From owner-freebsd-numerics@FreeBSD.ORG Sun Aug 12 23:00:13 2012 Return-Path: Delivered-To: freebsd-numerics@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2DB5F106566C for ; Sun, 12 Aug 2012 23:00:13 +0000 (UTC) (envelope-from peter@rulingia.com) Received: from vps.rulingia.com (host-122-100-2-194.octopus.com.au [122.100.2.194]) by mx1.freebsd.org (Postfix) with ESMTP id BABFA8FC0A for ; Sun, 12 Aug 2012 23:00:10 +0000 (UTC) Received: from server.rulingia.com (c220-239-249-137.belrs5.nsw.optusnet.com.au [220.239.249.137]) by vps.rulingia.com (8.14.5/8.14.5) with ESMTP id q7CN0AKb075562 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 13 Aug 2012 09:00:10 +1000 (EST) (envelope-from peter@rulingia.com) X-Bogosity: Ham, spamicity=0.000000 Received: from server.rulingia.com (localhost.rulingia.com [127.0.0.1]) by server.rulingia.com (8.14.5/8.14.5) with ESMTP id q7CN04kk021016 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 13 Aug 2012 09:00:04 +1000 (EST) (envelope-from peter@server.rulingia.com) Received: (from peter@localhost) by server.rulingia.com (8.14.5/8.14.5/Submit) id q7CN043G021015 for freebsd-numerics@freebsd.org; Mon, 13 Aug 2012 09:00:04 +1000 (EST) (envelope-from peter) Resent-From: Peter Jeremy Resent-Date: Mon, 13 Aug 2012 09:00:04 +1000 Resent-Message-ID: <20120812230004.GQ20453@server.rulingia.com> Resent-To: freebsd-numerics@freebsd.org Received: from vps.rulingia.com (host-122-100-2-194.octopus.com.au [122.100.2.194]) by server.rulingia.com (8.14.5/8.14.5) with ESMTP id q6K6Sl37026185 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 20 Jul 2012 16:28:48 +1000 (EST) (envelope-from brde@optusnet.com.au) Received: from mail35.syd.optusnet.com.au (mail35.syd.optusnet.com.au [211.29.133.51]) by vps.rulingia.com (8.14.5/8.14.5) with ESMTP id q6K6Slip085664 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Fri, 20 Jul 2012 16:28:47 +1000 (EST) (envelope-from brde@optusnet.com.au) Received: from c122-106-171-246.carlnfd1.nsw.optusnet.com.au (c122-106-171-246.carlnfd1.nsw.optusnet.com.au [122.106.171.246]) by mail35.syd.optusnet.com.au (8.13.1/8.13.1) with ESMTP id q6K6SK0h002631 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 20 Jul 2012 16:28:22 +1000 From: Bruce Evans Mail-Followup-To: freebsd-numerics@freebsd.org X-X-Sender: bde@besplex.bde.org To: Steve Kargl In-Reply-To: <20120720043004.GA7404@troutmask.apl.washington.edu> Message-ID: <20120720162633.B2162@besplex.bde.org> References: <20120717040118.GA86840@troutmask.apl.washington.edu> <20120717042125.GF66913@server.rulingia.com> <20120717043848.GB87001@troutmask.apl.washington.edu> <20120717225328.GA86902@server.rulingia.com> <20120717232740.GA95026@troutmask.apl.washington.edu> <20120718001337.GA87817@server.rulingia.com> <20120718123627.D1575@besplex.bde.org> <20120719213944.GA21199@server.rulingia.com> <20120719234425.GA6280@troutmask.apl.washington.edu> <20120720130309.P814@besplex.bde.org> <20120720043004.GA7404@troutmask.apl.washington.edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Mailman-Approved-At: Sun, 12 Aug 2012 23:55:59 +0000 Cc: Diane Bruce , John Baldwin , David Chisnall , Stephen Montgomery-Smith , Bruce Evans , Bruce Evans , David Schultz , Peter Jeremy , Warner Losh Subject: Re: Use of C99 extra long double math functions after r236148 X-BeenThere: freebsd-numerics@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Discussions of high quality implementation of libm functions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Date: Sun, 12 Aug 2012 23:00:13 -0000 X-Original-Date: Fri, 20 Jul 2012 16:28:20 +1000 (EST) X-List-Received-Date: Sun, 12 Aug 2012 23:00:13 -0000 On Thu, 19 Jul 2012, Steve Kargl wrote: > On Fri, Jul 20, 2012 at 02:12:20PM +1000, Bruce Evans wrote: >> On Thu, 19 Jul 2012, Steve Kargl wrote: >> >>> I collected some of the float and double into a cheat sheet. >>> >>> Idioms used in libm with float type: >>> >>> int32_t xsb; >>> u_int32_t hx; >>> >>> GET_FLOAT_WORD(hx, x); >>> >>> /* Get the sign bit of x */ >>> xsb = (hx >> 31) & 1; >> >> Getting it without shifting it (hx & 0x8000) is more efficient and common. >> You don't need to shift it in this example. > > I collected these from msun/src, when I was trying to understand > the magic numbers. I suppose someone should audit the code for > consistency. :-) > > laptop:kargl[219] grep " (hx>>31)&1" *c > e_exp.c: xsb = (hx>>31)&1; /* sign bit of x */ > e_expf.c: xsb = (hx>>31)&1; /* sign bit of x */ The full example of e_exp*.c uses xsb as an index in a table later (not a very good method, but perhaps better than a branch). Bruce