Add a -l flag to Swift and use it to provide autolinking information.

The spelling of the flag can certainly be changed; I just wanted to get
something up and running.

Swift SVN r7582

include/swift/AST/Module.h

@@ -279,13 +279,15 @@ public:
 /// external references in a translation unit, which is one file.
 class TranslationUnit : public Module {
 private:
-
   /// This is the list of modules that are imported by this module, with the
   /// second element of the pair declaring whether the module is reexported.
   ///
   /// This is filled in by the Name Binding phase.
   ArrayRef<std::pair<ImportedModule, bool>> Imports;
 
+  /// The list of libraries specified as link-time dependencies at compile time.
+  ArrayRef<LinkLibrary> LinkLibraries;
+
 public:
   /// Kind - This is the sort of file the translation unit was parsed for, which
   /// can affect some type checking and other behavior.
@@ -330,6 +332,14 @@ public:
     Imports = IM;
   }
 
+  void setLinkLibraries(ArrayRef<LinkLibrary> libs) {
+    assert(LinkLibraries.empty() && "link libraries already set");
+    LinkLibraries = libs;
+  }
+  ArrayRef<LinkLibrary> getLinkLibraries() const {
+    return LinkLibraries;
+  }
+
   void clearLookupCache();
 
   void cacheVisibleDecls(SmallVectorImpl<ValueDecl *> &&globals) const;

include/swift/Frontend/Frontend.h

@@ -22,6 +22,7 @@
 #include "swift/Basic/LangOptions.h"
 #include "swift/Basic/SourceManager.h"
 #include "swift/AST/DiagnosticEngine.h"
+#include "swift/AST/LinkLibrary.h"
 #include "swift/AST/Module.h"
 #include "swift/Parse/CodeCompletionCallbacks.h"
 #include "swift/Parse/Parser.h"
@@ -44,6 +45,7 @@ class CompilerInvocation {
   std::string ClangModuleCachePath;
   std::vector<std::string> ImportSearchPaths;
   std::vector<std::string> FrameworkSearchPaths;
+  SmallVector<LinkLibrary, 4> LinkLibraries;
   std::string RuntimeIncludePath;
   std::string SDKPath;
 
@@ -107,6 +109,14 @@ public:
     return FrameworkSearchPaths;
   }
 
+  void addLinkLibrary(StringRef name, LibraryKind kind) {
+    LinkLibraries.push_back({name, kind});
+  }
+
+  ArrayRef<LinkLibrary> getLinkLibraries() const {
+    return LinkLibraries;
+  }
+
   void setMainExecutablePath(StringRef Path);
 
   void setRuntimeIncludePath(StringRef Path) {

lib/AST/Module.cpp

@@ -15,6 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "swift/AST/Diagnostics.h"
+#include "swift/AST/LinkLibrary.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/ModuleLoader.h"
 #include "swift/AST/NameLookup.h"
@@ -535,8 +536,9 @@ void Module::collectLinkLibraries(LinkLibraryCallback callback) {
       return true;
     }
     
-    if (isa<TranslationUnit>(module)) {
+    if (auto TU = dyn_cast<TranslationUnit>(module)) {
-      // FIXME: Should we include libraries specified by the user here?
+      for (auto lib : TU->getLinkLibraries())
+        callback(lib);
       return true;
     }
     

lib/Frontend/CompilerInvocation.cpp

@@ -123,6 +123,10 @@ bool CompilerInvocation::parseArgs(ArrayRef<const char *> Args,
     case OPT_enable_definite_init:
       LangOpts.UseDefiniteInit = true;
       break;
+
+    case OPT_link_library:
+      addLinkLibrary(InputArg->getValue(), LibraryKind::Library);
+      break;
     }
   }
 

lib/Frontend/Frontend.cpp

@@ -124,6 +124,7 @@ void swift::CompilerInstance::doIt() {
   Context->LoadedModules[ID.str()] = TU;
 
   TU->HasBuiltinModuleAccess = Invocation.getParseStdlib();
+  TU->setLinkLibraries(Invocation.getLinkLibraries());
 
   // If we're in SIL mode, don't auto import any libraries.
   // Also don't perform auto import if we are not going to do semantic

lib/Frontend/FrontendOptions.td

@@ -20,6 +20,9 @@ def parse_as_library : Flag<["-"], "parse-as-library">,
 def parse_stdlib : Flag<["-"], "parse-stdlib">,
   HelpText<"Parse the input as the swift standard library">;
 
+def link_library : Joined<["-"], "l">,
+  HelpText<"Link the given library into the output product">;
+
 // LangOptions
 def debug_constraints : Flag<["-"], "debug-constraints">,
   HelpText<"Debug the constraint-based type checker">;

test/Serialization/autolinking.swift

@@ -0,0 +1,5 @@
+// RUN: %swift -emit-llvm -lmagic %s | FileCheck %s
+
+// CHECK: !{{[0-9]+}} = metadata !{i32 6, metadata !"Linker Options", metadata ![[LINK_LIST:[0-9]+]]}
+// CHECK: ![[LINK_LIST]] = metadata !{
+// CHECK-DAG: !{{[0-9]+}} = metadata !{metadata !"-lmagic"}