From 7d0b2575416aec2717e8665287d0ab77826a0ade Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Tue, 28 Apr 2015 17:27:02 +0000 Subject: 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 . 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. --- sysdeps/ieee754/ldbl-128/s_roundl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'sysdeps/ieee754/ldbl-128') 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) { -- cgit 1.4.1