[Speex-dev] Speex on TI C6x, Problem with TI C5x Patch

[Jim Crichton]

>> Nice call.  The culprit is SHRL32.  This is not used in many places, and 
>> in
>> most of those, the operand comes from EXTEND32.  The only really 
>> suspicious
>> instances is in lsp.c (lsp_interpolate):
>>
>>    spx_word16_t tmp = DIV32_16(SHL32(1 + subframe,14),nb_subframes);
>> (subframe is an int)
>> ...
>> I see that your changes include adding an EXTEND32 to the line above.  I
>> made ONLY this change to the 1.1.8 base that I am working from, and the
>> problem is gone.
>
> Good. So I guess you are still having your low MIPS count, right? How
> much is that?

About 42 MIPs peak for encode/decode, complexity 1, 8kbps, no preprocessor 
or jitter buffer or echo canceller (yet).

>> I will go back to using fixed_generic.h for now, but it may still be
>> worthwhile to make a custom version that takes advantage of the compiler
>> intrinsics, which include 32-bit shifts, 16x16=32 and 32x16=32 MPY, and
>> 32+16x16=32 MAC (with and without rounding).  The multiply arithmetic all
>> returns saturated results.  It seems to me that can't hurt.  Do you see 
>> any
>> problem with using saturated MPY and MACs?
>
> Saturation never hurts. That's actually what I would have used if all
> platforms supported it (which is at least not the case when ARMv4). If
> you send me a file with only the macros you want to override from
> fixed_generic.h, I can include it in the tree.

Good, but I will not get around to this for a while.  My next step is 
getting a multichannel version working on C64x.

>> By the way, the lsp.c change also fixes the TI C54x build, as expected.
>
> What do you mean? Before that, it worked on C55, but not C54?

No, they have always produced the same results.  The C54x seems to take 
about 5x as many cycles to do the task.  I can see that 32x32 multiplies are 
being done by library calls rather than inline, so I will play with this a 
bit more.  Others have used C54x successfully, so significant improvement is 
possible.

- Jim Crichton