openpower/isa/bcd.mdwn

   1 <!-- Instructions here described in PowerISA Version 3.0 B Book 1 -->
   2
   3 <!-- Section 3.3.15 Binary Coded Decimal (BCD) Assist Instructions. Page 111 -->
   4
   5 <!-- The Binary Coded Decimal Assist instructions operate on Binary Coded Decimal -->
   6 <!-- operands (cbcdtd and addg6s) and Decimal Floating-Point operands (cdtbcd) -->
   7 <!-- See Chapter 5. for additional information. -->
   8
   9
  10 # Convert Declets To Binary Coded Decimal
  11
  12 X-Form
  13
  14 * cdtbcd RA, RS
  15
  16 Pseudo-code:
  17
  18     do i = 0 to 1
  19       n <- i * 32
  20       RA[n+0:n+7] <- 0
  21       RA[n+8:n+19 ] <- DPD_TO_BCD ( (RS)[n+12:n+21] )
  22       RA[n+20:n+31] <- DPD_TO_BCD ( (RS)[n+22:n+31] )
  23
  24 Special Registers Altered:
  25
  26     None
  27
  28 # Add and Generate Sixes
  29
  30 XO-Form
  31
  32 * addg6s RT,RA,RB
  33
  34 Pseudo-code:
  35
  36     dc <- [0]*16
  37     do i = 0 to 15
  38         temp <- (0b0 || RA[4*i:63]) + (0b0 || RB[4*i:63])
  39         dc[i] <- temp[0]
  40     c <- ([dc[0]]*4 || [dc[1]]*4 || [dc[2]]*4 || [dc[3]]*4 ||
  41             [dc[4]]*4 || [dc[5]]*4 || [dc[6]]*4 || [dc[7]]*4 ||
  42             [dc[8]]*4 || [dc[9]]*4 || [dc[10]]*4 || [dc[11]]*4 ||
  43             [dc[12]]*4 || [dc[13]]*4 || [dc[14]]*4 || [dc[15]]*4)
  44     RT <- (¬c) & 0x6666_6666_6666_6666
  45
  46 Special Registers Altered:
  47
  48     None
  49
  50 # Convert Binary Coded Decimal To Declets
  51
  52 X-Form
  53
  54 * cbcdtd RA, RS
  55
  56 Pseudo-code:
  57
  58     do i = 0 to 1
  59       n <- i * 32
  60       RA[n+0:n+11] <- 0
  61       RA[n+12:n+21] <- BCD_TO_DPD ( (RS)[n+8:n+19] )
  62       RA[n+22:n+31] <- BCD_TO_DPD ( (RS)[n+20:n+31] )
  63
  64 Special Registers Altered:
  65
  66     None
  67
  68 <!-- Checked March 2021 -->