Make comments a little bit more clear.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56463 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvmc2/doc/LLVMC-Reference.rst

@@ -375,16 +375,16 @@ use TableGen inheritance instead.
 
   - ``input_languages_contain`` - Returns true if a given language
     belongs to the current input language set. Example:
-    ```(input_languages_contain "c++")``.
+    ``(input_languages_contain "c++")``.
 
   - ``in_language`` - Evaluates to true if the language of the input
-    file equals to the argument. Valid only when using ``case``
-    expression in a ``cmd_line`` tool property. Example:
-    ```(in_language "c++")``.
+    file equals to the argument. At the moment works only with
+    ``cmd_line`` property 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. Example: ```(not_empty "o")``.
+    user. Example: ``(not_empty "o")``.
 
   - ``default`` - Always evaluates to true. Should always be the last
     test in the ``case`` expression.

utils/TableGen/LLVMCConfigurationEmitter.cpp

@@ -826,8 +826,10 @@ bool EmitCaseTest1Arg(const std::string& TestName,
     O << "InLangs.count(\"" << OptName << "\") != 0";
     return true;
   } else if (TestName == "in_language") {
-    // TODO: remove this restriction
-    // Works only for cmd_line!
+    // This works only for single-argument Tool::GenerateAction. Join
+    // 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") {