PowerPC: Fix nearbyintl failure for few inputs

This patch fixes few failures in nearbyintl() where the fraction part is
close to 0.5.i  The new tests added report few extra failures in
nearbyint_downward and nearbyint_towardzero which is a known issue.

Fixes #17031.

This is a backport of 754c5a08aacb44895d1ab97c553ce424eb43f761.

diff --git a/ChangeLog b/ChangeLog
index a8a24b512783f3e205251ae5fabd784d9aa01b18..95dcce84ac7db12e77d605d928f0fba67eed894b 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2014-16-17  Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
+
+       [BZ #17031]
+       * sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c: Consider the low
+       double, adjusted for any remainder from the high double.
+       * math/libm-test.inc (nearbyint): Add tests.
+       (rint): Likewise.
+
 2014-06-11  Vidya Ranganathan  <vidya@linux.vnet.ibm.com>
 
        * sysdeps/powerpc/powerpc64/power7/strcmp.S: New file: Optimization.

diff --git a/NEWS b/NEWS
index 99bda3c9b89d4a6389d10f880c1d2976690b9d4e..96b7621c0f2e34f71adb2f1f740d768ee932e8e4 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -9,7 +9,8 @@ Version 2.19.1
 
 * The following bugs are resolved with this release:
 
-  16545, 16683, 16689, 16701, 16706, 16707, 16739, 16815, 16619, 16740.
+  16545, 16683, 16689, 16701, 16706, 16707, 16739, 16815, 16619, 16740,
+  17031.
 \f
 Version 2.19
 

diff --git a/math/libm-test.inc b/math/libm-test.inc
index 1c5c022f4f6c6282e858dc34ff20de59e95d3335..848b89ee7b86ec5865a371a04759bbaded604e2e 100644 (file)
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -10519,6 +10519,10 @@ static const struct test_f_f_data nearbyint_test_data[] =
     TEST_f_f (nearbyint,  34503599627370498.515625L, 34503599627370499.0L),
     TEST_f_f (nearbyint, -34503599627370498.515625L, -34503599627370499.0L),
 # if LDBL_MANT_DIG >= 106
+    TEST_f_f (nearbyint, 1024.5000000000001L, 1025.0L, NO_INEXACT_EXCEPTION),
+    TEST_f_f (nearbyint, 1025.5000000000001L, 1026.0L, NO_INEXACT_EXCEPTION),
+    TEST_f_f (nearbyint, -1024.5000000000001L, -1025.0L, NO_INEXACT_EXCEPTION),
+    TEST_f_f (nearbyint, -1025.5000000000001L, -1026.0L, NO_INEXACT_EXCEPTION),
     TEST_f_f (nearbyint,  1192568192774434123539907640624.484375L, 1192568192774434123539907640624.0L),
     TEST_f_f (nearbyint, -1192568192774434123539907640624.484375L, -1192568192774434123539907640624.0L),
 # endif
@@ -11335,6 +11339,10 @@ static const struct test_f_f_data rint_test_data[] =
     TEST_f_f (rint, 4503599627370497.5L, 4503599627370498.0L, INEXACT_EXCEPTION),
 
 # if LDBL_MANT_DIG > 100
+    TEST_f_f (rint, 1024.5000000000001L, 1025.0L, INEXACT_EXCEPTION),
+    TEST_f_f (rint, 1025.5000000000001L, 1026.0L, INEXACT_EXCEPTION),
+    TEST_f_f (rint, -1024.5000000000001L, -1025.0L, INEXACT_EXCEPTION),
+    TEST_f_f (rint, -1025.5000000000001L, -1026.0L, INEXACT_EXCEPTION),
     TEST_f_f (rint, 4503599627370494.5000000000001L, 4503599627370495.0L, INEXACT_EXCEPTION),
     TEST_f_f (rint, 4503599627370495.5000000000001L, 4503599627370496.0L, INEXACT_EXCEPTION),
     TEST_f_f (rint, 4503599627370496.5000000000001L, 4503599627370497.0L, INEXACT_EXCEPTION),

diff --git a/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c b/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c
index 4e997a68f9a70d139da9b6001efdbf5664f708fc..8f34604f54cc1d0c21c3193030d1d9939182660a 100644 (file)
--- a/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c
@@ -38,6 +38,7 @@ __nearbyintl (long double x)
 
   if (fabs (u.d[0].d) < TWO52)
     {
+      double xh = u.d[0].d;
       double high = u.d[0].d;
       feholdexcept (&env);
       if (high > 0.0)
@@ -52,6 +53,10 @@ __nearbyintl (long double x)
          high += TWO52;
           if (high == 0.0) high = -0.0;
        }
+      if (u.d[1].d > 0.0 && (xh - high == 0.5))
+        high += 1.0;
+      else if (u.d[1].d < 0.0 && (-(xh - high) == 0.5))
+        high -= 1.0;
       u.d[0].d = high;
       u.d[1].d = 0.0;
       math_force_eval (u.d[0]);