diff --git a/tools/llvmc/doc/LLVMC-Reference.rst b/tools/llvmc/doc/LLVMC-Reference.rst
index d160e75..6409608 100644
--- a/tools/llvmc/doc/LLVMC-Reference.rst
+++ b/tools/llvmc/doc/LLVMC-Reference.rst
@@ -456,22 +456,22 @@
 * Possible tests are:
 
   - ``switch_on`` - Returns true if a given command-line switch is provided by
-    the user. Can be given a list as argument, in that case ``(switch_on ["foo",
-    "bar", "baz"])`` is equivalent to ``(and (switch_on "foo"), (switch_on
+    the user. Can be given multiple arguments, in that case ``(switch_on "foo",
+    "bar", "baz")`` is equivalent to ``(and (switch_on "foo"), (switch_on
     "bar"), (switch_on "baz"))``.
     Example: ``(switch_on "opt")``.
 
-  - ``any_switch_on`` - Given a list of switch options, returns true if any of
+  - ``any_switch_on`` - Given a number of switch options, returns true if any of
     the switches is turned on.
-    Example: ``(any_switch_on ["foo", "bar", "baz"])`` is equivalent to ``(or
+    Example: ``(any_switch_on "foo", "bar", "baz")`` is equivalent to ``(or
     (switch_on "foo"), (switch_on "bar"), (switch_on "baz"))``.
 
-  - ``parameter_equals`` - Returns true if a command-line parameter equals
-    a given value.
+  - ``parameter_equals`` - Returns true if a command-line parameter (first
+    argument) equals a given value (second argument).
     Example: ``(parameter_equals "W", "all")``.
 
-  - ``element_in_list`` - Returns true if a command-line parameter
-    list contains a given value.
+  - ``element_in_list`` - Returns true if a command-line parameter list (first
+    argument) contains a given value (second argument).
     Example: ``(element_in_list "l", "pthread")``.
 
   - ``input_languages_contain`` - Returns true if a given language
@@ -479,27 +479,27 @@
     Example: ``(input_languages_contain "c++")``.
 
   - ``in_language`` - Evaluates to true if the input file language is equal to
-    the argument. At the moment works only with ``cmd_line`` and ``actions`` (on
+    the argument. At the moment works only with ``command`` and ``actions`` (on
     non-join nodes).
     Example: ``(in_language "c++")``.
 
   - ``not_empty`` - Returns true if a given option (which should be either a
     parameter or a parameter list) is set by the user. Like ``switch_on``, can
-    be also given a list as argument.
-    Example: ``(not_empty "o")``.
+    be also given multiple arguments.
+    Examples: ``(not_empty "o")``, ``(not_empty "o", "l")``.
 
   - ``any_not_empty`` - Returns true if ``not_empty`` returns true for any of
-    the options in the list.
-    Example: ``(any_not_empty ["foo", "bar", "baz"])`` is equivalent to ``(or
+    the provided options.
+    Example: ``(any_not_empty "foo", "bar", "baz")`` is equivalent to ``(or
     (not_empty "foo"), (not_empty "bar"), (not_empty "baz"))``.
 
   - ``empty`` - The opposite of ``not_empty``. Equivalent to ``(not (not_empty
-    X))``. Provided for convenience. Can be given a list as argument.
+    X))``. Can be given multiple arguments.
 
   - ``any_not_empty`` - Returns true if ``not_empty`` returns true for any of
-    the options in the list.
-    Example: ``(any_empty ["foo", "bar", "baz"])`` is equivalent to ``(not (and
-    (not_empty "foo"), (not_empty "bar"), (not_empty "baz")))``.
+    the provided options.
+    Example: ``(any_empty "foo", "bar", "baz")`` is equivalent to ``(or
+    (not_empty "foo"), (not_empty "bar"), (not_empty "baz"))``.
 
