From patchwork Thu Jun 11 19:43:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 280703 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B4F6C433DF for ; Thu, 11 Jun 2020 20:22:48 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D465720720 for ; Thu, 11 Jun 2020 20:22:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="godjkGwe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D465720720 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59956 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jjTip-0001L6-2E for qemu-devel@archiver.kernel.org; Thu, 11 Jun 2020 16:22:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55056) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jjT90-00082M-Bu for qemu-devel@nongnu.org; Thu, 11 Jun 2020 15:45:46 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:50740 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jjT8x-00016y-Fc for qemu-devel@nongnu.org; Thu, 11 Jun 2020 15:45:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591904742; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6DTxtOc5LdYdP17d4UDiZN2OUZYIKMNt5E0uvZNLm+g=; b=godjkGweT2sWc3ak0rBpVyK0QBtdgJK22UByJXTn34oo6XmuImJ4oNAF8tzcq+AkWAJI56 LVXRqOhTnDQz/k+9MNTN31tjohZCRIw9oSaBaib4vL74nGoKmneZXEFIneDlQ9nv/l/nct tKTp91ve1+YKNckcd9duBCWc/NyOMoo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-409-IYNd9nSgOUatmNfMtw6ZlA-1; Thu, 11 Jun 2020 15:45:36 -0400 X-MC-Unique: IYNd9nSgOUatmNfMtw6ZlA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0221419057BF; Thu, 11 Jun 2020 19:45:35 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 920938FF7E; Thu, 11 Jun 2020 19:45:34 +0000 (UTC) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 054/115] target/i386: fix fscale handling of infinite exponents Date: Thu, 11 Jun 2020 15:43:48 -0400 Message-Id: <20200611194449.31468-55-pbonzini@redhat.com> In-Reply-To: <20200611194449.31468-1-pbonzini@redhat.com> References: <20200611194449.31468-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=207.211.31.120; envelope-from=pbonzini@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/11 08:37:10 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Joseph Myers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Joseph Myers The fscale implementation passes infinite exponents through to generic code that rounds the exponent to a 32-bit integer before using floatx80_scalbn. In round-to-nearest mode, and ignoring exceptions, this works in many cases. But it fails to handle the special cases of scaling 0 by a +Inf exponent or an infinity by a -Inf exponent, which should produce a NaN, and because it produces an inexact result for finite nonzero numbers being scaled, the result is sometimes incorrect in other rounding modes. Add appropriate handling of infinite exponents to produce a NaN or an appropriately signed exact zero or infinity as a result. Signed-off-by: Joseph Myers Message-Id: Signed-off-by: Paolo Bonzini --- target/i386/fpu_helper.c | 22 ++++++++++++++++++++++ tests/tcg/i386/test-i386-fscale.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 51 insertions(+) diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c index 10ff90370e..72d1e77eb0 100644 --- a/target/i386/fpu_helper.c +++ b/target/i386/fpu_helper.c @@ -977,6 +977,28 @@ void helper_fscale(CPUX86State *env) float_raise(float_flag_invalid, &env->fp_status); ST0 = floatx80_silence_nan(ST0, &env->fp_status); } + } else if (floatx80_is_infinity(ST1) && + !floatx80_invalid_encoding(ST0) && + !floatx80_is_any_nan(ST0)) { + if (floatx80_is_neg(ST1)) { + if (floatx80_is_infinity(ST0)) { + float_raise(float_flag_invalid, &env->fp_status); + ST0 = floatx80_default_nan(&env->fp_status); + } else { + ST0 = (floatx80_is_neg(ST0) ? + floatx80_chs(floatx80_zero) : + floatx80_zero); + } + } else { + if (floatx80_is_zero(ST0)) { + float_raise(float_flag_invalid, &env->fp_status); + ST0 = floatx80_default_nan(&env->fp_status); + } else { + ST0 = (floatx80_is_neg(ST0) ? + floatx80_chs(floatx80_infinity) : + floatx80_infinity); + } + } } else { int n = floatx80_to_int32_round_to_zero(ST1, &env->fp_status); ST0 = floatx80_scalbn(ST0, n, &env->fp_status); diff --git a/tests/tcg/i386/test-i386-fscale.c b/tests/tcg/i386/test-i386-fscale.c index b65a055d0a..b953e7c563 100644 --- a/tests/tcg/i386/test-i386-fscale.c +++ b/tests/tcg/i386/test-i386-fscale.c @@ -31,6 +31,7 @@ int issignaling_ld(long double x) int main(void) { + short cw; int ret = 0; __asm__ volatile ("fscale" : "=t" (ld_res) : "0" (2.5L), "u" (__builtin_nansl(""))); @@ -62,5 +63,33 @@ int main(void) printf("FAIL: fscale invalid 4\n"); ret = 1; } + __asm__ volatile ("fscale" : "=t" (ld_res) : + "0" (0.0L), "u" (__builtin_infl())); + if (!isnan_ld(ld_res) || issignaling_ld(ld_res)) { + printf("FAIL: fscale 0 up inf\n"); + ret = 1; + } + __asm__ volatile ("fscale" : "=t" (ld_res) : + "0" (__builtin_infl()), "u" (-__builtin_infl())); + if (!isnan_ld(ld_res) || issignaling_ld(ld_res)) { + printf("FAIL: fscale inf down inf\n"); + ret = 1; + } + /* Set round-downward. */ + __asm__ volatile ("fnstcw %0" : "=m" (cw)); + cw = (cw & ~0xc00) | 0x400; + __asm__ volatile ("fldcw %0" : : "m" (cw)); + __asm__ volatile ("fscale" : "=t" (ld_res) : + "0" (1.0L), "u" (__builtin_infl())); + if (ld_res != __builtin_infl()) { + printf("FAIL: fscale finite up inf\n"); + ret = 1; + } + __asm__ volatile ("fscale" : "=t" (ld_res) : + "0" (-1.0L), "u" (-__builtin_infl())); + if (ld_res != -0.0L || __builtin_copysignl(1.0L, ld_res) != -1.0L) { + printf("FAIL: fscale finite down inf\n"); + ret = 1; + } return ret; }