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authorJoseph Myers <joseph@codesourcery.com>2013-12-18 11:38:27 +0000
committerJoseph Myers <joseph@codesourcery.com>2013-12-18 11:38:27 +0000
commit2dec468fd82c6d968f622c2c519fcb8dc09bddac (patch)
treeebc7e3f72a6474d7aa3f6a042bb01a2917562bc3 /sysdeps/x86_64
parent4d84e6addd62bdc256627af334ba85489112e008 (diff)
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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/x86_64')
-rw-r--r--sysdeps/x86_64/fpu/libm-test-ulps3
1 files changed, 3 insertions, 0 deletions
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