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| 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.tar.gz glibc-fa752c698146ca3e9f7747d33059fbef9bb02b0e.tar.xz glibc-fa752c698146ca3e9f7747d33059fbef9bb02b0e.zip | |
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
diff --git a/NEWS b/NEWS index 168e641120..aa9ca4bc9d 100644 --- a/NEWS +++ b/NEWS @@ -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. |