1dnl Check whether the target supports TLS.
2AC_DEFUN([GCC_CHECK_TLS], [
3  GCC_ENABLE(tls, yes, [Use thread-local storage])
4  AC_CACHE_CHECK([whether the target supports thread-local storage],
5		 have_tls, [
6    AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
7      [dnl If the test case passed with dynamic linking, try again with
8      dnl static linking.  This fails at least with some older Red Hat
9      dnl releases.
10      save_LDFLAGS="$LDFLAGS"
11      LDFLAGS="-static $LDFLAGS"
12      AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
13		    [have_tls=yes], [have_tls=no], [])
14      LDFLAGS="$save_LDFLAGS"],
15      [have_tls=no],
16      [AC_COMPILE_IFELSE([__thread int foo;], [have_tls=yes], [have_tls=no])]
17    )])
18  if test "$enable_tls $have_tls" = "yes yes"; then
19    AC_DEFINE(HAVE_TLS, 1,
20	      [Define to 1 if the target supports thread-local storage.])
21  fi])
22