## Schemes which split (a scalar) integer reg into mask "chunks"
These ideas are based on the principle that each chunk of 8 (or 16)
-bits of a scalar integer register may be covered by its own DM row.
+bits of a scalar integer register may be covered by its own DM column
+ in FU-REGs.
8 chunks of a scalar 64-bit integer register for use as a bit-level
predicate mask onto 64 vector elements would for example require 8
DM entries.