Reorganize llvmc code.

Move the code from 'llvmc/driver' into a new CompilerDriver library, and change
the build system accordingly. Makes it easier for projects using LLVM to build
their own llvmc-based drivers.

Tested with objdir != srcdir.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65821 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvmc/driver/Main.cpp b/tools/llvmc/driver/Main.cpp
new file mode 100644
index 0000000..16b91a8
--- /dev/null
+++ b/tools/llvmc/driver/Main.cpp
@@ -0,0 +1,126 @@
+//===--- Main.cpp - The LLVM Compiler Driver -------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open
+// Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This tool provides a single point of access to the LLVM
+//  compilation tools.  It has many options. To discover the options
+//  supported please refer to the tools' manual page or run the tool
+//  with the --help option.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CompilerDriver/CompilationGraph.h"
+#include "llvm/CompilerDriver/Error.h"
+#include "llvm/CompilerDriver/Plugin.h"
+
+#include "llvm/System/Path.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/PluginLoader.h"
+
+#include <iostream>
+#include <stdexcept>
+#include <string>
+
+namespace cl = llvm::cl;
+namespace sys = llvm::sys;
+using namespace llvmc;
+
+// Built-in command-line options.
+// External linkage here is intentional.
+
+cl::list<std::string> InputFilenames(cl::Positional, cl::desc("<input file>"),
+                                     cl::ZeroOrMore);
+cl::opt<std::string> OutputFilename("o", cl::desc("Output file name"),
+                                    cl::value_desc("file"), cl::Prefix);
+cl::list<std::string> Languages("x",
+          cl::desc("Specify the language of the following input files"),
+          cl::ZeroOrMore);
+cl::opt<bool> DryRun("dry-run",
+                     cl::desc("Only pretend to run commands"));
+cl::opt<bool> VerboseMode("v",
+                          cl::desc("Enable verbose mode"));
+
+cl::opt<bool> CheckGraph("check-graph",
+                         cl::desc("Check the compilation graph for errors"),
+                         cl::Hidden);
+cl::opt<bool> WriteGraph("write-graph",
+                         cl::desc("Write compilation-graph.dot file"),
+                         cl::Hidden);
+cl::opt<bool> ViewGraph("view-graph",
+                         cl::desc("Show compilation graph in GhostView"),
+                         cl::Hidden);
+cl::opt<bool> SaveTemps("save-temps",
+                         cl::desc("Keep temporary files"),
+                         cl::Hidden);
+
+namespace {
+  /// BuildTargets - A small wrapper for CompilationGraph::Build.
+  int BuildTargets(CompilationGraph& graph, const LanguageMap& langMap) {
+    int ret;
+    const sys::Path& tempDir = SaveTemps
+      ? sys::Path("")
+      : sys::Path(sys::Path::GetTemporaryDirectory());
+
+    try {
+      ret = graph.Build(tempDir, langMap);
+    }
+    catch(...) {
+      tempDir.eraseFromDisk(true);
+      throw;
+    }
+
+    if (!SaveTemps)
+      tempDir.eraseFromDisk(true);
+    return ret;
+  }
+}
+
+int main(int argc, char** argv) {
+  try {
+    LanguageMap langMap;
+    CompilationGraph graph;
+
+    cl::ParseCommandLineOptions
+      (argc, argv, "LLVM Compiler Driver (Work In Progress)", true);
+
+    PluginLoader Plugins;
+    Plugins.PopulateLanguageMap(langMap);
+    Plugins.PopulateCompilationGraph(graph);
+
+    if (CheckGraph) {
+      return graph.Check();
+    }
+
+    if (ViewGraph) {
+      graph.viewGraph();
+      if (!WriteGraph)
+        return 0;
+    }
+
+    if (WriteGraph) {
+      graph.writeGraph();
+      return 0;
+    }
+
+    if (InputFilenames.empty()) {
+      throw std::runtime_error("no input files");
+    }
+
+    return BuildTargets(graph, langMap);
+  }
+  catch(llvmc::error_code& ec) {
+    return ec.code();
+  }
+  catch(const std::exception& ex) {
+    std::cerr << argv[0] << ": " << ex.what() << '\n';
+  }
+  catch(...) {
+    std::cerr << argv[0] << ": unknown error!\n";
+  }
+  return 1;
+}