From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Cédric Le Goater" <clg@kaod.org>,
"David Gibson" <david@gibson.dropbear.id.au>
Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org,
Alexander Graf <agraf@suse.de>
Subject: Re: [Qemu-devel] [PATCH v2 4/7] ppc/pnv: add a core mask to PnvChip
Date: Mon, 05 Sep 2016 21:30:10 +1000 [thread overview]
Message-ID: <1473075010.2313.48.camel@kernel.crashing.org> (raw)
In-Reply-To: <6d21432e-6752-4b5b-6bcc-f027eb5944c7@kaod.org>
On Mon, 2016-09-05 at 13:13 +0200, Cédric Le Goater wrote:
> > Is it worth having this cores_max field, since AFAICT you can
> > calculate it as hweight(~cores_mask)?
>
> Sure. I looked for it and missed it.
>
> Here is a slightly improved version from Brian Kernighan :
>
> unsigned int v; // count the number of bits set in v
> unsigned int c; // c accumulates the total bits set in v
>
> for (c = 0; v; c++)
> {
> v &= v - 1; // clear the least significant bit set
> }
Use the accessor (ie, hweight). The compiler might turn it into a
popcnt instruction of some sort if the CPU has one :-)
Ben.
next prev parent reply other threads:[~2016-09-05 11:30 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-31 16:34 [Qemu-devel] [PATCH v2 0/7] ppc/pnv: add a minimal platform Cédric Le Goater
2016-08-31 16:34 ` [Qemu-devel] [PATCH v2 1/7] ppc/pnv: add skeleton PowerNV platform Cédric Le Goater
2016-09-01 16:31 ` [Qemu-devel] [Qemu-ppc] " Greg Kurz
2016-09-02 6:32 ` Cédric Le Goater
2016-09-02 6:39 ` Benjamin Herrenschmidt
2016-09-05 2:48 ` [Qemu-devel] " David Gibson
2016-09-05 6:06 ` Cédric Le Goater
2016-08-31 16:34 ` [Qemu-devel] [PATCH v2 2/7] ppc/pnv: add a PnvChip object Cédric Le Goater
2016-09-01 17:21 ` [Qemu-devel] [Qemu-ppc] " Greg Kurz
2016-09-02 6:34 ` Cédric Le Goater
2016-09-05 2:58 ` [Qemu-devel] " David Gibson
2016-09-05 6:59 ` Benjamin Herrenschmidt
2016-09-05 7:41 ` Cédric Le Goater
2016-09-05 8:28 ` Benjamin Herrenschmidt
2016-09-06 0:49 ` David Gibson
2016-09-06 6:21 ` Cédric Le Goater
2016-09-05 7:41 ` David Gibson
2016-09-05 9:10 ` Cédric Le Goater
2016-09-06 0:50 ` David Gibson
2016-09-05 7:56 ` Cédric Le Goater
2016-09-06 0:52 ` David Gibson
2016-08-31 16:34 ` [Qemu-devel] [PATCH v2 3/7] ppc/pnv: Add XSCOM infrastructure Cédric Le Goater
2016-09-05 3:39 ` David Gibson
2016-09-05 7:11 ` Benjamin Herrenschmidt
2016-09-06 0:48 ` David Gibson
2016-09-06 14:42 ` Cédric Le Goater
2016-09-06 21:47 ` Benjamin Herrenschmidt
2016-09-06 21:49 ` Benjamin Herrenschmidt
2016-09-07 15:55 ` Cédric Le Goater
2016-09-07 19:48 ` Benjamin Herrenschmidt
2016-09-07 2:03 ` David Gibson
2016-09-07 15:47 ` Cédric Le Goater
2016-09-07 21:53 ` Benjamin Herrenschmidt
2016-09-08 8:52 ` Cédric Le Goater
2016-09-07 2:01 ` David Gibson
2016-09-06 14:42 ` Cédric Le Goater
2016-09-06 21:45 ` Benjamin Herrenschmidt
2016-09-07 2:02 ` David Gibson
2016-09-07 16:40 ` Cédric Le Goater
2016-09-07 1:59 ` David Gibson
2016-09-07 5:27 ` Benjamin Herrenschmidt
2016-09-07 5:46 ` David Gibson
2016-09-07 8:29 ` Benjamin Herrenschmidt
2016-09-05 4:16 ` [Qemu-devel] [Qemu-ppc] " Sam Bobroff
2016-09-06 14:51 ` Cédric Le Goater
2016-08-31 16:34 ` [Qemu-devel] [PATCH v2 4/7] ppc/pnv: add a core mask to PnvChip Cédric Le Goater
2016-09-02 8:03 ` Cédric Le Goater
2016-09-05 3:42 ` David Gibson
2016-09-05 11:13 ` Cédric Le Goater
2016-09-05 11:30 ` Benjamin Herrenschmidt [this message]
2016-08-31 16:34 ` [Qemu-devel] [PATCH v2 5/7] ppc/pnv: add a PnvCore object Cédric Le Goater
2016-09-05 4:02 ` David Gibson
2016-09-06 6:14 ` Cédric Le Goater
2016-09-07 1:48 ` David Gibson
2016-08-31 16:34 ` [Qemu-devel] [PATCH v2 6/7] ppc/pnv: add a XScomDevice to PnvCore Cédric Le Goater
2016-09-05 4:19 ` David Gibson
2016-09-06 13:54 ` Cédric Le Goater
2016-09-07 1:51 ` David Gibson
2016-08-31 16:34 ` [Qemu-devel] [PATCH v2 7/7] monitor: fix crash for platforms without a CPU 0 Cédric Le Goater
2016-09-05 4:27 ` David Gibson
2016-09-06 6:28 ` Cédric Le Goater
2016-09-07 1:49 ` David Gibson
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