Re: Help with Hand-Optimized Assembly

[Bill Woessner]

On Jan 13, 4:59 am, Terje Mathisen <"terje.mathisen at
tmsw.no"@giganews.com> wrote:
> I'll second James' suggestion about SSE2!

I'm open to using SSE2.  The only reason I used x87 is that I started
with the assembly code that g++ generated.  By default, it generates
x87 instructions.  But I'm certainly willing to try with SSE2
instructions.

> Anyway, it seem that what you are trying to do is to take the
> difference between two angles and then make sure that said
> difference will be in the [-pi .. pi> range, right?

That's it exactly.  It's such a simple thing, but I can't come up with
a really elegant way to do it.  The code generated by g++ involves a
jump.  But I think this should be possible without a jump by using a
conditional move.

> Anyway, trying your original algorithm:

I'll give your implementation a try.  A big part of the challenge (for
me, at least) is figuring out how to get this in to a form that g++
will understand.  I don't really care where or how this is
implemented, but I need to be able to call it from C++.  And it really
should be inline, as well.  Otherwise, all the efficiency gained by
tweaking the assembly will be lost.  :-p

Thanks,
Bill