4 files changed, 40 insertions, 15 deletions
diff --git a/src/passes/ExtractFunction.cpp b/src/passes/ExtractFunction.cpp
index 626ac1ee7..77c0cabb6 100644
--- a/src/passes/ExtractFunction.cpp
+++ b/src/passes/ExtractFunction.cpp
@@ -28,8 +28,8 @@ namespace wasm {
 struct ExtractFunction : public Pass {
   void run(PassRunner* runner, Module* module) override {
     Name name = runner->options.getArgument(
-      "extract",
-      "ExtractFunction usage:  wasm-opt --pass-arg=extract@FUNCTION_NAME");
+      "extract-function",
+      "ExtractFunction usage:  wasm-opt --extract-function@FUNCTION_NAME");
     std::cerr << "extracting " << name << "\n";
     bool found = false;
     for (auto& func : module->functions) {
diff --git a/src/support/command-line.cpp b/src/support/command-line.cpp
index 0e638173e..1b9f64295 100644
--- a/src/support/command-line.cpp
+++ b/src/support/command-line.cpp
@@ -136,11 +136,13 @@ void Options::parse(int argc, const char* argv[]) {
       // Positional.
       switch (positional) {
         case Arguments::Zero:
+          // Optional arguments must use --flag=A format, and not separated by
+          // spaces (which would be ambiguous).
+        case Arguments::Optional:
           std::cerr << "Unexpected positional argument '" << currentOption
                     << "'\n";
           exit(EXIT_FAILURE);
         case Arguments::One:
-        case Arguments::Optional:
           if (positionalsSeen) {
             std::cerr << "Unexpected second positional argument '"
                       << currentOption << "' for " << positionalName << '\n';
@@ -198,11 +200,6 @@ void Options::parse(int argc, const char* argv[]) {
         }
         break;
       case Arguments::Optional:
-        if (!argument.size()) {
-          if (i + 1 != e) {
-            argument = argv[++i];
-          }
-        }
         break;
     }
     option->action(this, argument);
diff --git a/src/support/command-line.h b/src/support/command-line.h
index 53bdbff28..99d98eec9 100644
--- a/src/support/command-line.h
+++ b/src/support/command-line.h
@@ -34,7 +34,19 @@ namespace wasm {
 class Options {
 public:
   using Action = std::function<void(Options*, const std::string&)>;
-  enum class Arguments { Zero, One, N, Optional };
+
+  enum class Arguments {
+    // No arguments.
+    Zero,
+    // One argument, in the form  --flag A  or  --flag=A
+    One,
+    // Multiple arguments, in the form --flag A B C
+    N,
+    // An optional single argument, in the form --flag=A (we disallow --flag A
+    // as that would be ambiguous regarding whether A is another flag, or an
+    // argument to us).
+    Optional
+  };
 
   bool debug;
   std::map<std::string, std::string> extra;
diff --git a/src/tools/optimization-options.h b/src/tools/optimization-options.h
index 0e6157473..b7db5d531 100644
--- a/src/tools/optimization-options.h
+++ b/src/tools/optimization-options.h
@@ -202,12 +202,28 @@ struct OptimizationOptions : public ToolOptions {
            });
     // add passes in registry
     for (const auto& p : PassRegistry::get()->getRegisteredNames()) {
-      (*this).add(
-        std::string("--") + p,
-        "",
-        PassRegistry::get()->getPassDescription(p),
-        Options::Arguments::Zero,
-        [this, p](Options*, const std::string&) { passes.push_back(p); });
+      (*this).add(std::string("--") + p,
+                  "",
+                  PassRegistry::get()->getPassDescription(p),
+                  // Allow an optional parameter to a pass. If provided, it is
+                  // the same as if using --pass-arg, that is,
+                  //
+                  //   --foo=ARG
+                  //
+                  // is the same as
+                  //
+                  //   --foo --pass-arg=foo@ARG
+                  Options::Arguments::Optional,
+                  [this, p](Options*, const std::string& arg) {
+                    if (!arg.empty()) {
+                      if (passOptions.arguments.count(p)) {
+                        Fatal()
+                          << "Cannot pass multiple pass arguments to " << p;
+                      }
+                      passOptions.arguments[p] = arg;
+                    }
+                    passes.push_back(p);
+                  });
     }
   }