[vorbis-dev] casting/rounding ASM committed to beta3 branch

[Jack Moffitt]

> Jack, I got the asm we were working last night committed ont he beta 3 branch.
> It's in use in both vorbisfile:ov_read() and the lsp lookup (when using float
> lookups)

I just did a checkout of prebranch_beta3 and unless I did something
wrong, vorbisfile.c does NOT have the float to int assembly
optimizations.  I still has (int)f stuff.

> I'd like to have a patch of the other things you did in the past day or so, even if you don't want to commit yet.

Here's the patch from a fresh checkout of branch_prebeta3.  It includes
my own assembly stuff, so you'll have to hand apply (you always do
anyway). 

Those of you on the rest of the list might like to take a peek too.
If I can help make this much of a difference in speed in such little
time, I'm wondering what others on this list can do who are better at
optimization than me :)

There's basically 3 things going on:

1) float to int of gcc is nasty.  we inlined it with one 'fistp'. (HUGE
speedup)  (there's two places this is critical for speed.  float -> int
conversion in vorbisfile.c for the sample output, and in lookup.c for
the cosine,squareroot,etc lookups for lsp_to_curve).
2) lsp.c had two for loops that i took to one do/while while also
chaning array indexing to constant offsets and pointer math.  (this was
a HUGE speedup)
3) I unrolled a bit a loop in mdct_kernel  this is also a pretty good
speedup.

This was my first time with loop unrolling.  I would appreciate it if
someone who knows more than me could look at it and see if it can be
done even better.

(Andrew of the Sonique team helped with the lsp.c loop)

mdct_kernel is now much slower than anything else in the code (it used
to be a 3 way tie between the float->int sample conversion, mdct_kernel
and lsp_to_curve).

jack.


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