diff --git a/autoconf/configure.ac b/autoconf/configure.ac
index cb217a5143b..56853e96bf1 100644
--- a/autoconf/configure.ac
+++ b/autoconf/configure.ac
@@ -372,7 +372,6 @@ case "$enableval" in
   default) AC_SUBST(ENABLE_THREADS,[1]) ;;
   *) AC_MSG_ERROR([Invalid setting for --enable-threads. Use "yes" or "no"]) ;;
 esac
-AC_DEFINE_UNQUOTED([ENABLE_THREADS],$ENABLE_THREADS,[Define if threads enabled])
 
 dnl Allow building without position independent code
 AC_ARG_ENABLE(pic,
@@ -897,6 +896,26 @@ if test "$llvm_cv_platform_type" = "Unix" ; then
   fi
 fi
 
+dnl atomic builtins are required for threading support.
+if test "$ENABLE_THREADS" -eq 1 ; then
+  AC_MSG_CHECKING(for GCC atomic builtins)
+  AC_LINK_IFELSE(
+	AC_LANG_SOURCE(
+          [[int main() { 
+              volatile unsigned long val = 1;
+              __sync_synchronize();
+              __sync_val_compare_and_swap(&val, 1, 0);
+              return 0;
+            }
+          ]]),
+        AC_MSG_RESULT(yes),
+        AC_MSG_RESULT(no)
+        AC_SUBST(ENABLE_THREADS, [0])
+        AC_MSG_WARN([Threading support disabled because atomic builtins are missing]))
+fi
+
+AC_DEFINE_UNQUOTED([ENABLE_THREADS],$ENABLE_THREADS,[Define if threads enabled])
+
 dnl===-----------------------------------------------------------------------===
 dnl===
 dnl=== SECTION 9: Additional checks, variables, etc.
diff --git a/configure b/configure
index 3a352775197..20e3b4fa303 100755
--- a/configure
+++ b/configure
@@ -4870,11 +4870,6 @@ echo "$as_me: error: Invalid setting for --enable-threads. Use \"yes\" or \"no\"
    { (exit 1); exit 1; }; } ;;
 esac
 
-cat >>confdefs.h <<_ACEOF
-#define ENABLE_THREADS $ENABLE_THREADS
-_ACEOF
-
-
 # Check whether --enable-pic was given.
 if test "${enable_pic+set}" = set; then
   enableval=$enable_pic;
@@ -10575,7 +10570,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 10578 "configure"
+#line 10573 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12719,7 +12714,7 @@ ia64-*-hpux*)
   ;;
 *-*-irix6*)
   # Find out which ABI we are using.
-  echo '#line 12722 "configure"' > conftest.$ac_ext
+  echo '#line 12717 "configure"' > conftest.$ac_ext
   if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
   (eval $ac_compile) 2>&5
   ac_status=$?
@@ -14437,11 +14432,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:14440: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:14435: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:14444: \$? = $ac_status" >&5
+   echo "$as_me:14439: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -14705,11 +14700,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:14708: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:14703: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:14712: \$? = $ac_status" >&5
+   echo "$as_me:14707: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -14809,11 +14804,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:14812: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:14807: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:14816: \$? = $ac_status" >&5
+   echo "$as_me:14811: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -17261,7 +17256,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 17264 "configure"
+#line 17259 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -17361,7 +17356,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 17364 "configure"
+#line 17359 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -19729,11 +19724,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:19732: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:19727: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:19736: \$? = $ac_status" >&5
+   echo "$as_me:19731: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -19833,11 +19828,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:19836: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:19831: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:19840: \$? = $ac_status" >&5
+   echo "$as_me:19835: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -21403,11 +21398,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:21406: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:21401: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:21410: \$? = $ac_status" >&5
+   echo "$as_me:21405: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -21507,11 +21502,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:21510: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:21505: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:21514: \$? = $ac_status" >&5
+   echo "$as_me:21509: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -23742,11 +23737,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:23745: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:23740: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:23749: \$? = $ac_status" >&5
+   echo "$as_me:23744: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -24010,11 +24005,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:24013: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:24008: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>conftest.err)
    ac_status=$?
    cat conftest.err >&5
-   echo "$as_me:24017: \$? = $ac_status" >&5
+   echo "$as_me:24012: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s "$ac_outfile"; then
      # The compiler can only warn and ignore the option if not recognized
      # So say no if there are warnings other than the usual output.
@@ -24114,11 +24109,11 @@ else
    -e 's:.*FLAGS}\{0,1\} :&$lt_compiler_flag :; t' \
    -e 's: [^ ]*conftest\.: $lt_compiler_flag&:; t' \
    -e 's:$: $lt_compiler_flag:'`
-   (eval echo "\"\$as_me:24117: $lt_compile\"" >&5)
+   (eval echo "\"\$as_me:24112: $lt_compile\"" >&5)
    (eval "$lt_compile" 2>out/conftest.err)
    ac_status=$?
    cat out/conftest.err >&5
-   echo "$as_me:24121: \$? = $ac_status" >&5
+   echo "$as_me:24116: \$? = $ac_status" >&5
    if (exit $ac_status) && test -s out/conftest2.$ac_objext
    then
      # The compiler can only warn and ignore the option if not recognized
@@ -33607,6 +33602,81 @@ echo "$as_me: WARNING: mmap() of files required but not found" >&2;}
   fi
 fi
 
+if test "$ENABLE_THREADS" -eq 1 ; then
+  { echo "$as_me:$LINENO: checking for GCC atomic builtins" >&5
+echo $ECHO_N "checking for GCC atomic builtins... $ECHO_C" >&6; }
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+int main() {
+              volatile unsigned long val = 1;
+              __sync_synchronize();
+              __sync_val_compare_and_swap(&val, 1, 0);
+              return 0;
+            }
+
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_link") 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+	 { ac_try='test -z "$ac_c_werror_flag" || test ! -s conftest.err'
+  { (case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+	 { ac_try='test -s conftest$ac_exeext'
+  { (case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval "echo \"\$as_me:$LINENO: $ac_try_echo\"") >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  { echo "$as_me:$LINENO: result: yes" >&5
+echo "${ECHO_T}yes" >&6; }
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	{ echo "$as_me:$LINENO: result: no" >&5
+echo "${ECHO_T}no" >&6; }
+        ENABLE_THREADS=0
+
+        { echo "$as_me:$LINENO: WARNING: Threading support disabled because atomic builtins are missing" >&5
+echo "$as_me: WARNING: Threading support disabled because atomic builtins are missing" >&2;}
+fi
+
+rm -f core conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+fi
+
+
+cat >>confdefs.h <<_ACEOF
+#define ENABLE_THREADS $ENABLE_THREADS
+_ACEOF
+
+
 
 
 for ac_func in __dso_handle