
 }
 
 const AttrListPtr &AttrListPtr::operator=(const AttrListPtr &RHS) {
+  sys::SmartScopedLock<true> Lock(*ALMutex);
   if (AttrList == RHS.AttrList) return *this;
   if (AttrList) AttrList->DropRef();
   AttrList = RHS.AttrList;