From: Christoffer Dall <christoffer.dall@linaro.org>
To: Andrew Jones <drjones@redhat.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, gleb@redhat.com
Subject: Re: [PATCH 7/9] arm: replace arbitrary divisions
Date: Thu, 17 Oct 2013 11:59:26 -0700 [thread overview]
Message-ID: <20131017185926.GR24837@cbox> (raw)
In-Reply-To: <20131017100322.GC2172@hawk.usersys.redhat.com>
On Thu, Oct 17, 2013 at 12:03:23PM +0200, Andrew Jones wrote:
> On Wed, Oct 16, 2013 at 06:06:29PM -0700, Christoffer Dall wrote:
> > On Mon, Oct 14, 2013 at 06:23:33PM +0200, Andrew Jones wrote:
> > > arm can't do arbitrary divisions without software support. Usually
> > > libgcc would jump in here, but depending on the toolchain used that may
> > > or may not work. Luckily, we only care about two types of divisions.
> > > Divide by 10 and divide by 16. Divide by 16 is already covered by gcc
> > > since it's a power of two. Divide by 10 can be hacked up using a
> > > multiplication and shift.
> >
> > Isn't this just a matter of supplying a few libc implementations to
> > handle div_by_0 and that sort? I'm pretty sure we had that working in
> > the kvm-selftest for ARM thingy that allowed you to use the standard '/'
> > operator in C code.... I suspect there will be more users of this
> > eventually.
> >
> > Or wait, do you mean 'long long' operations by arbitrary? In that case,
> > I'm less sure... A library implementation to support the operator would
> > still be preferred IMHO.
>
> No, that's not what I meant, nor can I pretend that's what I meant now :-)
> I saw that you had brought lib1funcs.S into kvm-selftest, but I'm not sure
> why I rejected doing the same thing... Probably because my reflex was to
> not adopt a bunch of assembler that I didn't want to maintain. But I guess
> there's nothing to maintain there. It works, and will always work. I'll
> switch to using it.
>
I think so, and I'll gladly help you maintain those bits.
-Christoffer
next prev parent reply other threads:[~2013-10-17 18:58 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-14 16:23 [PATCH 0/9] kvm-unit-tests/arm: initial drop Andrew Jones
2013-10-14 16:23 ` [PATCH 1/9] remove unused files Andrew Jones
2013-10-16 12:52 ` Gleb Natapov
2013-10-16 13:13 ` Alexander Graf
2013-10-16 13:18 ` Andrew Jones
2013-10-14 16:23 ` [PATCH 2/9] makefile and run_tests tweaks Andrew Jones
2013-10-14 16:23 ` [PATCH 3/9] clean root dir of all x86-ness Andrew Jones
2013-10-17 1:06 ` Christoffer Dall
2013-10-17 9:35 ` Andrew Jones
2013-10-17 19:01 ` Christoffer Dall
2013-10-20 16:37 ` Andrew Jones
2013-10-14 16:23 ` [PATCH 4/9] Introduce a simple iomap structure Andrew Jones
2013-10-14 16:23 ` [PATCH 5/9] Add halt() and some error codes Andrew Jones
2013-10-14 16:23 ` [PATCH 6/9] Introduce virtio-testdev Andrew Jones
2013-10-15 8:39 ` Andrew Jones
2013-10-17 1:06 ` Christoffer Dall
2013-10-17 9:51 ` Andrew Jones
2013-10-17 19:01 ` Christoffer Dall
2013-10-17 1:06 ` Christoffer Dall
2013-10-14 16:23 ` [PATCH 7/9] arm: replace arbitrary divisions Andrew Jones
2013-10-17 1:06 ` Christoffer Dall
2013-10-17 10:03 ` Andrew Jones
2013-10-17 18:59 ` Christoffer Dall [this message]
2013-10-14 16:23 ` [PATCH 8/9] arm: initial drop Andrew Jones
2013-10-17 1:06 ` Christoffer Dall
2013-10-17 10:16 ` Andrew Jones
2013-10-17 13:28 ` Andrew Jones
2013-10-17 18:39 ` Christoffer Dall
2013-10-14 16:23 ` [PATCH 9/9] arm: add vectors support Andrew Jones
2013-10-17 1:06 ` Christoffer Dall
2013-10-17 10:38 ` Andrew Jones
2013-10-17 18:58 ` Christoffer Dall
2013-10-20 16:35 ` Andrew Jones
2013-10-21 9:59 ` Christoffer Dall
2013-11-20 23:06 ` [PATCH 0/9] kvm-unit-tests/arm: initial drop María Soler Heredia
2013-11-26 17:23 ` Andrew Jones
2013-12-29 9:24 ` Christoffer Dall
2014-01-02 18:56 ` Andrew Jones
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