openpower/sv/po9_encoding/discussion.mdwn

   1 # alternative 32-64 encoding
   2
   3 ```
   4 | 0-5 | 6-28 29 | 30-31| 32 |33-63| Description                        |
   5 |-----|---------|------|----|-----|------------------------------------|
   6 | PO9 | xxx | 0 | 0  0 | 000000 DWd | SVP64:EXT900                       |
   7 | PO9 | xxx | 1 | 0  0 |            32-bit EXT900                      |
   8 | PO9 |   !zero | 0  0 |  1 | DWd | SVP64Single:EXT232-263             |
   9 | PO9 |   0000  | 0  0 |  1 | DWd | Scalar EXT232-263                  |
  10 | PO9 |   nnnn  | 1  0 |  1 | DWd | SVP64:EXT232-263                   |
  11 | PO9 |   0000  | 0  1 |  x | xxxx| 32-bit Unvectorizable (in 64-bit)  |
  12 | PO9 |   !zero | 0  1 |  n | DWd | SVP64Single:EXT000-063             |
  13 | PO9 |   nnnn  | 1  1 |  n | DWd | SVP64:EXT000-063                   |
  14 ```
  15
  16 Length detection:
  17
  18 ```
  19     if PO1                   return 64
  20     elif not PO9             return 32
  21     elif Word[31] = 1        return 64
  22     elif Word[29:30] = 0b10  return 32
  23     elif Word[29:30] = 0b00  return 64
  24     else                     return 32
  25 ```
  26