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| author | Joseph Myers <joseph@codesourcery.com> | 2015-02-26 21:06:34 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-02-26 21:06:34 +0000 |
| commit | 1d9ab20c14211abbf45514e63c190dfeec27fa5e (patch) | |
| tree | cbe705e320799863f477d32c3062f6260c0c72a2 /sysdeps | |
| parent | ec0ce0d3be4ae21add09139c705852ed8bb114c7 (diff) | |
| download | glibc-1d9ab20c14211abbf45514e63c190dfeec27fa5e.zip glibc-1d9ab20c14211abbf45514e63c190dfeec27fa5e.tar.gz glibc-1d9ab20c14211abbf45514e63c190dfeec27fa5e.tar.bz2 | |
Fix ldbl-128/ldbl-128ibm acosl inaccuracy (bug 18038, bug 18039).
The ldbl-128 and ldbl-128ibm implementations of acosl have similar
bugs, using a threshold of 0x1p-57L to determine when they just return
pi/2. Since the result pi/2 - asinl (x) is roughly pi/2 - x for small
x, the relevant cut-off is actually x being < 0.5ulp of 1. This patch
fixes the implementations to use that cut-off and adds tests of small
acos arguments.
Tested for powerpc and mips64. Also tested for x86_64 and x86; no
ulps updates needed.
[BZ #18038]
[BZ #18039]
* sysdeps/ieee754/ldbl-128/e_acosl.c (__ieee754_acosl): Only
return pi/2 for arguments below 0x1p-113L.
* sysdeps/ieee754/ldbl-128ibm/e_acosl.c (__ieee754_acosl): Only
return pi/2 for arguments below 0x1p-106L.
* math/auto-libm-test-in: Add more tests of acos.
* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128/e_acosl.c | 2 | ||||
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/e_acosl.c | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/sysdeps/ieee754/ldbl-128/e_acosl.c b/sysdeps/ieee754/ldbl-128/e_acosl.c index 28c94ed..8c8ec93 100644 --- a/sysdeps/ieee754/ldbl-128/e_acosl.c +++ b/sysdeps/ieee754/ldbl-128/e_acosl.c @@ -173,7 +173,7 @@ __ieee754_acosl (long double x) } else if (ix < 0x3ffe0000) /* |x| < 0.5 */ { - if (ix < 0x3fc60000) /* |x| < 2**-57 */ + if (ix < 0x3f8e0000) /* |x| < 2**-113 */ return pio2_hi + pio2_lo; if (ix < 0x3ffde000) /* |x| < .4375 */ { diff --git a/sysdeps/ieee754/ldbl-128ibm/e_acosl.c b/sysdeps/ieee754/ldbl-128ibm/e_acosl.c index 2cb2882..e5030f1 100644 --- a/sysdeps/ieee754/ldbl-128ibm/e_acosl.c +++ b/sysdeps/ieee754/ldbl-128ibm/e_acosl.c @@ -169,7 +169,7 @@ __ieee754_acosl (long double x) } if (a < 0.5L) { - if (a < 6.938893903907228e-18L) /* |x| < 2**-57 */ + if (a < 0x1p-106L) return pio2_hi + pio2_lo; if (a < 0.4375L) { |