   - ``single_input_file`` - Returns true if there was only one input file
     provided on the command-line. Used without arguments:
@@ -511,16 +511,18 @@
   - ``default`` - Always evaluates to true. Should always be the last
     test in the ``case`` expression.
 
-  - ``and`` - A standard binary logical combinator that returns true iff all of
+  - ``and`` - A standard logical combinator that returns true iff all of
     its arguments return true. Used like this: ``(and (test1), (test2),
     ... (testN))``. Nesting of ``and`` and ``or`` is allowed, but not
     encouraged.
 
-  - ``or`` - A binary logical combinator that returns true iff any of its
-    arguments returns true. Example: ``(or (test1), (test2), ... (testN))``.
+  - ``or`` - A logical combinator that returns true iff any of its arguments
+    return true.
+    Example: ``(or (test1), (test2), ... (testN))``.
 
   - ``not`` - Standard unary logical combinator that negates its
-    argument. Example: ``(not (or (test1), (test2), ... (testN)))``.
+    argument.
+    Example: ``(not (or (test1), (test2), ... (testN)))``.
 
 
 
@@ -549,10 +551,10 @@
 
 * Possible tool properties:
 
-  - ``in_language`` - input language name. Can be either a string or a
-    list, in case the tool supports multiple input languages.
+  - ``in_language`` - input language name. Can be given multiple arguments, in
+    case the tool supports multiple input languages.
 
-  - ``out_language`` - output language name. Multiple output languages are not
+  - ``out_language`` - output language name. Multiple output languages are
     allowed.
 
   - ``output_suffix`` - output file suffix. Can also be changed
@@ -687,12 +689,12 @@
 
 
     def Preprocess : OptionPreprocessor<
-    (case (not (any_switch_on ["O0", "O1", "O2", "O3"])),
+    (case (not (any_switch_on "O0", "O1", "O2", "O3")),
                (set_option "O2"),
-          (and (switch_on "O3"), (any_switch_on ["O0", "O1", "O2"])),
-               (unset_option ["O0", "O1", "O2"]),
-          (and (switch_on "O2"), (any_switch_on ["O0", "O1"])),
-               (unset_option ["O0", "O1"]),
+          (and (switch_on "O3"), (any_switch_on "O0", "O1", "O2")),
+               (unset_option "O0", "O1", "O2"),
+          (and (switch_on "O2"), (any_switch_on "O0", "O1")),
+               (unset_option "O0", "O1"),
           (and (switch_on "O1"), (switch_on "O0")),
                (unset_option "O0"))
     >;
@@ -709,10 +711,10 @@
 two-argument form: ``(set_option "parameter", VALUE)``. Here, ``VALUE`` can be
 either a string, a string list, or a boolean constant.
 
-For convenience, ``set_option`` and ``unset_option`` also work on lists. That
-is, instead of ``[(unset_option "A"), (unset_option "B")]`` you can use
-``(unset_option ["A", "B"])``. Obviously, ``(set_option ["A", "B"])`` is valid
-only if both ``A`` and ``B`` are switches.
+For convenience, ``set_option`` and ``unset_option`` also work with multiple
+arguments. That is, instead of ``[(unset_option "A"), (unset_option "B")]`` you
+can use ``(unset_option "A", "B")``. Obviously, ``(set_option "A", "B")`` is
+only valid if both ``A`` and ``B`` are switches.
 
 
 More advanced topics
diff --git a/tools/llvmc/src/Base.td.in b/tools/llvmc/src/Base.td.in
index a53ac9e..cefaf48 100644
--- a/tools/llvmc/src/Base.td.in
+++ b/tools/llvmc/src/Base.td.in
@@ -152,23 +152,22 @@
 // Option preprocessor.
 
 def Preprocess : OptionPreprocessor<
-(case (not (any_switch_on ["O0", "O1", "O2", "O3"])),
+(case (not (any_switch_on "O0", "O1", "O2", "O3")),
            (set_option "O2"),
-      (and (switch_on "O3"), (any_switch_on ["O0", "O1", "O2"])),
-           (unset_option ["O0", "O1", "O2"]),
-      (and (switch_on "O2"), (any_switch_on ["O0", "O1"])),
-           (unset_option ["O0", "O1"]),
-      (switch_on ["O1", "O0"]),
+      (and (switch_on "O3"), (any_switch_on "O0", "O1", "O2")),
+           (unset_option "O0", "O1", "O2"),
+      (and (switch_on "O2"), (any_switch_on "O0", "O1")),
+           (unset_option "O0", "O1"),
+      (switch_on "O1", "O0"),
            (unset_option "O0"))
 >;
 
 // Tools
 
-class llvm_gcc_based <string cmd, string in_lang,
-                      string E_ext, list<string> out_lang,
+class llvm_gcc_based <string cmd, string in_lang, string E_ext, dag out_lang,
                       string out_ext> : Tool<
 [(in_language in_lang),
- (out_language out_lang),
+ out_lang,
  (output_suffix out_ext),
  (command cmd),
  (actions
@@ -184,7 +183,7 @@
          (and (switch_on "emit-llvm"), (not (switch_on "opt"))),
               (stop_compilation),
          // ('-S' && '-emit-llvm') && !('opt') -> output .ll
-         (and (switch_on ["emit-llvm", "S"]), (not (switch_on "opt"))),
+         (and (switch_on "emit-llvm", "S"), (not (switch_on "opt"))),
               [(forward "S"), (output_suffix "ll")],
          // Ususally just output .bc
          (not (switch_on "fsyntax-only")),
@@ -222,10 +221,12 @@
 ]>;
 
 class llvm_gcc_comp_based <string cmd, string in_lang, string E_ext>
-: llvm_gcc_based<cmd, in_lang, E_ext, ["llvm-bitcode", "object-code"], "bc">;
+: llvm_gcc_based<cmd, in_lang, E_ext,
+  (out_language "llvm-bitcode", "object-code"), "bc">;
 
 class llvm_gcc_pch_based <string cmd, string in_lang, string E_ext>
-: llvm_gcc_based<cmd, in_lang, E_ext, ["precompiled-header"], "gch">;
+: llvm_gcc_based<cmd, in_lang, E_ext,
+  (out_language "precompiled-header"), "gch">;
 
 def llvm_gcc_c : llvm_gcc_comp_based
     <"@LLVMGCCCOMMAND@ -x c", "c", "i">;
@@ -250,7 +251,7 @@
  (out_language "llvm-bitcode"),
  (output_suffix "opt.bc"),
  (actions (case (switch_on "emit-llvm"), (stop_compilation),
-                (switch_on ["emit-llvm", "S"]),
+                (switch_on "emit-llvm", "S"),
                 [(append_cmd "-S"), (output_suffix "ll")],
                 (not_empty "Wo,"), (forward_value "Wo,"),
                 (switch_on "O1"), (forward "O1"),
@@ -282,7 +283,7 @@
 ]>;
 
 def llc : Tool<
-[(in_language ["llvm-bitcode", "llvm-assembler"]),
+[(in_language "llvm-bitcode", "llvm-assembler"),
  (out_language "assembler"),
  (output_suffix "s"),
  (command "llc"),
@@ -304,7 +305,7 @@
 
 // Base class for linkers
 class llvm_gcc_based_linker <string cmd, dag on_empty> : Tool<
-[(in_language ["object-code", "static-library", "dynamic-library"]),
+[(in_language "object-code", "static-library", "dynamic-library"),
  (out_language "executable"),
  (output_suffix "out"),
  (command cmd),
diff --git a/tools/llvmc/src/Clang.td b/tools/llvmc/src/Clang.td
index 1d75743..e2d32e8 100644
--- a/tools/llvmc/src/Clang.td
+++ b/tools/llvmc/src/Clang.td
@@ -25,12 +25,12 @@
                     [(forward "E"), (stop_compilation), (output_suffix ext_E)],
                 (and (switch_on "E"), (empty "o")), (no_out_file),
                 (switch_on "fsyntax-only"), (stop_compilation),
-                (switch_on ["S", "emit-llvm"]),
+                (switch_on "S", "emit-llvm"),
                            [(append_cmd "-emit-llvm"),
                             (stop_compilation), (output_suffix "ll")],
-                (not (switch_on ["S", "emit-llvm"])),
+                (not (switch_on "S", "emit-llvm")),
                      (append_cmd "-emit-llvm-bc"),
-                (switch_on ["c", "emit-llvm"]),
+                (switch_on "c", "emit-llvm"),
                            (stop_compilation),
                 (not_empty "include"), (forward "include"),
                 (not_empty "I"), (forward "I"))),
diff --git a/utils/TableGen/LLVMCConfigurationEmitter.cpp b/utils/TableGen/LLVMCConfigurationEmitter.cpp
index 7ad981f..b7ac85c 100644
--- a/utils/TableGen/LLVMCConfigurationEmitter.cpp
+++ b/utils/TableGen/LLVMCConfigurationEmitter.cpp
@@ -25,6 +25,7 @@
 #include <string>
 #include <typeinfo>
 
+
 using namespace llvm;
 
 namespace {
@@ -164,18 +165,6 @@
     throw ErrorString;
 }
 
-// apply is needed because C++'s syntax doesn't let us construct a function
-// object and call it in the same statement.
-template<typename F, typename T0>
-void apply(F Fun, T0& Arg0) {
-  return Fun(Arg0);
-}
-
-template<typename F, typename T0, typename T1>
-void apply(F Fun, T0& Arg0, T1& Arg1) {
-  return Fun(Arg0, Arg1);
-}
-
 //===----------------------------------------------------------------------===//
 /// Back-end specific code
 
@@ -809,13 +798,12 @@
                                 OptionDescriptions& OptDescs)
 {
   // For every OptionList:
-  for (RecordVector::const_iterator B = V.begin(),
-         E = V.end(); B!=E; ++B) {
+  for (RecordVector::const_iterator B = V.begin(), E = V.end(); B!=E; ++B)
+  {
     // Throws an exception if the value does not exist.
     ListInit* PropList = (*B)->getValueAsListInit("options");
 
-    // For every option description in this list:
-    // collect the information and
+    // For every option description in this list: invoke AddOption.
     std::for_each(PropList->begin(), PropList->end(), AddOption(OptDescs));
   }
 }
@@ -922,26 +910,16 @@
   /// onInOutLanguage - Common implementation of on{In,Out}Language().
   void onInOutLanguage (const DagInit& d, StrVector& OutVec) {
     CheckNumberOfArguments(d, 1);
-    Init* arg = d.getArg(0);
 
-    // Find out the argument's type.
-    if (typeid(*arg) == typeid(StringInit)) {
-      // It's a string.
-      OutVec.push_back(InitPtrToString(arg));
+    // Copy strings to the output vector.
+    for (unsigned i = 0, NumArgs = d.getNumArgs(); i < NumArgs; ++i) {
+      OutVec.push_back(InitPtrToString(d.getArg(i)));
     }
-    else {
-      // It's a list.
-      const ListInit& lst = InitPtrToList(arg);
 
-      // Copy strings to the output vector.
-      for (ListInit::const_iterator B = lst.begin(), E = lst.end(); B != E; ++B)
-        OutVec.push_back(InitPtrToString(*B));
-
-      // Remove duplicates.
-      std::sort(OutVec.begin(), OutVec.end());
-      StrVector::iterator newE = std::unique(OutVec.begin(), OutVec.end());
-      OutVec.erase(newE, OutVec.end());
-    }
+    // Remove duplicates.
+    std::sort(OutVec.begin(), OutVec.end());
+    StrVector::iterator newE = std::unique(OutVec.begin(), OutVec.end());
+    OutVec.erase(newE, OutVec.end());
   }
 
 
@@ -1195,25 +1173,20 @@
     if (ActionName == "forward" || ActionName == "forward_as" ||
         ActionName == "forward_value" ||
         ActionName == "forward_transformed_value" ||
-        ActionName == "switch_on" || ActionName == "any_switch_on" ||
-        ActionName == "parameter_equals" ||
-        ActionName == "element_in_list" || ActionName == "not_empty" ||
-        ActionName == "empty") {
+        ActionName == "parameter_equals" || ActionName == "element_in_list") {
       CheckNumberOfArguments(Stmt, 1);
 
       Init* Arg = Stmt.getArg(0);
-      if (typeid(*Arg) == typeid(StringInit)) {
-        const std::string& Name = InitPtrToString(Arg);
-        OptionNames_.insert(Name);
-      }
-      else {
-        // It's a list.
-        const ListInit& List = InitPtrToList(Arg);
-        for (ListInit::const_iterator B = List.begin(), E = List.end();
-             B != E; ++B) {
-          const std::string& Name = InitPtrToString(*B);
-          OptionNames_.insert(Name);
-        }
+      if (typeid(*Arg) == typeid(StringInit))
+        OptionNames_.insert(InitPtrToString(Arg));
+    }
+    else if (ActionName == "any_switch_on" || ActionName == "switch_on" ||
+             ActionName == "any_not_empty" || ActionName == "any_empty" ||
+             ActionName == "not_empty" || ActionName == "empty") {
+      for (unsigned i = 0, NumArgs = Stmt.getNumArgs(); i < NumArgs; ++i) {
+        Init* Arg = Stmt.getArg(i);
+        if (typeid(*Arg) == typeid(StringInit))
+          OptionNames_.insert(InitPtrToString(Arg));
       }
     }
     else if (ActionName == "and" || ActionName == "or" || ActionName == "not") {
@@ -1228,6 +1201,7 @@
   {}
 
   void operator()(const Init* Statement) {
+    // Statement is either a dag, or a list of dags.
     if (typeid(*Statement) == typeid(ListInit)) {
       const ListInit& DagList = *static_cast<const ListInit*>(Statement);
       for (ListInit::const_iterator B = DagList.begin(), E = DagList.end();
@@ -1308,24 +1282,20 @@
   return false;
 }
 
-/// EmitListTest - Helper function used by EmitCaseTest1ArgList().
+/// EmitMultipleArgumentTest - Helper function used by
+/// EmitCaseTestMultipleArgs()
 template <typename F>
-void EmitListTest(const ListInit& L, const char* LogicOp,
-                  F Callback, raw_ostream& O)
+void EmitMultipleArgumentTest(const DagInit& D, const char* LogicOp,
+                              F Callback, raw_ostream& O)
 {
-  // This is a lot like EmitLogicalOperationTest, but works on ListInits instead
-  // of Dags...
-  bool isFirst = true;
-  for (ListInit::const_iterator B = L.begin(), E = L.end(); B != E; ++B) {
-    if (isFirst)
-      isFirst = false;
-    else
-      O << ' ' << LogicOp << ' ';
-    Callback(InitPtrToString(*B), O);
+  for (unsigned i = 0, NumArgs = D.getNumArgs(); i < NumArgs; ++i) {
+    if (i != 0)
+       O << ' ' << LogicOp << ' ';
+    Callback(InitPtrToString(D.getArg(i)), O);
   }
 }
 
-// Callbacks for use with EmitListTest.
+// Callbacks for use with EmitMultipleArgumentTest
 
 class EmitSwitchOn {
   const OptionDescriptions& OptDescs_;
@@ -1363,54 +1333,48 @@
 };
 
