* runtime/memory.c (xmallocarray): Avoid division for the common case.

From-SVN: r213593

libgfortran/ChangeLog

+2014-08-04  Jakub Jelinek  <jakub@redhat.com>
+
+	* runtime/memory.c (xmallocarray): Avoid division for the common case.
+
 2014-07-20  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR libgfortran/61632

libgfortran/runtime/memory.c

@@ -56,7 +56,9 @@ xmallocarray (size_t nmemb, size_t size)
 
   if (!nmemb || !size)
     size = nmemb = 1;
-  else if (nmemb > SIZE_MAX / size)
+#define HALF_SIZE_T (((size_t) 1) << (__CHAR_BIT__ * sizeof (size_t) / 2))
+  else if (__builtin_expect ((nmemb | size) >= HALF_SIZE_T, 0)
+	   && nmemb > SIZE_MAX / size)
     {
       errno = ENOMEM;
       os_error ("Integer overflow in xmallocarray");