code review 7286044: cmd/dist: support for NetBSD/ARM

cmd/dist: support for NetBSD/ARM
1. when executing a unsupported VFP instruction, the NetBSD kernel somehow
doesn't report SIGILL, and instead just spin and spin, we add a alarm(2)
to detect this case (albeit this is a kernel bug).
2. NetBSD/ARM's VFP11 support is not complete, so temporarily disable it.
3. The default gcc shipped with NetBSD-current mis-optimizes our code
at -O2, so lower the optimization level to -O1 on NetBSD/ARM.

[dave_cheney.net, 2013-02-03 23:55:42]

Not tested, but SGTM. Please consider adding the same exceptions for __FreeBSD__

https://codereview.appspot.com/7286044/diff/2001/src/cmd/dist/arm.c
File src/cmd/dist/arm.c (right):

https://codereview.appspot.com/7286044/diff/2001/src/cmd/dist/arm.c#newcode20
src/cmd/dist/arm.c:20: #ifdef __NetBSD__
Please extend this to FreeBSD as well, there are similar problems with kernel
side VFP support there as well

https://codereview.appspot.com/7286044/diff/2001/src/cmd/dist/build.c
File src/cmd/dist/build.c (right):

https://codereview.appspot.com/7286044/diff/2001/src/cmd/dist/build.c#newcode417
src/cmd/dist/build.c:417: #endif
I think this is fine to submit, we can easily revert it once/when NetBSD patch
their compiler

[rsc, 2013-02-08 20:07:14]

LGTM

[minux1, 2013-03-02 22:50:11]

Hello dave@cheney.net, rsc@golang.org (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go/

[minux1, 2013-03-02 22:50:30]

*** Submitted as https://code.google.com/p/go/source/detail?r=c1c2750f9aba ***

cmd/dist: support for NetBSD/ARM
1. when executing a unsupported VFP instruction, the NetBSD kernel somehow
doesn't report SIGILL, and instead just spin and spin, we add a alarm(2)
to detect this case (albeit this is a kernel bug).
2. NetBSD/ARM's VFP11 support is not complete, so temporarily disable it.
3. The default gcc shipped with NetBSD-current mis-optimizes our code
at -O2, so lower the optimization level to -O1 on NetBSD/ARM.

R=dave, rsc
CC=golang-dev
https://codereview.appspot.com/7286044

[dave_cheney.net, 2013-03-02 23:00:21]

LGTM. Untested, but I'm sure you have tested it. 

On 03/03/2013, at 9:50, minux.ma@gmail.com wrote:

> +    // FreeBSD also have broken VFP support, so disable VFP also
> +    // on FreeBSD.

// VFPv2 support is currently broken on FreeBSD, so disable all VFP on FreeBSD.


I have heard that it is just the kernel support for v2, aka RPi, v3 is reported
to work but images for beaglebones and pandaboards are hard to come by and
unstable. 

[minux1, 2013-03-02 23:02:32]

On Sun, Mar 3, 2013 at 6:59 AM, Dave Cheney <dave@cheney.net> wrote:

> LGTM. Untested, but I'm sure you have tested it.
>
the new qemu builder actually supports VFPv1 (GOARM=6).
but for RPI, we stil have to use soft FP, sadly.

>
> On 03/03/2013, at 9:50, minux.ma@gmail.com wrote:
>
> > +    // FreeBSD also have broken VFP support, so disable VFP also
> > +    // on FreeBSD.
>
> // VFPv2 support is currently broken on FreeBSD, so disable all VFP on
> FreeBSD.
>
> I have heard that it is just the kernel support for v2, aka RPi, v3 is
> reported to work but images for beaglebones and pandaboards are hard to
> come by and unstable.

Does GOARM=6 work for FreeBSD on RPI?