This is my Driver refactoring patch. 

The major changes are:
1) LinkerOptions has been merged into TargetInfo
2) LinkerInvocation has been merged into Driver
3) Drivers no longer convert arguments into an intermediate (core) argument 
   list, but instead create a TargetInfo object and call setter methods on 
   it. This is only how in-process linking would work. That is, you can 
   programmatically set up a TargetInfo object which controls the linking.
4) Lots of tweaks to test suite to work with driver changes
5) Add the DarwinDriver
6) I heavily doxygen commented TargetInfo.h

Things to do after this patch is committed:
a) Consider renaming TargetInfo, given its new roll. 
b) Consider pulling the list of input files out of TargetInfo. This will 
   enable in-process clients to create one TargetInfo the re-use it with 
   different input file lists.
c) Work out a way for Drivers to format the warnings and error done in 
   core linking.

llvm-svn: 178776
diff --git a/lld/lib/Driver/Driver.cpp b/lld/lib/Driver/Driver.cpp
index 5f7f4e6..cb3c611 100644
--- a/lld/lib/Driver/Driver.cpp
+++ b/lld/lib/Driver/Driver.cpp
@@ -8,7 +8,81 @@
 //===----------------------------------------------------------------------===//
 
 #include "lld/Driver/Driver.h"
+#include "lld/Core/LLVM.h"
+#include "lld/Core/InputFiles.h"
+#include "lld/Core/Resolver.h"
+#include "lld/Core/PassManager.h"
+#include "lld/ReaderWriter/Reader.h"
+#include "lld/ReaderWriter/Writer.h"
 
-using namespace lld;
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Option/Arg.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
 
-Driver::~Driver() {}
+namespace lld {
+
+/// This is where the link is actually performed.
+bool Driver::link(const TargetInfo &targetInfo, raw_ostream &diagnostics) {
+  // Honor -mllvm
+  if (!targetInfo.llvmOptions().empty()) {
+    unsigned numArgs = targetInfo.llvmOptions().size();
+    const char **args = new const char*[numArgs + 2];
+    args[0] = "lld (LLVM option parsing)";
+    for (unsigned i = 0; i != numArgs; ++i)
+      args[i + 1] = targetInfo.llvmOptions()[i];
+    args[numArgs + 1] = 0;
+    llvm::cl::ParseCommandLineOptions(numArgs + 1, args);
+  }
+
+  // Read inputs
+  InputFiles inputs;
+  for (const auto &input : targetInfo.inputFiles()) {
+    std::vector<std::unique_ptr<File>> files;
+    if (targetInfo.logInputFiles())
+      llvm::outs() << input.getPath() << "\n";
+      
+    error_code ec = targetInfo.readFile(input.getPath(), files);
+    if (ec) {
+      diagnostics   << "Failed to read file: " << input.getPath() << ": "
+                    << ec.message() << "\n";
+      return true;
+    }
+    inputs.appendFiles(files);
+  }
+
+  // Give target a chance to add files.
+  targetInfo.addImplicitFiles(inputs);
+
+  // assign an ordinal to each file so sort() can preserve command line order
+  inputs.assignFileOrdinals();
+
+  // Do core linking.
+  Resolver resolver(targetInfo, inputs);
+  if (resolver.resolve()) {
+    if (!targetInfo.allowRemainingUndefines())
+      return true;
+  }
+  MutableFile &merged = resolver.resultFile();
+
+  // Run passes on linked atoms.
+  PassManager pm;
+  targetInfo.addPasses(pm);
+  pm.runOnFile(merged);
+
+  // Give linked atoms to Writer to generate output file.
+  if (error_code ec = targetInfo.writeFile(merged)) {
+    diagnostics << "Failed to write file '" << targetInfo.outputPath() 
+                << "': " << ec.message() << "\n";
+    return true;
+  }
+
+  return false;
+}
+
+
+} // namespace
+