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Fix sign of remquo zero remainder in round-downward mode (bug 17987) [committed]
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Tue, 17 Feb 2015 00:42:37 +0000
- Subject: Fix sign of remquo zero remainder in round-downward mode (bug 17987) [committed]
- Authentication-results: sourceware.org; auth=none
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. Committed.
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.
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 1cf80e3..85d8b67 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -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
diff --git a/sysdeps/ieee754/dbl-64/s_remquo.c b/sysdeps/ieee754/dbl-64/s_remquo.c
index e07efa8..b081d26 100644
--- a/sysdeps/ieee754/dbl-64/s_remquo.c
+++ b/sysdeps/ieee754/dbl-64/s_remquo.c
@@ -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;
diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
index ab56178..304e9d0 100644
--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
@@ -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;
diff --git a/sysdeps/ieee754/flt-32/s_remquof.c b/sysdeps/ieee754/flt-32/s_remquof.c
index 04944fd..36cf359 100644
--- a/sysdeps/ieee754/flt-32/s_remquof.c
+++ b/sysdeps/ieee754/flt-32/s_remquof.c
@@ -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;
diff --git a/sysdeps/ieee754/ldbl-128/s_remquol.c b/sysdeps/ieee754/ldbl-128/s_remquol.c
index da175a1..82cdf1a 100644
--- a/sysdeps/ieee754/ldbl-128/s_remquol.c
+++ b/sysdeps/ieee754/ldbl-128/s_remquol.c
@@ -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;
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_remquol.c b/sysdeps/ieee754/ldbl-128ibm/s_remquol.c
index ac22879..57c5059 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_remquol.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_remquol.c
@@ -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;
diff --git a/sysdeps/ieee754/ldbl-96/s_remquol.c b/sysdeps/ieee754/ldbl-96/s_remquol.c
index 1462b54..8d6b10e 100644
--- a/sysdeps/ieee754/ldbl-96/s_remquol.c
+++ b/sysdeps/ieee754/ldbl-96/s_remquol.c
@@ -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;
--
Joseph S. Myers
joseph@codesourcery.com