[Option] Support MultiArg in --help

Currently, if you use a MultiArg<> option, then printing out the help/usage
message will cause an assert.  This fixes getOptionHelpName() to work with
MultiArg Options.

llvm-svn: 215770

1 files changed, 12 insertions, 1 deletions

diff --git a/llvm/lib/Option/OptTable.cpp b/llvm/lib/Option/OptTable.cpp
index 6842f4d5791..ef9a3e75a15 100644
--- a/llvm/lib/Option/OptTable.cpp
+++ b/llvm/lib/Option/OptTable.cpp
@@ -300,7 +300,18 @@ static std::string getOptionHelpName(const OptTable &Opts, OptSpecifier Id) {
     llvm_unreachable("Invalid option with help text.");
 
   case Option::MultiArgClass:
-    llvm_unreachable("Cannot print metavar for this kind of option.");
+    if (const char *MetaVarName = Opts.getOptionMetaVar(Id)) {
+      // For MultiArgs, metavar is full list of all argument names.
+      Name += ' ';
+      Name += MetaVarName;
+    }
+    else {
+      // For MultiArgs<N>, if metavar not supplied, print <value> N times.
+      for (unsigned i=0, e=O.getNumArgs(); i< e; ++i) {
+        Name += " <value>";
+      }
+    }
+    break;
 
   case Option::FlagClass:
     break;