From f7be737659813220e1f29c8850c386a9654d549a Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Fri, 21 Mar 2014 18:13:58 +0000 Subject: Fix log (1) in round-downward mode (bug 16731). According to ISO C Annex F, log (1) should be +0 in all rounding modes, but some implementations in glibc wrongly return -0 in round-downward mode (mapping to log1p (x - 1) is problematic because 1 - 1 is -0 in round-downward mode, and log1p (-0) is -0). This patch fixes this. (It helps with some implementations of other functions such as acosh, log2 and log10 that call out to log, but not enough to enable all-rounding-modes testing for those functions without further fixes to other implementations of them.) Tested x86_64 and x86 and ulps updated accordingly, and did spot tests for mips64 for the ldbl-128 fix, and i586 for the sysdeps/i386/fpu implementations shadowed by those in sysdeps/i386/i686/fpu. [BZ #16731] * sysdeps/i386/fpu/e_log.S (__ieee754_log): Take absolute value when x - 1 is zero. * sysdeps/i386/fpu/e_logf.S (__ieee754_logf): Likewise. * sysdeps/i386/fpu/e_logl.S (__ieee754_logl): Likewise. * sysdeps/i386/i686/fpu/e_logl.S (__ieee754_logl): Likewise. * sysdeps/ieee754/dbl-64/e_log.c (__ieee754_log): Return +0 when argument is 1. * sysdeps/ieee754/ldbl-128/e_logl.c (__ieee754_logl): Likewise. * sysdeps/x86_64/fpu/e_logl.S: Take absolute value when x - 1 is zero. * math/libm-test.inc (log_test): Use ALL_RM_TEST. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise. --- ChangeLog | 17 +++++++++++++++++ NEWS | 2 +- math/libm-test.inc | 4 +--- sysdeps/i386/fpu/e_log.S | 8 +++++++- sysdeps/i386/fpu/e_logf.S | 8 +++++++- sysdeps/i386/fpu/e_logl.S | 8 +++++++- sysdeps/i386/fpu/libm-test-ulps | 12 ++++++++++++ sysdeps/i386/i686/fpu/e_logl.S | 8 +++++++- sysdeps/ieee754/dbl-64/e_log.c | 4 ++++ sysdeps/ieee754/ldbl-128/e_logl.c | 2 ++ sysdeps/x86_64/fpu/e_logl.S | 8 +++++++- sysdeps/x86_64/fpu/libm-test-ulps | 16 ++++++++++++++++ 12 files changed, 88 insertions(+), 9 deletions(-) diff --git a/ChangeLog b/ChangeLog index f8f87bdb06..e3601495d0 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,20 @@ +2014-03-21 Joseph Myers + + [BZ #16731] + * sysdeps/i386/fpu/e_log.S (__ieee754_log): Take absolute value + when x - 1 is zero. + * sysdeps/i386/fpu/e_logf.S (__ieee754_logf): Likewise. + * sysdeps/i386/fpu/e_logl.S (__ieee754_logl): Likewise. + * sysdeps/i386/i686/fpu/e_logl.S (__ieee754_logl): Likewise. + * sysdeps/ieee754/dbl-64/e_log.c (__ieee754_log): Return +0 when + argument is 1. + * sysdeps/ieee754/ldbl-128/e_logl.c (__ieee754_logl): Likewise. + * sysdeps/x86_64/fpu/e_logl.S: Take absolute value when x - 1 is + zero. + * math/libm-test.inc (log_test): Use ALL_RM_TEST. + * sysdeps/i386/fpu/libm-test-ulps: Update. + * sysdeps/x86_64/fpu/libm-test-ulps: Likewise. + 2014-03-21 Siddhesh Poyarekar * scripts/bench.pl: Remove file. diff --git a/NEWS b/NEWS index 5f9ffcc569..5df0277bee 100644 --- a/NEWS +++ b/NEWS @@ -11,7 +11,7 @@ Version 2.20 15347, 15804, 15894, 16447, 16532, 16545, 16574, 16600, 16609, 16610, 16611, 16613, 16623, 16632, 16639, 16642, 16649, 16670, 16674, 16677, - 16680, 16683, 16689, 16695, 16701, 16706, 16707. + 16680, 16683, 16689, 16695, 16701, 16706, 16707, 16731. * Running the testsuite no longer terminates as soon as a test fails. Instead, a file tests.sum (xtests.sum from "make xcheck") is generated, diff --git a/math/libm-test.inc b/math/libm-test.inc index 7abc7c14b5..5e50f0ee3d 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -7786,9 +7786,7 @@ static const struct test_f_f_data log_test_data[] = static void log_test (void) { - START (log, 0); - RUN_TEST_LOOP_f_f (log, log_test_data, ); - END; + ALL_RM_TEST (log, 0, log_test_data, RUN_TEST_LOOP_f_f, END); } diff --git a/sysdeps/i386/fpu/e_log.S