[Bug math/16353] expm1 missing underflows

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https://sourceware.org/bugzilla/show_bug.cgi?id=16353

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4060283decf711ed95a6c4993ffeaba39f8cd40a

commit 4060283decf711ed95a6c4993ffeaba39f8cd40a
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Tue Jun 24 21:00:08 2014 +0000

    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.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                   |    8 ++++
 NEWS                        |   22 ++++++------
 math/auto-libm-test-in      |    2 +
 math/auto-libm-test-out     |   81 +++++++++++++++++++++++++++++++++++++++++++
 sysdeps/i386/fpu/e_expl.S   |   10 +++++
 sysdeps/x86_64/fpu/e_expl.S |   10 +++++
 6 files changed, 122 insertions(+), 11 deletions(-)

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