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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 /math/auto-libm-test-in | |
| parent | 6ace39382120dd0668b2168591611f71b04ac8f3 (diff) | |
| download | glibc-fa752c698146ca3e9f7747d33059fbef9bb02b0e.tar.gz | |
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 'math/auto-libm-test-in')
| -rw-r--r-- | math/auto-libm-test-in | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in index 4b93857efb..e86be23fc8 100644 --- a/math/auto-libm-test-in +++ b/math/auto-libm-test-in @@ -3219,6 +3219,7 @@ pow 0x1.ce78f2p+0 -0x2.7f1f78p+4 pow 0xf.fffffp+124 -0x5.b5b648p+0 pow 0x1.430d4cp+0 0x5.0e462p+4 pow 0x9.8b82ap-4 -0x1.99907ap+12 +pow 0xd.73035p-4 -0x1.47bb8p+8 sin 0 sin -0 |