From: Aurelien Jarno <aurelien@aurel32.net>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 1/5] softfloat: fix float{32, 64}_muladd options
Date: Sun, 9 Sep 2012 12:04:45 +0200 [thread overview]
Message-ID: <20120909100445.GR17750@hall.aurel32.net> (raw)
In-Reply-To: <CAFEAcA8LRNWyRyQZ0Rw2zY58Line0xo3iAaxALO7A_6J30GQGg@mail.gmail.com>
On Sun, Sep 09, 2012 at 10:47:52AM +0100, Peter Maydell wrote:
> On 9 September 2012 10:24, Aurelien Jarno <aurelien@aurel32.net> wrote:
> > On Sun, Sep 09, 2012 at 01:40:52AM +0400, Max Filippov wrote:
> >> I've also stumbled upon this bug, have a patch for it in the xtensa tree.
> >> I guess that the interface was designed to allow combining these flags, why
> >> don't just make them independent:
> >
> > My idea was that negating both the product and c is equivalent to
> > negating the result, so there is no need to allow all of them
> > independent.
>
> But at least some of them can reasonably be independent, so
> at that point you might as well make them all independent flags.
>
> In fact my reading of the PPC ISA is that it needs several combinations:
> fmadd : no flags
> fnmadd : negate_result
> fmsub : negate_c
> fnmsub : negate_result | negate_c
>
> ...and it looks like your patch is incorrectly only setting negate_result
> for the fnmsub case. (I can't see anything handling the fnmadd and fmsub
> insns, do we not implement them?)
fnmadd and fmsub are provided as part as floating point instructions
(something else to clean), not as part as altivec instructions.
> (negate_product will be used by x86 and SPARC, among others.)
>
> thanks
> \x10-- PMM
>
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
next prev parent reply other threads:[~2012-09-09 10:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-08 21:12 [Qemu-devel] [PATCH 1/5] softfloat: fix float{32, 64}_muladd options Aurelien Jarno
2012-09-08 21:12 ` [Qemu-devel] [PATCH 2/5] target-ppc: simplify NaN propagation for vector functions Aurelien Jarno
2012-09-08 21:12 ` [Qemu-devel] [PATCH 3/5] target-ppc: use the softfloat min/max functions Aurelien Jarno
2012-09-08 21:12 ` [Qemu-devel] [PATCH 4/5] target-ppc: use the softfloat float32_muladd function Aurelien Jarno
2012-09-09 9:51 ` Peter Maydell
2012-09-09 10:03 ` Aurelien Jarno
2012-09-08 21:12 ` [Qemu-devel] [PATCH 5/5] target-ppc: get rid of the HANDLE_NAN{1, 2, 3} macros Aurelien Jarno
2012-09-08 22:40 ` Peter Maydell
2012-09-08 21:40 ` [Qemu-devel] [PATCH 1/5] softfloat: fix float{32, 64}_muladd options Max Filippov
2012-09-08 22:29 ` Peter Maydell
2012-09-09 9:24 ` Aurelien Jarno
2012-09-09 9:47 ` Peter Maydell
2012-09-09 10:04 ` Aurelien Jarno [this message]
2012-09-09 10:25 ` Peter Maydell
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120909100445.GR17750@hall.aurel32.net \
--to=aurelien@aurel32.net \
--cc=jcmvbkbc@gmail.com \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.