In order to get faster access to the HWCAP/HWCAP2 bits and platform number without the overhead of reading from the auxiliary vector, we now reserve space for them in the Thread Control Block (TCB). This is a TLS ABI change for GLIBC 2.23 added by commit 67385a0.
New __builtin_cpu_is() / __builtin_cpu_supports() functions in GCC will be available (probably) in the next release, providing similar functionality to Intel x86 equivalent functions. I will keep you updated on when this is available in GCC.