> -----Original Message----- > > Cool. I think we should run the benchmarks again to be safe, though.
Ok, sure go ahead. :) > >> I forgot to mention that I also want to understand whether we can > >> actually assume availability of XGETBV when CPUID says we support > >> AVX512: > > > > You cannot assume as there are edge cases where AVX-512 was found on > > system one during compile but it's not actually available in a kernel > > on a second system at runtime despite the CPU actually having the > > hardware feature. > > Yeah, I understand that much, but I want to know how portable the XGETBV > instruction is. Unless I can assume that all x86_64 systems and compilers > support that instruction, we might need an additional configure check and/or > CPUID check. It looks like MSVC has had support for the _xgetbv intrinsic for > quite a while, but I'm still researching the other cases. I see google web references to the xgetbv instruction as far back as 2009 for Intel 64 bit HW and 2010 for AMD 64bit HW, maybe you could test for _xgetbv() MSVC built-in. How far back do you need to go? Thanks, Paul
