Is Neon coprocessor being used?

Question

I am using the FFTW3 library on Beagleboard xM in a C application to perform r2c FFTs of floats. I read on this page that FFTW3 includes support for Neon, which is part of the xM architecture.

Is there a way to tell if the Neon coprocessor is actually being used?

For example, can I lists symbols from the object files and parse for some special Neon symbols? Alternatively, can I look through gcc -S assembler output for any Neon instructions? What instruction(s) would I look for? (I'm not familiar with what Neon assembly looks like).

Answer 1

Look at the disassembly. NEON instructions that operate on float data have a .f32 suffix and the NEON registers have names of the form dN or qN (where N is an integer). So if you see instructions that look like:

vadd.f32 q0, q1, q2

then NEON is being used.