From patchwork Mon Jun 9 22:55:28 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joseph Myers X-Patchwork-Id: 1408 Received: (qmail 29450 invoked by alias); 9 Jun 2014 22:55:37 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 29438 invoked by uid 89); 9 Jun 2014 22:55:36 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=AWL, BAYES_00 autolearn=ham version=3.3.2 X-HELO: relay1.mentorg.com Date: Mon, 9 Jun 2014 22:55:28 +0000 From: "Joseph S. Myers" To: Subject: Fix log2 (1) in round-downward mode (bug 17042) Message-ID: MIME-Version: 1.0 As with other issues of this kind, bug 17042 is log2 (1) wrongly returning -0 instead of +0 in round-downward mode because of implementations effectively in terms of log1p (x - 1). This patch fixes the issue in the same way used for log and log10. Tested x86_64 and x86 and ulps updated accordingly. Also tested for mips64 to confirm a fix was needed for ldbl-128 and to validate that fix (also applied to ldbl-128ibm since that version of log2l is essentially the same as the ldbl-128 one). (Other functions remaining to be converted to all-rounding-mode testing with all inputs are pow , cexp, cpow, jn, tgamma, yn.) 2014-06-09 Joseph Myers [BZ #17042] * sysdeps/i386/fpu/e_log2.S (__ieee754_log2): Take absolete value when x - 1 is zero. * sysdeps/i386/fpu/e_log2f.S (__ieee754_log2f): Likewise. * sysdeps/i386/fpu/e_log2l.S (__ieee754_log2l): Likewise. * sysdeps/ieee754/ldbl-128/e_log2l.c (__ieee754_log2l): Return 0.0L for an argument of 1.0L. * sysdeps/ieee754/ldbl-128ibm/e_log2l.c (__ieee754_log2l): Likewise. * sysdeps/x86_64/fpu/e_log2l.S (__ieee754_log2l): Take absolute value when x - 1 is zero. * math/libm-test.inc (log2_test): Use ALL_RM_TEST. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise. diff --git a/math/libm-test.inc b/math/libm-test.inc index 0d467a2..fa8e238 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -7840,9 +7840,7 @@ static const struct test_f_f_data log2_test_data[] = static void log2_test (void) { - START (log2, 0); - RUN_TEST_LOOP_f_f (log2, log2_test_data, ); - END; + ALL_RM_TEST (log2, 0, log2_test_data, RUN_TEST_LOOP_f_f, END); } diff --git a/sysdeps/i386/fpu/e_log2.S b/sysdeps/i386/fpu/e_log2.S index a202bc7..73ff0ff 100644 --- a/sysdeps/i386/fpu/e_log2.S +++ b/sysdeps/i386/fpu/e_log2.S @@ -47,7 +47,13 @@ ENTRY(__ieee754_log2) fnstsw // x-1 : x : 1 andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : 1 + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log2(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : 1 fyl2xp1 // log(x) ret diff --git a/sysdeps/i386/fpu/e_log2f.S b/sysdeps/i386/fpu/e_log2f.S index f4f9a8c..344eeb4 100644 --- a/sysdeps/i386/fpu/e_log2f.S +++ b/sysdeps/i386/fpu/e_log2f.S @@ -47,7 +47,13 @@ ENTRY(__ieee754_log2f) fnstsw // x-1 : x : 1 andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : 1 + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log2(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : 1 fyl2xp1 // log(x) ret diff --git a/sysdeps/i386/fpu/e_log2l.S b/sysdeps/i386/fpu/e_log2l.S index bd51b56..0f5f7e5 100644 --- a/sysdeps/i386/fpu/e_log2l.S +++ b/sysdeps/i386/fpu/e_log2l.S @@ -47,7 +47,13 @@ ENTRY(__ieee754_log2l) fnstsw // x-1 : x : 1 andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : 1 + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log2(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : 1 fyl2xp1 // log(x) ret diff --git a/sysdeps/i386/fpu/libm-test-ulps b/sysdeps/i386/fpu/libm-test-ulps index 1e89284..d7424a6 100644 --- a/sysdeps/i386/fpu/libm-test-ulps +++ b/sysdeps/i386/fpu/libm-test-ulps @@ -1588,6 +1588,22 @@ ifloat: 1 ildouble: 1 ldouble: 1 +Function: "log2_towardzero": +double: 1 +float: 1 +idouble: 1 +ifloat: 1 +ildouble: 1 +ldouble: 1 + +Function: "log2_upward": +double: 1 +float: 1 +idouble: 1 +ifloat: 1 +ildouble: 1 +ldouble: 1 + Function: "log_downward": ildouble: 1 ldouble: 1 diff --git a/sysdeps/ieee754/ldbl-128/e_log2l.c b/sysdeps/ieee754/ldbl-128/e_log2l.c index 6c7da0e..991a3b7 100644 --- a/sysdeps/ieee754/ldbl-128/e_log2l.c +++ b/sysdeps/ieee754/ldbl-128/e_log2l.c @@ -188,6 +188,9 @@ __ieee754_log2l (x) if (hx >= 0x7fff000000000000LL) return (x + x); + if (x == 1.0L) + return 0.0L; + /* separate mantissa from exponent */ /* Note, frexp is used so that denormal numbers diff --git a/sysdeps/ieee754/ldbl-128ibm/e_log2l.c b/sysdeps/ieee754/ldbl-128ibm/e_log2l.c index 323ded0..442ad97 100644 --- a/sysdeps/ieee754/ldbl-128ibm/e_log2l.c +++ b/sysdeps/ieee754/ldbl-128ibm/e_log2l.c @@ -190,6 +190,9 @@ __ieee754_log2l (x) if (hx >= 0x7ff0000000000000LL) return (x + x); + if (x == 1.0L) + return 0.0L; + /* separate mantissa from exponent */ /* Note, frexp is used so that denormal numbers diff --git a/sysdeps/x86_64/fpu/e_log2l.S b/sysdeps/x86_64/fpu/e_log2l.S index 956489f..c12906d 100644 --- a/sysdeps/x86_64/fpu/e_log2l.S +++ b/sysdeps/x86_64/fpu/e_log2l.S @@ -45,7 +45,13 @@ ENTRY(__ieee754_log2l) fnstsw // x-1 : x : 1 andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : 1 + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log2(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : 1 fyl2xp1 // log(x) ret diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps index bb549d2..92fef5a 100644 --- a/sysdeps/x86_64/fpu/libm-test-ulps +++ b/sysdeps/x86_64/fpu/libm-test-ulps @@ -1665,6 +1665,28 @@ ifloat: 1 ildouble: 1 ldouble: 1 +Function: "log2_downward": +double: 2 +float: 2 +idouble: 2 +ifloat: 2 + +Function: "log2_towardzero": +double: 1 +float: 1 +idouble: 1 +ifloat: 1 +ildouble: 1 +ldouble: 1 + +Function: "log2_upward": +double: 2 +float: 2 +idouble: 2 +ifloat: 2 +ildouble: 1 +ldouble: 1 + Function: "log_downward": float: 1 ifloat: 1