From: Andrew Jones <drjones@redhat.com>
To: Christoffer Dall <christoffer.dall@linaro.org>
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 12:03:23 +0200 [thread overview]
Message-ID: <20131017100322.GC2172@hawk.usersys.redhat.com> (raw)
In-Reply-To: <20131017010629.GJ24837@cbox>
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.
drew
next prev parent reply other threads:[~2013-10-17 10:03 UTC|newest]
Thread overview: 39+ 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 13:13 ` 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 [this message]
2013-10-17 18:59 ` Christoffer Dall
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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