Only keep a "const char*" for the response file argument.

Author: dabelknap

include/swift/Driver/Job.h

@@ -277,7 +277,7 @@ class Job {
   /// Argument vector containing a single argument pointing to the response file
   /// path with the '@' prefix.
   /// The argument string must be kept alive as long as the Job is alive.
-  llvm::opt::ArgStringList ResponseFileArg;
+  const char *ResponseFileArg;
 
   /// The modification time of the main input file, if any.
   llvm::sys::TimePoint<> InputModTime = llvm::sys::TimePoint<>::max();
@@ -291,14 +291,14 @@ class Job {
       EnvironmentVector ExtraEnvironment = {},
       std::vector<FilelistInfo> Infos = {},
       const char *ResponseFilePath = nullptr,
-      llvm::opt::ArgStringList ResponseFileArg = {})
+      const char *ResponseFileArg = nullptr)
       : SourceAndCondition(&Source, Condition::Always),
         Inputs(std::move(Inputs)), Output(std::move(Output)),
         Executable(Executable), Arguments(std::move(Arguments)),
         ExtraEnvironment(std::move(ExtraEnvironment)),
         FilelistFileInfos(std::move(Infos)),
         ResponseFilePath(ResponseFilePath),
-        ResponseFileArg(std::move(ResponseFileArg)) {}
+        ResponseFileArg(ResponseFileArg) {}
 
   virtual ~Job();
 
@@ -308,7 +308,7 @@ class Job {
 
   const char *getExecutable() const { return Executable; }
   const llvm::opt::ArgStringList &getArguments() const { return Arguments; }
-  const llvm::opt::ArgStringList &getResponseFileArg() const { return ResponseFileArg; }
+  const char * const &getResponseFileArg() const { return ResponseFileArg; }
   ArrayRef<FilelistInfo> getFilelistInfos() const { return FilelistFileInfos; }
 
   ArrayRef<const Job *> getInputs() const { return Inputs; }

lib/Driver/Job.cpp

@@ -354,7 +354,7 @@ void Job::printCommandLine(raw_ostream &os, StringRef Terminator) const {
   escapeAndPrintString(os, Executable);
   os << ' ';
   if (hasResponseFile()) {
-    printArguments(os, ResponseFileArg);
+    printArguments(os, {ResponseFileArg});
   } else {
     printArguments(os, Arguments);
   }

lib/Driver/ToolChain.cpp

@@ -115,13 +115,12 @@ std::unique_ptr<Job> ToolChain::constructJob(
   }
 
   const char *responseFilePath = nullptr;
-  llvm::opt::ArgStringList responseFileArg = {};
+  const char *responseFileArg = nullptr;
   if (invocationInfo.allowsResponseFiles &&
       !llvm::sys::commandLineFitsWithinSystemLimits(
           executablePath, invocationInfo.Arguments)) {
     responseFilePath = context.getTemporaryFilePath("arguments", "resp");
-    responseFileArg.push_back(
-        C.getArgs().MakeArgString(Twine("@") + responseFilePath));
+    responseFileArg = C.getArgs().MakeArgString(Twine("@") + responseFilePath);
   }
 
   return llvm::make_unique<Job>(JA, std::move(inputs), std::move(output),
@@ -130,7 +129,7 @@ std::unique_ptr<Job> ToolChain::constructJob(
                                 std::move(invocationInfo.ExtraEnvironment),
                                 std::move(invocationInfo.FilelistInfos),
                                 responseFilePath,
-                                std::move(responseFileArg));
+                                responseFileArg);
 }
 
 std::string