New test to expose erroneous negative sign on logb(1) (bug 887).

3 files changed, 56 insertions, 14 deletions

diff --git a/ChangeLog b/ChangeLog
index 2035e58f35..e6eb8585b0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2012-04-27  Ryan S. Arnold  <rsa@linux.vnet.ibm.com>
+
+	[BZ #887]
+	* math/libm-test.inc (logb_test_downward): New test to expose
+	erroneous negative sign on -0.0 result of logb[l](1) in FE_DOWNWARD
+	rounding mode.
+
 2012-04-27  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #14027]
diff --git a/NEWS b/NEWS
index cd523640c0..0f060a7e6d 100644
--- a/NEWS
+++ b/NEWS
@@ -9,20 +9,20 @@ Version 2.16
 
 * The following bugs are resolved with this release:
 
-  174, 350, 369, 411, 706, 2074, 2541, 2547, 2548, 2551, 2552, 2553, 2554,
-  2562, 2563, 2565, 2566, 2576, 2636, 2678, 3335, 3768, 3866, 3868, 3976,
-  3992, 4026, 4108, 4596, 4822, 5077, 5461, 5805, 5993, 6471, 6486, 6578,
-  6649, 6730, 6770, 6794, 6884, 6890, 6894, 6895, 6907, 6911, 7064, 9739,
-  9902, 10110, 10135, 10140, 10153, 10210, 10254, 10346, 10545, 10716,
-  11174, 11322, 11365, 11451, 11494, 11521, 11959, 12047, 12340, 13058,
-  13525, 13526, 13527, 13528, 13529, 13530, 13531, 13532, 13533, 13547,
-  13551, 13552, 13553, 13555, 13559, 13566, 13583, 13592, 13618, 13637,
-  13656, 13658, 13673, 13691, 13695, 13704, 13705, 13706, 13726, 13738,
-  13739, 13760, 13761, 13786, 13792, 13806, 13824, 13840, 13841, 13844,
-  13846, 13851, 13852, 13854, 13871, 13872, 13873, 13879, 13883, 13886,
-  13892, 13895, 13908, 13910, 13911, 13912, 13913, 13915, 13916, 13917,
-  13918, 13919, 13920, 13921, 13926, 13927, 13928, 13938, 13963, 13967,
-  13970, 13973, 14027
+  174, 350, 369, 411, 887, 706, 2074, 2541, 2547, 2548, 2551, 2552, 2553,
+  2554, 2562, 2563, 2565, 2566, 2576, 2636, 2678, 3335, 3768, 3866, 3868,
+  3976, 3992, 4026, 4108, 4596, 4822, 5077, 5461, 5805, 5993, 6471, 6486,
+  6578, 6649, 6730, 6770, 6794, 6884, 6890, 6894, 6895, 6907, 6911, 7064,
+  9739, 9902, 10110, 10135, 10140, 10153, 10210, 10254, 10346, 10545,
+  10716, 11174, 11322, 11365, 11451, 11494, 11521, 11959, 12047, 12340,
+  13058, 13525, 13526, 13527, 13528, 13529, 13530, 13531, 13532, 13533,
+  13547, 13551, 13552, 13553, 13555, 13559, 13566, 13583, 13592, 13618,
+  13637, 13656, 13658, 13673, 13691, 13695, 13704, 13705, 13706, 13726,
+  13738, 13739, 13760, 13761, 13786, 13792, 13806, 13824, 13840, 13841,
+  13844, 13846, 13851, 13852, 13854, 13871, 13872, 13873, 13879, 13883,
+  13886, 13892, 13895, 13908, 13910, 13911, 13912, 13913, 13915, 13916,
+  13917, 13918, 13919, 13920, 13921, 13926, 13927, 13928, 13938, 13963,
+  13967, 13970, 13973, 14027
 
 * ISO C11 support:
 
diff --git a/math/libm-test.inc b/math/libm-test.inc
index e0ac6131da..d11cd1ff86 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -5101,6 +5101,40 @@ logb_test (void)
   END (logb);
 }
 
+static void
+logb_test_downward (void)
+{
+  int save_round_mode;
+  errno = 0;
+
+  FUNC(logb) (0);
+  if (errno == ENOSYS)
+    /* Function not implemented.  */
+    return;
+
+  START (logb_downward);
+
+  save_round_mode = fegetround ();
+
+  if (!fesetround (FE_DOWNWARD))
+    {
+
+      /* IEEE 754-2008 says (section 5.3.3) that "logB(1) is +0.".  Libm
+         should not return -0 from logb in any rounding mode.  PowerPC32 has
+         failed with this test for power4 logb (and logbl on all PowerPC
+         platforms) in the past due to instruction selection.  GCC PR 52775
+         provides the availability of the fcfid insn in 32-bit mode which
+         eliminates the use of fsub in this instance and prevents the negative
+         signed 0.0.  */
+
+      /* BZ #887  .*/
+      TEST_f_f (logb, 1.000e+0, plus_zero);
+    }
+
+  fesetround (save_round_mode);
+
+  END (logb_downward);
+}
 
 static void
 lround_test (void)
@@ -8210,6 +8244,7 @@ main (int argc, char **argv)
   log1p_test ();
   log2_test ();
   logb_test ();
+  logb_test_downward ();
   modf_test ();
   ilogb_test ();
   scalb_test ();