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Wed, 24 Jun 2020 10:51:07 +0000 (UTC) Received: from virtlab511.virt.lab.eng.bos.redhat.com (virtlab511.virt.lab.eng.bos.redhat.com [10.19.152.198]) by smtp.corp.redhat.com (Postfix) with ESMTP id CE84B5D9C5; Wed, 24 Jun 2020 10:51:06 +0000 (UTC) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 17/31] softfloat: do not return pseudo-denormal from floatx80 remainder Date: Wed, 24 Jun 2020 06:50:34 -0400 Message-Id: <20200624105048.375353-17-pbonzini@redhat.com> In-Reply-To: <20200624104917.375143-1-pbonzini@redhat.com> References: <20200624104917.375143-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com 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 = 2020/06/24 03:27:53 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: Richard Henderson , Joseph Myers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Joseph Myers The floatx80 remainder implementation sometimes returns the numerator unchanged when the denominator is sufficiently larger than the numerator. But if the value to be returned unchanged is a pseudo-denormal, that is incorrect. Fix it to normalize the numerator in that case. Signed-off-by: Joseph Myers Reviewed-by: Richard Henderson Message-Id: Signed-off-by: Paolo Bonzini --- fpu/softfloat.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index f164b5c0ad..ab50088c35 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -5706,7 +5706,7 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod, float_status *status) { bool aSign, zSign; - int32_t aExp, bExp, expDiff; + int32_t aExp, bExp, expDiff, aExpOrig; uint64_t aSig0, aSig1, bSig; uint64_t q, term0, term1, alternateASig0, alternateASig1; @@ -5715,7 +5715,7 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod, return floatx80_default_nan(status); } aSig0 = extractFloatx80Frac( a ); - aExp = extractFloatx80Exp( a ); + aExpOrig = aExp = extractFloatx80Exp( a ); aSign = extractFloatx80Sign( a ); bSig = extractFloatx80Frac( b ); bExp = extractFloatx80Exp( b ); @@ -5730,6 +5730,13 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod, if ((uint64_t)(bSig << 1)) { return propagateFloatx80NaN(a, b, status); } + if (aExp == 0 && aSig0 >> 63) { + /* + * Pseudo-denormal argument must be returned in normalized + * form. + */ + return packFloatx80(aSign, 1, aSig0); + } return a; } if ( bExp == 0 ) { @@ -5749,7 +5756,16 @@ floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod, expDiff = aExp - bExp; aSig1 = 0; if ( expDiff < 0 ) { - if ( mod || expDiff < -1 ) return a; + if ( mod || expDiff < -1 ) { + if (aExp == 1 && aExpOrig == 0) { + /* + * Pseudo-denormal argument must be returned in + * normalized form. + */ + return packFloatx80(aSign, aExp, aSig0); + } + return a; + } shift128Right( aSig0, 0, 1, &aSig0, &aSig1 ); expDiff = 0; }