and destination element offsets progress incrementally in
lock-step.
+Example VL=2, SUBVL=3, PACK_en=1
+
+ 0 1 2
+ srcstep=0 0 1 2
+ srcstep=1 3 4 5
+
+ 0 1
+ dststep=0 0 1
+ dststep=1 2 3
+ dststep=2 4 5
+
+
Setting of both `PACK_en` and `UNPACK_en` is neither prohibited nor
`UNDEFINED` because the reordering is fully deterministic, and
additional REMAP reordering may be applied. For Matrix this would