This Architecture Extension is targeted when ``ARM_ARCH_MAJOR`` >= 8, or when
``ARM_ARCH_MAJOR`` == 8 and ``ARM_ARCH_MINOR`` >= 1.
-- The Compare and Swap instruction is used to implement spinlocks. Otherwise,
- the load-/store-exclusive instruction pair is used.
+- By default, a load-/store-exclusive instruction pair is used to implement
+ spinlocks. The ``USE_SPINLOCK_CAS`` build option when set to 1 selects the
+ spinlock implementation using the ARMv8.1-LSE Compare and Swap instruction.
+ Notice this instruction is only available in AArch64 execution state, so
+ the option is only available to AArch64 builds.
Armv8.2-A
~~~~~~~~~