Add test for __builtin_ctz.

configure

@@ -24265,6 +24265,20 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
+#
+# Check for non-standard builtin
+ac_fn_c_check_decl "$LINENO" "__builtin_ctz" "ac_cv_have_decl___builtin_ctz" "$ac_includes_default"
+if test "x$ac_cv_have_decl___builtin_ctz" = xyes; then :
+  ac_have_decl=1
+else
+  ac_have_decl=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_DECL___BUILTIN_CTZ $ac_have_decl
+_ACEOF
+
+
 # Check compiler version
 case "$CC" in
   pgcc*)  COMP_VERSION=`$CC -V | head -2 | tail -n 1`;;

configure.ac

@@ -70,6 +70,10 @@ AC_CHECK_FUNCS([getline])
 AC_CHECK_DECLS([isnan],,,[AC_INCLUDES_DEFAULT
 @%:@include <math.h>])
 
+#
+# Check for non-standard builtin
+AC_CHECK_DECLS([__builtin_ctz])
+
 # Check compiler version
 case "$CC" in
   pgcc*)  COMP_VERSION=`$CC -V | head -2 | tail -n 1`;;

src/config.h.in

@@ -16,6 +16,10 @@
    */
 #undef HAVE_DECL_ISNAN
 
+/* Define to 1 if you have the declaration of `__builtin_ctz', and to 0 if you
+   don't. */
+#undef HAVE_DECL___BUILTIN_CTZ
+
 /* Define to 1 if you have the <dlfcn.h> header file. */
 #undef HAVE_DLFCN_H