[Bug math/22690] [ldbl-128ibm] lrintl, lroundl missing "invalid" exceptions

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https://sourceware.org/bugzilla/show_bug.cgi?id=22690

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1272748886257ae4d73485eb7534756e89643091

commit 1272748886257ae4d73485eb7534756e89643091
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Jan 10 00:02:35 2018 +0000

    Fix ldbl-128ibm lrintl, lroundl missing "invalid" exceptions (bug 22690).

    The ldbl-128ibm implementations of lrintl and lroundl are missing
    "invalid" exceptions for certain overflow cases when compiled with GCC
    8.  The cause of this is after-the-fact integer overflow checks that
    fail when the compiler optimizes on the basis of integer overflow
    being undefined; GCC 8 must be able to detect new cases of
    undefinedness here.

    Failure: lrint (-0x80000001p0): Exception "Invalid operation" not set
    Failure: lrint_downward (-0x80000001p0): Exception "Invalid operation" not
set
    Failure: lrint_towardzero (-0x80000001p0): Exception "Invalid operation"
not set
    Failure: lrint_upward (-0x80000001p0): Exception "Invalid operation" not
set

    Failure: lround (-0x80000001p0): Exception "Invalid operation" not set
    Failure: lround_downward (-0x80000001p0): Exception "Invalid operation" not
set
    Failure: lround_towardzero (-0x80000001p0): Exception "Invalid operation"
not set
    Failure: lround_upward (-0x80000001p0): Exception "Invalid operation" not
set

    (Tested that these failures occur before the patch for powerpc
    soft-float, but the issue applies in principle for hard-float as well,
    whether or not the particular optimizations in fact occur there at
    present.)

    This patch fixes the bug by ensuring the additions / subtractions in
    question cast arguments to unsigned long int, or use 1UL as a constant
    argument, so that the arithmetic occurs in an unsigned type with the
    result then converted back to a signed type.

    Tested for powerpc (soft-float).

        [BZ #22690]
        * sysdeps/ieee754/ldbl-128ibm/s_lrintl.c (__lrintl): Use unsigned
        long int for arguments of possibly overflowing addition or
        subtraction.
        * sysdeps/ieee754/ldbl-128ibm/s_lroundl.c (__lroundl): Likewise.

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

Summary of changes:
 ChangeLog                               |    8 ++++++++
 sysdeps/ieee754/ldbl-128ibm/s_lrintl.c  |   14 +++++++-------
 sysdeps/ieee754/ldbl-128ibm/s_lroundl.c |   10 +++++-----
 3 files changed, 20 insertions(+), 12 deletions(-)

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