Arm Community
Site
Search
User
Site
Search
User
Groups
Arm Research
DesignStart
Education Hub
Graphics and Gaming
High Performance Computing
Innovation
Multimedia
Open Source Software and Platforms
Physical
Processors
Security
System
Software Tools
TrustZone for Armv8-M
中文社区
Blog
Announcements
Artificial Intelligence
Automotive
Healthcare
HPC
Infrastructure
Innovation
Internet of Things
Machine Learning
Mobile
Smart Homes
Wearables
Forums
All developer forums
IP Product forums
Tool & Software forums
Support
Open a support case
Documentation
Downloads
Training
Arm Approved program
Arm Design Reviews
Community Help
More
Cancel
Developer Community
Tools and Software
Software Tools
Jump...
Cancel
Software Tools
Arm Development Studio forum
Mixed-type division in DSP lib
Tools, Software and IDEs blog
Forums
Videos & Files
Help
Jump...
Cancel
New
Replies
2 replies
Subscribers
126 subscribers
Views
1860 views
Users
0 members are here
Related
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
Offline
Emilien Kofman
over 7 years ago
Note: This was originally posted on 3rd December 2012 at
http://forums.arm.com
Hi Bryan,
I was wondering the exact same thing as I got wrong results in my application... I ran the same kind of division with gcc and I also got a wrong result. Once I added the cast to blockSize it worked correctly.
Would this be related to "6.3.1.8 Usual arithmetic conversions" (C99) :
"[...] Otherwise, if the operand that has unsigned integer type has rank greater or
equal to the rank of the type of the other operand, then the operand with
signed integer type is converted to the type of the operand with unsigned
integer type."
Anyone knows if I'm doing it wrong or if the CMSIS routines need this cast?
Best regards,
--
Emilien
Cancel
Up
0
Down
Reply
Cancel
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
Cancel
Up
0
Down
Reply
Cancel
More questions in this forum
By title
By date
By reply count
By view count
By most asked
By votes
By quality
Descending
Ascending
All recent questions
Unread questions
Questions you've participated in
Questions you've asked
Unanswered questions
Answered questions
Questions with suggested answers
Questions with no replies
Suggested Answer
error encountered when try to connect FVP
0
1341
views
7
replies
Latest
10 days ago
by
fantim.zhang
Answered
Key difference between GCC arm-none-eabi and arm-eabi
0
compiler
GCC
Getting Started
parameters
GNU
eabi
52418
views
6
replies
Latest
12 days ago
by
Juvanta
Suggested Answer
Can anyone please help me on how evalution development studio 2020.1 work s and which compiler is needed and how it can be setup?
0
931
views
3
replies
Latest
15 days ago
by
Ronan Synnott
Suggested Answer
Can anyone tell me the difference between DSTREAM and DSTREAM-ST?
0
1158
views
2
replies
Latest
20 days ago
by
Xiang
Not Answered
Would you be interested in a VScode extension to handle ARM toolchain?
0
1053
views
0
replies
Started
22 days ago
by
vix
<
>
View all questions in Arm Development Studio forum