I hope they're able to get this ISA-level feedback to people at RVI
replies(2):
We figured out yesterday [1], that the example in the article can already be done in four risc-v instructions, it's just a bit trickier to come up with it:
# a0 = rax, a1 = rbx
slli t0, a1, 64-8
rori a0, a0, 16
add a0, a0, t0
rori a0, a0, 64-16
[1] https://www.reddit.com/r/RISCV/comments/1f1mnxf/box64_and_ri...