Make iseqsig handle excess precision.

iseqsig, like other type-generic comparison macros, should behave like
a comparison operator in not removing excess range and precision from
its arguments (see C11 F.10.11).  This patch implements this by making
definitions of iseqsig appropriately conditional on
__FLT_EVAL_METHOD__ (including support for TS 18661-3 values of that
macro), with a corresponding testcase (that failed for 32-bit x86 in
the absence of the math.h changes) being added.  (Of course the
definitions may need reworking when float128 support is added, just as
with other type-generic macros.)

Tested for x86_64 and x86.

	* math/math.h [__GLIBC_USE (IEC_60559_BFP_EXT)] (iseqsig): Define
	conditional on value of [__FLT_EVAL_METHOD__].
	* math/test-iseqsig-excess-precision.c: New file.
	* math/Makefile (tests): Add test-iseqsig-excess-precision.

1 files changed, 80 insertions, 0 deletions

diff --git a/math/test-iseqsig-excess-precision.c b/math/test-iseqsig-excess-precision.c
new file mode 100644
index 0000000000..01dea1c0a1
--- /dev/null
+++ b/math/test-iseqsig-excess-precision.c
@@ -0,0 +1,80 @@
+/* Test iseqsig with excess precision.
+   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>
+
+static int
+do_test (void)
+{
+  int result = 0;
+
+  if (FLT_EVAL_METHOD == 1 || FLT_EVAL_METHOD == 2 || FLT_EVAL_METHOD > 32)
+    {
+      /* Excess precision for float.  */
+      if (iseqsig (1.0f, 1.0f + (float) DBL_EPSILON))
+	{
+	  puts ("iseqsig removes excess precision float -> double");
+	  result = 1;
+	}
+      else
+	puts ("iseqsig preserves excess precision float -> double");
+      if (iseqsig (__builtin_inff (), FLT_MAX * FLT_MAX))
+	{
+	  puts ("iseqsig removes excess range float -> double");
+	  result = 1;
+	}
+      else
+	puts ("iseqsig preserves excess range float -> double");
+    }
+
+  if (FLT_EVAL_METHOD == 2 || FLT_EVAL_METHOD > 64)
+    {
+      /* Excess precision for float and double.  */
+      if (iseqsig (1.0f, 1.0f + (float) LDBL_EPSILON))
+	{
+	  puts ("iseqsig removes excess precision float -> long double");
+	  result = 1;
+	}
+      else
+	puts ("iseqsig preserves excess precision float -> long double");
+      if (iseqsig (1.0, 1.0 + (double) LDBL_EPSILON))
+	{
+	  puts ("iseqsig removes excess precision double -> long double");
+	  result = 1;
+	}
+      else
+	puts ("iseqsig preserves excess precision double -> long double");
+      if (LDBL_MAX_EXP >= 2 * DBL_MAX_EXP)
+	{
+	  if (iseqsig (__builtin_inf (), DBL_MAX * DBL_MAX))
+	    {
+	      puts ("iseqsig removes excess range double -> long double");
+	      result = 1;
+	    }
+	    else
+	      puts ("iseqsig preserves excess range double -> long double");
+	}
+    }
+
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"