[Speex-dev] Shift count warning messages

Jim Crichton jim.crichton at comcast.net
Mon Jan 28 12:52:44 PST 2008 

Jean-Marc,

fixed_generic.h:  PSHR32, PSHR (though this is only used for 15-bit shift)
fixed_debug.h:  PSHR32, MULT16_32_PX, MULT16_32_QX

I do not see anything else, though it looks like the byte packing (readint 
and writint) in speexenc.c and speexdec.c would not compile because of 
24-bit shifts.  But those two files do not use the Speex type definitions, 
and are outside of the codec proper, anyway.

- 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: Saturday, January 26, 2008 5:30 AM
Subject: Re: [Speex-dev] Shift count warning messages


> 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ------------------------------------------------------------------------
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________ Speex-dev mailing
>>>>>>> list Speex-dev at xiph.org
>>>>>>> http://lists.xiph.org/mailman/listinfo/speex-dev
>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________ Speex-dev mailing
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>>>>>>
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