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dnl Check whether the target supports TLS.

AC_DEFUN([GCC_CHECK_TLS], [

  GCC_ENABLE(tls, yes, [], [Use thread-local storage])

  AC_CACHE_CHECK([whether the target supports thread-local storage],

                 gcc_cv_have_tls, [

    AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],

      [dnl If the test case passed with dynamic linking, try again with

       dnl static linking, but only if static linking is supported (not

       dnl on Solaris 10).  This fails with some older Red Hat releases.

      chktls_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; }],

                      [gcc_cv_have_tls=yes], [gcc_cv_have_tls=no],[]),

        [gcc_cv_have_tls=yes])

      LDFLAGS="$chktls_save_LDFLAGS"

      if test $gcc_cv_have_tls = yes; then

        dnl So far, the binutils and the compiler support TLS.

        dnl Also check whether the libc supports TLS, i.e. whether a variable

        dnl with __thread linkage has a different address in different threads.

        dnl First, find the thread_CFLAGS necessary for linking a program that

        dnl calls pthread_create.

        chktls_save_CFLAGS="$CFLAGS"

        thread_CFLAGS=failed

        for flag in '' '-pthread' '-lpthread'; do

          CFLAGS="$flag $chktls_save_CFLAGS"

          AC_LINK_IFELSE(

            [AC_LANG_PROGRAM(

               [#include <pthread.h>

                void *g(void *d) { return NULL; }],

               [pthread_t t; pthread_create(&t,NULL,g,NULL);])],

            [thread_CFLAGS="$flag"])

          if test "X$thread_CFLAGS" != Xfailed; then

            break

          fi

        done

        CFLAGS="$chktls_save_CFLAGS"

        if test "X$thread_CFLAGS" != Xfailed; then

          CFLAGS="$thread_CFLAGS $chktls_save_CFLAGS"

          AC_RUN_IFELSE(

            [AC_LANG_PROGRAM(

               [#include <pthread.h>

                __thread int a;

                static int *a_in_other_thread;

                static void *

                thread_func (void *arg)

                {

                  a_in_other_thread = &a;

                  return (void *)0;

                }],

               [pthread_t thread;

                void *thread_retval;

                int *a_in_main_thread;

                if (pthread_create (&thread, (pthread_attr_t *)0,

                                    thread_func, (void *)0))

                  return 0;

                a_in_main_thread = &a;

                if (pthread_join (thread, &thread_retval))

                  return 0;

                return (a_in_other_thread == a_in_main_thread);])],

             [gcc_cv_have_tls=yes], [gcc_cv_have_tls=no], [])

          CFLAGS="$chktls_save_CFLAGS"

        fi

      fi],

      [gcc_cv_have_tls=no],

      [dnl This is the cross-compiling case. Assume libc supports TLS if the

       dnl binutils and the compiler do.

       AC_LINK_IFELSE([__thread int a; int b; int main() { return a = b; }],

                      [gcc_cv_have_tls=yes], [gcc_cv_have_tls=no])

      ]

    )])

  if test "$enable_tls $gcc_cv_have_tls" = "yes yes"; then

    AC_DEFINE(HAVE_TLS, 1,

              [Define to 1 if the target supports thread-local storage.])

  fi])

dnl Check whether the target assembler supports TLS.

AC_DEFUN([GCC_CHECK_CC_TLS], [

  GCC_ENABLE(tls, yes, [], [Use thread-local storage])

  AC_CACHE_CHECK([whether the target assembler supports thread-local storage],

                 gcc_cv_have_cc_tls, [

    AC_COMPILE_IFELSE([__thread int a; int b; int main() { return a = b; }],

      [gcc_cv_have_cc_tls=yes], [gcc_cv_have_cc_tls=no])]

    )])

  if test "$enable_tls $gcc_cv_have_cc_tls" = "yes yes"; then

    AC_DEFINE(HAVE_CC_TLS, 1,

              [Define to 1 if the target assembler supports thread-local storage.])

  fi])