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, but only if static linking is supported (not
9       dnl on Solaris 10).  This fails with some older Red Hat releases.
10      save_LDFLAGS="$LDFLAGS"
11      LDFLAGS="-static $LDFLAGS"
12      AC_LINK_IFELSE([int main() { return 0; }],
13	AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
14		      [have_tls=yes], [have_tls=no],[]),
15	[have_tls=yes])
16      LDFLAGS="$save_LDFLAGS"],
17      [have_tls=no],
18      [AC_COMPILE_IFELSE([__thread int foo;], [have_tls=yes], [have_tls=no])]
19    )])
20  if test "$enable_tls $have_tls" = "yes yes"; then
21    AC_DEFINE(HAVE_TLS, 1,
22	      [Define to 1 if the target supports thread-local storage.])
23  fi])
24