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Demos Amiga Demoscene Archive Forum / Coding / AsmOne label syntax

 

Author Message
sdw
 Member
#1 - Posted: 22 Jun 2013 20:25
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So, I've been doing some coding in good-old Asmone on the Amiga 500 for the first time in years (or rather decades almost...)

Having a bit of trouble recalling the syntax of how stuff is done though, and I can't find any manual online.

Right now I'm struggling with labels inside REPT blocks. I'm not even sure if there is a solution for this:


	REPT 20
	move.b (a0)+,d0
	sub.b d1,d0	
	bpl skip
	eor.b d0,d0
skip:			
	move.b d0,(a1)+
	ENDR



As it is now, I ofcourse get 20 redifinitions of skip, and it won't compile. Using local variables won't help either, since a non-local variable is needed before it is allowed to assign it again.
Is there a way to get around this?
skp
 Member
#2 - Posted: 22 Jun 2013 22:12 - Edited
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Hey sdw, try the following thing: move your inner REPT code in a macro and change the label skip by skip\@ then in your REPT simply call the macro...
sdw
 Member
#3 - Posted: 23 Jun 2013 00:44
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Ah yes, thank you, that worked fine!
Raylight
 Member
#4 - Posted: 23 Jun 2013 13:40 - Edited
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sdw:
So, I've been doing some coding in good-old Asmone on the Amiga 500 for the first time in years (or rather decades almost...)

Glad to hear! :-)

...just a optimization thought... If you want to work with bytes and have a register to spare, perhaps this would be slightly faster?

                       ; >=0       <0
                       ;
      sub.b   d1,d0    ;  4        4
      spl     d2       ;  6        4
      and.b   d2,d0    ;  4        4
                       ; 14(3/0)  12(3/0)


..compared to:

      sub.b   d1,d0    ;  4        4
      bpl     .skip    ; 10        8
      eor.b   d0,d0    ;  -        4
.skip                  ; 14(3/0)  16(3/0)


I haven't coded A500 for ages so I might very well be missing something here, but if not it should save 4 cycles in the "underflow" case. :-)

 

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A.D.A. Amiga Demoscene Archive, Version 3.0