# [DRAFT] Integer Butterfly Multiply Add/Sub FFT/DCT
-DCTI-Form
+A-Form
-* maddsubrs RT,RA,RB,SH
+* maddsubrs RT,RA,SH,RB
Pseudo-code:
+ n <- SH
sum <- (RT) + (RA)
diff <- (RT) - (RA)
- prod1 <- MUL(RB, sum)
- prod2 <- MUL(RB, diff)
- res1 <- ROTL64(prod1, XLEN-SH)
- res2 <- ROTL64(prod2, XLEN-SH)
- RT <- (RT) + res1
- RS <- (RS) + res2
+ prod1 <- MULS(RB, sum)
+ prod2 <- MULS(RB, diff)
+ if n = 0 then
+ prod1_lo <- prod1[XLEN:(XLEN*2)-1]
+ prod2_lo <- prod2[XLEN:(XLEN*2)-1]
+ RT <- prod1_lo
+ RS <- prod2_lo
+ else
+ if XLEN = 64 then
+ prod1_lo <- prod1[XLEN:(XLEN*2)-1]
+ prod2_lo <- prod2[XLEN:(XLEN*2)-1]
+ round <- [0]*XLEN
+ round[XLEN -n] <- 1
+ prod1_lo <- prod1_lo + round
+ prod2_lo <- prod2_lo + round
+ m <- MASK(n, (XLEN-1))
+ res1 <- ROTL64(prod1_lo, XLEN-n) & m
+ res2 <- ROTL64(prod2_lo, XLEN-n) & m
+ signbit1 <- prod1_lo[0]
+ signbit2 <- prod2_lo[0]
+ smask1 <- ([signbit1]*XLEN) & ¬m
+ smask2 <- ([signbit2]*XLEN) & ¬m
+ RT <- (res1 | smask1)
+ RS <- (res2 | smask2)
+ else
+ round <- [0]*(XLEN*2)
+ round[XLEN*2 -n] <- 1
+ prod1 <- prod1 + round
+ prod2 <- prod2 + round
+ m <- MASK(XLEN-n, XLEN-1)
+ res1 <- prod1[XLEN-n:XLEN*2 -n -1]
+ res2 <- prod2[XLEN-n:XLEN*2 -n -1]
+ signbit1 <- prod1[0]
+ signbit2 <- prod2[0]
+ smask1 <- ([signbit1]*XLEN) & ¬m
+ smask2 <- ([signbit2]*XLEN) & ¬m
+ RT <- (res1 | smask1)
+ RS <- (res2 | smask2)
+
+Special Registers Altered:
+
+ None
+
+# [DRAFT] Integer Butterfly Multiply Add and Accumulate FFT/DCT
+
+A-Form
+
+* maddrs RT,RA,SH,RB
+
+Pseudo-code:
+
+ n <- SH
+ prod <- MULS(RB, RA)
+ if n = 0 then
+ prod_lo <- prod[XLEN:(XLEN*2)-1]
+ RT <- (RT) + prod_lo
+ RS <- (RS) - prod_lo
+ else
+ if XLEN = 64 then
+ prod_lo <- prod[XLEN:(XLEN*2)-1]
+ res1 <- (RT) + prod_lo
+ res2 <- (RS) - prod_lo
+ round <- [0]*XLEN
+ round[XLEN -n] <- 1
+ res1 <- res1 + round
+ res2 <- res2 + round
+ signbit1 <- res1[0]
+ signbit2 <- res2[0]
+ m <- MASK(n, (XLEN-1))
+ res1 <- ROTL64(res1, XLEN-n) & m
+ res2 <- ROTL64(res2, XLEN-n) & m
+ smask1 <- ([signbit1]*XLEN) & ¬m
+ smask2 <- ([signbit2]*XLEN) & ¬m
+ RT <- (res1 | smask1)
+ RS <- (res2 | smask2)
+ else
+ res1 <- (RT) + prod
+ res2 <- (RS) - prod
+ round <- [0]*XLEN*2
+ round[XLEN*2 -n] <- 1
+ res1 <- res1 + round
+ res2 <- res2 + round
+ signbit1 <- res1[0]
+ signbit2 <- res2[0]
+ m <- MASK(XLEN-n, (XLEN-1))
+ res1 <- prod1[XLEN-n:XLEN*2 -n -1]
+ res2 <- prod2[XLEN-n:XLEN*2 -n -1]
+ smask1 <- ([signbit1]*XLEN) & ¬m
+ smask2 <- ([signbit2]*XLEN) & ¬m
+ RT <- (res1 | smask1)
+ RS <- (res2 | smask2)
Special Registers Altered: