Index: include/llvm/Option/OptTable.h
===================================================================
--- include/llvm/Option/OptTable.h
+++ include/llvm/Option/OptTable.h
@@ -147,11 +147,33 @@
   /// Zero is the default which includes all flags.
   /// \param FlagsToExclude - Don't parse options with this flag.  Zero
   /// is the default and means exclude nothing.
+  /// \param IndexToTranslate - If not null, points to the index of option in
+  /// \c Args, on exit provides index of corresponding element in the returned
+  /// array.
   /// \return An InputArgList; on error this will contain all the options
   /// which could be parsed.
+  ///
+  /// Argument \c IndexToTranslate is added to assist using configuration file.
+  /// It allows to determine correspondence between elements of \c Args that
+  /// came from configuration file and elements in the result list that
+  /// correspond to them. Due to options that require separate arguments these
+  /// numbers can be different. For instance, the two elements in \c Argc:
+  /// \verbatim
+  ///   -triple x86_64-apple-darwin
+  /// \endverbatim
+  /// result in one argument.
+  ///
+  /// If \c IndexToTranslate is not null, the function expects it points to a
+  /// variable that contains index of the first element past the content of
+  /// config file. Upon exit this variable is assigned the index of
+  /// corresponding element in the result. If the last option in config file
+  /// requires separate argument and that argument is not provided in the file
+  /// (for instance, config file contains only \c -triple), the index is written
+  /// with negative sign.
   InputArgList ParseArgs(ArrayRef<const char *> Args, unsigned &MissingArgIndex,
                          unsigned &MissingArgCount, unsigned FlagsToInclude = 0,
-                         unsigned FlagsToExclude = 0) const;
+                         unsigned FlagsToExclude = 0,
+                         int *IndexToTranslate = nullptr) const;
 
   /// \brief Render the help text for an option table.
   ///
Index: lib/Option/OptTable.cpp
===================================================================
--- lib/Option/OptTable.cpp
+++ lib/Option/OptTable.cpp
@@ -249,12 +249,16 @@
                                  unsigned &MissingArgIndex,
                                  unsigned &MissingArgCount,
                                  unsigned FlagsToInclude,
-                                 unsigned FlagsToExclude) const {
+                                 unsigned FlagsToExclude,
+                                 int *IndexToTranslate) const {
   InputArgList Args(ArgArr.begin(), ArgArr.end());
 
   // FIXME: Handle '@' args (or at least error on them).
 
   MissingArgIndex = MissingArgCount = 0;
+  unsigned ToTranslate = 0;
+  if (IndexToTranslate)
+    ToTranslate = static_cast<int>(*IndexToTranslate);
   unsigned Index = 0, End = ArgArr.size();
   while (Index < End) {
     // Ingore nullptrs, they are response file's EOL markers
@@ -283,6 +287,17 @@
     }
 
     Args.append(A);
+
+    // Check if the index to translate is reached.
+    if (ToTranslate && Prev < ToTranslate) {
+      if (Index == ToTranslate) {
+        *IndexToTranslate = static_cast<int>(Args.size());
+        ToTranslate = 0;
+      } else if (Index > ToTranslate) {
+        *IndexToTranslate = -static_cast<int>(Args.size());
+        ToTranslate = 0;
+      }
+    }
   }
 
   return Args;
Index: unittests/Option/OptionParsingTest.cpp
===================================================================
--- unittests/Option/OptionParsingTest.cpp
+++ unittests/Option/OptionParsingTest.cpp
@@ -265,3 +265,38 @@
   EXPECT_EQ(1U, AL.getAllArgValues(OPT_B).size());
   EXPECT_EQ("", AL.getAllArgValues(OPT_B)[0]);
 }
+
+TEST(Option, IndexTranslation) {
+  TestOptTable T;
+  unsigned MAI, MAC;
+
+  // Check that the number of config options successfully converted into the
+  // number of arguments.
+  const char *MyArgs[] = { "-A", "-C", "000", "-C", "foo", "-Bbar" };
+  int Ndx = 5;
+  InputArgList AL = T.ParseArgs(MyArgs, MAI, MAC, 0, 0, &Ndx);
+  EXPECT_EQ(AL.size(), 4U);
+  EXPECT_TRUE(AL.hasArg(OPT_A));
+  EXPECT_TRUE(AL.hasArg(OPT_B));
+  EXPECT_EQ("bar", AL.getLastArgValue(OPT_B));
+  EXPECT_TRUE(AL.hasArg(OPT_C));
+  EXPECT_EQ("foo", AL.getLastArgValue(OPT_C));
+  EXPECT_EQ(Ndx, 3);
+}
+
+TEST(Option, IndexTranslationWrong) {
+  TestOptTable T;
+  unsigned MAI, MAC;
+
+  // Check that the the case when an option is split in the middle is detected.
+  const char *MyArgs[] = { "-A", "-C", "000", "-C", "foo", "-Bbar" };
+  int Ndx = 4;
+  InputArgList AL = T.ParseArgs(MyArgs, MAI, MAC, 0, 0, &Ndx);
+  EXPECT_EQ(AL.size(), 4U);
+  EXPECT_TRUE(AL.hasArg(OPT_A));
+  EXPECT_TRUE(AL.hasArg(OPT_B));
+  EXPECT_EQ("bar", AL.getLastArgValue(OPT_B));
+  EXPECT_TRUE(AL.hasArg(OPT_C));
+  EXPECT_EQ("foo", AL.getLastArgValue(OPT_C));
+  EXPECT_EQ(Ndx, -3);
+}