From owner-freebsd-toolchain@freebsd.org  Sat Sep  9 19:25:06 2017
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From: Jan Beich <jbeich@FreeBSD.org>
To: Warner Losh <imp@bsdimp.com>
Cc: Jan Beich <jbeich@vfemail.net>,
 "freebsd-arm\@freebsd.org" <freebsd-arm@freebsd.org>,
 "freebsd-toolchain\@FreeBSD.org" <freebsd-toolchain@freebsd.org>
Subject: Re: FCP-100: armv7 plan
References: <CANCZdfrCwdVOGWunSAjuxHzGcqhuH24iRQg63rvPFXXSmm-C6Q__2138.43810274756$1504912296$gmane$org@mail.gmail.com>
 <ingr-3d62-wny@FreeBSD.org>
 <CANCZdfondSykr1UM0CNTYpVr-6hzyROYn-C_jNC_+hO1r6SB2w@mail.gmail.com>
Date: Sat, 09 Sep 2017 21:25:01 +0200
In-Reply-To: <CANCZdfondSykr1UM0CNTYpVr-6hzyROYn-C_jNC_+hO1r6SB2w@mail.gmail.com>
 (Warner Losh's message of "Sat, 9 Sep 2017 13:14:36 -0600")
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Warner Losh <imp@bsdimp.com> writes:

> On Sat, Sep 9, 2017 at 1:05 PM, Jan Beich <jbeich@vfemail.net> wrote:
>
>> Warner Losh <imp@bsdimp.com> writes:
>>
>> > Greetings,
>> >
>> > This will serve as 'Last Call' for any objections to the plan to create
>> an
>> > armv7 MACHINE_ARCH in FreeBSD, as documented in FCP-0100.
>> [...]
>>
>> Some ports want NEON support but FCP-0100 is vague about FreeBSD-specific
>> differences between armv6 and armv7. Clang appears to enable NEON for all
>> *-gnueabi* targets but I have no clue about GCC. Apparently, Android and
>> Debian don't assume NEON on armv7.
>>
>> related: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221898
>>
>
> Yes. We are vague about it on purpose. Just like we're vague about MMX,
> MMX2, etc on x86 because different processors can/want use different
> things.

Do you mean similar to how FreeBSD i386 is vague about not supporting
real i386, only i486 or later?

> The goal, if it doesn't work already, is for NEON to work if used,
> but not be required, just like all the other optional features of a CPU.

FreeBSD doesn't support detecting NEON at runtime unlike Linux. Do you
mean at compile time? If so then the following probably needs to change

$ cc -target armv7-unknown-freebsd12.0-gnueabihf -dM -E -</dev/null |& fgrep -i neon
#define __ARM_NEON 1
#define __ARM_NEON_FP 0x4
#define __ARM_NEON__ 1