From mboxrd@z Thu Jan 1 00:00:00 1970 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 109DDC433DF for ; Thu, 11 Jun 2020 20:13:14 +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 CFDA1206C3 for ; Thu, 11 Jun 2020 20:13:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gGlsxl5U" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CFDA1206C3 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]:49418 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jjTZY-0000Op-O8 for qemu-devel@archiver.kernel.org; Thu, 11 Jun 2020 16:13:12 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54938) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jjT8x-0007xb-7M for qemu-devel@nongnu.org; Thu, 11 Jun 2020 15:45:43 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:48332 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 1jjT8t-00012O-Mp for qemu-devel@nongnu.org; Thu, 11 Jun 2020 15:45:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591904738; 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=UDBHQtVitR2UF3gM0easaFDJXNK3KOw8227wlXl8uXk=; b=gGlsxl5U1NMMBvZiOpZ8qAhGx19aSQWwmAYZNwsVxHJmb+SsUkCCS/kaiUtOONKl/dY0SI OnqrfUJr35WT53kDbgJtutb2oOklBcageSX8U9VDPFxa/qK7Rhgxv6PA79p9yaVlaaF6Zt wa2y/G5BsN+ObJTUxUG3i+dQajGquuA= 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-394-Chn9K9sdN4Cp-6v131tnIw-1; Thu, 11 Jun 2020 15:45:36 -0400 X-MC-Unique: Chn9K9sdN4Cp-6v131tnIw-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 7CB078064DD; 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 2053997B12; Thu, 11 Jun 2020 19:45:35 +0000 (UTC) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 055/115] target/i386: fix fscale handling of rounding precision Date: Thu, 11 Jun 2020 15:43:49 -0400 Message-Id: <20200611194449.31468-56-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 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=pbonzini@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/11 14:52:10 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_H4=-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 uses floatx80_scalbn for the final scaling operation. floatx80_scalbn ends up rounding the result using the dynamic rounding precision configured for the FPU. But only a limited set of x87 floating-point instructions are supposed to respect the dynamic rounding precision, and fscale is not in that set. Fix the implementation to save and restore the rounding precision around the call to floatx80_scalbn. Signed-off-by: Joseph Myers Message-Id: Signed-off-by: Paolo Bonzini --- target/i386/fpu_helper.c | 3 +++ tests/tcg/i386/test-i386-fscale.c | 13 +++++++++++++ 2 files changed, 16 insertions(+) diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c index 72d1e77eb0..4d14c1ca24 100644 --- a/target/i386/fpu_helper.c +++ b/target/i386/fpu_helper.c @@ -1001,7 +1001,10 @@ void helper_fscale(CPUX86State *env) } } else { int n = floatx80_to_int32_round_to_zero(ST1, &env->fp_status); + signed char save = env->fp_status.floatx80_rounding_precision; + env->fp_status.floatx80_rounding_precision = 80; ST0 = floatx80_scalbn(ST0, n, &env->fp_status); + env->fp_status.floatx80_rounding_precision = save; } } diff --git a/tests/tcg/i386/test-i386-fscale.c b/tests/tcg/i386/test-i386-fscale.c index b953e7c563..d23b3cfeec 100644 --- a/tests/tcg/i386/test-i386-fscale.c +++ b/tests/tcg/i386/test-i386-fscale.c @@ -8,6 +8,8 @@ union u { long double ld; }; +volatile long double ld_third = 1.0L / 3.0L; +volatile long double ld_four_thirds = 4.0L / 3.0L; volatile union u ld_invalid_1 = { .s = { 1, 1234 } }; volatile union u ld_invalid_2 = { .s = { 0, 1234 } }; volatile union u ld_invalid_3 = { .s = { 0, 0x7fff } }; @@ -91,5 +93,16 @@ int main(void) printf("FAIL: fscale finite down inf\n"); ret = 1; } + /* Set round-to-nearest with single-precision rounding. */ + cw = cw & ~0xf00; + __asm__ volatile ("fldcw %0" : : "m" (cw)); + __asm__ volatile ("fscale" : "=t" (ld_res) : + "0" (ld_third), "u" (2.0L)); + cw = cw | 0x300; + __asm__ volatile ("fldcw %0" : : "m" (cw)); + if (ld_res != ld_four_thirds) { + printf("FAIL: fscale single-precision\n"); + ret = 1; + } return ret; } -- 2.26.2