On Fri, Mar 29, 2024 at 12:30:14PM -0400, Tom Lane wrote: > Nathan Bossart <nathandboss...@gmail.com> writes: >>> 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? > >> Hm. It seems unlikely that a compiler would understand AVX512 intrinsics >> and not XGETBV then. I guess the other question is whether CPUID >> indicating AVX512 is enabled implies the availability of XGETBV on the CPU. >> If that's not safe, we might need to add another CPUID test. > > Some quick googling says that (1) XGETBV predates AVX and (2) if you > are worried about old CPUs, you should check CPUID to verify whether > XGETBV exists before trying to use it. I did not look for the > bit-level details on how to do that.
That extra CPUID check should translate to exactly one additional line of code, so I think I'm inclined to just add it. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
