openpower/sv/bmask.py

   1 def bmask(bm, RA, RB=None, zero=False, XLEN=64):
   2     mask = RB if RB is not None else ((1<<XLEN)-1)
   3     ra = RA & mask
   4     mode1 = bm&1
   5     a1 = ra if mode1 else ~ra
   6     mode2 = (bm >> 1) & 0b11
   7     if mode2 == 0: a2 = -ra
   8     if mode2 == 1: a2 = ra-1
   9     if mode2 == 2: a2 = ra+1
  10     if mode2 == 3: a2 = ~(ra+1)
  11     a1 = a1 & mask
  12     a2 = a2 & mask
  13     mode3 = (bm >> 3) & 0b11
  14     if mode3 == 0: RS = a1 | a2
  15     if mode3 == 1: RS = a1 & a2
  16     if mode3 == 2: RS = a1 ^ a2
  17     if mode3 == 3: RS = 0 # RESERVED
  18     RS &= mask
  19     if not zero:
  20         # put back masked-out bits of RA
  21         RS |= RA & ~mask
  22     return RS
  23
  24 SBF = 0b01010 # set before first
  25 SOF = 0b01001 # set only first
  26 SIF = 0b10000 # set including first 10011 also works no idea why yet