From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29734 invoked by alias); 8 Jan 2013 07:28:17 -0000 Received: (qmail 29724 invoked by uid 22791); 8 Jan 2013 07:28:16 -0000 X-SWARE-Spam-Status: No, hits=-3.6 required=5.0 tests=AWL,BAYES_00,DKIM_ADSP_CUSTOM_MED,DKIM_SIGNED,DKIM_VALID,FREEMAIL_FROM,KHOP_RCVD_TRUST,NML_ADSP_CUSTOM_MED,RCVD_IN_DNSWL_LOW,RCVD_IN_HOSTKARMA_YE X-Spam-Check-By: sourceware.org Received: from mail-we0-f170.google.com (HELO mail-we0-f170.google.com) (74.125.82.170) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 08 Jan 2013 07:28:10 +0000 Received: by mail-we0-f170.google.com with SMTP id r1so67271wey.15 for ; Mon, 07 Jan 2013 23:28:09 -0800 (PST) X-Received: by 10.180.93.133 with SMTP id cu5mr12900414wib.32.1357630089254; Mon, 07 Jan 2013 23:28:09 -0800 (PST) Received: from localhost ([2.26.203.77]) by mx.google.com with ESMTPS id t17sm17153349wiv.6.2013.01.07.23.28.07 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 07 Jan 2013 23:28:08 -0800 (PST) From: Richard Sandiford To: "Maciej W. Rozycki" Mail-Followup-To: "Maciej W. Rozycki" , =?utf-8?Q?J=C3=BCrgen?= Urban , , rdsandiford@googlemail.com Cc: =?utf-8?Q?J=C3=BCrgen?= Urban , Subject: Re: Support for MIPS r5900 References: <20130106225645.190700@gmx.net> <87y5g43bkf.fsf@talisman.default> Date: Tue, 08 Jan 2013 07:28:00 -0000 In-Reply-To: (Maciej W. Rozycki's message of "Tue, 8 Jan 2013 00:23:22 +0000") Message-ID: <87ip782kxl.fsf@talisman.default> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain 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 X-SW-Source: 2013-01/txt/msg00386.txt.bz2 "Maciej W. Rozycki" writes: >> > I disabled 64 bit FPU instructions by "-msoft-float". This works, but >> > using "-msingle-float" fails. This would be the better >> > configuration. There are still 64 bit FPU instructions used (e.g. "dmfc1 >> > $2,$f0" when using "long double" multiplication). So "-msingle-float" >> > doesn't seem to work on generic mips64-linux-gnu. >> >> Right. That combination hasn't really been defined. What happens >> for plain doubles? Do you pass those in FPRs or GPRs? > > IIUC the R5900 has an FPU that is functionally the same as that of the > R4640/R4650. If that is the case, then there is no way to pass doubles in > FPRs -- there is no room to store the upper halves. My point was that you could pass them in consecutive FPRs, like n32 does for long double. There's no architectural support for long double either, but the decision was still to pass them in FPRs rather than GPRs. I'm not saying that that's a sensible precendent to copy. I was just using it as one example of why an ABI has to be defined. Richard