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From: BALATON Zoltan <balaton@eik.bme.hu>
To: qemu-devel@nongnu.org
Cc: John Arbuckle <programmingkidx@gmail.com>,
	David Gibson <david@gibson.dropbear.id.au>,
	qemu-ppc@nongnu.org, Paul Clarke <pc@us.ibm.com>,
	Howard Spoelstra <hsp.cat7@gmail.com>
Subject: Re: [RFC PATCH v2] target/ppc: Enable hardfloat for PPC
Date: Tue, 18 Feb 2020 18:38:20 +0100 (CET)	[thread overview]
Message-ID: <alpine.BSF.2.22.395.2002181834470.39889@zero.eik.bme.hu> (raw)
In-Reply-To: <20200218171702.979F074637D@zero.eik.bme.hu>

On Tue, 18 Feb 2020, BALATON Zoltan wrote:
> While other targets take advantage of using host FPU to do floating
> point computations, this was disabled for PPC target because always
> clearing exception flags before every FP op made it slightly slower
> than emulating everyting with softfloat. To emulate some FPSCR bits,
> clearing of fp_status may be necessary (unless these could be handled
> e.g. using FP exceptions on host but there's no API for that in QEMU
> yet) but preserving at least the inexact flag makes hardfloat usable
> and faster than softfloat. Since most clients don't actually care
> about this flag, we can gain some speed trading some emulation
> accuracy.
>
> This patch implements a simple way to keep the inexact flag set for
> hardfloat while still allowing to revert to softfloat for workloads
> that need more accurate albeit slower emulation. (Set hardfloat
> property of CPU, i.e. -cpu name,hardfloat=false for that.) There may
> still be room for further improvement but this seems to increase
> floating point performance. Unfortunately the softfloat case is slower
> than before this patch so this patch only makes sense if the default
> is also set to enable hardfloat.
>
> Because of the above this patch at the moment is mainly for testing
> different workloads to evaluate how viable would this be in practice.
> Thus, RFC and not ready for merge yet.
>
> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> ---

Forgot to say, in case that's not clear that this should currently apply 
to David's ppc-for-5.0 branch because there are some clean up patches from 
me queued there so until those reach master this patch may not apply 
cleanly. Just in case someone wanted to try it and get errors.

Regards,
BALATON Zoltan


  reply	other threads:[~2020-02-18 17:39 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-18 17:10 [RFC PATCH v2] target/ppc: Enable hardfloat for PPC BALATON Zoltan
2020-02-18 17:38 ` BALATON Zoltan [this message]
2020-02-19  2:27 ` Programmingkid
2020-02-19 15:35   ` BALATON Zoltan
2020-02-19 18:28     ` Howard Spoelstra
2020-02-19 19:28       ` BALATON Zoltan
2020-02-20  5:43         ` Howard Spoelstra
2020-02-25  3:07     ` Programmingkid
2020-02-25 12:09       ` BALATON Zoltan
2020-02-26 10:46         ` Programmingkid
2020-02-26 11:28           ` BALATON Zoltan
2020-02-26 13:00             ` R: " luigi burdo
2020-02-26 13:08               ` Dino Papararo
2020-02-26 14:28                 ` Alex Bennée
2020-02-26 15:50                   ` Aleksandar Markovic
2020-02-26 17:04                     ` G 3
2020-02-26 17:27                       ` Aleksandar Markovic
2020-02-26 18:14                         ` R: " Dino Papararo
2020-02-26 18:51                           ` Aleksandar Markovic
2020-02-27  2:43                         ` Programmingkid
2020-02-27  7:16                           ` Aleksandar Markovic
2020-02-27 11:54                             ` BALATON Zoltan
2020-02-26 18:09                       ` R: " Alex Bennée
2020-03-02  0:13                         ` Programmingkid
2020-03-02  4:28                           ` Richard Henderson
2020-03-02 11:42                             ` BALATON Zoltan
2020-03-02 16:55                               ` Richard Henderson
2020-03-02 23:16                                 ` BALATON Zoltan
2020-03-03  0:11                                   ` Richard Henderson
     [not found]                                   ` <CAKyx-3Pt2qLPXWQjBwrHn-nxR-9e++TioGp4cKFC3adMN3rtiw@mail.gmail.com>
2020-03-04 18:43                                     ` Fwd: " G 3
2020-03-05 19:25                                       ` Richard Henderson
2020-03-02 17:10                               ` Alex Bennée
2020-03-02 23:01                                 ` BALATON Zoltan
2020-02-26 22:51                   ` R: " BALATON Zoltan
2020-02-20 20:13 ` Richard Henderson
2020-02-21 16:04   ` BALATON Zoltan
2020-02-21 16:11     ` Peter Maydell
2020-02-21 16:51       ` Aleksandar Markovic
2020-02-21 18:04       ` BALATON Zoltan
2020-02-21 18:26         ` Peter Maydell
2020-02-21 19:52           ` BALATON Zoltan
2020-02-26 12:28             ` Alex Bennée
2020-02-26 13:07               ` BALATON Zoltan
2020-04-10 13:50 ` 罗勇刚(Yonggang Luo)
2020-04-10 18:04   ` BALATON Zoltan

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