Teach the frontend how to pass through -Xllvm commands.

This patch allows you to pass through commands to llvm from the driver so now
one can when compiling swift files get debug messages!

Swift SVN r13761

include/swift/Driver/Options.td

@@ -237,6 +237,10 @@ def Xcc : Separate<["-"], "Xcc">, Flags<[DriverOption, FrontendOption]>,
   MetaVarName<"<arg>">,
   HelpText<"Pass <arg> to the C/C++/Objective-C compiler">;
 
+def Xllvm : Separate<["-"], "Xllvm">, Flags<[DriverOption, FrontendOption]>,
+  MetaVarName<"<arg>">,
+  HelpText<"Pass <arg> to llvm.">;
+
 def target : Joined<["--"], "target=">, Flags<[DriverOption, FrontendOption]>,
   HelpText<"Generate code for the given target">;
 def target_legacy_spelling : Separate<["-"], "target">,

include/swift/Frontend/FrontendOptions.h

@@ -89,6 +89,10 @@ public:
   /// Arguments which should be passed in immediate mode.
   std::vector<std::string> ImmediateArgv;
 
+  /// \brief A list of arguments to forward to LLVM's option processing; this
+  /// should only be used for debugging and experimental features.
+  std::vector<std::string> LLVMArgs;
+
   enum ActionType {
     Parse, ///< Parse and type-check only
     DumpParse, ///< Parse only and dump AST

lib/Driver/Tools.cpp

@@ -110,6 +110,9 @@ static void addCommonFrontendArgs(const ToolChain &TC,
   inputArgs.AddAllArgs(arguments, options::OPT_I);
 
   inputArgs.AddLastArg(arguments, options::OPT_g);
+
+  // Pass through any -Xllvm flags.
+  inputArgs.AddAllArgs(arguments, options::OPT_Xllvm);
 }
 
 

lib/Frontend/CompilerInvocation.cpp

@@ -455,6 +455,7 @@ static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
 
   Opts.EnableSourceImport = Args.hasArg(OPT_enable_source_import);
   Opts.SILSerializeAll = Args.hasArg(OPT_sil_serialize_all);
+  Opts.LLVMArgs = Args.getAllArgValues(OPT_Xllvm);
 
   return false;
 }

lib/Frontend/Frontend.cpp

@@ -25,6 +25,8 @@
 #include "swift/Parse/Lexer.h"
 #include "swift/SIL/SILModule.h"
 #include "swift/Serialization/SerializedModuleLoader.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 
@@ -38,6 +40,17 @@ void swift::CompilerInstance::createSILModule() {
 bool swift::CompilerInstance::setup(const CompilerInvocation &Invok) {
   Invocation = Invok;
 
+  // Honor -Xllvm.
+  if (!Invok.getFrontendOptions().LLVMArgs.empty()) {
+    llvm::SmallVector<const char *, 4> Args;
+    Args.push_back("swift (LLVM option parsing)");
+    for (unsigned i = 0, e = Invok.getFrontendOptions().LLVMArgs.size(); i != e;
+         ++i)
+      Args.push_back(Invok.getFrontendOptions().LLVMArgs[i].c_str());
+    Args.push_back(nullptr);
+    llvm::cl::ParseCommandLineOptions(Args.size(), Args.data());
+  }
+
   Context.reset(new ASTContext(Invocation.getLangOptions(),
                                Invocation.getSearchPathOptions(),
                                SourceMgr, Diagnostics));