From f8ba1b5654d876c8db4c9a020e6fa976d434f988 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Tue, 10 Jun 2014 12:07:15 +0000 Subject: Fix log2 (1) in round-downward mode (bug 17042). 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). [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. --- sysdeps/x86_64/fpu/libm-test-ulps | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'sysdeps/x86_64/fpu/libm-test-ulps') diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps index bb549d2b0d..92fef5a134 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 -- cgit 1.4.1