[Bug math/18019] [ldbl-128ibm] acoshl inaccurate

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https://sourceware.org/bugzilla/show_bug.cgi?id=18019

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=440169d681cc9f422e8486f1324079bef0e0c35a

commit 440169d681cc9f422e8486f1324079bef0e0c35a
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Feb 25 00:01:15 2015 +0000

    Fix ldbl-128ibm acoshl inaccuracy (bug 18019).

    The ldbl-128ibm implementation of acoshl uses a cut-off of 0x1p28 to
    determine when to use log(x) + log(2) as a formula.  That cut-off is
    too small for this format, resulting in large errors.  This patch
    changes it to a more appropriate cut-off of 0x1p56, adding tests
    around the cut-offs for various floating-point formats.

    Tested for powerpc.  Also tested for x86_64 and x86 and updated ulps.

        [BZ #18019]
        * sysdeps/ieee754/ldbl-128ibm/e_acoshl.c (__ieee754_acoshl): Use
        2**56 not 2**28 as threshold for log (2x) formula.
        * math/auto-libm-test-in: Add more tests of acosh.
        * math/auto-libm-test-out: Regenerated.
        * sysdeps/i386/fpu/libm-test-ulps: Update.
        * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.

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

Summary of changes:
 ChangeLog                              |   10 +
 NEWS                                   |    3 +-
 math/auto-libm-test-in                 |   31 ++
 math/auto-libm-test-out                |  835 ++++++++++++++++++++++++++++++++
 sysdeps/i386/fpu/libm-test-ulps        |    4 +
 sysdeps/ieee754/ldbl-128ibm/e_acoshl.c |    4 +-
 sysdeps/x86_64/fpu/libm-test-ulps      |   17 +-
 7 files changed, 899 insertions(+), 5 deletions(-)

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