这段代码的意思，程序中sac.r是什么意思

push W4
push W5
mov    W0, W4
mov    W1, W5
mpy W4*W5, A
sac.r A, W0
pop W5
pop W4
return

sac.r是Store Rounded Accumulator指令
http://ww1.microchip.com/downloads/en/devicedoc/70157c.pdf