DOS ain't dead

Assembler optimalisation - how to avoid a jump? (Developers)

posted by Laaca , Czech republic, 13.05.2012, 20:38

I write some kind of RLE sprite routine with clipping.
I would like to write nice code. I know I could somehow remove the ugly jump "jnc @RLE_CLIP_MOVE_CONT" but I don't know how.

In EDX is length of displayable scanline (computed by clipping routine)
In ECX is number of pixels which could be copyied. It is always>0
After clipping I sometimes can't copy all ECX bytes but only EDX bytes.
That it what this code does.

@RLE_CLIP_MOVE:
sub edx,ecx
jnc @RLE_CLIP_MOVE_CONT

add ecx,edx

@RLE_CLIP_MOVE_CONT:
shr ecx,1;rep movsd;adc ecx,ecx;rep movsw {fast 32bit write}

cmp edx,0
jle @RLE_CLIP_END_LOOP
jmp @RLE_CLIP_SCANLINE_LOOP

---
DOS-u-akbar!

Complete thread:

• Assembler optimalisation - how to avoid a jump? - Laaca, 13.05.2012, 20:38 (Developers)
  • Assembler optimalisation - how to avoid a jump? - Rugxulo, 13.05.2012, 21:10
    • Assembler optimalisation - how to avoid a jump? - Laaca, 13.05.2012, 22:15
      • Assembler optimalisation - how to avoid a jump? - marcov, 13.05.2012, 23:22
  • Assembler optimisation - how to avoid a jump? - ecm, 13.05.2012, 23:32
    • Assembler optimisation - how to avoid a jump? - Laaca, 14.05.2012, 18:15
      • Assembler optimisation - variant 3, sbb - ecm, 14.05.2012, 18:22
      • Assembler optimisation - how to avoid a jump? - Rugxulo, 16.05.2012, 10:34
        • Assembler optimisation - how to avoid a jump? - bretjohn, 16.05.2012, 16:42
          • Assembler optimisation - speed, size, etc - ecm, 16.05.2012, 16:59