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. Reserved values are always all zeros.
+to allow emulation of future instruction sets. Unless otherwise stated, 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.