From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756203Ab2IXOyB (ORCPT ); Mon, 24 Sep 2012 10:54:01 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:50421 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753963Ab2IXOx6 (ORCPT ); Mon, 24 Sep 2012 10:53:58 -0400 From: Michal Nazarewicz To: George Spelvin , akpm@linux-foundation.org, linux@horizon.com, rabin@rab.in Cc: hughd@google.com, linux-kernel@vger.kernel.org, vda.linux@googlemail.com Subject: Re: [PATCH 3/4] lib: vsprintf: Optimize put_dec_trunc8 In-Reply-To: <20120924143305.30771.qmail@science.horizon.com> Organization: Google Inc References: <20120924143305.30771.qmail@science.horizon.com> User-Agent: Notmuch/0.14+22~g8bdc16b (http://notmuchmail.org) Emacs/24.2.50.1 (x86_64-unknown-linux-gnu) X-Face: PbkBB1w#)bOqd`iCe"Ds{e+!C7`pkC9a|f)Qo^BMQvy\q5x3?vDQJeN(DS?|-^$uMti[3D*#^_Ts"pU$jBQLq~Ud6iNwAw_r_o_4]|JO?]}P_}Nc&"p#D(ZgUb4uCNPe7~a[DbPG0T~!&c.y$Ur,=N4RT>]dNpd;KFrfMCylc}gc??'U2j,!8%xdD Face: 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 X-PGP: 50751FF4 X-PGP-FP: AC1F 5F5C D418 88F8 CC84 5858 2060 4012 5075 1FF4 Date: Mon, 24 Sep 2012 16:53:48 +0200 Message-ID: MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="=-=-=" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Mon, Sep 24 2012, George Spelvin wrote: > The fix is straightforward: > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index e755083..9872855 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -180,8 +180,6 @@ char *put_dec_trunc8(char *buf, unsigned r) > *buf++ =3D q - 10*r; > } >=20=20 > - if (r =3D=3D 0) > - return buf; > q =3D (r * 0x199a) >> 16; /* r <=3D 9999 */ > *buf++ =3D (r - 10 * q) + '0'; > if (q =3D=3D 0) > > Inspired by Michal Nazarewicz, I have some ideas for more tweaking to > that code. Ah, right. I also thought about that first but than started worrying that it could produce unnecessary zeros if the loop iterates at least once and exits with r being zero, but now I see that this cannot happen since if the loop condition was true, r >=3D 10000 and it has been divided by 10000 in the loop so now it's at least 1. --=20 Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=3D./ `o ..o | Computer Science, Micha=C5=82 =E2=80=9Cmina86=E2=80=9D Nazarewicz = (o o) ooo +------------------ooO--(_)--Ooo-- --=-=-= Content-Type: multipart/signed; boundary="==-=-="; micalg=pgp-sha1; protocol="application/pgp-signature" --==-=-= Content-Type: text/plain --==-=-= Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQIcBAEBAgAGBQJQYHP8AAoJECBgQBJQdR/0GlgP/320ld1YFw5iBWuMXCwo6QUn CWfCyeTtzlali8PvSaJvjAuBWqe3Nck80W8QBekA6GINuhrzezqvh6vBqlbOsTRc Ijo/6ZBsF5Q1tnoV5yordVQ74dRuFLjUvJbKLsuIVSKlfF45WvTszbEC3IRqcZzi wlu0Ialp+EOQ9KR/diIKs989mfiFXD3jgnKN9nYxPfl8/3DfHGcrDqB44GdvZlxq XDdveyIremGlUCaPBWikCy08lk4vXefWmYVyyu60i3YJcmBKxmLSFis5HBDnCyoA lzoYmiQFKnJT03Ov5i14pWH+NO+lva4D3NShMqIAkNWbBZUtGVMfu7z/cIrzK65I uWJ0/YmaRlhXrX+DC8ty50OsuX0TCGZVfD0ou1nyfFKJVeThjClmKJdkc7xFxAoR L4v7nXdJBJ8qn5jEZBDa8JzNvX3M4FDOBl2aVybHjp5Ov+uEqx3jEEAJCIkNV2tO TcVrh08TL1Hqoav/UDPxwU0JkoxDHCApZ2sn1VKFSjy/3A+wyny7vmNoNoKcdGp5 uAqzMspUcEtKzTwZ8FoBcQp4yNiaTlAGmKCRDkg+J8KJynFVEVlInnAJYZ1B1O2Z aiuCRz/KoL54ECIQvxjQ09g4WBbR890a/b+DGU6uz1IZyqmE6Tr+KZU1r9DjrQOR 0FYUIaj9MzgDD2MQIy3a =qtix -----END PGP SIGNATURE----- --==-=-=-- --=-=-=--