[Bug math/15479] ceil, floor and round and trunc raise inexact exception

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https://sourceware.org/bugzilla/show_bug.cgi?id=15479

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=21378ae0d390c45ef382e8c95cc3593845ebb6ea

commit 21378ae0d390c45ef382e8c95cc3593845ebb6ea
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Nov 12 19:00:06 2015 +0000

    Fix powerpc round, roundf spurious "inexact" (bug 19238).

    The powerpc hard-float round and roundf functions, both 32-bit and
    64-bit, raise spurious "inexact" exceptions for integer arguments from
    adding 0.5 and rounding to integer toward zero.

    Since these functions already save and restore the rounding mode, it's
    natural to make them restore the full floating-point state instead to
    fix this bug, which this patch does.  The save of the state is moved
    after the first floating-point operation on the input so that any
    "invalid" exceptions from signaling NaN inputs are properly
    preserved.  As a consequence of this approach to the fix, "inexact"
    for noninteger arguments (disallowed by TS 18661-1 but not by C99/C11,
    see bug 15479) is also avoided for these implementations; this is
    *not* a general fix for bug 15479 since plenty of other
    implementations of various functions still raise spurious "inexact"
    for noninteger arguments.

    This issue and fix do not apply to builds using power5+ versions of
    round and roundf, which use the frin instruction and avoid "inexact"
    exceptions that way.

    This patch should get hard-float powerpc32 and powerpc64 (default
    function implementations) back to a state where test-float and
    test-double will pass after ulps regeneration.

    Tested for powerpc32 and powerpc64.

        [BZ #15479]
        [BZ #19238]
        * sysdeps/powerpc/powerpc32/fpu/s_round.S (__round): Save
        floating-point state after first operation on input.  Restore full
        state rather than just rounding mode.
        * sysdeps/powerpc/powerpc32/fpu/s_roundf.S (__roundf): Likewise.
        * sysdeps/powerpc/powerpc64/fpu/s_round.S (__round): Likewise.
        * sysdeps/powerpc/powerpc64/fpu/s_roundf.S (__roundf): Likewise.

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

Summary of changes:
 ChangeLog                                |    9 +++++++++
 sysdeps/powerpc/powerpc32/fpu/s_round.S  |    9 ++++++---
 sysdeps/powerpc/powerpc32/fpu/s_roundf.S |    9 ++++++---
 sysdeps/powerpc/powerpc64/fpu/s_round.S  |    9 ++++++---
 sysdeps/powerpc/powerpc64/fpu/s_roundf.S |    9 ++++++---
 5 files changed, 33 insertions(+), 12 deletions(-)

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