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The ldbl-128ibm implementation of remainderl has logic resulting in
incorrect tests for equality of the absolute values of the arguments
in the case of zero low parts. If the low parts are both zero but
with different signs, this can wrongly cause equal arguments to be
treated as different, resulting in turn in incorrect signs of zero
result in nondefault rounding modes arising from the subtractions done
when the arguments are not equal.
This patch fixes the logic to convert -0 low parts into +0 before the
comparison (remquo already has separate logic to deal with signs of
zero results, so doesn't need such a change). Tests are added for
remainderl and remquol similar to that for fmodl, and based on a
refactoring of it, since the bug depends on low parts which should not
be relied upon in tests not setting the representation explicitly
(although in fact the bug shows up in test-ldouble with current GCC).
Tested for powerpc.
[BZ #19677]
* sysdeps/ieee754/ldbl-128ibm/e_remainderl.c
(__ieee754_remainderl): Put zero low parts in canonical form.
* sysdeps/ieee754/ldbl-128ibm/test-fmodrem-ldbl-128ibm.c: New
file. Based on
sysdeps/ieee754/ldbl-128ibm/test-fmodl-ldbl-128ibm.c.
* sysdeps/ieee754/ldbl-128ibm/test-fmodl-ldbl-128ibm.c: Replace
with wrapper round test-fmodrem-ldbl-128ibm.c.
* sysdeps/ieee754/ldbl-128ibm/test-remainderl-ldbl-128ibm.c: New
file.
* sysdeps/ieee754/ldbl-128ibm/test-remquol-ldbl-128ibm.c:
Likewise.
* sysdeps/ieee754/ldbl-128ibm/Makefile (tests): Add
test-remainderl-ldbl-128ibm and test-remquol-ldbl-128ibm.
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