Move the -frontend logic into its own library to allow re-use

and abstraction (to come).

Author: rjmccall

include/swift/Frontend/Frontend.h

@@ -47,6 +47,15 @@ namespace swift {
 
 class SerializedModuleLoader;
 
+/// The abstract configuration of the compiler, including:
+///   - options for all stages of translation,
+///   - information about the build environment,
+///   - information about the job being performed, and
+///   - lists of inputs.
+///
+/// A CompilerInvocation can be built from a frontend command line
+/// using parseArgs.  It can then be used to build a CompilerInstance,
+/// which manages the actual compiler execution.
 class CompilerInvocation {
   LangOptions LangOpts;
   FrontendOptions FrontendOpts;
@@ -282,6 +291,14 @@ class CompilerInvocation {
   }
 };
 
+/// A class which manages the state and execution of the compiler.
+/// This owns the primary compiler singletons, such as the ASTContext,
+/// as well as various build products such as the SILModule.
+///
+/// Before a CompilerInstance can be used, it must be configured by
+/// calling \a setup.  If successful, this will create an ASTContext
+/// and set up the basic compiler invariants.  Calling \a setup multiple
+/// times on a single CompilerInstance is not permitted.
 class CompilerInstance {
   CompilerInvocation Invocation;
   SourceManager SourceMgr;

include/swift/Subsystems.h

@@ -88,6 +88,20 @@ namespace swift {
 
   /// @}
 
+  /// Perform all the operations of the frontend, exactly as if invoked
+  /// with -frontend.
+  ///
+  /// \param args the arguments to use as the arguments to the frontend
+  /// \param argv0 the name used as the frontend executable
+  /// \param mainAddr an address from the main executable
+  ///
+  /// \return the exit value of the frontend: 0 or 1 on success unless
+  ///   the frontend executes in immediate mode, in which case this will be
+  ///   the exit value of the script, assuming it exits normally
+  int performFrontend(ArrayRef<const char *> args,
+                      const char *argv0,
+                      void *mainAddr);
+
   /// \brief Parse a single buffer into the given source file.
   ///
   /// If the source file is the main file, stop parsing after the next

lib/CMakeLists.txt

@@ -4,6 +4,7 @@ add_subdirectory(Basic)
 add_subdirectory(ClangImporter)
 add_subdirectory(Driver)
 add_subdirectory(Frontend)
+add_subdirectory(FrontendTool)
 add_subdirectory(Index)
 add_subdirectory(IDE)
 add_subdirectory(Immediate)

lib/FrontendTool/CMakeLists.txt

@@ -0,0 +1,13 @@
+add_swift_library(swiftFrontendTool
+  FrontendTool.cpp
+  LINK_LIBRARIES
+    swiftIDE
+    swiftIRGen swiftSIL swiftSILGen swiftSILOptimizer
+    swiftImmediate
+    swiftSerialization
+    swiftPrintAsObjC
+    swiftFrontend
+    swiftClangImporter
+    swiftOption
+    clangAPINotes
+)

tools/driver/frontend_main.cpp renamed to lib/FrontendTool/FrontendTool.cpp

@@ -1,4 +1,4 @@
-//===--- frontend_main.cpp - Swift Compiler Frontend ----------------------===//
+//===--- FrontendTool.cpp - Swift Compiler Frontend ----------------------===//
 //
 // This source file is part of the Swift.org open source project
 //
@@ -15,6 +15,9 @@
 /// implements the core compiler functionality along with a number of additional
 /// tools for demonstration and testing purposes.
 ///
+/// This is separate from the rest of libFrontend to reduce the dependencies
+/// required by that library.
+///
 //===----------------------------------------------------------------------===//
 
 #include "swift/Subsystems.h"
@@ -993,8 +996,8 @@ static bool dumpAPI(Module *Mod, StringRef OutDir) {
   return false;
 }
 
-int frontend_main(ArrayRef<const char *>Args,
-                  const char *Argv0, void *MainAddr) {
+int swift::performFrontend(ArrayRef<const char *> Args,
+                           const char *Argv0, void *MainAddr) {
   llvm::InitializeAllTargets();
   llvm::InitializeAllTargetMCs();
   llvm::InitializeAllAsmPrinters();

tools/driver/CMakeLists.txt

@@ -2,18 +2,10 @@ add_swift_executable(swift
   api_notes.cpp
   driver.cpp
   autolink_extract_main.cpp
-  frontend_main.cpp
   modulewrap_main.cpp
   LINK_LIBRARIES
-    swiftIDE
-    swiftDriver swiftIRGen swiftSIL swiftSILGen swiftSILOptimizer
-    swiftImmediate
-    swiftSerialization
-    swiftPrintAsObjC
-    swiftFrontend
-    swiftClangImporter
-    swiftOption
-    clangAPINotes
+    swiftDriver
+    swiftFrontendTool
 )
 
 target_link_libraries(swift edit)

tools/driver/driver.cpp

@@ -24,6 +24,7 @@
 #include "swift/Driver/Job.h"
 #include "swift/Frontend/Frontend.h"
 #include "swift/Frontend/PrintingDiagnosticConsumer.h"
+#include "swift/Subsystems.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Errno.h"
@@ -49,9 +50,6 @@ std::string getExecutablePath(const char *FirstArg) {
   return llvm::sys::fs::getMainExecutable(FirstArg, P);
 }
 
-extern int frontend_main(ArrayRef<const char *> Args, const char *Argv0,
-                         void *MainAddr);
-
 /// Run 'swift-autolink-extract'.
 extern int autolink_extract_main(ArrayRef<const char *> Args, const char *Argv0,
                                  void *MainAddr);
@@ -155,9 +153,9 @@ int main(int argc_, const char **argv_) {
   if (argv.size() > 1){
     StringRef FirstArg(argv[1]);
     if (FirstArg == "-frontend") {
-      return frontend_main(llvm::makeArrayRef(argv.data()+2,
-                                              argv.data()+argv.size()),
-                           argv[0], (void *)(intptr_t)getExecutablePath);
+      return performFrontend(llvm::makeArrayRef(argv.data()+2,
+                                                argv.data()+argv.size()),
+                             argv[0], (void *)(intptr_t)getExecutablePath);
     }
     if (FirstArg == "-modulewrap") {
       return modulewrap_main(llvm::makeArrayRef(argv.data()+2,