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| author | Joseph Myers <joseph@codesourcery.com> | 2015-04-28 17:27:02 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-04-28 17:27:02 +0000 |
| commit | 7d0b2575416aec2717e8665287d0ab77826a0ade (patch) | |
| tree | d264ccfa2e441db9d74e41947567112a293a2f06 /sysdeps/ieee754 | |
| parent | fb4041ae532fd21a82618c2be09898ea8979dec5 (diff) | |
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Fix ldbl-128 roundl for exponents in [31, 47] (bug 18346).
The implementation of roundl for ldbl-128 involves undefined behavior
for arguments with exponents from 31 to 47 inclusive, from the shift:
u_int64_t i = -1ULL >> (j0 - 48);
For example, on mips64, this means roundl (0xffffffffffff.8p0L)
wrongly returns its argument, which is not an integer. A condition
checking for exponents < 31 should actually be checking for exponents
< 48, and this patch makes it do so. (That condition is for whether
the bit representing 0.5 is in the high 64-bit half of the
floating-point number. The value 31 might have arisen from an
incorrect conversion of the ldbl-96 version to handle ldbl-128.)
This was originally reported as a GCC libquadmath bug
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65757>.
Tested for mips64; also tested for x86_64 and x86 to make sure the new
tests pass there.
[BZ #18346]
* sysdeps/ieee754/ldbl-128/s_roundl.c (__roundl): Handle all
exponents less than 48 as cases where high part of mantissa needs
examining to determine whether argument is integral.
* math/libm-test.inc (round_test_data): Add more tests.
Diffstat (limited to 'sysdeps/ieee754')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128/s_roundl.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/sysdeps/ieee754/ldbl-128/s_roundl.c b/sysdeps/ieee754/ldbl-128/s_roundl.c index 9df0092ce8..3ff6ebe7cc 100644 --- a/sysdeps/ieee754/ldbl-128/s_roundl.c +++ b/sysdeps/ieee754/ldbl-128/s_roundl.c @@ -34,7 +34,7 @@ __roundl (long double x) GET_LDOUBLE_WORDS64 (i0, i1, x); j0 = ((i0 >> 48) & 0x7fff) - 0x3fff; - if (j0 < 31) + if (j0 < 48) { if (j0 < 0) { |