From b72592e75fdecb34e2ac5f931730409a1fb68e8a Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Fri, 23 May 2014 12:07:50 +0000 Subject: Fix log10 (1) in round-downward mode (bug 16977). As with various other issues of this kind, bug 16977 is log10 (1) wrongly returning -0 rather than +0 in round-downward mode because of an implementation effectively in terms of log1p (x - 1). This patch fixes the issue in the same way used for log. 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 logl is essentially the same as the ldbl-128 one). [BZ #16977] * sysdeps/i386/fpu/e_log10.S (__ieee754_log10): Take absolute value when x - 1 is zero. * sysdeps/i386/fpu/e_log10f.S (__ieee754_log10f): Likewise. * sysdeps/i386/fpu/e_log10l.S (__ieee754_log10l): Likewise. * sysdeps/ieee754/ldbl-128/e_log10l.c (__ieee754_log10l): Return 0.0L for an argument of 1.0L. * sysdeps/ieee754/ldbl-128ibm/e_log10l.c (__ieee754_log10l): Likewise. * sysdeps/x86_64/fpu/e_log10l.S (__ieee754_log10l): Take absolute value when x - 1 is zero. * math/libm-test.inc (log10_test): Use ALL_RM_TEST. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise. --- sysdeps/ieee754/ldbl-128/e_log10l.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'sysdeps/ieee754/ldbl-128') diff --git a/sysdeps/ieee754/ldbl-128/e_log10l.c b/sysdeps/ieee754/ldbl-128/e_log10l.c index b403f815fb..618255f2fa 100644 --- a/sysdeps/ieee754/ldbl-128/e_log10l.c +++ b/sysdeps/ieee754/ldbl-128/e_log10l.c @@ -193,6 +193,9 @@ __ieee754_log10l (long double 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 -- cgit 1.4.1