[Bug target/71659] _xgetbv intrinsic missing

[noloader at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71659

--- Comment #3 from Jeffrey Walton <noloader at gmail dot com> ---
(In reply to postmaster from comment #2)
> Portability is one main reason to add missing intrinsics... with combination
> of cpuid check and _xgetbv() we can cleanly check if AVX or MPX is available
> at run-time. We can also check specific instructions during configure
> process to see if we need to add workarounds for bad or missing
> functions/intrinsics.

+1. We were trying to use Intel's algorithm described at
https://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled . We should
only need __get_cpuid and _xgetbv. We should not need that nasty GCC inline
assembly.