For the new fields added in SVP64, instructions that have any of their
fields set to a reserved value must cause an illegal instruction trap,
-to allow emulation of future instruction sets.
+to allow emulation of future instruction sets. Reserved values are always all zeros.
This is unlike OpenPower ISA v3.1, which in many instances does not require a trap if reserved fields are nonzero.
| MASK | `1:3` | Execution Mask |
| ELWIDTH | `4:5` | Element Width |
| SUBVL | `6:7` | Sub-vector length |
-| MODE | `19:23` | changes Vector behaviour |
+| MODE | `19:23` | changes Vector behaviour |
Bits 9 to 18 are further decoded depending on RM category for the instruction.