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bh=PixQXutwcGEY5jlx8dUr7LAWNxKmNvIVWkqYGwJzOgI=; b=KW3y33LL9Yodz1KZb/Ks+Cjwft9TZ95PWZmoWDHUL8EPK3n3KoSSVDzLqoj8naT8lCHWSN pNT47L1M3crl/bKnbseOYTX9XbX7mkAPJY4xTkjD0mwD4i0x4Szn7C4Q4aPjS+wgfoF5Gr T2RNoKopQxtZ27PuQJbMz3hqFaS7imU= X-MC-Unique: AUEd9WlAOrWLVLnWeRo31Q-1 From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 062/115] target/i386: fix fbstp handling of negative zero Date: Thu, 11 Jun 2020 15:43:56 -0400 Message-Id: <20200611194449.31468-63-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 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: Joseph Myers The fbstp implementation stores +0 when the rounded result should be -0 because it compares an integer value with 0 to determine the sign. Fix this by checking the sign bit of the operand instead. Signed-off-by: Joseph Myers Message-Id: Signed-off-by: Paolo Bonzini --- target/i386/fpu_helper.c | 5 ++++- tests/tcg/i386/test-i386-fbstp.c | 25 +++++++++++++++++++++++++ 2 files changed, 29 insertions(+), 1 deletion(-) create mode 100644 tests/tcg/i386/test-i386-fbstp.c diff --git a/target/i386/fpu_helper.c b/target/i386/fpu_helper.c index 185493db8e..f0a57099ca 100644 --- a/target/i386/fpu_helper.c +++ b/target/i386/fpu_helper.c @@ -726,11 +726,14 @@ void helper_fbst_ST0(CPUX86State *env, target_ulong p= tr) int v; target_ulong mem_ref, mem_end; int64_t val; + CPU_LDoubleU temp; + + temp.d =3D ST0; =20 val =3D floatx80_to_int64(ST0, &env->fp_status); mem_ref =3D ptr; mem_end =3D mem_ref + 9; - if (val < 0) { + if (SIGND(temp)) { cpu_stb_data_ra(env, mem_end, 0x80, GETPC()); val =3D -val; } else { diff --git a/tests/tcg/i386/test-i386-fbstp.c b/tests/tcg/i386/test-i386-fb= stp.c new file mode 100644 index 0000000000..d368949188 --- /dev/null +++ b/tests/tcg/i386/test-i386-fbstp.c @@ -0,0 +1,25 @@ +/* Test fbstp instruction. */ + +#include +#include + +int main(void) +{ + int ret =3D 0; + unsigned char out[10]; + memset(out, 0xfe, sizeof out); + __asm__ volatile ("fbstp %0" : "=3Dm" (out) : "t" (-0.0L) : "st"); + out[9] &=3D 0x80; + if (memcmp(out, "\0\0\0\0\0\0\0\0\0\x80", sizeof out) !=3D 0) { + printf("FAIL: fbstp -0\n"); + ret =3D 1; + } + memset(out, 0x12, sizeof out); + __asm__ volatile ("fbstp %0" : "=3Dm" (out) : "t" (-0.1L) : "st"); + out[9] &=3D 0x80; + if (memcmp(out, "\0\0\0\0\0\0\0\0\0\x80", sizeof out) !=3D 0) { + printf("FAIL: fbstp -0.1\n"); + ret =3D 1; + } + return ret; +} --=20 2.26.2