[Libre-soc-dev] efficient decoding algorithm for variable-length instructions

[Luke Kenneth Casson Leighton]

y'know what?  suddenly occurred to me: i don't think we're being
radical enough.  how about: we design something more akin to RISC-V
RVC 16/32/48/64 that uses 6 bits maximum to encode, and just do a
total re-map of all OpenPOWER 3.1B Major opcodes?

all bits *other* than the Major Opcodes would be left entirely
unmodified.  EXT004 would map to 0b0001, EXT031 to 0b0010, EXT19 to
0b0011 etc. etc. etc.

l.