Autolinking: include all imported modules.

Although Cocoa.framework re-exports AppKit, Foundation, and CoreData, an
arbitrary library does not re-export most of its imports. Normally this
would be fine, but the Clang importer can pull in types too eagerly and
then generate thunks and wrappers for things we don't care about. At least
for now, return to the behavior of autolinking /anything/ that gets visibly
imported.

<rdar://problem/15705923>

Swift SVN r11844

lib/IRGen/IRGenModule.cpp

@@ -329,8 +329,61 @@ llvm::Constant *IRGenModule::getSize(Size size) {
   return llvm::ConstantInt::get(SizeTy, size.getValue());
 }
 
+void IRGenModule::addLinkLibrary(const LinkLibrary &linkLib) {
+  llvm::LLVMContext &ctx = Module.getContext();
+
+  switch (linkLib.getKind()) {
+  case LibraryKind::Library: {
+    // FIXME: Use target-independent linker option.
+    // Clang uses CGM.getTargetCodeGenInfo().getDependentLibraryOption(...).
+    llvm::SmallString<32> buf;
+    buf += "-l";
+    buf += linkLib.getName();
+    auto flag = llvm::MDString::get(ctx, buf);
+    AutolinkEntries.push_back(llvm::MDNode::get(ctx, flag));
+    break;
+  }
+  case LibraryKind::Framework:
+    llvm::Value *args[] = {
+      llvm::MDString::get(ctx, "-framework"),
+      llvm::MDString::get(ctx, linkLib.getName())
+    };
+    AutolinkEntries.push_back(llvm::MDNode::get(ctx, args));
+    break;
+  }
+}
+
+// FIXME: This should just be the implementation of
+// llvm::array_pod_sort_comparator. The only difference is that it uses
+// std::less instead of operator<.
+template <typename T>
+static int pointerPODSortComparator(T * const *lhs, T * const *rhs) {
+  std::less<T *> lt;
+  if (lt(*lhs, *rhs))
+    return -1;
+  if (lt(*rhs, *lhs))
+    return -1;
+  return 0;
+}
+
+void IRGenModule::emitAutolinkInfo() {
+  // FIXME: This constant should be vended by LLVM somewhere.
+  static const char * const LinkerOptionsFlagName = "Linker Options";
+
+  // Remove duplicates.
+  llvm::array_pod_sort(AutolinkEntries.begin(), AutolinkEntries.end(),
+                       pointerPODSortComparator);
+  auto newEnd = std::unique(AutolinkEntries.begin(), AutolinkEntries.end());
+  AutolinkEntries.erase(newEnd, AutolinkEntries.end());
+
+  llvm::LLVMContext &ctx = Module.getContext();
+  Module.addModuleFlag(llvm::Module::AppendUnique, LinkerOptionsFlagName,
+                       llvm::MDNode::get(ctx, AutolinkEntries));
+}
+
 void IRGenModule::finalize() {
   emitGlobalLists();
+  emitAutolinkInfo();
   if (DebugInfo)
     DebugInfo->finalize();
 }