From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/10810 Path: news.gmane.org!.POSTED!not-for-mail From: u-uy74@aetey.se Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] use lookup table for malloc bin index instead of float conversion Date: Sat, 17 Dec 2016 08:36:00 +0100 Message-ID: <20161217073600.GZ18078@example.net> References: <20161127141541.GZ5749@port70.net> <20161217055058.GG1555@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1481960209 2212 195.159.176.226 (17 Dec 2016 07:36:49 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 17 Dec 2016 07:36:49 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-10823-gllmg-musl=m.gmane.org@lists.openwall.com Sat Dec 17 08:36:44 2016 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1cI9Xw-0007uX-2S for gllmg-musl@m.gmane.org; Sat, 17 Dec 2016 08:36:44 +0100 Original-Received: (qmail 26388 invoked by uid 550); 17 Dec 2016 07:36:46 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 26370 invoked from network); 17 Dec 2016 07:36:46 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=fripost.org; h= in-reply-to:content-disposition:content-type:content-type :mime-version:references:message-id:subject:subject:from:from :date:date; s=20140703; t=1481960195; x=1483774596; bh=ud505Zmql CAqN3A1CIMU/3d2Uft8WT183+aRFlIz86k=; b=Gcw0h8UnKURze2oqkWhKqnLtS 3EfnqgZa56V+hazXbo2U5cR8Tl1Iw8q/F/OCo5aaaJuXA5QsESF5nHd4P5K30EgF d2co56pX+X+2TsdJwXa8IylewPZpE8oPGOoXFHjpNARkg5Rdcsb11kVnn1CrX/ro BTA6D+GvV+s8oyAajo= X-Virus-Scanned: Debian amavisd-new at fripost.org Content-Disposition: inline In-Reply-To: <20161217055058.GG1555@brightrain.aerifal.cx> Xref: news.gmane.org gmane.linux.lib.musl.general:10810 Archived-At: On Sat, Dec 17, 2016 at 12:50:58AM -0500, Rich Felker wrote: > On Sun, Nov 27, 2016 at 03:15:41PM +0100, Szabolcs Nagy wrote: > > +static const unsigned char bin_tab[64] = { > > + 0, 0, 0, 0,32,33,34,35,36,36,37,37,38,38,39,39, > > + 40,40,40,40,41,41,41,41,42,42,42,42,43,43,43,43, > > + 44,44,44,44,44,44,44,44,45,45,45,45,45,45,45,45, > > + 46,46,46,46,46,46,46,46,47,47,47,47,47,47,47,47, > > +}; > > + > > static int bin_index(size_t x) > > { > > x = x / SIZE_ALIGN - 1; > > if (x <= 32) return x; > > + if (x < 512) return bin_tab[x/8]; > > if (x > 0x1c00) return 63; > > - return ((union { float v; uint32_t r; }){(int)x}.r>>21) - 496; > > + return bin_tab[x/128] + 16; > > } > > > > static int bin_index_up(size_t x) > > { > > x = x / SIZE_ALIGN - 1; > > if (x <= 32) return x; > > - return ((union { float v; uint32_t r; }){(int)x}.r+0x1fffff>>21) - 496; > > + x--; > > + if (x < 512) return bin_tab[x/8] + 1; > > + return bin_tab[x/128] + 17; > > } > > > > #if 0 > > -- > > 2.10.2 > Looks good mostly, but wouldn't it be better to drop the 4 unused > entries from the table and add -4's to the indices? Wouldn't this enlarge the code more than reduce the data? Rune