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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).