[libre-riscv-dev] fp special functions

[Luke Kenneth Casson Leighton]

On Sun, Aug 4, 2019 at 7:17 PM Jacob Lifshay <programmerjake at gmail.com> wrote:

> trig-pi functions (range reduction is trivial (x mod 2.0)):
> * sinpi
> * cospi
> * sincospi (non-standard; like sincos)
> * atan2pi

oof.  that's... 85% of funct5=01011 taken up:
https://libre-riscv.org/rv_major_opcode_1010011/#transcendentals_1op

please review / check, make sure i didn't miss any from the list.
this is *1-op* only, i'll do 2-op later.

sincos and sincospi do simultaneous sin and cosine result, i'd
recommend those be done as fused macro-ops, that's generally how
2-result-op is done in RISC-V.

l.