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| author | Joseph Myers <joseph@codesourcery.com> | 2013-12-18 11:38:27 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2013-12-18 11:38:27 +0000 |
| commit | 2dec468fd82c6d968f622c2c519fcb8dc09bddac (patch) | |
| tree | ebc7e3f72a6474d7aa3f6a042bb01a2917562bc3 /sysdeps | |
| parent | 4d84e6addd62bdc256627af334ba85489112e008 (diff) | |
| download | glibc-2dec468fd82c6d968f622c2c519fcb8dc09bddac.tar.gz glibc-2dec468fd82c6d968f622c2c519fcb8dc09bddac.tar.xz glibc-2dec468fd82c6d968f622c2c519fcb8dc09bddac.zip | |
Fix ldbl-128 logl for subnormals (bug 16338).
This patch fixes bug 16338, ldbl-128 logl not handling subnormals (with consequent inaccuracy for lgammal as well). The fix is simply to use __frexpl when determining the exponent, as done already in log2l and log10l. Given the lack of testing of small arguments to any of the log* functions, appropriate tests are added for all of them. Tested x86_64 and x86 and ulps updated accordingly, and spot tests also run for mips64 to confirm the ldbl-128 fix. Note that while this fixes lgammal inaccuracy for small positive arguments, I suspect that there will still be problems with spurious underflows in that case. * sysdeps/ieee754/ldbl-128/e_logl.c (__ieee754_logl): Use __frexpl to determine exponent and adjust argument to have exponent of -1. * math/auto-libm-test-in: Add more tests of log, log10, log1p and log2. * math/auto-libm-test-out: Regenerated. * sysdeps/x86_64/fpu/libm-test-ulps: Update.
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/i386/fpu/libm-test-ulps | 3 | ||||
| -rw-r--r-- | sysdeps/ieee754/ldbl-128/e_logl.c | 5 | ||||
| -rw-r--r-- | sysdeps/x86_64/fpu/libm-test-ulps | 3 |
3 files changed, 8 insertions, 3 deletions
diff --git a/sysdeps/i386/fpu/libm-test-ulps b/sysdeps/i386/fpu/libm-test-ulps index ce4e631bbe..5ed3feefc9 100644 --- a/sysdeps/i386/fpu/libm-test-ulps +++ b/sysdeps/i386/fpu/libm-test-ulps @@ -6684,6 +6684,9 @@ ldouble: 1 Test "log10 (0x2.b7e151628aed2p+0)": ildouble: 1 ldouble: 1 +Test "log10 (0x4p-128)": +ildouble: 1 +ldouble: 1 Test "log10 (0xcp-4)": ildouble: 1 ldouble: 1 diff --git a/sysdeps/ieee754/ldbl-128/e_logl.c b/sysdeps/ieee754/ldbl-128/e_logl.c index 395a76302a..3d1034dd61 100644 --- a/sysdeps/ieee754/ldbl-128/e_logl.c +++ b/sysdeps/ieee754/ldbl-128/e_logl.c @@ -212,9 +212,8 @@ __ieee754_logl(long double x) } /* Extract exponent and reduce domain to 0.703125 <= u < 1.40625 */ - e = (int) (m >> 16) - (int) 0x3ffe; - m &= 0xffff; - u.parts32.w0 = m | 0x3ffe0000; + u.value = __frexpl (x, &e); + m = u.parts32.w0 & 0xffff; m |= 0x10000; /* Find lookup table index k from high order bits of the significand. */ if (m < 0x16800) diff --git a/sysdeps/x86_64/fpu/libm-test-ulps b/sysdeps/x86_64/fpu/libm-test-ulps index 398594533b..d36b76a047 100644 --- a/sysdeps/x86_64/fpu/libm-test-ulps +++ b/sysdeps/x86_64/fpu/libm-test-ulps @@ -7675,6 +7675,9 @@ ldouble: 1 Test "log10 (0x2.b7e154p+0)": float: 1 ifloat: 1 +Test "log10 (0x4p-128)": +ildouble: 1 +ldouble: 1 Test "log10 (0xcp-4)": double: 1 float: 2 |