Initial set of changes to add a new 'swift_driver' executable.

- Added a couple of new targets:
  - libswiftDriver, which contains most of the driver implementation
  - swift_driver, which produces the actual executable

- Added centralized version information into libswiftBasic.

- Added a new "Driver Design & Internals" document, which currently describes
  the high-level design of the Swift driver.

- Implemented an early version of the functionality of the driver, including
  versions of the Parse, Pipeline, Bind, Translate, and Execute driver stages.
  Parse, Pipeline, and Bind are largely implemented; Translate and Execute are
  early placeholders. (Translate produces "swift_driver --version" and "ld -v"
  commands, while Execute performs all subtasks sequentially, rather than in
  parallel.)

This is just the starting point for the Swift driver. Tests for the existing
behavior are forthcoming.

Swift SVN r10933

lib/Driver/Tools.cpp

@@ -0,0 +1,90 @@
+//===--- Tools.cpp - Tools Implementations --------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include "Tools.h"
+#include "ToolChains.h"
+
+#include "swift/Driver/Driver.h"
+#include "swift/Driver/Job.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Option/Arg.h"
+#include "llvm/Option/ArgList.h"
+
+using namespace swift::driver;
+using namespace swift::driver::tools;
+using namespace llvm::opt;
+
+/// Swift Tool
+
+std::unique_ptr<Job> Swift::constructJob(const JobAction &JA,
+                                         std::unique_ptr<JobList> Inputs,
+                                         std::unique_ptr<CommandOutput> Output,
+                                         const ActionList &InputActions,
+                                         const ArgList &Args,
+                                         StringRef LinkingOutput) const {
+  ArgStringList Arguments;
+
+  Arguments.push_back("--version");
+
+  const char *Exec = getToolChain().getDriver().getSwiftProgramPath();
+
+  std::unique_ptr<Job> Cmd(new Command(JA, *this, std::move(Inputs),
+                                       std::move(Output),
+                                       Exec, Arguments));
+  return Cmd;
+}
+
+/// Darwin Tools
+
+llvm::Triple::ArchType darwin::getArchTypeForDarwinArchName(StringRef Arch) {
+  return llvm::StringSwitch<llvm::Triple::ArchType>(Arch)
+    .Cases("i386", "i486", "i486SX", "i586", "i686", llvm::Triple::x86)
+    .Cases("pentium", "pentpro", "pentIIm3", "pentIIm5", "pentium4",
+           llvm::Triple::x86)
+
+    .Case("x86_64", llvm::Triple::x86_64)
+
+    .Cases("arm", "armv4t", "armv5", "armv6", "armv6m", llvm::Triple::arm)
+    .Cases("armv7", "armv7em", "armv7f", "armv7k", "armv7m", llvm::Triple::arm)
+    .Cases("armv7s", "xscale", llvm::Triple::arm)
+
+    .Default(llvm::Triple::UnknownArch);
+}
+
+void darwin::DarwinTool::anchor() {}
+
+void darwin::DarwinTool::AddDarwinArch(const ArgList &Args,
+                                       ArgStringList &CmdArgs) const {
+  StringRef ArchName = getDarwinToolChain().getDarwinArchName(Args);
+
+  CmdArgs.push_back("-arch");
+  CmdArgs.push_back(Args.MakeArgString(ArchName));
+}
+
+std::unique_ptr<Job>
+darwin::Linker::constructJob(const JobAction &JA,
+                             std::unique_ptr<JobList> Inputs,
+                             std::unique_ptr<CommandOutput> Output,
+                             const ActionList &InputActions,
+                             const ArgList &Args,
+                             StringRef LinkingOutput) const {
+  ArgStringList Arguments;
+  Arguments.push_back("-v");
+
+  std::string Exec = getToolChain().getDriver().getProgramPath("ld",
+                                                               getToolChain());
+
+  std::unique_ptr<Job>Cmd (new Command(JA, *this, std::move(Inputs),
+                                       std::move(Output),
+                                       Args.MakeArgString(Exec), Arguments));
+  return Cmd;
+}