[Libre-soc-bugs] [Bug 656] add v3.0B BCD instructions to simulator

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=656

--- Comment #1 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
dmitry the pseudocode for cdtbcd and cbcdtd uses a couple of helper functions
which need to be added before they can "work".  addg6s on the other hand
you can do straight away without this.

i found in "v3.0B p787 Book I Appendix B.1 and B.2" the following
pseudocode:

B.1 BCD-to-DPD Translation
The translation from a 3-digit BCD number to a 10-bit
DPD can be performed through the following Boolean
operations.

 p = (f & a & i & ¬e) | (j & a & ¬i) | (b & ¬a)
 q = (g & a & i & ¬e) | (k & a & ¬i) | (c & ¬a)
 r = d
 s = (j  &  ¬a & e & ¬i) | (f & ¬i & ¬e) |
      (f &  ¬a & ¬e) | (e & i)
 t = (k  &  ¬a & e & ¬i) | (g & ¬i & ¬e) |
      (g &  ¬a & ¬e) | (a & i)
 u = h
 v = a | e | i
 w = (¬e & j & ¬i) | (e & i) | a
 x = (¬a & k & ¬i) | (a & i) | e
 y = m

B.2 DPD-to-BCD Translation

The translation from a 10-bit DPD to a 3-digit BCD
number can be performed through the following Bool-
ean operations.

 a =  (¬s & v & w) | (t & v & w & s) | (v & w & ¬x)
 b =  (p & s & x & ¬t) | (p & ¬w) | (p & ¬v)
 c =  (q & s & x & ¬t) | (q & ¬w) | (q & ¬v)
 d =  r
 e = (v & ¬w & x) | (s & v & w & x) |
      (¬t & v & x & w)
 f = (p & t & v & w & x & ¬s) | (s & ¬x & v) |
      (s & ¬v)
 g = (q & t & w & v & x & ¬s) | (t & ¬x & v) |
      (t & ¬v)
 h = u
 i = (t  & v & w & x) | (s & v & w & x) |
      (v & ¬w & ¬x)
 j = (p  & ¬s & ¬t & w & v) | (s & v & ¬w & x) |
      (p & w & ¬x & v) | (w & ¬v)
 k = (q  & ¬s & ¬t & v & w) | (t & v & ¬w & x) |
      (q & v & w & ¬x) | (x & ¬v)
 m = y


after removing the silliness of *yet another* non-ASCII symbol for "¬"
being used, those will need to go into openpower/isafunctions/bcd.mdwn,
along with comments saying where they come from.  see here for example
to cut/paste:
https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=openpower/isafunctions/fpfromint.mdwn;hb=HEAD

then you can run "pyfnwriter" to generate the actual python code

then, in pywriter.py you will need to *add* those helper functions
*manually* (at the moment, really they should be done automatically)

https://git.libre-soc.org/?p=openpower-isa.git;a=blob;f=src/openpower/decoder/pseudo/pywriter.py;hb=HEAD

at line 33, add
from openpower.decoder.isafunctions.bcd import BCD_TO_DPD, DPD_TO_BCD

then re-run pywriter noall bcd in order to get the decoder/isa/bcd.py
to be re-compiled with the import of the helper function added.

or, cheat, and manually edit decoder/isa/bcd.py :)

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