[Bug math/16783] [i386, x86_64] scalb (qNaN, -Inf) spurious "invalid" exception

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https://sourceware.org/bugzilla/show_bug.cgi?id=16783

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9438b237abca11de201dd10483717299eafb1f0b

commit 9438b237abca11de201dd10483717299eafb1f0b
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Tue Feb 24 17:30:02 2015 +0000

    Fix x86/x86_64 scalb (qNaN, -Inf) (bug 16783).

    Various x86 / x86_64 versions of scalb / scalbf / scalbl produce
    spurious "invalid" exceptions for (qNaN, -Inf) arguments, because this
    is wrongly handled like (+/-Inf, -Inf) which *should* raise such an
    exception.  (In fact the NaN case of the code determining whether to
    quietly return a zero or a NaN for second argument -Inf was
    accidentally dead since the code had been made to return a NaN with
    exception.)  This patch fixes the code to do the proper test for an
    infinity as distinct from a NaN.

    (Since the existing code does nothing to distinguish qNaNs and sNaNs
    here, this patch doesn't either.  If in future we systematically
    implement proper sNaN semantics following TS 18661-1:2014, there will
    be lots of bugs to address - Thomas found lots of issues with his
    patch <https://sourceware.org/ml/libc-ports/2013-04/msg00008.html> to
    add SNaN tests (which never went in and would now require significant
    reworking).)

    Tested for x86_64 and x86.  Committed.

        [BZ #16783]
        * sysdeps/i386/fpu/e_scalb.S (__ieee754_scalb): Do not handle
        arguments (NaN, -Inf) the same as (+/-Inf, -Inf).
        * sysdeps/i386/fpu/e_scalbf.S (__ieee754_scalbf): Likewise.
        * sysdeps/i386/fpu/e_scalbl.S (__ieee754_scalbl): Likewise.
        * sysdeps/x86_64/fpu/e_scalbl.S (__ieee754_scalbl): Likewise.
        * math/libm-test.inc (scalb_test_data): Add more tests.

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

Summary of changes:
 ChangeLog                     |   10 ++++++++++
 NEWS                          |    6 +++---
 math/libm-test.inc            |    2 ++
 sysdeps/i386/fpu/e_scalb.S    |    4 +++-
 sysdeps/i386/fpu/e_scalbf.S   |    4 +++-
 sysdeps/i386/fpu/e_scalbl.S   |    4 +++-
 sysdeps/x86_64/fpu/e_scalbl.S |    4 +++-
 7 files changed, 27 insertions(+), 7 deletions(-)

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