diff --git a/llvm/autoconf/configure.ac b/llvm/autoconf/configure.ac
index a1c6d5fc5324..9d9762d4855f 100644
--- a/llvm/autoconf/configure.ac
+++ b/llvm/autoconf/configure.ac
@@ -443,7 +443,8 @@ dnl===-----------------------------------------------------------------------===
 
 AC_CHECK_FUNCS([backtrace getcwd getpagesize getrusage gettimeofday isatty ])
 AC_CHECK_FUNCS([mkdtemp mkstemp mktemp ])
-AC_CHECK_FUNCS([realpath setrlimit strdup strtoq strtoll sysconf ])
+AC_CHECK_FUNCS([realpath setrlimit strdup strerror strerror_r strtoll strtoq ])
+AC_CHECK_FUNCS([sysconf])
 AC_C_PRINTF_A
 AC_FUNC_ALLOCA
 AC_FUNC_RAND48
@@ -459,9 +460,11 @@ AC_FUNC_ISNAN
 AC_FUNC_ISINF
 
 dnl Check for mmap and mprotect support. We need both to do the JIT and for
-dnl bytecode loading, etc.
+dnl bytecode loading, etc. We also need to know if /dev/zero is required to
+dnl be opened for allocating RWX memory.
 AC_FUNC_MMAP
 AC_FUNC_MMAP_FILE
+AC_NEED_DEV_ZERO_FOR_MMAP
 AC_CHECK_FUNC(mprotect,,
               AC_MSG_ERROR([Function mprotect() required but not found]))
 
diff --git a/llvm/configure b/llvm/configure
index 711ae0e8d398..e5ab827b931a 100755
--- a/llvm/configure
+++ b/llvm/configure
@@ -24601,7 +24601,7 @@ esac
 ETAGSFLAGS=$ETAGSFLAGS
 
 
-if test "$WITH_LLVMGCCDIR" != "default" ; then
+if test "$WITH_LLVMGCCDIR" = "default" ; then
   # Extract the first word of "llvm-gcc", so it can be a program name with args.
 set dummy llvm-gcc; ac_word=$2
 echo "$as_me:$LINENO: checking for $ac_word" >&5
@@ -25750,7 +25750,7 @@ echo "${ECHO_T}$ac_cv_header_mmap_anon" >&6
 if test "$ac_cv_header_mmap_anon" = yes; then
 
 cat >>confdefs.h <<\_ACEOF
-#define HAVE_MMAP_ANONYMOUS
+#define HAVE_MMAP_ANONYMOUS 1
 _ACEOF
 
 fi
@@ -27269,7 +27269,110 @@ done
 
 
 
-for ac_func in realpath setrlimit strdup strtoq strtoll sysconf
+
+for ac_func in realpath setrlimit strdup strerror strerror_r strtoll strtoq
+do
+as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
+echo "$as_me:$LINENO: checking for $ac_func" >&5
+echo $ECHO_N "checking for $ac_func... $ECHO_C" >&6
+if eval "test \"\${$as_ac_var+set}\" = set"; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+/* Define $ac_func to an innocuous variant, in case <limits.h> declares $ac_func.
+   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
+#define $ac_func innocuous_$ac_func
+
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $ac_func (); below.
+    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+    <limits.h> exists even on freestanding compilers.  */
+
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+
+#undef $ac_func
+
+/* Override any gcc2 internal prototype to avoid an error.  */
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+/* We use char because int might match the return type of a gcc2
+   builtin and then its argument prototype would still apply.  */
+char $ac_func ();
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined (__stub_$ac_func) || defined (__stub___$ac_func)
+choke me
+#else
+char (*f) () = $ac_func;
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+int
+main ()
+{
+return f != $ac_func;
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&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'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&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'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  eval "$as_ac_var=yes"
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+eval "$as_ac_var=no"
+fi
+rm -f conftest.err conftest.$ac_objext \
+      conftest$ac_exeext conftest.$ac_ext
+fi
+echo "$as_me:$LINENO: result: `eval echo '${'$as_ac_var'}'`" >&5
+echo "${ECHO_T}`eval echo '${'$as_ac_var'}'`" >&6
+if test `eval echo '${'$as_ac_var'}'` = yes; then
+  cat >>confdefs.h <<_ACEOF
+#define `echo "HAVE_$ac_func" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+done
+
+
+for ac_func in sysconf
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 echo "$as_me:$LINENO: checking for $ac_func" >&5
@@ -29747,6 +29850,27 @@ _ACEOF
 
 fi
 
+echo "$as_me:$LINENO: checking if /dev/zero is needed for mmap" >&5
+echo $ECHO_N "checking if /dev/zero is needed for mmap... $ECHO_C" >&6
+if test "${ac_cv_need_dev_zero_for_mmap+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+  if test "$llvm_cv_os_type" == "Interix" ; then
+   ac_cv_need_dev_zero_for_mmap=yes
+ else
+   ac_cv_need_dev_zero_for_mmap=no
+ fi
+
+fi
+echo "$as_me:$LINENO: result: $ac_cv_need_dev_zero_for_mmap" >&5
+echo "${ECHO_T}$ac_cv_need_dev_zero_for_mmap" >&6
+if test "$ac_cv_need_dev_zero_for_mmap" = yes; then
+
+cat >>confdefs.h <<\_ACEOF
+#define NEED_DEV_ZERO_FOR_MMAP 1
+_ACEOF
+
+fi
 echo "$as_me:$LINENO: checking for mprotect" >&5
 echo $ECHO_N "checking for mprotect... $ECHO_C" >&6
 if test "${ac_cv_func_mprotect+set}" = set; then
diff --git a/llvm/include/llvm/Config/config.h.in b/llvm/include/llvm/Config/config.h.in
index d3d0aadbcfa4..372901d16414 100644
--- a/llvm/include/llvm/Config/config.h.in
+++ b/llvm/include/llvm/Config/config.h.in
@@ -270,6 +270,12 @@
 /* Define to 1 if you have the `strdup' function. */
 #undef HAVE_STRDUP
 
+/* Define to 1 if you have the `strerror' function. */
+#undef HAVE_STRERROR
+
+/* Define to 1 if you have the `strerror_r' function. */
+#undef HAVE_STRERROR_R
+
 /* Define to 1 if you have the <strings.h> header file. */
 #undef HAVE_STRINGS_H
 
@@ -385,6 +391,10 @@
 /* Define to the system default library search path. */
 #undef LTDL_SYSSEARCHPATH
 
+/* Define if /dev/zero should be used when mapping RWX memory, or undefine if
+   its not necessary */
+#undef NEED_DEV_ZERO_FOR_MMAP
+
 /* Define if dlsym() requires a leading underscore in symbol names. */
 #undef NEED_USCORE