[Bug math/18594] cexp, ccos, ccosh, csin, csinh spurious underflows

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https://sourceware.org/bugzilla/show_bug.cgi?id=18594

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a67894c505d44c3a5292804c37d318684d2be469

commit a67894c505d44c3a5292804c37d318684d2be469
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Jun 24 21:04:51 2015 +0000

    Fix cexp, ccos, ccosh, csin, csinh spurious underflows (bug 18594).

    cexp, ccos, ccosh, csin and csinh have spurious underflows in cases
    where they compute sin of the smallest normal, that produces an
    underflow exception (depending on which sin implementation is in use)
    but the final result does not underflow.  ctan and ctanh may also have
    such underflows, or they may be latent (the issue there is that
    e.g. ctan (DBL_MIN) should, rounded upwards, be the next double value
    above DBL_MIN, which under glibc's accuracy goals may not have an
    underflow exception, but the intermediate computation of sin (DBL_MIN)
    would legitimately underflow on before-rounding architectures).

    This patch fixes all those functions so they use plain comparisons (>
    DBL_MIN etc.) instead of comparing the result of fpclassify with
    FP_SUBNORMAL (in all these cases, we already know the number being
    compared is finite).  Note that in the case of csin / csinf / csinl,
    there is no need for fabs calls in the comparison because the real
    part has already been reduced to its absolute value.

    As the patch fixes the failures that previously obstructed moving
    tests of cexp to use ALL_RM_TEST, those tests are moved to ALL_RM_TEST
    by the patch (two functions remain yet to be converted).

    Tested for x86_64 and x86 and ulps updated accordingly.

        [BZ #18594]
        * math/s_ccosh.c (__ccosh): Compare with least normal value
        instead of comparing class with FP_SUBNORMAL.
        * math/s_ccoshf.c (__ccoshf): Likewise.
        * math/s_ccoshl.c (__ccoshl): Likewise.
        * math/s_cexp.c (__cexp): Likewise.
        * math/s_cexpf.c (__cexpf): Likewise.
        * math/s_cexpl.c (__cexpl): Likewise.
        * math/s_csin.c (__csin): Likewise.
        * math/s_csinf.c (__csinf): Likewise.
        * math/s_csinh.c (__csinh): Likewise.
        * math/s_csinhf.c (__csinhf): Likewise.
        * math/s_csinhl.c (__csinhl): Likewise.
        * math/s_csinl.c (__csinl): Likewise.
        * math/s_ctan.c (__ctan): Likewise.
        * math/s_ctanf.c (__ctanf): Likewise.
        * math/s_ctanh.c (__ctanh): Likewise.
        * math/s_ctanhf.c (__ctanhf): Likewise.
        * math/s_ctanhl.c (__ctanhl): Likewise.
        * math/s_ctanl.c (__ctanl): Likewise.
        * math/auto-libm-test-in: Add more tests of ccos, ccosh, cexp,
        csin, csinh, ctan and ctanh.
        * math/auto-libm-test-out: Regenerated.
        * math/libm-test.inc (cexp_test): Use ALL_RM_TEST.
        * sysdeps/i386/fpu/libm-test-ulps: Update.
        * sysdeps/x86_64/fpu/libm-test-ulps: Likewise.

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

Summary of changes:
 ChangeLog                         |   29 +
 NEWS                              |    2 +-
 math/auto-libm-test-in            |   37 +
 math/auto-libm-test-out           | 2212 +++++++++++++++++++++++++++++++++++++
 math/libm-test.inc                |    4 +-
 math/s_ccosh.c                    |    4 +-
 math/s_ccoshf.c                   |    4 +-
 math/s_ccoshl.c                   |    4 +-
 math/s_cexp.c                     |    4 +-
 math/s_cexpf.c                    |    4 +-
 math/s_cexpl.c                    |    4 +-
 math/s_csin.c                     |    4 +-
 math/s_csinf.c                    |    4 +-
 math/s_csinh.c                    |    4 +-
 math/s_csinhf.c                   |    4 +-
 math/s_csinhl.c                   |    4 +-
 math/s_csinl.c                    |    4 +-
 math/s_ctan.c                     |    3 +-
 math/s_ctanf.c                    |    2 +-
 math/s_ctanh.c                    |    3 +-
 math/s_ctanhf.c                   |    2 +-
 math/s_ctanhl.c                   |    3 +-
 math/s_ctanl.c                    |    3 +-
 sysdeps/i386/fpu/libm-test-ulps   |   52 +
 sysdeps/x86_64/fpu/libm-test-ulps |   52 +
 25 files changed, 2414 insertions(+), 38 deletions(-)

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