Having prototyped my new polygon filler to my satisfaction in C, today
I've been converting it to assembler. With the iPhone stuff and an
Acorn Electron project I've been working on, I haven't done any z80 in
far too long and am not particularly optimistic that I'm writing good
stuff. Actually, it
Just a quick glimps of the code shows you can save 8-clocks every
itteration of your plotloop by getting rid of the SET 7,D instructions
and putting a SCF before a RR D instruction. Replacing the SRL D's
with RR D's.
But as you're not likely to be using this particular plotloop in the final
Oh, yeah, the plotloop is a complete placeholder, just so I can
compare output to the C prototype. That said, I'd done exactly the
same thing on scf versus set 7,d in my line drawing code (don't worry:
just once, outside the loop). I must find time to finish documenting
my vector drawing code as
On 24 Oct 2009, at 20:08, Thomas Harte wrote:
Anyway, if some of you z80 experts could have a quick look and tell me
if I'm making any obvious style errors or otherwise missing obvious
optimisations — even if only on a peephole level — I'd be infinitely
grateful.
One trick I almost always
One trick I almost always use, is instead of:
[...]
Oh, yes, smart move! I'm pretty sure I had at least one copy of
Electron User that thought this technique so magnificent that it got a
front page mention as discover extra registers or something like
that.
By the way:
ld d,
On 24 Oct 2009, at 23:46, Thomas Harte wrote:
By the way:
ld d, (NUMVERTS)
I don't think you can do this?
No, you're right, you can't. It silently substituted ld a, (NUMVERTS),
so that loop was running quite a bit longer than it needed to and the
result not being visibly different
With most of Andrew's comments not yet incorporated, the source code
that at least does a complete poly fill is below. So I've implemented
the scanning for x negative and written a quick DrawScanline function.
I guess the latter is going to be the only new interesting bit. And I
know I'm posting
Oh, your implied guess was quite right, I was a version behind. I'd
say you fooled me by leaving Version 1.1, released 13 April 2007 at
the top of the read me despite having updated the version history but
actually I spotted 1.2, downloaded it and then failed to do anything
more whatsoever.
