-/* clearing psr.i is implicitly serialized (visible by next insn) */
-/* setting psr.i requires data serialization */
+/*
+ * - clearing psr.i is implicitly serialized (visible by next insn)
+ * - setting psr.i requires data serialization
+ * - we need a stop-bit before reading PSR because we sometimes
+ * write a floating-point register right before reading the PSR
+ * and that writes to PSR.mfl
+ */