From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26107 invoked by alias); 21 Dec 2018 17:59:58 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 26058 invoked by uid 89); 21 Dec 2018 17:59:57 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-0.9 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY autolearn=no version=3.3.2 spammy=xn, MAX_EXPR, 08AM, max_expr X-HELO: troutmask.apl.washington.edu Received: from troutmask.apl.washington.edu (HELO troutmask.apl.washington.edu) (128.95.76.21) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Fri, 21 Dec 2018 17:59:55 +0000 Received: from troutmask.apl.washington.edu (localhost [127.0.0.1]) by troutmask.apl.washington.edu (8.15.2/8.15.2) with ESMTPS id wBLHxrlC004022 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Fri, 21 Dec 2018 09:59:53 -0800 (PST) (envelope-from sgk@troutmask.apl.washington.edu) Received: (from sgk@localhost) by troutmask.apl.washington.edu (8.15.2/8.15.2/Submit) id wBLHxr1w004021; Fri, 21 Dec 2018 09:59:53 -0800 (PST) (envelope-from sgk) Date: Fri, 21 Dec 2018 17:59:00 -0000 From: Steve Kargl To: Janne Blomqvist Cc: Fortran List , GCC Patches Subject: Re: [PATCH] fortran/69121 -- Make IEEE_SCALB generic Message-ID: <20181221175953.GA3659@troutmask.apl.washington.edu> Reply-To: sgk@troutmask.apl.washington.edu References: <20181220214739.GA86993@troutmask.apl.washington.edu> <20181221062240.GA99794@troutmask.apl.washington.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-SW-Source: 2018-12/txt/msg01591.txt.bz2 On Fri, Dec 21, 2018 at 11:07:08AM +0200, Janne Blomqvist wrote: > On Fri, Dec 21, 2018 at 8:22 AM Steve Kargl < > sgk@troutmask.apl.washington.edu> wrote: > > > On Thu, Dec 20, 2018 at 01:47:39PM -0800, Steve Kargl wrote: > > > The attached patch has been tested on x86_64-*-freebsd. > > > > > > OK to commit? > > > > > > 2018-12-20 Steven G. Kargl > > > > > > PR fortran/69121 > > > * libgfortran/ieee/ieee_arithmetic.F90: Provide missing functions > > > in interface for IEEE_SCALB. > > > > > > 2018-12-20 Steven G. Kargl > > > > > > PR fortran/69121 > > > * gfortran.dg/ieee/ieee_9.f90: New test. > > > > Now, tested on i586-*-freebsd. > > > > Hi, looks ok for trunk. > > A few questions popped into my mind while looking into this: > > 1) Why are none of the _gfortran_ieee_scalb_X_Y functions mentioned in > gfortran.map? I guess they should all be there? > > 2) Currently all the intrinsics map to the scalbn{,f,l} builtins. However, > when the integer argument is of kind int64 or int128 we should instead use > scalbln{,f,l}. This also applies to other intrinsics that use scalbn under > the hood. > > To clarify, fixing these is not a prerequisite for accepting the patch (I > already accepted it), but more like topics for further work. > I forgot to address your had a 2) item above. ieee_scalb appears to do the right thing. FX addressed that with his implementation. The 2nd argument is always cast to integer after reducing the range to that of integer(4). The binary floating point representation for a REAL(16) finite number is x=f*2**e with f in [0.5,1) and e in [-16059,16384]. scalb(x,n) is x*2**n, which becomes f*2**e*2**n = f*2**(e+n). If x is the smallest positive subnormal number, then n can be at most 32443 to still return a finite REAL(16) number. Any larger value overflows to infinity. If x is the largest positive finite number, then n can be -32443 to return the small positive subnormal number. Any more negative value of n underflows to zero. (Note, I could be off-by-one, but that is just a detail.) Consider function foo(x,i) use ieee_arithmetic real(16) foo, c integer(8) i print *, ieee_scalb(c, i) end function foo -fdump-tree-original gives D.3853 = *i; __result_foo = scalbnq (c, (integer(kind=4)) MAX_EXPR , -2147483647>); The range [-32443,32443] is a subset of [-huge(),huge(0)]. -- Steve