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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 /math | |
| parent | fb4041ae532fd21a82618c2be09898ea8979dec5 (diff) | |
| download | glibc-7d0b2575416aec2717e8665287d0ab77826a0ade.tar.gz glibc-7d0b2575416aec2717e8665287d0ab77826a0ade.tar.xz glibc-7d0b2575416aec2717e8665287d0ab77826a0ade.zip | |
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 'math')
| -rw-r--r-- | math/libm-test.inc | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/math/libm-test.inc b/math/libm-test.inc index 5d7f5a25c8..4cade14925 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -9012,6 +9012,17 @@ static const struct test_f_f_data round_test_data[] = TEST_f_f (round, 2097152.5, 2097153), TEST_f_f (round, -2097152.5, -2097153), +#ifndef TEST_FLOAT + TEST_f_f (round, 0xffffffffffff.0p0L, 0xffffffffffff.0p0L), + TEST_f_f (round, 0xffffffffffff.4p0L, 0xffffffffffff.0p0L), + TEST_f_f (round, 0xffffffffffff.8p0L, 0x1000000000000.0p0L), + TEST_f_f (round, 0xffffffffffff.cp0L, 0x1000000000000.0p0L), + TEST_f_f (round, -0xffffffffffff.0p0L, -0xffffffffffff.0p0L), + TEST_f_f (round, -0xffffffffffff.4p0L, -0xffffffffffff.0p0L), + TEST_f_f (round, -0xffffffffffff.8p0L, -0x1000000000000.0p0L), + TEST_f_f (round, -0xffffffffffff.cp0L, -0x1000000000000.0p0L), +#endif + #ifdef TEST_LDOUBLE /* The result can only be represented in long double. */ TEST_f_f (round, 4503599627370495.5L, 4503599627370496.0L), |