Use AVX/AVX512 selectively

[Alexander Monakov]

On Thu, 3 Mar 2016, Florian Weimer wrote:
> Both hardware with amd without avx512f capability.  There is run-time
> detection for it, but for it to be effective, most of the program has
> to be compiled without -mavx512f, otherwise the program will use
> avx512f instructions before getting to the detection code.

I think separate compilation is the proper tool for this.  Your initial
message seems to imply you seek another method; why?

Thanks.
Alexander