 
-/// EmitCaseTest1ArgList - Helper function used by EmitCaseTest1Arg();
-bool EmitCaseTest1ArgList(const std::string& TestName,
-                          const DagInit& d,
-                          const OptionDescriptions& OptDescs,
-                          raw_ostream& O) {
-  const ListInit& L = InitPtrToList(d.getArg(0));
-
+/// EmitCaseTestMultipleArgs - Helper function used by EmitCaseTest1Arg()
+bool EmitCaseTestMultipleArgs (const std::string& TestName,
+                               const DagInit& d,
+                               const OptionDescriptions& OptDescs,
+                               raw_ostream& O) {
   if (TestName == "any_switch_on") {
-    EmitListTest(L, "||", EmitSwitchOn(OptDescs), O);
+    EmitMultipleArgumentTest(d, "||", EmitSwitchOn(OptDescs), O);
     return true;
   }
   else if (TestName == "switch_on") {
-    EmitListTest(L, "&&", EmitSwitchOn(OptDescs), O);
+    EmitMultipleArgumentTest(d, "&&", EmitSwitchOn(OptDescs), O);
     return true;
   }
   else if (TestName == "any_not_empty") {
-    EmitListTest(L, "||", EmitEmptyTest(true, OptDescs), O);
+    EmitMultipleArgumentTest(d, "||", EmitEmptyTest(true, OptDescs), O);
     return true;
   }
   else if (TestName == "any_empty") {
-    EmitListTest(L, "||", EmitEmptyTest(false, OptDescs), O);
+    EmitMultipleArgumentTest(d, "||", EmitEmptyTest(false, OptDescs), O);
     return true;
   }
   else if (TestName == "not_empty") {
-    EmitListTest(L, "&&", EmitEmptyTest(true, OptDescs), O);
+    EmitMultipleArgumentTest(d, "&&", EmitEmptyTest(true, OptDescs), O);
     return true;
   }
   else if (TestName == "empty") {
-    EmitListTest(L, "&&", EmitEmptyTest(false, OptDescs), O);
+    EmitMultipleArgumentTest(d, "&&", EmitEmptyTest(false, OptDescs), O);
     return true;
   }
 
   return false;
 }
 
-/// EmitCaseTest1ArgStr - Helper function used by EmitCaseTest1Arg();
-bool EmitCaseTest1ArgStr(const std::string& TestName,
-                         const DagInit& d,
-                         const OptionDescriptions& OptDescs,
-                         raw_ostream& O) {
-  const std::string& OptName = InitPtrToString(d.getArg(0));
+/// EmitCaseTest1Arg - Helper function used by EmitCaseTest1OrMoreArgs()
+bool EmitCaseTest1Arg (const std::string& TestName,
+                       const DagInit& d,
+                       const OptionDescriptions& OptDescs,
+                       raw_ostream& O) {
+  const std::string& Arg = InitPtrToString(d.getArg(0));
 
-  if (TestName == "switch_on") {
-    apply(EmitSwitchOn(OptDescs), OptName, O);
-    return true;
-  }
-  else if (TestName == "input_languages_contain") {
-    O << "InLangs.count(\"" << OptName << "\") != 0";
+  if (TestName == "input_languages_contain") {
+    O << "InLangs.count(\"" << Arg << "\") != 0";
     return true;
   }
   else if (TestName == "in_language") {
@@ -1418,28 +1382,22 @@
     // tools can process several files in different languages simultaneously.
 
     // TODO: make this work with Edge::Weight (if possible).
-    O << "LangMap.GetLanguage(inFile) == \"" << OptName << '\"';
-    return true;
-  }
-  else if (TestName == "not_empty" || TestName == "empty") {
-    bool EmitNegate = (TestName == "not_empty");
-    apply(EmitEmptyTest(EmitNegate, OptDescs), OptName, O);
+    O << "LangMap.GetLanguage(inFile) == \"" << Arg << '\"';
     return true;
   }
 
