[Speex-dev] Shift count warning messages

[Jean-Marc Valin]

Thanks Jim for looking into that, I was really starting to wonder what
was going on. Let me know if you find a way to tell the compiler to stop
complaining.

	Jean-Marc

Jim Crichton a écrit :
> I looked back at my old C55 EC build, and I had the same warning in
> mdf.c which Mike found.  The assembly code did have a valid shift, and
> this build did cancel echo.
> 
> When I built with the SVN head, I saw the errors in kiss_fft.c also. 
> The assembly there also has valid shifts.
> 
> So, I suspect that these warnings do not indicate a real problem.  It
> might be interesting to break down the offending lines into a sequence
> of simpler instructions, to see if the compiler can be placated in that
> way.
> 
> - Jim
> 
> ----- Original Message ----- From: "Jean-Marc Valin"
> <jean-marc.valin at usherbrooke.ca>
> To: "Jim Crichton" <jim.crichton at comcast.net>
> Cc: "Michael Jacobson" <Michael.Jacobson at ultratec.com>;
> <speex-dev at xiph.org>
> Sent: Tuesday, January 22, 2008 4:00 PM
> Subject: Re: [Speex-dev] Shift count warning messages
> 
> 
>> Jim Crichton a écrit :
>>> I played briefly with the echo canceller on the C5509A back in May
>>> 2006.  I got the same compiler warnings, and sent a message to the
>>> list which included this:
>>>
>>> "I got several compiler warnings for "shift out of range" in mdf.c,
>>> which I fixed by adding EXTEND32 to all of the SHL32s with 16 bit
>>> operands (st->frame_size in 6 places, st->wtmp2 in 1 place)."
>>
>> Yes, I remember those and I'm pretty sure they're fixed now. I think the
>> problem comes from other changes I made later on, but I can't understand
>> what's wrong.
>>
>>> I sent a patch with some fixes later that month, but I have not built
>>> the echo canceller since then (no room for it).  It is very likely
>>> that you are seeing the same issue, and the fix should be the same
>>> also.  The trickier problems are the ones that the compiler does not
>>> find.  EXTEND32 is usually the cure there also.
>>>
>>> Now that I look at mdf.c, though, W is declares as spx_word32_t, so
>>> there should not be a problem, unless spx_word32_t is being mapped to
>>> 16-bits.  That should not happen if you compile with CONFIG_TI_C54X
>>> defined.  This is odd.
>>
>> In both cases, what I'm seeing is that the code does a shift right by
>> more than 16 bits. Is it possible that the C5x doesn't want to do that,
>> even for 32-bit operands? It's either that or there's a build problem
>> that causes the operands to be 16 bit instead of 32. This is indeed very
>> odd. Can you investigate a bit and check what the types are on both
>> sides of the shift?
>>
>> Cheers,
>>
>> Jean-Marc
>>
>>
>>
>>
>>> - Jim
>>>
>>>
>>> ----- Original Message ----- From: Michael Jacobson To: Jean-Marc
>>> Valin Cc: speex-dev at xiph.org Sent: Tuesday, January 22, 2008 9:54 AM
>>> Subject: Re: [Speex-dev] Shift count warning messages
>>>
>>>
>>> yes, our DSP is 16 bit based, and if those bits of code aren't using
>>> 32 bit variables then yes that is what the warnings would be.  Does
>>> this mean that the preprocessor and echo canceller won't work as well
>>> because of this?
>>>
>>> -Mike
>>>
>>>>>> Jean-Marc Valin <jean-marc.valin at usherbrooke.ca> 01/18/08 8:42
>>>>>> PM >>>
>>>
>>> I think these warnings are due to your DSP being 16-bit and that bit
>>> of code not being 16-bit safe (unlike the encoder and decoder). Can
>>> you confirm?
>>>
>>> Jean-Marc
>>>
>>> Michael Jacobson a écrit :
>>>> Hi, I'm using 1.2beta3 on a 5416 DSP
>>>>
>>>> I have been getting warning messages that say: "kiss_fft.c", line
>>>> 142: warning: shift count is too large
>>>>
>>>>
>>>> I've noticed this on the echo canceller and the preprocessor.  all
>>>> pretty much related to these two lines of code:
>>>>
>>>> kiss_fft C_MUL4(scratch[0],Fout[m] , *tw1 );
>>>>
>>>> mdf.c st->wtmp2[i] =
>>>> EXTRACT16(PSHR32(st->W[j*N+i],NORMALIZE_SCALEDOWN+16));
>>>>
>>>> Is there some kind of switch I was supposed to throw to not get
>>>> these messages? if not-are they hurting anything?
>>>>
>>>> -Mike
>>>>
>>>>
>>>>
>>>> ------------------------------------------------------------------------
>>>>
>>>>
>>>>
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