OpenBSD 7.1 onwards expose the aarch64 ISAR0 and ISAR1 registers via sysctl:
$ sysctl machdep
machdep.compatible=apple,j274
machdep.id_aa64isar0=153421459058925856
machdep.id_aa64isar1=1172796674562
Implement CPU feature detection for openbsd/arm64 based on this information.
Updates golang/go#31746
Change-Id: I6dc473d93ccff720582c05b75456de51269bc3e5
Reviewed-on: https://go-review.googlesource.com/c/sys/+/421799
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
