Index: cfe/trunk/docs/JSONCompilationDatabase.rst
===================================================================
--- cfe/trunk/docs/JSONCompilationDatabase.rst
+++ cfe/trunk/docs/JSONCompilationDatabase.rst
@@ -80,6 +80,9 @@
    supported.
 -  **arguments:** The compile command executed as list of strings.
    Either **arguments** or **command** is required.
+-  **output:** The name of the output created by this compilation step.
+   This field is optional. It can be used to distinguish different processing
+   modes of the same input file.
 
 Build System Integration
 ========================
Index: cfe/trunk/include/clang/Tooling/CompilationDatabase.h
===================================================================
--- cfe/trunk/include/clang/Tooling/CompilationDatabase.h
+++ cfe/trunk/include/clang/Tooling/CompilationDatabase.h
@@ -43,10 +43,11 @@
 struct CompileCommand {
   CompileCommand() {}
   CompileCommand(Twine Directory, Twine Filename,
-                 std::vector<std::string> CommandLine)
+                 std::vector<std::string> CommandLine, Twine Output)
       : Directory(Directory.str()),
         Filename(Filename.str()),
-        CommandLine(std::move(CommandLine)) {}
+        CommandLine(std::move(CommandLine)),
+        Output(Output.str()){}
 
   /// \brief The working directory the command was executed from.
   std::string Directory;
@@ -57,6 +58,9 @@
   /// \brief The command line that was executed.
   std::vector<std::string> CommandLine;
 
+  /// The output file associated with the command.
+  std::string Output;
+
   /// \brief An optional mapping from each file's path to its content for all
   /// files needed for the compilation that are not available via the file
   /// system.
Index: cfe/trunk/include/clang/Tooling/JSONCompilationDatabase.h
===================================================================
--- cfe/trunk/include/clang/Tooling/JSONCompilationDatabase.h
+++ cfe/trunk/include/clang/Tooling/JSONCompilationDatabase.h
@@ -103,15 +103,17 @@
   /// failed.
   bool parse(std::string &ErrorMessage);
 
-  // Tuple (directory, filename, commandline) where 'commandline' points to the
-  // corresponding scalar nodes in the YAML stream.
+  // Tuple (directory, filename, commandline, output) where 'commandline'
+  // points to the corresponding scalar nodes in the YAML stream.
   // If the command line contains a single argument, it is a shell-escaped
   // command line.
   // Otherwise, each entry in the command line vector is a literal
   // argument to the compiler.
+  // The output field may be a nullptr.
   typedef std::tuple<llvm::yaml::ScalarNode *,
                      llvm::yaml::ScalarNode *,
-                    std::vector<llvm::yaml::ScalarNode *>> CompileCommandRef;
+                     std::vector<llvm::yaml::ScalarNode *>,
+                     llvm::yaml::ScalarNode *> CompileCommandRef;
 
   /// \brief Converts the given array of CompileCommandRefs to CompileCommands.
   void getCommands(ArrayRef<CompileCommandRef> CommandsRef,
Index: cfe/trunk/lib/Tooling/CompilationDatabase.cpp
===================================================================
--- cfe/trunk/lib/Tooling/CompilationDatabase.cpp
+++ cfe/trunk/lib/Tooling/CompilationDatabase.cpp
@@ -300,7 +300,8 @@
   ToolCommandLine.insert(ToolCommandLine.end(),
                          CommandLine.begin(), CommandLine.end());
   CompileCommands.emplace_back(Directory, StringRef(),
-                               std::move(ToolCommandLine));
+                               std::move(ToolCommandLine),
+                               StringRef());
 }
 
 std::vector<CompileCommand>
Index: cfe/trunk/lib/Tooling/JSONCompilationDatabase.cpp
===================================================================
--- cfe/trunk/lib/Tooling/JSONCompilationDatabase.cpp
+++ cfe/trunk/lib/Tooling/JSONCompilationDatabase.cpp
@@ -257,10 +257,13 @@
   for (int I = 0, E = CommandsRef.size(); I != E; ++I) {
     SmallString<8> DirectoryStorage;
     SmallString<32> FilenameStorage;
+    SmallString<32> OutputStorage;
+    auto Output = std::get<3>(CommandsRef[I]);
     Commands.emplace_back(
         std::get<0>(CommandsRef[I])->getValue(DirectoryStorage),
         std::get<1>(CommandsRef[I])->getValue(FilenameStorage),
-        nodeToCommandLine(Syntax, std::get<2>(CommandsRef[I])));
+        nodeToCommandLine(Syntax, std::get<2>(CommandsRef[I])),
+        Output ? Output->getValue(OutputStorage) : "");
   }
 }
 
