Don't use dbl-64/wordsize-64 lround based on llround for ILP32 (bug 19079)

[Joseph Myers <joseph at codesourcery dot com>]

The implementation of lround in dbl-64/wordsize-64 as an alias or
wrapper for llround is always incorrect when long is not 64-bit,
because it misses required exceptions in overflow cases, as shown by
my recently added tests.  This patch removes that alias / wrapper in
the non-LP64 case, together with the REGISTER_CAST_INT32_TO_INT64
macro, restoring the previous version of lround for dbl-64/wordsize-64
(newly conditioned on !_LP64).

Tested for x86_64, and for mips64 with use of dbl-64/wordsize-64
enabled.

2015-10-07  Joseph Myers  <joseph@codesourcery.com>

	[BZ #19079]
	* sysdeps/ieee754/dbl-64/wordsize-64/s_lround.c: Restore previous
	file, conditioned on [!_LP64].
	* sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c
	[!_LP64] (__lround): Do not define as function or alias.
	[!_LP64] (lround): Likewise.
	[!_LP64] (__lroundl): Likewise.
	[!_LP64] (lroundl): Likewise.
	* sysdeps/tile/sysdep.h (REGISTER_CAST_INT32_TO_INT64): Remove
	macro.
	* sysdeps/x86_64/x32/sysdep.h (REGISTER_CAST_INT32_TO_INT64):
	Likewise.

diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c
index 8bb5252..483d4a0 100644
--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c
@@ -69,23 +69,10 @@ strong_alias (__llround, __llroundl)
 weak_alias (__llround, llroundl)
 #endif
 
-/* long has the same width as long long on LP64 machines, so use an alias.
-   If building for ILP32 on a machine with 64-bit registers, however,
-   use a cast if necessary.  */
+/* long has the same width as long long on LP64 machines, so use an alias.  */
 #undef lround
 #undef __lround
-#if !defined (_LP64) && REGISTER_CAST_INT32_TO_INT64
-long int
-__lround (double x)
-{
-  return __llround (x);
-}
-weak_alias (__lround, lround)
-# ifdef NO_LONG_DOUBLE
-strong_alias (__lround, __lroundl)
-weak_alias (__lround, lroundl)
-# endif
-#else
+#ifdef _LP64
 strong_alias (__llround, __lround)
 weak_alias (__llround, lround)
 # ifdef NO_LONG_DOUBLE
diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_lround.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_lround.c
index 1e06fcb..390e733 100644
--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_lround.c
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_lround.c
@@ -1 +1,69 @@
-/* The code is the same as llround.  Use an alias, see s_llround.c.  */
+/* Round double value to long int.
+   Copyright (C) 1997-2015 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 <math.h>
+
+#include <math_private.h>
+
+/* For LP64, lround is an alias for llround.  */
+#ifndef _LP64
+
+long int
+__lround (double x)
+{
+  int32_t j0;
+  int64_t i0;
+  long int result;
+  int sign;
+
+  EXTRACT_WORDS64 (i0, x);
+  j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
+  sign = i0 < 0 ? -1 : 1;
+  i0 &= UINT64_C(0xfffffffffffff);
+  i0 |= UINT64_C(0x10000000000000);
+
+  if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
+    {
+      if (j0 < 0)
+	return j0 < -1 ? 0 : sign;
+      else if (j0 >= 52)
+	result = i0 << (j0 - 52);
+      else
+	{
+	  i0 += UINT64_C(0x8000000000000) >> j0;
+
+	  result = i0 >> (52 - j0);
+	}
+    }
+  else
+    {
+      /* The number is too large.  It is left implementation defined
+	 what happens.  */
+      return (long int) x;
+    }
+
+  return sign * result;
+}
+
+weak_alias (__lround, lround)
+# ifdef NO_LONG_DOUBLE
+strong_alias (__lround, __lroundl)
+weak_alias (__lround, lroundl)
+# endif
+
+#endif
diff --git a/sysdeps/tile/sysdep.h b/sysdeps/tile/sysdep.h
index 7b3d873..ead9dba 100644
--- a/sysdeps/tile/sysdep.h
+++ b/sysdeps/tile/sysdep.h
@@ -108,7 +108,3 @@
 #endif
 
 #endif /* __ASSEMBLER__ */
-
-/* On tilegx, 32-bit values must have their high 32 bits sign extended;
-   random values are not allowed.  */
-#define REGISTER_CAST_INT32_TO_INT64 1
diff --git a/sysdeps/x86_64/x32/sysdep.h b/sysdeps/x86_64/x32/sysdep.h
index 0cbc1a0..9b87005 100644
--- a/sysdeps/x86_64/x32/sysdep.h
+++ b/sysdeps/x86_64/x32/sysdep.h
@@ -90,7 +90,3 @@
 # define R15_LP	"r15d"
 
 #endif	/* __ASSEMBLER__ */
-
-/* On x32, it is not required to normalize a 64-bit value before using
-   it as a 32-bit value.  */
-#define REGISTER_CAST_INT32_TO_INT64 0

-- 
Joseph S. Myers
joseph@codesourcery.com