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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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
ChangeLog
View File

@ -1,3 +1,17 @@
2015-02-16 Joseph Myers <joseph@codesourcery.com>
[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.
2015-02-16 Paul Eggert <eggert@cs.ucla.edu>
* manual/time.texi (TZ Variable): glibc no longer comes with tzdata.

2
NEWS
View File

@ -10,7 +10,7 @@ Version 2.22
* The following bugs are resolved with this release:
4719, 15467, 15790, 16560, 17569, 17792, 17912, 17932, 17944, 17949,
17964, 17965, 17967, 17969, 17978.
17964, 17965, 17967, 17969, 17978, 17987.
Version 2.21

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

3
sysdeps/ieee754/dbl-64/s_remquo.c
View File

@ -101,6 +101,9 @@ __remquo (double x, double y, int *quo)
*quo = qs ? -cquo : cquo;
/* Ensure correct sign of zero result in round-downward mode. */
if (x == 0.0)
x = 0.0;
if (sx)
x = -x;
return x;

3
sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
View File

@ -100,6 +100,9 @@ __remquo (double x, double y, int *quo)
*quo = qs ? -cquo : cquo;
/* Ensure correct sign of zero result in round-downward mode. */
if (x == 0.0)
x = 0.0;
if (sx)
x = -x;
return x;

3
sysdeps/ieee754/flt-32/s_remquof.c
View File

@ -100,6 +100,9 @@ __remquof (float x, float y, int *quo)
*quo = qs ? -cquo : cquo;
/* Ensure correct sign of zero result in round-downward mode. */
if (x == 0.0f)
x = 0.0f;
if (sx)
x = -x;
return x;

3
sysdeps/ieee754/ldbl-128/s_remquol.c
View File

@ -102,6 +102,9 @@ __remquol (long double x, long double y, int *quo)
*quo = qs ? -cquo : cquo;
/* Ensure correct sign of zero result in round-downward mode. */
if (x == 0.0L)
x = 0.0L;
if (sx)
x = -x;
return x;

3
sysdeps/ieee754/ldbl-128ibm/s_remquol.c
View File

@ -107,6 +107,9 @@ __remquol (long double x, long double y, int *quo)
*quo = qs ? -cquo : cquo;
/* Ensure correct sign of zero result in round-downward mode. */
if (x == 0.0L)
x = 0.0L;
if (sx)
x = -x;
return x;

3
sysdeps/ieee754/ldbl-96/s_remquol.c
View File

@ -101,6 +101,9 @@ __remquol (long double x, long double p, int *quo)
*quo = qs ? -cquo : cquo;
/* Ensure correct sign of zero result in round-downward mode. */
if (x == 0.0L)
x = 0.0L;
if (sx)
x = -x;
return x;