Is there some single instruction like WRC but setting ALL bits?

Comments

• ManAtWork Posts: 2,338

  2026-04-20 08:30

  You can use MUXC or MUXZ D,##$FFFFFFFF which also uses two longs. But if you need it more than once you can store the S operand in a register instead of using ##.
• Wuerfel_21 Posts: 5,842

  2026-04-20 11:05

  With the C flag, you can also use SUBX with the same register in both slots.
• TonyB_ Posts: 2,277

  2026-04-20 11:21 edited 2026-04-20 11:24

  @"Christof Eb." said:
  Hi,
  for my Forth, at the moment I use WRZ and WRC to get a logic result as true or false onto the stack. However it would be better to have $FFFFFFFF for true instead of 1. I had a look into the list of instructions https://p2docs.github.io/p2_optable.html , but perhaps I have overlooked something?
  WRZ followed by NEG is best then?
  Thanks, Christof

  It can be done in one instruction for C and Z (latter needs a constant long).

  'a = 0/$FFFF_FFFF if c or z = 0/1
  
  'c
          subx    a,a        'or bitc    a,b
  'z
          bitz    a,b
  
  b       long    0 + 31 << 5
  
• Christof Eb. Posts: 1,554

  2026-04-20 14:46

  Thank you all very much!
  (((I must admit, that "Bits D[S[9:5]+S[4:0]:S[4:0]]" is rather obscure to me, the "+S[4:0]". Is this some kind of relative addressing of the bits? Why on earth?)))
  As cog registers are very precious at the moment, I am happy to use subx.
• TonyB_ Posts: 2,277

  2026-04-20 15:10 edited 2026-04-20 15:19

  @"Christof Eb." said:
  Thank you all very much!
  (((I must admit, that "Bits D[S[9:5]+S[4:0]:S[4:0]]" is rather obscure to me, the "+S[4:0]". Is this some kind of relative addressing of the bits? Why on earth?)))
  As cog registers are very precious at the moment, I am happy to use subx.

  S[4:0] is the rightmost bit and S[9:5] is the number of extra contiguous bits to the left of that. If S[9:5] = 0 only one bit is changed as given by S[4:0]. A 9-bit #S can change up to 16 bits, hence need for register b above to change all 32 bits in a single 2-cycle instruction.