[Libre-soc-dev] new svp64 page

[Luke Kenneth Casson Leighton]

https://libre-soc.org/openpower/sv/svp_rewrite/svp64/discussion/

i don't entirely know why we haven't yet raised this one as a
bugreport :) perhaps i just like the different perspective.

in looking at the AV opcodes i realised that DSP Audio saturation (if
sum greater than max int range set to 0xffff) would either need a ton
of ops (yuk) or an SPR bit (yuk) or, much better, a spare bit or two
in the 24 bits from the SV Prefix

these may potentially also be used for FP to introduce rounding modes
rather than require an SPR as at present.  something to think about.

overall, accepting far less pressure to jam VL, MAXVL and swizzle into
only 24 bits gives us much more leeway.

l.