GLIBC a mechanism for picking the best routines to use based on the CPU capabilities. This means that GLIBC can include A8 and A9 versions both with and without NEON, Ubuntu can ship all of these versions, and the dynamic linker can choose the best one based on the chip it is running on.
I've had a quick look at HWCAP in eglibc and I didn't see it used anywhere. Anyway you can detect whether NEON is supported or not. But the CPU (A8 vs A9) is not detected. Therefore you can detect the cortext-A9 platforms supports NEON but it doesn't mean NEON memcpy is the best solution (actually the performance is not better and the power consumption is worse!)
Could you point me at a reference on the power consumption of the NEON unit? It will take power, but I don't know how much or how significant it is.
As far as I know there is no data on it (it's difficult to measure the consumption inside the SoC) Anyway the NEON unit is a big part of the CPU. So you can conclude it consumes a non negligible amount of energy.
Guillaume
-- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.