Merge pull request riscv#215 from ved-rivos/frz_1

Note that not all MOP.RR.7 or MOP.R.28 encodings are used for Zicfiss

src/cfi_backward.adoc

@@ -98,10 +98,10 @@ The Zicfiss extension introduces the following instructions:
 * Perform an atomic swap from a shadow stack location (See <<SSAMOSWAP>>)
 ** `SSAMOSWAP.W` and `SSAMOSWAP.D`
 
-When a `MOP.RR.7` or `MOP.R.28` encoding is not utilized by the Zicfiss
-extension, the instruction adheres to its Zimop-defined behavior, unless it is
-employed by another extension. In such cases, the instruction follows the
-behavior specified by that other extension.
+Zicfiss does not use all encodings of `MOP.RR.7` or `MOP.R.28`. When a
+`MOP.RR.7` or `MOP.R.28` encoding is not used by the Zicfiss extension, the
+corresponding instruction adheres to its Zimop-defined behavior, unless
+redefined by another extension.
 
 If a shadow stack (SS) instruction raises an access-fault, page-fault, or
 guest-page-fault exception that is supposed to indicate the original instruction