--- src/lib/libast/sfio/sfcvt.c
+++ src/lib/libast/sfio/sfcvt.c	2008-12-17 11:56:17.000000000 +0000
@@ -56,6 +56,16 @@ static char		*Zero = "0";
 #define _lib_signbit	1
 #endif
 
+#if defined(__ia64__) && defined(signbit)
+# if defined __GNUC__ && __GNUC__ >= 4
+#  define __signbitl(f)		__builtin_signbitl(f)
+# else
+#  if _lib_copysignl
+#   define __signbitl(f)	(int)(copysignl(1.0,(f))<0.0)
+#  endif
+# endif
+#endif
+
 #if ! _lib_signbit
 #if ! _ast_fltmax_double
 static int neg0ld(Sfdouble_t f)
--- src/cmd/ksh93/features/math.sh
+++ src/cmd/ksh93/features/math.sh	2012-01-20 14:23:37.587145847 +0000
@@ -130,6 +130,18 @@ echo "#include <math.h>"
 case $_hdr_ieeefp in
 1)	echo "#include <ieeefp.h>" ;;
 esac
+cat <<!
+#if defined(__ia64__) && defined(signbit)
+# if defined __GNUC__ && __GNUC__ >= 4
+#  define __signbitl(f)		__builtin_signbitl(f)
+# else
+#  include <ast_float.h>
+#  if _lib_copysignl
+#   define __signbitl(f)	(int)(copysignl(1.0,(f))<0.0)
+#  endif
+# endif
+#endif
+!
 echo
 
 : generate the intercept functions and table entries