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Fix sign of remquo zero remainder in round-downward mode (bug 17987).

Browse Source 
Various remquo implementations produce a zero remainder with the wrong
sign (a zero remainder should always have the sign of the first
argument, as specified in IEEE 754) in round-downward mode, resulting
from the sign of 0 - 0.  This patch checks for zero results and fixes
their sign accordingly.

Tested for x86_64, x86, mips64 and powerpc.

	[BZ #17987]
	* sysdeps/ieee754/dbl-64/s_remquo.c (__remquo): Ensure sign of
	zero result does not depend on the sign resulting from
	subtraction.
	* sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c (__remquo):
	Likewise.
	* sysdeps/ieee754/flt-32/s_remquof.c (__remquof): Likewise.
	* sysdeps/ieee754/ldbl-128/s_remquol.c (__remquol): Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_remquol.c (__remquol): Likewise.
	* sysdeps/ieee754/ldbl-96/s_remquol.c (__remquol): Likewise.
	* math/libm-test.inc (remquo_test_data): Add more tests.
This commit is contained in:
Joseph Myers
2015-02-17 00:41:50 +00:00
parent 0d7036bdb1
commit ce8fc784e6
9 changed files with 43 additions and 1 deletions
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10
math/libm-test.inc
View File

@ -8818,6 +8818,16 @@ static const struct test_ffI_f1_data remquo_test_data[] =
TEST_ffI_f1 (remquo, -1, -max_value / 4, -1, 0, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, -1, max_value / 8, -1, 0, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, -1, -max_value / 8, -1, 0, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, max_value, max_value / 2, plus_zero, 2, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, max_value, -max_value / 2, plus_zero, -2, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, -max_value, max_value / 2, minus_zero, -2, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, -max_value, -max_value / 2, minus_zero, 2, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, 2, 1, plus_zero, 2, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, 2, -1, plus_zero, -2, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, -2, 1, minus_zero, -2, NO_INEXACT_EXCEPTION),
TEST_ffI_f1 (remquo, -2, -1, minus_zero, 2, NO_INEXACT_EXCEPTION),
};
static void