1 <!-- SVP64 Butterfly DCT Instructions here described are based on -->
3 <!-- PLEASE NOTE THESE ARE UNAPPROVED AND DRAFT, NOT SUBMITTED TO OPF ISA WG -->
5 # [DRAFT] Integer Butterfly Multiply Add/Sub FFT/DCT
9 * maddsubrs RT,RA,SH,RB
16 prod1 <- MULS(RB, sum)
17 prod1_lo <- prod1[XLEN:(XLEN*2)-1]
18 prod2 <- MULS(RB, diff)
19 prod2_lo <- prod2[XLEN:(XLEN*2)-1]
25 round <- [0]*(XLEN -n) || [1]*1
27 round <- [0]*(XLEN -n) || [1]*1 || [0]*(n-1)
28 prod1_lo <- prod1_lo + round
29 prod2_lo <- prod2_lo + round
30 m <- MASK(n, (XLEN-1))
31 res1 <- ROTL64(prod1_lo, XLEN-n) & m
32 res2 <- ROTL64(prod2_lo, XLEN-n) & m
33 signbit1 <- prod1_lo[0]
34 signbit2 <- prod2_lo[0]
35 smask1 <- ([signbit1]*XLEN) & ¬m
36 smask2 <- ([signbit2]*XLEN) & ¬m
40 Special Registers Altered: