3 files changed, 88 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/Makefile b/sysdeps/ieee754/ldbl-128ibm/Makefile
index 5591814..b633172 100644
--- a/sysdeps/ieee754/ldbl-128ibm/Makefile
+++ b/sysdeps/ieee754/ldbl-128ibm/Makefile
@@ -8,3 +8,7 @@ ifeq ($(subdir),stdlib)
 tests += tst-strtold-ldbl-128ibm
 $(objpfx)tst-strtold-ldbl-128ibm: $(libm)
 endif
+
+ifeq ($(subdir),math)
+tests += test-fmodl-ldbl-128ibm
+endif
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_fmodl.c b/sysdeps/ieee754/ldbl-128ibm/e_fmodl.c
index d756e3e..5284fd0 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_fmodl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_fmodl.c
@@ -55,6 +55,13 @@ __ieee754_fmodl (long double x, long double y)
 	      return x;
 	    /* At this point the absolute value of the high doubles of
 	       x and y must be equal.  */
+	    if ((lx & 0x7fffffffffffffffLL) == 0
+		&& (ly & 0x7fffffffffffffffLL) == 0)
+	      /* Both low parts are zero.  The result should be an
+		 appropriately signed zero, but the subsequent logic
+		 could treat them as unequal, depending on the signs
+		 of the low parts.  */
+	      return Zero[(uint64_t) sx >> 63];
 	    /* If the low double of y is the same sign as the high
 	       double of y (ie. the low double increases |y|)...  */
 	    if (((ly ^ sy) & 0x8000000000000000LL) == 0
diff --git a/sysdeps/ieee754/ldbl-128ibm/test-fmodl-ldbl-128ibm.c b/sysdeps/ieee754/ldbl-128ibm/test-fmodl-ldbl-128ibm.c
new file mode 100644
index 0000000..3717c90
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/test-fmodl-ldbl-128ibm.c
@@ -0,0 +1,77 @@
+/* Test for ldbl-128ibm fmodl handling of equal values (bug 19602).
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <float.h>
+#include <math.h>
+#include <stdio.h>
+
+union u
+{
+  long double ld;
+  double d[2];
+};
+
+volatile union u p1 = { .d = { DBL_MIN, 0.0 } };
+volatile union u p2 = { .d = { DBL_MIN, -0.0 } };
+volatile union u m1 = { .d = { -DBL_MIN, 0.0 } };
+volatile union u m2 = { .d = { -DBL_MIN, -0.0 } };
+
+static int
+test_fmodl (const char *s, long double x, long double y, long double expected)
+{
+  volatile long double r;
+  r = fmodl (x, y);
+  if (r != expected || copysignl (1.0, r) != copysignl (1.0, expected))
+    {
+      printf ("FAIL: fmodl (%s)\n", s);
+      return 1;
+    }
+  else
+    {
+      printf ("PASS: fmodl (%s)\n", s);
+      return 0;
+    }
+}
+
+#define TEST_FMODL(a, b, e) test_fmodl (#a ", " #b, a, b, e)
+
+static int
+do_test (void)
+{
+  int result = 0;
+  result |= TEST_FMODL (p1.ld, p1.ld, 0.0L);
+  result |= TEST_FMODL (p1.ld, p2.ld, 0.0L);
+  result |= TEST_FMODL (p1.ld, m1.ld, 0.0L);
+  result |= TEST_FMODL (p1.ld, m2.ld, 0.0L);
+  result |= TEST_FMODL (p2.ld, p1.ld, 0.0L);
+  result |= TEST_FMODL (p2.ld, p2.ld, 0.0L);
+  result |= TEST_FMODL (p2.ld, m1.ld, 0.0L);
+  result |= TEST_FMODL (p2.ld, m2.ld, 0.0L);
+  result |= TEST_FMODL (m1.ld, p1.ld, -0.0L);
+  result |= TEST_FMODL (m1.ld, p2.ld, -0.0L);
+  result |= TEST_FMODL (m1.ld, m1.ld, -0.0L);
+  result |= TEST_FMODL (m1.ld, m2.ld, -0.0L);
+  result |= TEST_FMODL (m2.ld, p1.ld, -0.0L);
+  result |= TEST_FMODL (m2.ld, p2.ld, -0.0L);
+  result |= TEST_FMODL (m2.ld, m1.ld, -0.0L);
+  result |= TEST_FMODL (m2.ld, m2.ld, -0.0L);
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../../../test-skeleton.c"