[Bug math/16357] [i386] atanhl spurious underflow on x86

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https://sourceware.org/bugzilla/show_bug.cgi?id=16357

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=046651c1688ff0eaa385d555dc4f24fd51a64460

commit 046651c1688ff0eaa385d555dc4f24fd51a64460
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Tue Mar 25 12:26:06 2014 +0000

    Relax gen-auto-libm-tests may-underflow rules, test log1p in all rounding
modes.

    gen-auto-libm-tests presently allows but does not require underflow
    exceptions for results with magnitude in the range (greatest
    subnormal, least normal].

    In some cases, the magnitude of the exact result is very slightly
    above the least normal, but rounding in the implementation results in
    it effectively computing an infinite-precision result that is slightly
    below the least normal, so raising an underflow exception.  This is in
    accordance with the documented accuracy goals, but results in
    testsuite failures.

    This patch changes the logic to allow underflows when the mathematical
    result is up to 0.5ulp above the least normal (so in any case where
    the round-to-nearest result is the least normal).  Ideally underflows
    in all these cases would be accepted only when an underflow with the
    actual result is consistent with the rounding mode (in FE_TOWARDZERO
    mode, a return value of the least normal implies that the
    infinite-precision result did not underflow so there should be no
    underflow exception, for example), so as to match the documented goals
    more precisely - whereas at present the tests for exceptions are
    completely independent of the tests of the returned values.  (The same
    applies to overflow exceptions as well - they too should be checked
    for consistency with the result, as in FE_TOWARDZERO mode a result
    1ulp below the largest finite value should be inconsistent with an
    overflow exception and cause a failure with overflow rather than
    simply being considered a 1ulp error when overflow is expected.)  But
    the present patch at least deals with the cases causing spurious
    failures so that (a) certain existing tests no longer need to be
    marked as having spurious exceptions (such markings in
    auto-libm-test-in end up applying to more cases than just those they
    are needed for) and (b) log1p can be tested in all rounding modes
    without introducing more such failures.  This patch duly moves tests
    of log1p to ALL_RM_TEST.

    Tested x86_64 and x86 and ulps updated accordingly.

        [BZ #16357]
        [BZ #16599]
        * math/gen-auto-libm-tests.c (fp_format_desc): Add field
        min_plus_half.
        (fp_formats): Update initializers.
        (init_fp_formats): Initialize new field.
        (output_for_one_input_case): Allow underflow for results up to
        min_plus_half.
        * math/libm-test.inc (log1p_test): Use ALL_RM_TEST.
        * math/auto-libm-test-in: Don't mark some underflows from asin and
        atanh as spurious.
        * 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                         |   17 ++
 NEWS                              |    8 +-
 math/auto-libm-test-in            |    8 +-
 math/auto-libm-test-out           |  558 ++++++++++++++++++------------------
 math/gen-auto-libm-tests.c        |   23 +-
 math/libm-test.inc                |    4 +-
 sysdeps/i386/fpu/libm-test-ulps   |   24 ++
 sysdeps/x86_64/fpu/libm-test-ulps |   24 ++
 8 files changed, 367 insertions(+), 299 deletions(-)

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