From: Andrei Gherzan <andrei@gherzan.ro>
To: Khem Raj <raj.khem@gmail.com>
Cc: yocto@yoctoproject.org, Andrei Gherzan <andrei@resin.io>
Subject: Re: [meta-raspberrypi][PATCH 2/2] x264: Fix build for armv6 RaspberryPi boards
Date: Mon, 17 Apr 2017 03:09:20 +0100 [thread overview]
Message-ID: <20170417020920.GL16624@carbonA> (raw)
In-Reply-To: <CAMKF1srqpcaGHKCgZW=Dqx+obGvFdc5qmke04x6sOynGRb6PsQ@mail.gmail.com>
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On Mon, Apr 17, 2017 at 02:00:20AM +0000, Khem Raj wrote:
> On Sun, Apr 16, 2017 at 6:14 PM Andrei Gherzan <andrei@resin.io> wrote:
>
> > quant-a.S uses rbit thumb instruction unconditionally even though only
> > from ARMV6T2 this is available (which is not the case for RPI1, RPI0
> > etc). Avoid this by disabling asm.
>
>
> It would be bette to control it in component's own build system how much do
> we lose in performance if any do you know
>
I haven't tested myself but I know people who did and reported a 10%
performance hit.
Now I see two more options - other than this one:
1. Deactivate in configure ASM if not HAVE_ARMV6T2 - don't see any
fuctional difference
2. emulate rbit if not HAVE_ARMV6T2 - do you have any ideas on how to do
this? I'd like this solution as rbit is the only instruction failing so
we could take advantage of the other optimisations.
PS: in the meanwhile i merged it to unblock the builds.
--
Andrei Gherzan
gpg: rsa4096/D4D94F67AD0E9640 | t: @agherzan
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next prev parent reply other threads:[~2017-04-17 2:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-17 1:12 [meta-raspberrypi][PATCH 1/2] omxplayer: Bump to head and fix missing native dependency Andrei Gherzan
2017-04-17 1:12 ` [meta-raspberrypi][PATCH 2/2] x264: Fix build for armv6 RaspberryPi boards Andrei Gherzan
2017-04-17 2:00 ` Khem Raj
2017-04-17 2:09 ` Andrei Gherzan [this message]
2017-04-17 1:27 ` [meta-raspberrypi][PATCH 1/2] omxplayer: Bump to head and fix missing native dependency Andrei Gherzan
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