--- /dev/null
+AC_DEFUN([CC_CHECK_TLS], [
+ AC_CACHE_CHECK([whether $CC knows __thread for Thread-Local Storage],
+ cc_cv_tls___thread,
+ [AC_COMPILE_IFELSE(
+ AC_LANG_PROGRAM(
+ [[static __thread int a = 6;]],
+ [[a = 5;]]),
+ [cc_cv_tls___thread=yes],
+ [cc_cv_tls___thread=no])
+ ])
+
+ AS_IF([test "x$cc_cv_tls___thread" = "xyes"],
+ [AC_DEFINE([SUPPORT_TLS___THREAD], 1,
+ [Define this if the compiler supports __thread for Thread-Local Storage])
+ $1],
+ [$2])
+])