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From: Jan Beich <jbeich@FreeBSD.org>
To: Alexey Dokuchaev <danfe@freebsd.org>
Cc: svn-ports-head@freebsd.org, svn-ports-all@freebsd.org,
 Gleb Popov <arrowd@freebsd.org>, ports-committers@freebsd.org
Subject: Re: svn commit: r520468 - in head/sysutils: . cpuid2cpuflags
References: <201912200518.xBK5IHPq022253@repo.freebsd.org>
 <CALH631m10+0eDY_8BKQxErA2Bpo2dv6B6h7DRb77yO3cJCboSw@mail.gmail.com>
 <20191220084532.GA30042@FreeBSD.org> <v9qb-ff6r-wny@FreeBSD.org>
Date: Fri, 20 Dec 2019 12:11:57 +0100
In-Reply-To: <v9qb-ff6r-wny@FreeBSD.org> (Jan Beich's message of "Fri, 20 Dec
 2019 11:45:48 +0100")
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(Sorry, I need to proofread more)

Jan Beich <jbeich@FreeBSD.org> writes:

> Neither supports non-x86 architectures[1] on FreeBSD. Even on x86 both
> are incomplete compared to "cc -march=native -v" e.g., cpuid2cpuflags
> lacks avx512bf16 while hs-cputype doesn't support avx512 at all.
>
> [1] Here're various ways to detect CPU features:
>
> aarch64:
> - READ_SPECIALREG(id_aa64isar0)

Typo: READ_SPECIALREG(id_aa64isar0_el1)

> - elf_aux_info: AT_HWCAP (on FreeBSD 13+)
>
> armv6 and armv7:
> - sysctl(KERN_PROC_AUXV): AT_HWCAP + AT_HWCAP2
> - elf_aux_info: AT_HWCAP + AT_HWCAP2 (on FreeBSD 12+)
>
> powerpc and powerpc64:
> - sysctlbyname: kern.cpu_features + kern.cpu_features2

Typo: kern. -> hw.

There's also hw.altivec as useful as hw.instruction_sse ;)

> - elf_aux_info: AT_HWCAP + AT_HWCAP2 (on FreeBSD 12+)
>
> riscv64:
> - elf_aux_info: AT_HWCAP (on FreeBSD 13+)

In the ports tree there're many examples checking a particular feature
(e.g., AES, NEON, ALTIVEC) but none try to list everything supported.