[libcxxabi] __cxa_guard_require: test guard byte with != 0 instead of == 1

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@369109 91177308-0d34-0410-b5e6-96231b3b80d8

src/cxa_guard_impl.h

diff --git a/src/cxa_guard_impl.h b/src/cxa_guard_impl.h
index 545731b..98e42ba 100644
--- a/src/cxa_guard_impl.h
+++ b/src/cxa_guard_impl.h
@@ -175,7 +175,7 @@
   /// Implements __cxa_guard_acquire
   AcquireResult cxa_guard_acquire() {
     AtomicInt<uint8_t> guard_byte(guard_byte_address);
-    if (guard_byte.load(std::_AO_Acquire) == COMPLETE_BIT)
+    if (guard_byte.load(std::_AO_Acquire) != UNSET)
       return INIT_IS_DONE;
     return derived()->acquire_init_byte();
   }