[Bug math/19134] [powerpc32] lround, lroundf spurious exceptions

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https://sourceware.org/bugzilla/show_bug.cgi?id=19134

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=0c25f5b5bb48a9d550b5fb403b9a801ba04c146f

commit 0c25f5b5bb48a9d550b5fb403b9a801ba04c146f
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Oct 14 21:13:42 2015 +0000

    Fix powerpc32 lround, lroundf spurious exceptions (bug 19134).

    The powerpc32 implementation of lround and lroundf can produce
    spurious exceptions from adding 0.5 then converting to integer.  This
    includes "inexact" from the conversion to integer (not allowed for
    integer arguments to these functions), and, for larger integer
    arguments, "inexact", and "overflow" when rounding upward, from the
    addition.  In addition, "inexact" is not allowed together with
    "invalid" and so inexact addition must be avoided when the integer
    will be out of range of 32-bit long, whether or not the argument is an
    integer.

    This patch fixes these problems.  As in the powerpc64 llround
    implementation, a check is added for too-large arguments; in the
    powerpc64 case that means arguments at least 2^52 in magnitude (so
    that 0.5 cannot be added exactly), while in this case it means
    arguments for which the result would overflow "long".  In those cases
    a suitable overflowing value is used for the integer conversion
    without adding 0.5, while for smaller arguments it's tested whether
    the argument is an integer (by adding and subtracting 2^52 to the
    absolute value and comparing with the original absolute value) to
    avoid adding 0.5 to integers and generating spurious "inexact".

    This code is not used when the power5+ sysdeps directories are used,
    as there's a separate power5+ version of these functions..

    Tested for powerpc.  This gets test-float (for a default powerpc32
    hard-float build without any --with-cpu) back to the point where it
    should pass once powerpc ulps are regenerated; test-double still needs
    another problem with exceptions fixed to get back to that point (and I
    haven't looked lately at what default powerpc64 results are like).

        [BZ #19134]
        * sysdeps/powerpc/powerpc32/fpu/s_lround.S (.LC1): New object.
        (.LC2): Likewise.
        (.LC3): Likewise.
        (__lround): Do not add 0.5 to integer or out-of-range arguments.

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

Summary of changes:
 ChangeLog                                |    8 +++++
 NEWS                                     |    2 +-
 sysdeps/powerpc/powerpc32/fpu/s_lround.S |   43 ++++++++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 3 deletions(-)

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