diff options
| author | Joseph Myers <joseph@codesourcery.com> | 2015-09-26 00:27:06 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-09-26 00:27:06 +0000 |
| commit | fa752c698146ca3e9f7747d33059fbef9bb02b0e (patch) | |
| tree | a41295f8a99770d272a53c714effd0f5749b2735 /NEWS | |
| parent | 6ace39382120dd0668b2168591611f71b04ac8f3 (diff) | |
| download | glibc-fa752c698146ca3e9f7747d33059fbef9bb02b0e.zip glibc-fa752c698146ca3e9f7747d33059fbef9bb02b0e.tar.gz glibc-fa752c698146ca3e9f7747d33059fbef9bb02b0e.tar.bz2 | |
Fix powf inaccuracy (bug 18956).
The flt-32 version of powf can be inaccurate because of bugs in the
extra-precision calculation of (x-1)/(x+1) or (x-1.5)/(x+1.5) as part
of calculating log(x) with extra precision: a constant used (as part
of adding 1 or 1.5 through integer arithmetic) is incorrect, and then
the code fails to mask a computed high part before using it in
arithmetic that relies on s_h*t_h being exactly representable. This
patch fixes these bugs.
Tested for x86_64 and x86. x86_64 ulps for powf removed and
regenerated to reflect reduced ulps from the increased accuracy for
existing tests.
[BZ #18956]
* sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): Add 0x00400000
not 0x0040000 for high bit of mantissa. Mask with 0xfffff000 when
extracting high part.
* math/auto-libm-test-in: Add another test of pow.
* math/auto-libm-test-out: Regenerated.
* sysdeps/x86_64/fpu/libm-test-ulps: Update.
Diffstat (limited to 'NEWS')
| -rw-r--r-- | NEWS | 4 |
1 files changed, 2 insertions, 2 deletions
@@ -15,8 +15,8 @@ Version 2.23 18084, 18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595, 18610, 18618, 18647, 18661, 18674, 18675, 18681, 18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796, 18803, 18820, 18823, 18824, 18825, 18857, - 18863, 18870, 18872, 18873, 18875, 18887, 18921, 18951, 18952, 18961, - 18966, 18967, 18970, 18977, 18980, 18981, 19003. + 18863, 18870, 18872, 18873, 18875, 18887, 18921, 18951, 18952, 18956, + 18961, 18966, 18967, 18970, 18977, 18980, 18981, 19003. * The obsolete header <regexp.h> has been removed. Programs that require this header must be updated to use <regex.h> instead. |