Fix ldbl-128ibm logl inaccuracy (bug 16386).

This patch fixes bug 16386, ldbl-128ibm logl inaccuracy (with
consequent inaccuracy for lgammal) for arguments where the high double
is subnormal, which showed up while attempting to regenerate ulps for
powerpc-nofpu for 2.19.  The problem here is logic failing to allow
for subnormals when calculating the exponent of the argument.  Tested
for powerpc-nofpu.

	* sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): Adjust
	numbers with subnormal high part when calculating exponent.

diff --git a/ChangeLog b/ChangeLog
index 8200122..7f4d564 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2014-01-02  Joseph Myers  <joseph@codesourcery.com>
 
+       [BZ #16386]
+       * sysdeps/ieee754/ldbl-128ibm/e_logl.c (__ieee754_logl): Adjust
+       numbers with subnormal high part when calculating exponent.
+
        [BZ #16385]
        * sysdeps/ieee754/ldbl-128ibm/s_asinhl.c (__asinhl): Use fabsl not
        fabs.

diff --git a/NEWS b/NEWS
index c96c0e3..e0ea97a 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -23,7 +23,8 @@ 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, 16384, 16385.
+  16338, 16356, 16365, 16366, 16369, 16372, 16375, 16379, 16384, 16385,
+  16386.
 
 * 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_logl.c b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
index b7db2b9..58d6bc6 100644 (file)
--- a/sysdeps/ieee754/ldbl-128ibm/e_logl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_logl.c
@@ -229,6 +229,14 @@ __ieee754_logl(long double x)
       /* Extract exponent and reduce domain to 0.703125 <= u < 1.40625  */
       unsigned int w0;
       e = (int) (m >> 20) - (int) 0x3fe;
+      if (e == -1022)
+       {
+         x *= 0x1p106L;
+         xhi = ldbl_high (x);
+         EXTRACT_WORDS (hx, lx, xhi);
+         m = hx;
+         e = (int) (m >> 20) - (int) 0x3fe - 106;
+       }
       m &= 0xfffff;
       w0 = m | 0x3fe00000;
       m |= 0x100000;