   return false;
 }
 
-/// EmitCaseTest1Arg - Helper function used by EmitCaseConstructHandler();
-bool EmitCaseTest1Arg(const std::string& TestName,
-                      const DagInit& d,
-                      const OptionDescriptions& OptDescs,
-                      raw_ostream& O) {
+/// EmitCaseTest1OrMoreArgs - Helper function used by
+/// EmitCaseConstructHandler()
+bool EmitCaseTest1OrMoreArgs(const std::string& TestName,
+                             const DagInit& d,
+                             const OptionDescriptions& OptDescs,
+                             raw_ostream& O) {
   CheckNumberOfArguments(d, 1);
-  if (typeid(*d.getArg(0)) == typeid(ListInit))
-    return EmitCaseTest1ArgList(TestName, d, OptDescs, O);
-  else
-    return EmitCaseTest1ArgStr(TestName, d, OptDescs, O);
+  return EmitCaseTest1Arg(TestName, d, OptDescs, O) ||
+    EmitCaseTestMultipleArgs(TestName, d, OptDescs, O);
 }
 
 /// EmitCaseTest2Args - Helper function used by EmitCaseConstructHandler().
@@ -1483,10 +1441,10 @@
                               const OptionDescriptions& OptDescs,
                               raw_ostream& O) {
   O << '(';
-  for (unsigned j = 0, NumArgs = d.getNumArgs(); j < NumArgs; ++j) {
-    const DagInit& InnerTest = InitPtrToDag(d.getArg(j));
+  for (unsigned i = 0, NumArgs = d.getNumArgs(); i < NumArgs; ++i) {
+    const DagInit& InnerTest = InitPtrToDag(d.getArg(i));
     EmitCaseTest(InnerTest, IndentLevel, OptDescs, O);
-    if (j != NumArgs - 1) {
+    if (i != NumArgs - 1) {
       O << ")\n";
       O.indent(IndentLevel + Indent1) << ' ' << LogicOp << " (";
     }
@@ -1520,7 +1478,7 @@
     EmitLogicalNot(d, IndentLevel, OptDescs, O);
   else if (EmitCaseTest0Args(TestName, O))
     return;
-  else if (EmitCaseTest1Arg(TestName, d, OptDescs, O))
+  else if (EmitCaseTest1OrMoreArgs(TestName, d, OptDescs, O))
     return;
   else if (EmitCaseTest2Args(TestName, d, IndentLevel, OptDescs, O))
     return;
@@ -1567,10 +1525,12 @@
   {}
 
   void operator() (const Init* Statement, unsigned IndentLevel) {
+    // Is this a nested 'case'?
+    bool IsCase = dynamic_cast<const DagInit*>(Statement) &&
+      GetOperatorName(static_cast<const DagInit&>(*Statement)) == "case";
 
-    // Ignore nested 'case' DAG.
-    if (!(dynamic_cast<const DagInit*>(Statement) &&
-          GetOperatorName(static_cast<const DagInit&>(*Statement)) == "case")) {
+    // If so, ignore it, it is handled by our caller, WalkCase.
+    if (!IsCase) {
       if (typeid(*Statement) == typeid(ListInit)) {
         const ListInit& DagList = *static_cast<const ListInit*>(Statement);
         for (ListInit::const_iterator B = DagList.begin(), E = DagList.end();
@@ -2474,21 +2434,13 @@
 
   const OptionDescriptions& OptDescs_;
 
-  void onListOrDag(const DagInit& d, HandlerImpl h,
-                   unsigned IndentLevel, raw_ostream& O) const
+  void onEachArgument(const DagInit& d, HandlerImpl h,
+                      unsigned IndentLevel, raw_ostream& O) const
   {
     CheckNumberOfArguments(d, 1);
-    const Init* I = d.getArg(0);
 
