Index: clang/examples/CallSuperAttribute/CallSuperAttrInfo.cpp
===================================================================
--- clang/examples/CallSuperAttribute/CallSuperAttrInfo.cpp
+++ clang/examples/CallSuperAttribute/CallSuperAttrInfo.cpp
@@ -145,6 +145,14 @@
 
   bool ParseArgs(const CompilerInstance &CI,
                  const std::vector<std::string> &args) override {
+    if (!args.empty()) {
+      if (args[0] == "help") {
+        llvm::errs() << "Help text for CallSuper plugin goes here\n";
+      } else if (args[0] == "help-long") {
+        llvm::errs() << "A longer help text describing what the CallSuper "
+                     << "plugin does goes here\n";
+      }
+    }
     return true;
   }
 
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2501,6 +2501,9 @@
   NegFlag<SetFalse>>;
 def fplugin_EQ : Joined<["-"], "fplugin=">, Group<f_Group>, Flags<[NoXarchOption]>, MetaVarName<"<dsopath>">,
   HelpText<"Load the named plugin (dynamic shared object)">;
+def fplugin_arg : Joined<["-"], "fplugin-arg-">,
+  MetaVarName<"<name>-<arg>">,
+  HelpText<"Pass <arg> to plugin <name>">;
 def fpass_plugin_EQ : Joined<["-"], "fpass-plugin=">,
   Group<f_Group>, Flags<[CC1Option]>, MetaVarName<"<dsopath>">,
   HelpText<"Load pass plugin from a dynamic shared object file (only with new pass manager).">,
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -6612,6 +6612,25 @@
     A->claim();
   }
 
+  // Turn -fplugin-arg-pluginname-key=value into
+  // -plugin-arg-pluginname key=value
+  // GCC has an actual plugin_argument struct with key/value pairs that it
+  // passes to its plugins, but we don't, so just pass it on as-is.
+  //
+  // The syntax for -fplugin-arg- is ambiguous if both plugin name and
+  // argument key are allowed to contain dashes. GCC therefore only
+  // allows dashes in the key. We do the same.
+  for (const Arg *A : Args.filtered(options::OPT_fplugin_arg)) {
+    auto ArgValue = StringRef(A->getValue());
+    auto FirstDashIndex = ArgValue.find('-');
+    auto Arg = ArgValue.substr(FirstDashIndex + 1);
+    auto PluginName = ArgValue.substr(0, FirstDashIndex);
+
+    CmdArgs.push_back(Args.MakeArgString(Twine("-plugin-arg-") + PluginName));
+    CmdArgs.push_back(Args.MakeArgString(Arg));
+    A->claim();
+  }
+
   // Forward -fpass-plugin=name.so to -cc1.
   for (const Arg *A : Args.filtered(options::OPT_fpass_plugin_EQ)) {
     CmdArgs.push_back(