* <https://bugs.libre-soc.org/show_bug.cgi?id=905>
+encodings concepts:
+
+* 24 bits available
+* vectors not applicable thus EXTRA4 may bring 4 bits (CR Fields) quantity 3of
+ for a total of 12 bits.
+* elwidth src/dest is 2x4 for a total 4 bits
+* single predicate mask (one bit) is 1 for type, 3 for source, totals another 4 bits
+
+totals 20 bits leaving 4 for a "Mode".
+
+* arithmetic can have saturation
+* LD/ST-update needs Post-Increment, others incl. SEA (Signed Effective Address)
+ another bit adds CIA for PC-relative