[USRP-users] Compiling UHD Host Library: Problem Enabling ARM Neon Support

Kevin McGuire kmcg3413 at gmail.com
Thu Nov 9 04:22:36 EST 2017


I have noticed that neon support for the converter is not enabling. The
CMakeError.log has this output. I am not certain as I am not really
familiar with ARM and NEON, but I checked my CPU and it does support it.
Also, the error message below is saying it is just a matter of passing
certain flags.

/mnt/extra/usr/lib/gcc/arm-linux-gnueabihf/4.8/include/arm_neon.h:32:2:
error: #error You must enable NEON instructions (e.g. -mfloat-abi=softfp
-mfpu=neon) to use arm_neon.h
 #error You must enable NEON instructions (e.g. -mfloat-abi=softfp
-mfpu=neon) to use arm_neon.h

Normally, I would just fix it myself and move forward, but me and CMake mix
like oil and water. It is kind of embarrassing but I swear it never does
what I want it do - such as adding a darn flag. I even tried to force the
options, lol, and all be danged if CMake finds some way to error.

Will work on this tomorrow, but if anyone has a solution I am all ears. If
not then no problem and I will reply when I figure it out.

This came about when I noticed what really seemed like abnormally high CPU
usage on my ARM code for a simple shuffling of data out of the network
packets. I traced what I felt like was the biggest possible hot spot to the
converter routine. Anyway, that is my plan right now, to see if NEON might
help if the converter is having to swap byte order.
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