[Bug math/17987] remquo bad sign of zero remainder in round-downward mode

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https://sourceware.org/bugzilla/show_bug.cgi?id=17987

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=ce8fc784e619ada624dc41ed7603211131e66573

commit ce8fc784e619ada624dc41ed7603211131e66573
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Tue Feb 17 00:41:50 2015 +0000

    Fix sign of remquo zero remainder in round-downward mode (bug 17987).

    Various remquo implementations produce a zero remainder with the wrong
    sign (a zero remainder should always have the sign of the first
    argument, as specified in IEEE 754) in round-downward mode, resulting
    from the sign of 0 - 0.  This patch checks for zero results and fixes
    their sign accordingly.

    Tested for x86_64, x86, mips64 and powerpc.

        [BZ #17987]
        * sysdeps/ieee754/dbl-64/s_remquo.c (__remquo): Ensure sign of
        zero result does not depend on the sign resulting from
        subtraction.
        * sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c (__remquo):
        Likewise.
        * sysdeps/ieee754/flt-32/s_remquof.c (__remquof): Likewise.
        * sysdeps/ieee754/ldbl-128/s_remquol.c (__remquol): Likewise.
        * sysdeps/ieee754/ldbl-128ibm/s_remquol.c (__remquol): Likewise.
        * sysdeps/ieee754/ldbl-96/s_remquol.c (__remquol): Likewise.
        * math/libm-test.inc (remquo_test_data): Add more tests.

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

Summary of changes:
 ChangeLog                                     |   14 ++++++++++++++
 NEWS                                          |    2 +-
 math/libm-test.inc                            |   10 ++++++++++
 sysdeps/ieee754/dbl-64/s_remquo.c             |    3 +++
 sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c |    3 +++
 sysdeps/ieee754/flt-32/s_remquof.c            |    3 +++
 sysdeps/ieee754/ldbl-128/s_remquol.c          |    3 +++
 sysdeps/ieee754/ldbl-128ibm/s_remquol.c       |    3 +++
 sysdeps/ieee754/ldbl-96/s_remquol.c           |    3 +++
 9 files changed, 43 insertions(+), 1 deletions(-)

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