On Fri, Aug 26, 2022 at 10:45:10AM +0700, John Naylor wrote: > On Thu, Aug 25, 2022 at 11:57 AM Nathan Bossart > <nathandboss...@gmail.com> wrote: >> The ARM literature appears to indicate that Neon support is pretty standard >> on aarch64, and AFAICT it's pretty common to just assume it's available. > > This doesn't exactly rise to the level of "find out for sure", so I > went looking myself. This is the language I found [1]: > > "Both floating-point and NEON are required in all standard ARMv8 > implementations. However, implementations targeting specialized > markets may support the following combinations: > > No NEON or floating-point. > Full floating-point and SIMD support with exception trapping. > Full floating-point and SIMD support without exception trapping."
Sorry, I should've linked to the documentation I found. I saw similar language in a couple of manuals, which is what led me to the conclusion that Neon support is relatively standard. > Since we assume floating-point, I see no reason not to assume NEON, > but a case could be made for documenting that we require NEON on > aarch64, in addition to exception trapping (for CRC runtime check) and > floating point on any Arm. Or even just say "standard". I don't > believe anyone will want to run Postgres on specialized hardware > lacking these features, so maybe it's a moot point. I'm okay with assuming Neon support for now. It's probably easier to add the __ARM_NEON check if/when someone complains than it is to justify removing it once it's there. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com