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| author | Joseph Myers <joseph@codesourcery.com> | 2014-06-10 12:07:15 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2014-06-10 12:07:15 +0000 |
| commit | f8ba1b5654d876c8db4c9a020e6fa976d434f988 (patch) | |
| tree | f5e34ce57471cbb1c54ec4cd0492b665f94151bb /sysdeps/ieee754 | |
| parent | 2c3520d98d9773d9e092196c3c36150244eed1dd (diff) | |
| download | glibc-f8ba1b5654d876c8db4c9a020e6fa976d434f988.zip glibc-f8ba1b5654d876c8db4c9a020e6fa976d434f988.tar.gz glibc-f8ba1b5654d876c8db4c9a020e6fa976d434f988.tar.bz2 | |
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.
Diffstat (limited to 'sysdeps/ieee754')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128/e_log2l.c | 3 | ||||
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/e_log2l.c | 3 |
2 files changed, 6 insertions, 0 deletions
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 |