| -- | -- | --- | --- | ----- | -----|--| ------ | ----- |
| NN | RT | RA | s0-4 | im0-7 | 1 iv |s5| grevlogi | |
| NN | RT | RA | RB | im0-7 | 01 |0 | grevlog | |
-| NN | RT | RA | RB | im0-7 | 01 |1 | grevlogw | |
+
+An equivalent to `grevlogw` may be synthesised by setting the
+appropriate bits in RB to set the top half of RT to zero.
+Thus an explicit grevlogw instruction is not necessary.
# xperm