[tests] Add support for REQUIRES and XFAIL lines in libc++ tests.

- We parse up to the first non-empty non-comment (C++ style) line, otherwise
   the format and semantics match what is used for LLVM/Clang tests.

 - For now, the only interesting thing to test against is a user supplied
   target_triple test parameter.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@174440 91177308-0d34-0410-b5e6-96231b3b80d8

test/lit.cfg

@@ -11,6 +11,26 @@ import subprocess
 import errno
 import time
 
+# FIXME: For now, this is cribbed from lit.TestRunner, to avoid introducing a
+# dependency there. What we more ideally would like to do is lift the "xfail"
+# and "requires" handling to be a core lit framework feature.
+def isExpectedFail(test, xfails):
+    # Check if any of the xfails match an available feature or the target.
+    for item in xfails:
+        # If this is the wildcard, it always fails.
+        if item == '*':
+            return True
+
+        # If this is an exact match for one of the features, it fails.
+        if item in test.config.available_features:
+            return True
+
+        # If this is a part of the target triple, it fails.
+        if item in test.suite.config.target_triple:
+            return True
+
+    return False
+
 class LibcxxTestFormat(lit.formats.FileBasedTest):
     """
     Custom test format handler for use with the test format use by libc++.
@@ -55,6 +75,52 @@ class LibcxxTestFormat(lit.formats.FileBasedTest):
                 time.sleep(0.1)
 
     def _execute(self, test, lit_config):
+        # Extract test metadata from the test file.
+        xfails = []
+        requires = []
+        with open(test.getSourcePath()) as f:
+            for ln in f:
+                if 'XFAIL:' in ln:
+                    items = ln[ln.index('XFAIL:') + 6:].split(',')
+                    xfails.extend([s.strip() for s in items])
+                elif 'REQUIRES:' in ln:
+                    items = ln[ln.index('REQUIRES:') + 9:].split(',')
+                    requires.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.
+                    break
+
+        # Check that we have the required features.
+        #
+        # FIXME: For now, this is cribbed from lit.TestRunner, to avoid
+        # introducing a dependency there. What we more ideally would like to do
+        # is lift the "xfail" and "requires" handling to be a core lit framework
+        # feature.
+        missing_required_features = [f for f in requires
+                                     if f not in test.config.available_features]
+        if missing_required_features:
+            return (lit.Test.UNSUPPORTED,
+                    "Test requires the following features: %s" % (
+                      ', '.join(missing_required_features),))
+
+        # Determine if this test is an expected failure.
+        isXFail = isExpectedFail(test, xfails)
+
+        # Evaluate the test.
+        result, report = self._evaluate_test(test, lit_config)
+
+        # Convert the test result based on whether this is an expected failure.
+        if isXFail:
+            if result != lit.Test.FAIL:
+                report += "\n\nTest was expected to FAIL, but did not.\n"
+                result = lit.Test.XPASS
+            else:
+                result = lit.Test.XFAIL
+
+        return result, report
+
+    def _evaluate_test(self, test, lit_config):
         name = test.path_in_suite[-1]
         source_path = test.getSourcePath()
         source_dir = os.path.dirname(source_path)
@@ -210,4 +276,5 @@ config.test_format = LibcxxTestFormat(
     ld_flags = ['-nodefaultlibs'] + library_paths + ['-lc++'] + libraries,
     exec_env = exec_env)
 
-config.target_triple = None
+config.target_triple = lit.params.get(
+    'target_triple', 'unknown-unknown-unknown')