<!-- SVP64 Butterfly DCT Instructions here described are based on -->

<!-- PLEASE NOTE THESE ARE UNAPPROVED AND DRAFT, NOT SUBMITTED TO OPF ISA WG -->

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

A-Form

* maddrs  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