-    // If I is a list, apply h to each element.
-    if (typeid(*I) == typeid(ListInit)) {
-      const ListInit& L = *static_cast<const ListInit*>(I);
-      for (ListInit::const_iterator B = L.begin(), E = L.end(); B != E; ++B)
-        ((this)->*(h))(*B, IndentLevel, O);
-    }
-    // Otherwise, apply h to I.
-    else {
-      ((this)->*(h))(I, IndentLevel, O);
+    for (unsigned i = 0, NumArgs = d.getNumArgs(); i < NumArgs; ++i) {
+      ((this)->*(h))(d.getArg(i), IndentLevel, O);
     }
   }
 
@@ -2515,16 +2467,17 @@
   void onUnsetOption(const DagInit& d,
                      unsigned IndentLevel, raw_ostream& O) const
   {
-    this->onListOrDag(d, &EmitPreprocessOptionsCallback::onUnsetOptionImpl,
-                      IndentLevel, O);
+    this->onEachArgument(d, &EmitPreprocessOptionsCallback::onUnsetOptionImpl,
+                         IndentLevel, O);
   }
 
-  void onSetOptionImpl(const DagInit& d,
+  void onSetOptionImpl(const DagInit& D,
                        unsigned IndentLevel, raw_ostream& O) const {
-    CheckNumberOfArguments(d, 2);
-    const std::string& OptName = InitPtrToString(d.getArg(0));
-    const Init* Value = d.getArg(1);
+    CheckNumberOfArguments(D, 2);
+
+    const std::string& OptName = InitPtrToString(D.getArg(0));
     const OptionDescription& OptDesc = OptDescs_.FindOption(OptName);
+    const Init* Value = D.getArg(1);
 
     if (OptDesc.isList()) {
       const ListInit& List = InitPtrToList(Value);
@@ -2554,7 +2507,7 @@
                             << " = \"" << Str << "\";\n";
     }
     else {
-      throw "Can't apply 'set_option' to alias option -" + OptName + " !";
+      throw "Can't apply 'set_option' to alias option '" + OptName + "'!";
     }
   }
 
@@ -2574,15 +2527,22 @@
   {
     CheckNumberOfArguments(d, 1);
 
-    // Two arguments: (set_option "parameter", VALUE), where VALUE can be a
-    // boolean, a string or a string list.
-    if (d.getNumArgs() > 1)
-      this->onSetOptionImpl(d, IndentLevel, O);
-    // One argument: (set_option "switch")
-    // or (set_option ["switch1", "switch2", ...])
-    else
-      this->onListOrDag(d, &EmitPreprocessOptionsCallback::onSetSwitch,
-                        IndentLevel, O);
+    // 2-argument form: (set_option "A", true), (set_option "B", "C"),
+    // (set_option "D", ["E", "F"])
+    if (d.getNumArgs() == 2) {
+      const OptionDescription& OptDesc =
+        OptDescs_.FindOption(InitPtrToString(d.getArg(0)));
+      const Init* Opt2 = d.getArg(1);
+
+      if (!OptDesc.isSwitch() || typeid(*Opt2) != typeid(StringInit)) {
+        this->onSetOptionImpl(d, IndentLevel, O);
+        return;
+      }
+    }
+
+    // Multiple argument form: (set_option "A"), (set_option "B", "C", "D")
+    this->onEachArgument(d, &EmitPreprocessOptionsCallback::onSetSwitch,
+                         IndentLevel, O);
   }
 
 public:
@@ -2687,10 +2647,11 @@
 {
   O << "int PopulateLanguageMap (LanguageMap& langMap) {\n";
 
-  // For each LangMap:
+  // For each LanguageMap:
   const RecordVector& LangMaps =
     Records.getAllDerivedDefinitions("LanguageMap");
 
+  // Call DoEmitPopulateLanguageMap.
   for (RecordVector::const_iterator B = LangMaps.begin(),
          E = LangMaps.end(); B!=E; ++B) {
     ListInit* LangMap = (*B)->getValueAsListInit("map");
@@ -2925,7 +2886,7 @@
       return;
     }
 
-    // We're invoked on a command line.
+    // We're invoked on a command line string.
     this->onCmdLine(InitPtrToString(Arg));
   }