@@ -289,6 +292,7 @@
     llvm::yaml::ScalarNode *Directory = nullptr;
     llvm::Optional<std::vector<llvm::yaml::ScalarNode *>> Command;
     llvm::yaml::ScalarNode *File = nullptr;
+    llvm::yaml::ScalarNode *Output = nullptr;
     for (auto& NextKeyValue : *Object) {
       llvm::yaml::ScalarNode *KeyString =
           dyn_cast<llvm::yaml::ScalarNode>(NextKeyValue.getKey());
@@ -331,6 +335,8 @@
           Command = std::vector<llvm::yaml::ScalarNode *>(1, ValueString);
       } else if (KeyValue == "file") {
         File = ValueString;
+      } else if (KeyValue == "output") {
+        Output = ValueString;
       } else {
         ErrorMessage = ("Unknown key: \"" +
                         KeyString->getRawValue() + "\"").str();
@@ -361,7 +367,7 @@
     } else {
       llvm::sys::path::native(FileName, NativeFilePath);
     }
-    auto Cmd = CompileCommandRef(Directory, File, *Command);
+    auto Cmd = CompileCommandRef(Directory, File, *Command, Output);
     IndexByFile[NativeFilePath].push_back(Cmd);
     AllCommands.push_back(Cmd);
     MatchTrie.insert(NativeFilePath);
Index: cfe/trunk/unittests/Tooling/CompilationDatabaseTest.cpp
===================================================================
--- cfe/trunk/unittests/Tooling/CompilationDatabaseTest.cpp
+++ cfe/trunk/unittests/Tooling/CompilationDatabaseTest.cpp
@@ -44,6 +44,7 @@
   expectFailure("[{\"directory\":\"\",\"command\":[],\"file\":\"\"}]", "Command not string");
   expectFailure("[{\"directory\":\"\",\"arguments\":[[]],\"file\":\"\"}]",
                 "Arguments contain non-string");
+  expectFailure("[{\"output\":[]}]", "Expected strings as value.");
 }
 
 static std::vector<std::string> getAllFiles(StringRef JSONDatabase,
@@ -105,16 +106,19 @@
   StringRef Directory1("//net/dir1");
   StringRef FileName1("file1");
   StringRef Command1("command1");
+  StringRef Output1("file1.o");
   StringRef Directory2("//net/dir2");
   StringRef FileName2("file2");
   StringRef Command2("command2");
+  StringRef Output2("");
 
   std::vector<CompileCommand> Commands = getAllCompileCommands(
       JSONCommandLineSyntax::Gnu,
       ("[{\"directory\":\"" + Directory1 + "\"," + "\"command\":\"" + Command1 +
        "\","
        "\"file\":\"" +
-       FileName1 + "\"},"
+       FileName1 + "\", \"output\":\"" +
+       Output1 + "\"},"
                    " {\"directory\":\"" +
        Directory2 + "\"," + "\"command\":\"" + Command2 + "\","
                                                           "\"file\":\"" +
@@ -124,10 +128,12 @@
   EXPECT_EQ(2U, Commands.size()) << ErrorMessage;
   EXPECT_EQ(Directory1, Commands[0].Directory) << ErrorMessage;
   EXPECT_EQ(FileName1, Commands[0].Filename) << ErrorMessage;
+  EXPECT_EQ(Output1, Commands[0].Output) << ErrorMessage;
   ASSERT_EQ(1u, Commands[0].CommandLine.size());
   EXPECT_EQ(Command1, Commands[0].CommandLine[0]) << ErrorMessage;
   EXPECT_EQ(Directory2, Commands[1].Directory) << ErrorMessage;
   EXPECT_EQ(FileName2, Commands[1].Filename) << ErrorMessage;
+  EXPECT_EQ(Output2, Commands[1].Output) << ErrorMessage;
   ASSERT_EQ(1u, Commands[1].CommandLine.size());
   EXPECT_EQ(Command2, Commands[1].CommandLine[0]) << ErrorMessage;