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Mixed-type division in DSP lib
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Mixed-type division in DSP lib
Offline
Bryan Audiffred
over 7 years ago
Note: This was originally posted on 30th November 2012 at http://forums.arm.com
Some of the ARM CMSIS routines employ mixed-type division without explicit casting. See below. The last line is a q31_t/uint32_t operation. I could not find an explicit behavior for this situation in a recent C standard, but I believe both operands would be converted to unsigned using the K&R rules. My compiler is indeed providing the UDIV instruction which gives erroneous results if
sum
is negative.
Is this a code issue or compiler implementation issue?
***********************
void arm_mean_q15(
q15_t * pSrc,
uint32_t blockSize,
q15_t * pResult)
{
q31_t sum = 0; /* Temporary result storage */
...
*pResult = (q15_t) (sum / blockSize);
}
Regards,
Bryan
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Offline
Dr. Paul Beckmann
over 7 years ago
Note: This was originally posted on 3rd December 2012 at
http://forums.arm.com
Hi Bryan and Emilien,
Thanks for reporting this issue with the CMSIS library. This is indeed a bug and the signed sum result is converted to unsigned. We'll get this fixed in the next release of the CMSIS library.
-Paul
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Dr. Paul Beckmann
over 7 years ago
Note: This was originally posted on 3rd December 2012 at
http://forums.arm.com
Hi Bryan and Emilien,
Thanks for reporting this issue with the CMSIS library. This is indeed a bug and the signed sum result is converted to unsigned. We'll get this fixed in the next release of the CMSIS library.
-Paul
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