Optimization question for bitblit optimization

Brian Hurt bhurt at spnz.org
Thu Jan 29 15:38:26 CET 2004

This is in regards to the bitblit routine I posted yesterday.  In general, 
which should I be optimizing for: long bitblits (where the O(1) costs are 
insignifigant, the dominate cost is the main loops), or short bitblits 
(where the O(1) costs dominate)?

I'm looking at doing hand-tuned x86 versions of the main loops.  What I've
come up with so far (generic 386 code) increases the speed per bit by 20%
for long (1K word) bitblits- 0.277 clocks/bit vr.s 0.345 clocks/bit.  But
it slows down the short (<3 words) bitblits by 10%- 1.963 clocks/bit vr.s
1.779 clocks/bit.

I'm inclined to optimize for the long blits myself.  But I wanted to give 
the development community an opportunity to comment.

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