[COMMITTED] lround: provide cast for wordsize-64 version if needed

[Chris Metcalf <cmetcalf at ezchip dot com>]

Platforms with 64-bit registers where 32-bit values need to have the
high 32 bits set in a particular way need to have an explicit cast
when using the 64-bit sysdeps/ieee754/dbl-64/wordsize-64 version
of llround() as lround().  This includes tilegx32, and likely MIPS.
x32 does not need this, and AArch64 ILP32 will not either.  Require
it to be specified in sysdep.h to be explicit.
---
This is the version that I pushed.  HJ, I tried to build a working
x32 toolchain, but in the end I ran into enough difficulties that
I figured it might be reasonable just to ask you to double-check your
build next time to make sure lround() is still an alias for llround().
Thanks in advance.

 ChangeLog                                      |  9 +++++++++
 sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c | 28 ++++++++++++++++++++------
 sysdeps/tile/sysdep.h                          |  4 ++++
 sysdeps/x86_64/x32/sysdep.h                    |  4 ++++
 4 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 0e6e22492742..123b0b28fcd1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2015-01-05  Chris Metcalf  <cmetcalf@ezchip.com>
+
+	* sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c [!defined _LP64
+	&& REGISTER_CAST_INT32_TO_INT64]: Provide explicit lround()
+	function with cast from llround().
+	* sysdeps/tile/sysdep.h (REGISTER_CAST_INT32_TO_INT64): Define.
+	* sysdeps/x86_64/x32/sysdep.h (REGISTER_CAST_INT32_TO_INT64):
+	Define.
+
 2015-01-05  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #17793]
diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c
index 885260163e65..8bb52524b7f9 100644
--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_llround.c
@@ -21,6 +21,7 @@
 #define __lround __hidden___lround
 
 #include <math.h>
+#include <sysdep.h>
 
 #include <math_private.h>
 
@@ -64,16 +65,31 @@ __llround (double x)
 
 weak_alias (__llround, llround)
 #ifdef NO_LONG_DOUBLE
-strong_alias (__llround, __lroundl)
-weak_alias (__llround, lroundl)
+strong_alias (__llround, __llroundl)
+weak_alias (__llround, llroundl)
 #endif
 
-/* long has the same width as long long on 64-bit machines.  */
+/* 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.  */
 #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
 strong_alias (__llround, __lround)
 weak_alias (__llround, lround)
-#ifdef NO_LONG_DOUBLE
-strong_alias (__llround, __llroundl)
-weak_alias (__llround, llroundl)
+# ifdef NO_LONG_DOUBLE
+strong_alias (__llround, __lroundl)
+weak_alias (__llround, lroundl)
+# endif
 #endif
diff --git a/sysdeps/tile/sysdep.h b/sysdeps/tile/sysdep.h
index ead9dba0b4bb..7b3d8739d2e3 100644
--- a/sysdeps/tile/sysdep.h
+++ b/sysdeps/tile/sysdep.h
@@ -108,3 +108,7 @@
 #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 9b8700522f33..0cbc1a083fd4 100644
--- a/sysdeps/x86_64/x32/sysdep.h
+++ b/sysdeps/x86_64/x32/sysdep.h
@@ -90,3 +90,7 @@
 # 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
-- 
2.1.2