From: Richard Henderson <rth@twiddle.net>
To: David Gibson <david@gibson.dropbear.id.au>,
Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, bharata@linux.vnet.ibm.com
Subject: Re: [Qemu-devel] [PATCH v1] target/ppc: rewrite f[n]m[add, sub] using float64_muladd
Date: Thu, 2 Mar 2017 13:22:05 +1100 [thread overview]
Message-ID: <32926f1f-ec40-420f-210b-8f5991cc9d67@twiddle.net> (raw)
In-Reply-To: <20170302002933.GL12571@umbus.fritz.box>
On 03/02/2017 11:29 AM, David Gibson wrote:
> On Wed, Mar 01, 2017 at 08:54:14PM +0530, Nikunj A Dadhania wrote:
>> Use the softfloat api for fused multiply-add. Also, generate VXISI using
>> a helper function by computing intermediate result.
>
> Um.. I really need some information on why this is a good thing to
> do. Is it a bugfix? Enhancement? Simplification?
Looks like a bugfix to me. Previously we were attempting the operation via
float128 as an intermediate type, which can result in double rounding errors.
r~
next prev parent reply other threads:[~2017-03-02 2:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-01 15:24 [Qemu-devel] [PATCH v1] target/ppc: rewrite f[n]m[add, sub] using float64_muladd Nikunj A Dadhania
2017-03-02 0:29 ` David Gibson
2017-03-02 2:22 ` Richard Henderson [this message]
2017-03-02 4:08 ` [Qemu-devel] [Qemu-ppc] " Nikunj Dadhania
2017-03-02 5:03 ` Nikunj A Dadhania
2017-03-02 2:36 ` [Qemu-devel] " Richard Henderson
2017-03-02 4:14 ` [Qemu-devel] [Qemu-ppc] " Nikunj Dadhania
2017-03-02 5:04 ` Nikunj A Dadhania
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