AC_DEFUN([GCC_CHECK_TLS], [
GCC_ENABLE(tls, yes, [], [Use thread-local storage])
AC_CACHE_CHECK([whether the target supports thread-local storage],
have_tls, [
AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
[ save_LDFLAGS="$LDFLAGS"
LDFLAGS="-static $LDFLAGS"
AC_LINK_IFELSE([int main() { return 0; }],
AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
[have_tls=yes], [have_tls=no],[]),
[have_tls=yes])
LDFLAGS="$save_LDFLAGS"],
[have_tls=no],
[AC_COMPILE_IFELSE([__thread int foo;], [have_tls=yes], [have_tls=no])]
)])
if test "$enable_tls $have_tls" = "yes yes"; then
AC_DEFINE(HAVE_TLS, 1,
[Define to 1 if the target supports thread-local storage.])
fi])