Introduced Atomic8 and added no-barrier Atomic8 accessors.

src/atomicops_internals_arm64_gcc.h

Index: src/atomicops_internals_arm64_gcc.h
diff --git a/src/atomicops_internals_arm64_gcc.h b/src/atomicops_internals_arm64_gcc.h
index f6ed5de602695239e943a96ecb8744d22ae7cbff..254bba95ea422bd615d6fa0af1e40269225d2bbe 100644
--- a/src/atomicops_internals_arm64_gcc.h
+++ b/src/atomicops_internals_arm64_gcc.h
@@ -144,6 +144,10 @@ inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
   return prev;
 }
 
+inline void NoBarrier_Store(volatile Atomic8* ptr, Atomic8 value) {
+  *ptr = value;
+}
+
 inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
   *ptr = value;
 }
@@ -162,6 +166,10 @@ inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
   );  // NOLINT
 }
 
+inline Atomic8 NoBarrier_Load(volatile const Atomic8* ptr) {
+  return *ptr;
+}
+
 inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
   return *ptr;
 }