* Merge from mainline (r120733:123693).

git-svn-id: https://gcc.gnu.org/svn/gcc/branches/graphite@123703 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 55 insertions, 4 deletions

diff --git a/config/tls.m4 b/config/tls.m4
index 41f11ab3ea5f..c8f3ff0a3733 100644
--- a/config/tls.m4
+++ b/config/tls.m4
@@ -7,16 +7,67 @@ AC_DEFUN([GCC_CHECK_TLS], [
       [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.
-      save_LDFLAGS="$LDFLAGS"
+      chktls_save_LDFLAGS="$LDFLAGS"
       LDFLAGS="-static $LDFLAGS"
       AC_LINK_IFELSE([int main() { return 0; }],
 	AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
 		      [have_tls=yes], [have_tls=no],[]),
 	[have_tls=yes])
-      LDFLAGS="$save_LDFLAGS"],
+      LDFLAGS="$chktls_save_LDFLAGS"
+      if test $have_tls = yes; then
+	dnl So far, the binutils and the compiler support TLS.
+	dnl Also check whether the libc supports TLS, i.e. whether a variable
+	dnl with __thread linkage has a different address in different threads.
+	dnl First, find the thread_CFLAGS necessary for linking a program that
+	dnl calls pthread_create.
+	chktls_save_CFLAGS="$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 $chktls_save_CFLAGS"
+	  AC_RUN_IFELSE(
+	    [AC_LANG_PROGRAM(
+	       [#include <pthread.h>
+		__thread int a;
+		static int *a_in_other_thread;
+		static void *
+		thread_func (void *arg)
+		{
+		  a_in_other_thread = &a;
+		  return (void *)0;
+		}],
+	       [pthread_t thread;
+		void *thread_retval;
+		int *a_in_main_thread;
+		if (pthread_create (&thread, (pthread_attr_t *)0,
+				    thread_func, (void *)0))
+		  return 0;
+		a_in_main_thread = &a;
+		if (pthread_join (thread, &thread_retval))
+		  return 0;
+		return (a_in_other_thread == a_in_main_thread);])],
+	     [have_tls=yes], [have_tls=no], [])
+	  CFLAGS="$chktls_save_CFLAGS"
+	fi
+      fi],
       [have_tls=no],
-      [AC_LINK_IFELSE([__thread int a; int b; int main() { return a = b; }],
-	[have_tls=yes], [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; }],
+		      [have_tls=yes], [have_tls=no])
+      ]
     )])
   if test "$enable_tls $have_tls" = "yes yes"; then
     AC_DEFINE(HAVE_TLS, 1,