[DRAFT] Integer Butterfly Multiply Add and Accumulate FFT/DCT

A-Form

• msubrs RT,RA,RB,SH

Pseudo-code:

n <- SH
prod <- MULS(RB, RA)
if n = 0 then
    prod_lo <- prod[XLEN:(XLEN*2) - 1]
    RT <- (RT) - prod_lo
else
    res[0:XLEN*2-1] <- (EXTSXL((RT)[0], 1) || (RT)) - prod
    round <- [0]*XLEN*2
    round[XLEN*2 - n] <- 1
    res <- res + round
    RT <- res[XLEN - n:XLEN*2 - n -1]

Special Registers Altered:

None