Fix ldbl-128ibm acoshl inaccuracy (bug 16384).

This patch fixes bug 16384, ldbl-128ibm acoshl inaccuracy, which
showed up while attempting to regenerate ulps for powerpc-nofpu for
2.19.  There were two separate problems, use of __log1p instead of
__log1pl and an insufficiently accurate constant value for log 2
(which this patch replaces by use of M_LN2l), each of which could
cause substantial inaccuracy in affected cases.

Tested for powerpc-nofpu.

	* sysdeps/ieee754/ldbl-128ibm/e_acoshl.c (ln2): Initialize with
	M_LN2l.
	(__ieee754_acoshl): Use __log1pl not __log1p.

diff --git a/ChangeLog b/ChangeLog
index cb91ca7..4fae701 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2014-01-02  Joseph Myers  <joseph@codesourcery.com>
+
+       [BZ #16384]
+       * sysdeps/ieee754/ldbl-128ibm/e_acoshl.c (ln2): Initialize with
+       M_LN2l.
+       (__ieee754_acoshl): Use __log1pl not __log1p.
+
 2013-01-02  Ondřej Bílka  <neleai@seznam.cz>
 
        * malloc/arena.c (malloc_atfork, free_atfork, ptmalloc_lock_all,

diff --git a/NEWS b/NEWS
index 47ab121..c53be8a 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -23,7 +23,7 @@ Version 2.19
   16038, 16041, 16055, 16071, 16072, 16074, 16077, 16078, 16103, 16112,
   16143, 16144, 16146, 16150, 16151, 16153, 16167, 16172, 16195, 16214,
   16245, 16271, 16274, 16283, 16289, 16293, 16314, 16316, 16330, 16337,
-  16338, 16356, 16365, 16366, 16369, 16372, 16375, 16379.
+  16338, 16356, 16365, 16366, 16369, 16372, 16375, 16379, 16384.
 
 * Slovenian translations for glibc messages have been contributed by the
   Translation Project's Slovenian team of translators.

diff --git a/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c b/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c
index 8a4a5bb..b0b33f7 100644 (file)
--- a/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_acoshl.c
@@ -29,7 +29,7 @@
 
 static const long double
 one    = 1.0L,
-ln2    = 6.93147180559945286227e-01L;  /* 0x3FE62E42, 0xFEFA39EF */
+ln2    = M_LN2l;
 
 long double
 __ieee754_acoshl(long double x)
@@ -56,7 +56,7 @@ __ieee754_acoshl(long double x)
            return __ieee754_logl(2.0*x-one/(x+__ieee754_sqrtl(t-one)));
        } else {                        /* 1<x<2 */
            t = x-one;
-           return __log1p(t+__ieee754_sqrtl(2.0*t+t*t));
+           return __log1pl(t+__ieee754_sqrtl(2.0*t+t*t));
        }
 }
 strong_alias (__ieee754_acoshl, __acoshl_finite)