Index: libcxx/test/lit.cfg
===================================================================
--- libcxx/test/lit.cfg
+++ libcxx/test/lit.cfg
@@ -63,6 +63,7 @@
     def _execute(self, test, lit_config):
         # Extract test metadata from the test file.
         requires = []
+        requiresnot = []
         with open(test.getSourcePath()) as f:
             for ln in f:
                 if 'XFAIL:' in ln:
@@ -71,6 +72,9 @@
                 elif 'REQUIRES:' in ln:
                     items = ln[ln.index('REQUIRES:') + 9:].split(',')
                     requires.extend([s.strip() for s in items])
+                elif 'REQUIRES-NOT:' in ln:
+                    items = ln[ln.index('REQUIRES-NOT:') + 13:].split(',')
+                    requiresnot.extend([s.strip() for s in items])
                 elif not ln.startswith("//") and ln.strip():
                     # Stop at the first non-empty line that is not a C++
                     # comment.
@@ -88,6 +92,13 @@
                     "Test requires the following features: %s" % (
                       ', '.join(missing_required_features),))
 
+        incompatible_features = [f for f in requires
+                                if f in test.config.available_features]
+        if incompatible_features:
+            return (lit.Test.UNSUPPORTED,
+                    "Test is incompatible with the following features: %s" % (
+                    ', '.join(incompatible_features),))
+
         # Evaluate the test.
         return self._evaluate_test(test, lit_config)
 
@@ -125,6 +136,8 @@
             try:
                 compile_cmd = [self.cxx_under_test, '-o', exec_path,
                        source_path] + self.cpp_flags + self.ld_flags
+                if lit_config.useQEMU:
+                    compile_cmd.append('test_wrapper.cc')
                 cmd = compile_cmd
                 out, err, exitCode = self.execute_command(cmd)
                 if exitCode != 0:
@@ -139,20 +152,34 @@
                     return lit.Test.FAIL, report
 
                 cmd = []
-                if self.exec_env:
-                    cmd.append('env')
-                    cmd.extend('%s=%s' % (name, value)
-                               for name,value in self.exec_env.items())
+                # HACK(jroelofs): fix this the 'right' way
+#                if self.exec_env:
+#                    cmd.append('env')
+#                    cmd.extend('%s=%s' % (name, value)
+#                               for name,value in self.exec_env.items())
                 cmd.append(exec_path)
                 if lit_config.useValgrind:
                     cmd = lit_config.valgrindArgs + cmd
+                if lit_config.useQEMU:
+                    cmd = lit_config.qemuArgs + cmd
                 out, err, exitCode = self.execute_command(cmd, source_dir)
-                if exitCode != 0:
+                success = False
+                if lit_config.useQEMU:
+                    if out.startswith("FAIL"):
+                        success = False
+                    elif out.startswith("PASS"):
+                        success = True
+                    else:
+                        success = False
+                else:
+                    success = exitCode != 0
+                if not success:
                     report = """Compiled With: %s\n""" % \
                         ' '.join(["'%s'" % a for a in compile_cmd])
                     report += """Command: %s\n""" % \
                         ' '.join(["'%s'" % a for a in cmd])
-                    report += """Exit Code: %d\n""" % exitCode
+                    if not lit_config.useQEMU:
+                        report += """Exit Code: %d\n""" % exitCode
                     if out:
                         report += """Standard Output:\n--\n%s--""" % out
                     if err:
@@ -185,7 +212,7 @@
         clangxx = lit.util.which('clang++', config.environment['PATH'])
         if clangxx is not None:
             cxx_under_test = clangxx
-    lit_config.note("inferred cxx_under_test as: %r" % (cxx_under_test,))
+        lit_config.note("inferred cxx_under_test as: %r" % (cxx_under_test,))
 if cxx_under_test is None:
     lit_config.fatal('must specify user parameter cxx_under_test '
                      '(e.g., --param=cxx_under_test=clang++)')
@@ -218,6 +245,8 @@
 # locally built one; the former mode is useful for testing ABI compatibility
 # between the current headers and a shipping dynamic library.
 use_system_lib_str = lit_config.params.get('use_system_lib', None)
+if use_system_lib_str is None:
+    use_system_lib_str = getattr(config, 'use_system_lib', None)
 if use_system_lib_str is not None:
     if use_system_lib_str.lower() in ('1', 'true'):
         use_system_lib = True