According to C99 and C11 Annex F, acosh (1) should be +0 in all
rounding modes. However, some implementations in glibc wrongly return
-0 in round-downward mode (which is what you get if you end up
computing log1p (-0), via 1 - 1 being -0 in round-downward mode).
This patch fixes the problem implementations, by correcting the test
for an exact 1 value in the ldbl-96 implementation to allow for the
explicit high bit of the mantissa, and by inserting fabs instructions
in the i386 implementations; tests of acosh are duly converted to
ALL_RM_TEST. I believe all the other sysdeps/ieee754 implementations
are already OK (I haven't checked the ia64 versions, but if buggy then
that will be obvious from the results of test runs after this patch is
in).
Tested x86_64 and x86 and ulps updated accordingly.
[BZ #16927]
* sysdeps/i386/fpu/e_acosh.S (__ieee754_acosh): Use fabs on x-1
value.
* sysdeps/i386/fpu/e_acoshf.S (__ieee754_acoshf): Likewise.
* sysdeps/i386/fpu/e_acoshl.S (__ieee754_acoshl): Likewise.
* sysdeps/ieee754/ldbl-96/e_acoshl.c (__ieee754_acoshl): Correct
for explicit high bit of mantissa when testing for argument equal
to 1.
* math/libm-test.inc (acosh_test): Use ALL_RM_TEST.
* sysdeps/i386/fpu/libm-test-ulps: Update.
* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
2001-07-06 Paul Eggert <eggert@twinsun.com>
* manual/argp.texi: Remove ignored LGPL copyright notice; it's
not appropriate for documentation anyway.
* manual/libc-texinfo.sh: "Library General Public License" ->
"Lesser General Public License".
2001-07-06 Andreas Jaeger <aj@suse.de>
* All files under GPL/LGPL version 2: Place under LGPL version
2.1.
