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authorJoseph Myers <joseph@codesourcery.com>2014-06-24 21:00:08 +0000
committerJoseph Myers <joseph@codesourcery.com>2014-06-24 21:00:08 +0000
commit4060283decf711ed95a6c4993ffeaba39f8cd40a (patch)
treed303f8bcf7bd9fafbbb5edddc48c7c2be827f84e /ChangeLog
parente7dd3c8c1db8c6d293abb995e033893b7328ad19 (diff)
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Fix x86/x86_64 expm1l spurious underflow exceptions (bug 16539).
This patch fixes bug 16539, spurious underflow exceptions from x86 /
x86-64 expm1l.  The problem is that the computation of a base-2
exponent with extra precision involves spurious underflows for
arguments that are small but not subnormal, so a check is added to
just return the argument in those cases.  (If the argument *is*
subnormal, underflowing is correct and the existing code will always
underflow, so it suffices to keep using the existing code in that
case; some expm1 implementations have a bug (bug 16353) with missing
underflow exceptions, but I don't think there's such a bug in this
particular version.)

Tested x86_64 and x86; no ulps updates needed.

(auto-libm-test-out diffs omitted below.)

	[BZ #16539]
	* sysdeps/i386/fpu/e_expl.S (IEEE754_EXPL) [USE_AS_EXPM1L]: Just
	return the argument for normal arguments with exponent below -64.
	* sysdeps/x86_64/fpu/e_expl.S (IEEE754_EXPL) [USE_AS_EXPM1L]:
	Likewise.
	* math/auto-libm-test-in: Add another test of expm1.
	* math/auto-libm-test-out: Regenerated.
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 2014-06-24  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #16539]
+	* sysdeps/i386/fpu/e_expl.S (IEEE754_EXPL) [USE_AS_EXPM1L]: Just
+	return the argument for normal arguments with exponent below -64.
+	* sysdeps/x86_64/fpu/e_expl.S (IEEE754_EXPL) [USE_AS_EXPM1L]:
+	Likewise.
+	* math/auto-libm-test-in: Add another test of expm1.
+	* math/auto-libm-test-out: Regenerated.
+
 	[BZ #16287]
 	* sysdeps/ieee754/ldbl-128/s_erfl.c (__erfl): Return 1 without
 	calling __erfcl for arguments at least 16.