From a84e78c8b3c4de94b488fdc5321f71feeb99358f Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Wed, 2 Apr 2014 17:41:02 +0000 Subject: Fix catan, catanh, __ieee754_logf in round-downward mode (bug 16799, bug 16800). This patch fixes incorrect results from catan and catanh of certain special inputs in round-downward mode (bug 16799), and incorrect results of __ieee754_logf (+/-0) in round-downward mode (bug 16800) that show up through catan/catanh when tested in all rounding modes, but not directly in the testing for logf because the bug gets hidden by the wrappers. Both bugs involve a zero that should be +0 being -0 instead: one computed as (1-x)*(1+x) in the catan/catanh case, and one as (x-x) in the logf case. The fixes ensure positive zero is used. Testing of catan and catanh in all rounding modes is duly enabled. I expect there are various other bugs in special cases in __ieee754_* functions that are normally hidden by the wrappers but would show up for testing with -lieee (or in future with -fno-math-errno if we replace -lieee and _LIB_VERSION with compile-time redirection to new *_noerrno symbol names). Tested x86_64 and x86 and ulps updated accordingly. [BZ #16799] [BZ #16800] * math/s_catan.c (__catan): Avoid passing -0 denominator to atan2 with 0 numerator. * math/s_catanf.c (__catanf): Likewise. * math/s_catanh.c (__catanh): Likewise. * math/s_catanhf.c (__catanhf): Likewise. * math/s_catanhl.c (__catanhl): Likewise. * math/s_catanl.c (__catanl): Likewise. * sysdeps/ieee754/flt-32/e_logf.c (__ieee754_logf): Always divide by positive zero when computing -Inf result. * math/libm-test.inc (catan_test): Use ALL_RM_TEST. (catanh_test): Likewise. * sysdeps/i386/fpu/libm-test-ulps: Update. * sysdeps/x86_64/fpu/libm-test-ulps: Likewise. --- math/s_catanh.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'math/s_catanh.c') diff --git a/math/s_catanh.c b/math/s_catanh.c index 2ba1298bb6..7ef9142b0d 100644 --- a/math/s_catanh.c +++ b/math/s_catanh.c @@ -110,7 +110,11 @@ __catanh (__complex__ double x) } if (absy < DBL_EPSILON / 2.0) - den = (1.0 - absx) * (1.0 + absx); + { + den = (1.0 - absx) * (1.0 + absx); + if (den == -0.0) + den = 0.0; + } else if (absx >= 1.0) den = (1.0 - absx) * (1.0 + absx) - absy * absy; else if (absx >= 0.75 || absy >= 0.5) -- cgit v1.2.1