[PATCH x86_64][BZ #20139] Don't allow configure with not supporting AVX512 assembler w/o --disable-avx512.

[Florian Weimer]

On 06/27/2016 08:29 PM, H.J. Lu wrote:

> If ld.so doesn't the first 8 save/store ZMM registers, you
> may not pass parameters in ZMM registers with AVX512
> kernel on AVX512 machine.   We wan to make sure that
> ld.so in x86-64 glibc saves/stores ZMM registers unless
> glibc is configured to disable AVX512 support.

I still do not understand what is going on.

What can clobber the ZMM registers if glibc was compiled without AVX-512 
capabilities?

If ld.so support for AVX512 is a must before applications can use it, 
why has this not been built into the platform capability detection 
mechanism?

Thanks,
Florian