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qus
PostPosted: Mon Jun 29, 2020 10:34 am 
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Joined: Sat Apr 20, 2019 5:31 pm
Posts: 104
Yep:

Code:
__wolin_lab_loop_start_1:

; 12: add 53280[ubyte] = 53280[ubyte] , #1[ubyte]


    inc 53280

; 13: evalless CPU.NC[bool] = 53280[ubyte] , #255[ubyte]


    lda 53280
    cmp #255

; 14: bift CPU.NC[bool] , __wolin_lab_loop_start_1<while_start>[uword]


   bcc __wolin_lab_loop_start_1
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BillG
PostPosted: Mon Jun 29, 2020 2:07 pm 
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Joined: Thu Mar 12, 2020 10:04 pm
Posts: 690
Location: North Tejas
qus wrote:
; 13: evalless CPU.NC[bool] = 53280[ubyte] , #255[ubyte]

Code:
    lda 53280
    cmp #255



If X or Y is available, you can compare a byte with 255 (or 1) with something like:

Code:
    ldx    53280
    inx            ; (or dex)

    beq
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qus
PostPosted: Mon Jun 29, 2020 3:19 pm 
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Posts: 104
Heh, thanks. It will probably be good for 6502 asm optimization phase, though.
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dmsc
PostPosted: Tue Jun 30, 2020 2:40 am 
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Joined: Mon Sep 17, 2018 2:39 am
Posts: 132
Hi!

qus wrote:
Some compiler fun. I've compiled the same code with Wolin, cc65 and vbcc:

Wolin:

C (generated by Wolin C frontend :D)

Code:
  do {
      (*(unsigned char *)(53280))++;
   } while ( (*(unsigned char *)(53280)) < 255);


cc65:
Code:
L0015:   ldx     #$00
   lda     $D020
   inc     $D020
   ldx     #$00
   lda     $D020
   cmp     #$FF
   jsr     boolult
   jne     L0015


I wonder if I can make my bool operations any smarter and use V/C/N flags somehow (and obviously win brevity competition)... But I do like the way it works now - by storing the final bool result of an operation in SP reg. MAYBE instead of storing it at SP,x I just pretend I "stored" it at 6502 V/C/N?


You compiled the CC65 example without optimizations, here I get (using "cc65 -Osir test.c":

Code:
L000B:  inc     $D020
        lda     $D020
        cmp     #$FF
        bcc     L000B


Have Fun!
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qus
PostPosted: Tue Jun 30, 2020 6:37 am 
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Posts: 104
With such optimizations one has to wonder why are they turned off by default...
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Chromatix
PostPosted: Tue Jun 30, 2020 10:36 am 
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Posts: 1462
Most C compilers have no optimisation by default, so cc65 is not unusual in that respect. Unoptimised compilation results in code that does fewer unexpected things when single-stepping in a debugger.
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