b/sysdeps/i386/fpu/e_log.S index 0877924998..3fa32aad3c 100644 --- a/sysdeps/i386/fpu/e_log.S +++ b/sysdeps/i386/fpu/e_log.S @@ -46,7 +46,13 @@ ENTRY(__ieee754_log) fnstsw // x-1 : x : log(2) andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : log(2) + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : log(2) fyl2xp1 // log(x) ret diff --git a/sysdeps/i386/fpu/e_logf.S b/sysdeps/i386/fpu/e_logf.S index 485180e909..ca83d39cef 100644 --- a/sysdeps/i386/fpu/e_logf.S +++ b/sysdeps/i386/fpu/e_logf.S @@ -47,7 +47,13 @@ ENTRY(__ieee754_logf) fnstsw // x-1 : x : log(2) andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : log(2) + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : log(2) fyl2xp1 // log(x) ret diff --git a/sysdeps/i386/fpu/e_logl.S b/sysdeps/i386/fpu/e_logl.S index d7a459a627..edae1d70df 100644 --- a/sysdeps/i386/fpu/e_logl.S +++ b/sysdeps/i386/fpu/e_logl.S @@ -47,7 +47,13 @@ ENTRY(__ieee754_logl) fnstsw // x-1 : x : log(2) andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : log(2) + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : log(2) fyl2xp1 // log(x) ret diff --git a/sysdeps/i386/fpu/libm-test-ulps b/sysdeps/i386/fpu/libm-test-ulps index 3be1806826..b7b2e12b54 100644 --- a/sysdeps/i386/fpu/libm-test-ulps +++ b/sysdeps/i386/fpu/libm-test-ulps @@ -1096,6 +1096,18 @@ Function: "log1p": ildouble: 1 ldouble: 1 +Function: "log_downward": +ildouble: 1 +ldouble: 1 + +Function: "log_towardzero": +ildouble: 1 +ldouble: 1 + +Function: "log_upward": +ildouble: 1 +ldouble: 1 + Function: "pow": ildouble: 1 ldouble: 1 diff --git a/sysdeps/i386/i686/fpu/e_logl.S b/sysdeps/i386/i686/fpu/e_logl.S index 8a86222b13..a0d1107dc0 100644 --- a/sysdeps/i386/i686/fpu/e_logl.S +++ b/sysdeps/i386/i686/fpu/e_logl.S @@ -46,7 +46,13 @@ ENTRY(__ieee754_logl) fcomip %st(1) // |x-1| : x-1 : x : log(2) fstp %st(0) // x-1 : x : log(2) jc 2f - fstp %st(1) // x-1 : log(2) + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 4f + fabs // log(1) is +0 in all rounding modes. +4: fstp %st(1) // x-1 : log(2) fyl2xp1 // log(x) ret diff --git a/sysdeps/ieee754/dbl-64/e_log.c b/sysdeps/ieee754/dbl-64/e_log.c index 05d318b786..4ecd3722f5 100644 --- a/sysdeps/ieee754/dbl-64/e_log.c +++ b/sysdeps/ieee754/dbl-64/e_log.c @@ -96,6 +96,10 @@ __ieee754_log (double x) if (__glibc_likely (ABS (w) > U03)) goto case_03; + /* log (1) is +0 in all rounding modes. */ + if (w == 0.0) + return 0.0; + /*--- Stage I, the case abs(x-1) < 0.03 */ t8 = MHALF * w; diff --git a/sysdeps/ieee754/ldbl-128/e_logl.c b/sysdeps/ieee754/ldbl-128/e_logl.c index 3d1034dd61..cb43816793 100644 --- a/sysdeps/ieee754/ldbl-128/e_logl.c +++ b/sysdeps/ieee754/ldbl-128/e_logl.c @@ -240,6 +240,8 @@ __ieee754_logl(long double x) /* On this interval the table is not used due to cancellation error. */ if ((x <= 1.0078125L) && (x >= 0.9921875L)) { + if (x == 1.0L) + return 0.0L; z = x - 1.0L; k = 64; t.value = 1.0L; diff --git a/sysdeps/x86_64/fpu/e_logl.S b/sysdeps/x86_64/fpu/e_logl.S index a8e31084ba..315afc0033 100644 --- a/sysdeps/x86_64/fpu/e_logl.S +++ b/sysdeps/x86_64/fpu/e_logl.S @@ -45,7 +45,13 @@ ENTRY(__ieee754_logl) fnstsw // x-1 : x : log(2) andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : log(2) + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : log(2) fyl2xp1 // log(x) ret diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps index 5f4ab06050..301eaa6542 100644 --- a/sysdeps/x86_64/fpu/libm-test-ulps +++ b/sysdeps/x86_64/fpu/libm-test-ulps @@ -1170,6 +1170,22 @@ ifloat: 1 ildouble: 1 ldouble: 1 +Function: "log_downward": +float: 1 +ifloat: 1 +ildouble: 1 +ldouble: 1 + +Function: "log_towardzero": +ildouble: 1 +ldouble: 1 + +Function: "log_upward": +float: 1 +ifloat: 1 +ildouble: 1 +ldouble: 1 + Function: "pow": float: 1 ifloat: 1 -- cgit 1.4.1