From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: Evandro Menezes <e.menezes@samsung.com>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>, nd <nd@arm.com>
Subject: Re: [AArch64] Emit square root using the Newton series
Date: Fri, 11 Mar 2016 01:06:00 -0000 [thread overview]
Message-ID: <AM3PR08MB0088E16F5745DA0E7D463D2183B50@AM3PR08MB0088.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <56E1F1FB.6070405@samsung.com>
Evandro Menezes <e.menezes@samsung.com> wrote:
>
> That's what I had in mind too, but around the approximation for x^-1/2
> and using masks for vector cases thusly:
>
> fcmne v3.4s, v0.4s, #0.0
> frsqrte v1.4s, v0.4s
> fmul v2.4s, v1.4s, v1.4s
> frsqrts v2.4s, v0.4s, v2.4s
> fmul v1.4s, v1.4s, v2.4s
> fmul v2.4s, v1.4s, v1.4s
> frsqrts v2.4s, v0.4s, v2.4s
> fmul v1.4s, v1.4s, v2.4s
> and v1.4s, v3.4s
> fmul v0.4s, v1.4s, v0.4s
That's possible but the overall latency is higher - according to exynos-1.md the
above takes 44 cycles while my version would be 37.
Wilco
next prev parent reply other threads:[~2016-03-11 1:06 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <AM3PR08MB00886499882773F3C8B9F71D83B30@AM3PR08MB0088.eurprd08.prod.outlook.com>
[not found] ` <011d01d17a26$31b3ade0$951b09a0$@samsung.com>
2016-03-10 16:52 ` Wilco Dijkstra
2016-03-10 16:58 ` Evandro Menezes
2016-03-10 19:10 ` Wilco Dijkstra
2016-03-10 22:15 ` Evandro Menezes
2016-03-11 1:06 ` Wilco Dijkstra [this message]
2016-03-14 16:39 ` Evandro Menezes
2016-03-14 19:13 ` Wilco Dijkstra
2016-03-16 21:44 ` Evandro Menezes
2016-03-17 22:50 Evandro Menezes
2016-03-24 20:30 ` [AArch64] " Evandro Menezes
2016-04-01 22:45 ` Evandro Menezes
2016-04-04 16:32 ` Evandro Menezes
[not found] ` <DB3PR08MB008902F0F0AFA3B1F1C91511839E0@DB3PR08MB0089.eurprd08.prod.outlook.com>
2016-04-05 22:30 ` Evandro Menezes
2016-04-12 18:15 ` Evandro Menezes
2016-04-21 18:44 ` Evandro Menezes
2016-04-27 14:24 ` James Greenhalgh
2016-04-27 15:45 ` Evandro Menezes
-- strict thread matches above, loose matches on Subject: below --
2015-12-08 21:35 Evandro Menezes
2015-12-09 14:05 ` Marcus Shawcroft
2015-12-09 16:31 ` Evandro Menezes
2015-12-09 16:52 ` Kyrill Tkachov
2015-12-09 16:59 ` Evandro Menezes
2015-12-09 17:03 ` Kyrill Tkachov
2015-12-09 17:16 ` Kyrill Tkachov
2015-12-09 18:50 ` Evandro Menezes
2015-12-10 10:30 ` Kyrill Tkachov
2016-02-23 0:50 ` Evandro Menezes
2016-02-26 15:00 ` James Greenhalgh
2016-02-26 23:42 ` Evandro Menezes
2016-02-26 23:46 ` Evandro Menezes
2016-02-16 20:56 ` Evandro Menezes
2016-03-04 0:22 ` Evandro Menezes
2016-03-08 22:08 ` Evandro Menezes
2016-03-08 22:18 ` Evandro Menezes
2016-03-08 22:20 ` Evandro Menezes
2016-03-16 19:45 ` Evandro Menezes
2016-03-17 14:55 ` James Greenhalgh
2016-03-17 16:25 ` Evandro Menezes
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