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GNU C Library master sources branch master updated. glibc-2.21-130-g380bd0f
- From: jsm28 at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 26 Feb 2015 15:16:05 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.21-130-g380bd0f
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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=380bd0fd2418f8988217de950f8b8ff18af0cb2b
commit 380bd0fd2418f8988217de950f8b8ff18af0cb2b
Author: Joseph Myers <joseph@codesourcery.com>
Date: Thu Feb 26 15:13:22 2015 +0000
Fix ldbl-128ibm logbl near powers of 2 (bug 18030).
The ldbl-128ibm implementation of logbl produces incorrect results
when the high part of the argument is a power of 2 and the low part a
nonzero number with the opposite sign (and so the returned exponent
should be 1 less than that of the high part). For example, logbl
(0x1.ffffffffffffffp1L) returns 2 but should return 1. (This is
similar to (fixed) bug 16740 for frexpl, and (fixed) bug 18029 for
ilogbl.) This patch adds checks for that case.
Tested for powerpc.
[BZ #18030]
* sysdeps/ieee754/ldbl-128ibm/s_logbl.c (__logbl): Adjust exponent
of power of 2 down when low part has opposite sign.
* math/libm-test.inc (logb_test_data): Add more tests.
diff --git a/ChangeLog b/ChangeLog
index 90c42c8..ac6110b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2015-02-26 Joseph Myers <joseph@codesourcery.com>
+
+ [BZ #18030]
+ * sysdeps/ieee754/ldbl-128ibm/s_logbl.c (__logbl): Adjust exponent
+ of power of 2 down when low part has opposite sign.
+ * math/libm-test.inc (logb_test_data): Add more tests.
+
2015-02-26 Andreas Schwab <schwab@suse.de>
[BZ #18032]
diff --git a/NEWS b/NEWS
index 77e0814..f09ffb1 100644
--- a/NEWS
+++ b/NEWS
@@ -12,7 +12,7 @@ Version 2.22
4719, 14841, 13064, 14094, 15319, 15467, 15790, 15969, 16560, 16783,
17269, 17523, 17569, 17588, 17792, 17836, 17912, 17916, 17932, 17944,
17949, 17964, 17965, 17967, 17969, 17978, 17987, 17991, 17996, 17998,
- 17999, 18019, 18020, 18029, 18032.
+ 17999, 18019, 18020, 18029, 18030, 18032.
* Character encoding and ctype tables were updated to Unicode 7.0.0, using
new generator scripts contributed by Pravin Satpute and Mike FABIAN (Red
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 6045764..7acd29b 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -7868,6 +7868,11 @@ static const struct test_f_f_data logb_test_data[] =
TEST_f_f (logb, 0x1p-16400L, -16400, NO_INEXACT_EXCEPTION),
TEST_f_f (logb, 0x.00000000001p-16382L, -16426, NO_INEXACT_EXCEPTION),
#endif
+
+#if defined TEST_LDOUBLE && LDBL_MANT_DIG >= 57
+ TEST_f_f (logb, 0x1.ffffffffffffffp1L, 1, NO_INEXACT_EXCEPTION),
+ TEST_f_f (logb, -0x1.ffffffffffffffp1L, 1, NO_INEXACT_EXCEPTION),
+#endif
};
static void
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_logbl.c b/sysdeps/ieee754/ldbl-128ibm/s_logbl.c
index dbd3478..22e5fc2 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_logbl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_logbl.c
@@ -26,11 +26,12 @@
long double
__logbl (long double x)
{
- int64_t hx, rhx;
- double xhi;
+ int64_t hx, hxs, rhx;
+ double xhi, xlo;
- xhi = ldbl_high (x);
+ ldbl_unpack (x, &xhi, &xlo);
EXTRACT_WORDS64 (hx, xhi);
+ hxs = hx;
hx &= 0x7fffffffffffffffLL; /* high |x| */
if (hx == 0)
return -1.0 / fabs (x);
@@ -42,6 +43,16 @@ __logbl (long double x)
though it were normalized. */
rhx -= __builtin_clzll (hx) - 12;
}
+ else if ((hx & 0x000fffffffffffffLL) == 0)
+ {
+ /* If the high part is a power of 2, and the low part is nonzero
+ with the opposite sign, the low part affects the
+ exponent. */
+ int64_t lx;
+ EXTRACT_WORDS64 (lx, xlo);
+ if ((hxs ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0)
+ rhx--;
+ }
return (long double) (rhx - 1023);
}
#ifndef __logbl
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 7 +++++++
NEWS | 2 +-
math/libm-test.inc | 5 +++++
sysdeps/ieee754/ldbl-128ibm/s_logbl.c | 17 ++++++++++++++---
4 files changed, 27 insertions(+), 4 deletions(-)
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