[PATCH] powerpc: New feature - HWCAP/HWCAP2 bits in the TCB

[Roland McGrath]

> I believe the idea is to provide a fast way to emulate a functionality
> similar to __builtin_cpu_supports for powerpc.  For x86, this builtin
> will create 'cpuid' instruction, but since powerpc lacks a similar one
> it should rely on hardware capability information provided by kernel.

On x86 using cpuid is quite slow as instruction-level overheads go.
It's certainly nowhere near as fast as doing a direct load from memory.
So this analogue does not suggest anything like justification for the
kind of microoptimization being discussed.