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| author | Joseph Myers <joseph@codesourcery.com> | 2014-05-23 12:07:50 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2014-05-23 12:07:50 +0000 |
| commit | b72592e75fdecb34e2ac5f931730409a1fb68e8a (patch) | |
| tree | 9a7f71aecd06da02f507abf536a72a1bcbd69209 /sysdeps/x86_64/fpu/e_log10l.S | |
| parent | 2302d679ce8b36854022207b58e554b3e89dd8c7 (diff) | |
| download | glibc-b72592e75fdecb34e2ac5f931730409a1fb68e8a.tar glibc-b72592e75fdecb34e2ac5f931730409a1fb68e8a.tar.gz glibc-b72592e75fdecb34e2ac5f931730409a1fb68e8a.tar.bz2 glibc-b72592e75fdecb34e2ac5f931730409a1fb68e8a.zip | |
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.
Diffstat (limited to 'sysdeps/x86_64/fpu/e_log10l.S')
| -rw-r--r-- | sysdeps/x86_64/fpu/e_log10l.S | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/sysdeps/x86_64/fpu/e_log10l.S b/sysdeps/x86_64/fpu/e_log10l.S index 6c07024c19..2607ad199b 100644 --- a/sysdeps/x86_64/fpu/e_log10l.S +++ b/sysdeps/x86_64/fpu/e_log10l.S @@ -46,7 +46,13 @@ ENTRY(__ieee754_log10l) fnstsw // x-1 : x : log10(2) andb $0x45, %ah jz 2f - fstp %st(1) // x-1 : log10(2) + fxam + fnstsw + andb $0x45, %ah + cmpb $0x40, %ah + jne 5f + fabs // log10(1) is +0 in all rounding modes. +5: fstp %st(1) // x-1 : log10(2) fyl2xp1 // log10(x) ret |