This is also kind of interesting in a morbid sort of way: $ cpp -dM </dev/null | grep -i arm #define __ARM_NEON 1
According to http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053c/IHI0053C_acle_2_0.pdf, Section 12.1, __ARM_NEON is defined when ARM Neon Intrinsics are available: NEON intrinsics are available if the __ARM_NEON macro is predefined (see 6.5.4), but in order to access NEON intrinsics it is necessary to include the <arm_neon.h> header. Jeff