From patchwork Fri Feb 10 07:23:05 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bharata B Rao X-Patchwork-Id: 9566043 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 4E310602B6 for ; Fri, 10 Feb 2017 07:25:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 39D432852A for ; Fri, 10 Feb 2017 07:25:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2DF8728545; Fri, 10 Feb 2017 07:25:18 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id EA2552852A for ; Fri, 10 Feb 2017 07:25:16 +0000 (UTC) Received: from localhost ([::1]:42289 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cc5Zz-0007W8-Vf for patchwork-qemu-devel@patchwork.kernel.org; Fri, 10 Feb 2017 02:25:16 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60108) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cc5Z6-0007DV-Te for qemu-devel@nongnu.org; Fri, 10 Feb 2017 02:24:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cc5Z3-0000Kc-ML for qemu-devel@nongnu.org; Fri, 10 Feb 2017 02:24:20 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:58996 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cc5Z3-0000KP-Gk for qemu-devel@nongnu.org; Fri, 10 Feb 2017 02:24:17 -0500 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1A7In1Y053302 for ; Fri, 10 Feb 2017 02:24:17 -0500 Received: from e23smtp07.au.ibm.com (e23smtp07.au.ibm.com [202.81.31.140]) by mx0b-001b2d01.pphosted.com with ESMTP id 28h507fvr0-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 10 Feb 2017 02:24:16 -0500 Received: from localhost by e23smtp07.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Fri, 10 Feb 2017 17:24:11 +1000 Received: from d23relay08.au.ibm.com (d23relay08.au.ibm.com [9.185.71.33]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 4EEBB2BB0055; Fri, 10 Feb 2017 18:24:11 +1100 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay08.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1A7O3hR19398782; Fri, 10 Feb 2017 18:24:11 +1100 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v1A7NckF023512; Fri, 10 Feb 2017 18:23:38 +1100 Received: from bharata.in.ibm.com ([9.77.205.48]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id v1A7NYCq023032; Fri, 10 Feb 2017 18:23:36 +1100 From: Bharata B Rao To: qemu-devel@nongnu.org Date: Fri, 10 Feb 2017 12:53:05 +0530 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1486711391-12247-1-git-send-email-bharata@linux.vnet.ibm.com> References: <1486711391-12247-1-git-send-email-bharata@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17021007-0044-0000-0000-00000229066D X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17021007-0045-0000-0000-000006825524 Message-Id: <1486711391-12247-2-git-send-email-bharata@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-10_02:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702100074 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PATCH 1/7] softfloat: Add round-to-odd rounding mode X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: rth@twiddle.net, qemu-ppc@nongnu.org, Bharata B Rao , nikunj@linux.vnet.ibm.com, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Power ISA 3.0 introduces a few quadruple precision floating point instructions that support round-to-odd rounding mode. The round-to-odd mode is explained as under: Let Z be the intermediate arithmetic result or the operand of a convert operation. If Z can be represented exactly in the target format, the result is Z. Otherwise the result is either Z1 or Z2 whichever is odd. Here Z1 and Z2 are the next larger and smaller numbers representable in the target format respectively. Signed-off-by: Bharata B Rao Reviewed-by: Peter Maydell Reviewed-by: Richard Henderson --- Posted ealier separately at: https://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg01030.html fpu/softfloat.c | 21 ++++++++++++++++++++- include/fpu/softfloat.h | 2 ++ 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index c295f31..5ccba76 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -623,6 +623,9 @@ static float64 roundAndPackFloat64(flag zSign, int zExp, uint64_t zSig, case float_round_down: roundIncrement = zSign ? 0x3ff : 0; break; + case float_round_to_odd: + roundIncrement = (zSig & 0x400) ? 0 : 0x3ff; + break; default: abort(); } @@ -632,8 +635,10 @@ static float64 roundAndPackFloat64(flag zSign, int zExp, uint64_t zSig, || ( ( zExp == 0x7FD ) && ( (int64_t) ( zSig + roundIncrement ) < 0 ) ) ) { + bool overflow_to_inf = roundingMode != float_round_to_odd && + roundIncrement != 0; float_raise(float_flag_overflow | float_flag_inexact, status); - return packFloat64( zSign, 0x7FF, - ( roundIncrement == 0 )); + return packFloat64(zSign, 0x7FF, -(!overflow_to_inf)); } if ( zExp < 0 ) { if (status->flush_to_zero) { @@ -651,6 +656,13 @@ static float64 roundAndPackFloat64(flag zSign, int zExp, uint64_t zSig, if (isTiny && roundBits) { float_raise(float_flag_underflow, status); } + if (roundingMode == float_round_to_odd) { + /* + * For round-to-odd case, the roundIncrement depends on + * zSig which just changed. + */ + roundIncrement = (zSig & 0x400) ? 0 : 0x3ff; + } } } if (roundBits) { @@ -1149,6 +1161,9 @@ static float128 roundAndPackFloat128(flag zSign, int32_t zExp, case float_round_down: increment = zSign && zSig2; break; + case float_round_to_odd: + increment = !(zSig1 & 0x1) && zSig2; + break; default: abort(); } @@ -1168,6 +1183,7 @@ static float128 roundAndPackFloat128(flag zSign, int32_t zExp, if ( ( roundingMode == float_round_to_zero ) || ( zSign && ( roundingMode == float_round_up ) ) || ( ! zSign && ( roundingMode == float_round_down ) ) + || (roundingMode == float_round_to_odd) ) { return packFloat128( @@ -1215,6 +1231,9 @@ static float128 roundAndPackFloat128(flag zSign, int32_t zExp, case float_round_down: increment = zSign && zSig2; break; + case float_round_to_odd: + increment = !(zSig1 & 0x1) && zSig2; + break; default: abort(); } diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h index 842ec6b..8a39028 100644 --- a/include/fpu/softfloat.h +++ b/include/fpu/softfloat.h @@ -180,6 +180,8 @@ enum { float_round_up = 2, float_round_to_zero = 3, float_round_ties_away = 4, + /* Not an IEEE rounding mode: round to the closest odd mantissa value */ + float_round_to_odd = 5, }; /*----------------------------------------------------------------------------