+AC_SUBST(SUBARCHTYPE)
+
+[
+#if test "x$ARCHTYPE" = "xx86" -a "x$host_cpu" != "xi386" -a "x$host_cpu" != "xi486" -a "x$host_cpu" != "xi586"; then
+#For now, using lock; addl compatibility mode even for i686, because the
+#Pentium III is seen as a i686, but lacks mfence instruction.
+#Only using fence for x86_64.
+if test "x$ARCHTYPE" = "xx86" -a "x$host_cpu" != "xi386" -a "x$host_cpu" != "xi486" -a "x$host_cpu" != "xi586" -a "x$host_cpu" != "xi686"; then
+]
+ AC_DEFINE([CONFIG_URCU_HAVE_FENCE], [1])
+[
+fi
+]
+
+AC_MSG_CHECKING([sys_futex()])
+AC_TRY_COMPILE(
+[
+#include <sys/syscall.h>
+],
+[
+#ifndef __NR_futex
+#error "futexes not available"
+#endif
+],
+[
+ AC_MSG_RESULT([yes])
+ AC_DEFINE([CONFIG_URCU_HAVE_FUTEX], [1])
+ compat_futex_test=0
+]
+,
+[
+ AC_MSG_RESULT([no])
+ compat_futex_test=1
+]
+)
+
+AM_CONDITIONAL([COMPAT_FUTEX], [ test "x$compat_futex_test" = "x1" ])