[Speex-dev] Shift count warning messages

Sat Jan 26 02:30:22 PST 2008

Hi Jim,

Thanks a lot for investigating. It definitely makes sense now. I'll fix
the problem now. Is there any other place where you see that same (or
similar) problem?

	Jean-Marc

Jim Crichton a écrit :
> Jean-Marc,
> 
> I dug into this further, and found that the warning occurred when PSHR32
> had a shift greater than 15.
> 
> in fixed_generic.h, PSHR32 is defined as:
> 
> #define PSHR32(a,shift) (SHR32((a)+((1<<((shift))>>1)),shift))
> 
> For 16-bit compilers the "1" needs a cast:
> 
> #define PSHR32(a,shift) (SHR32((a)+((EXTEND32(1)<<((shift))>>1)),shift))
> 
> This change fixed the warning, and it did change the assembled code. 
> With the original file, the ((1<<((shift))>>1)) was optimized away.
> Note that fixed_debug.h has the same problem.
> 
> - Jim
> 
> ----- Original Message ----- From: "Jean-Marc Valin"
> <jean-marc.valin at usherbrooke.ca>
> To: "Jim Crichton" <jim.crichton at comcast.net>
> Cc: <speex-dev at xiph.org>; "Michael Jacobson"
> <Michael.Jacobson at ultratec.com>
> Sent: Wednesday, January 23, 2008 12:16 PM
> Subject: Re: [Speex-dev] Shift count warning messages
> 
> 
>> 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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>>>>>> http://lists.xiph.org/mailman/listinfo/speex-dev
>>>>>
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