Allow one to separately specify the ABI name of a module.

Introduce a new compiler flag `-module-abi-name <name>` that uses the
given name as the ABI name for the module (rather than the module's
name in source code). The ABI name impacts name mangling and metadata.

Author: DougGregor

include/swift/AST/Module.h

@@ -166,6 +166,9 @@ class ModuleDecl : public DeclContext, public TypeDecl {
   friend class DirectOperatorLookupRequest;
   friend class DirectPrecedenceGroupLookupRequest;
 
+  /// The ABI name of the module, if it differs from the module name.
+  Identifier ModuleABIName;
+
 public:
   /// Produces the components of a given module's full name in reverse order.
   ///
@@ -343,6 +346,17 @@ class ModuleDecl : public DeclContext, public TypeDecl {
   void getDeclaredCrossImportBystanders(
       SmallVectorImpl<Identifier> &bystanderNames);
 
+  /// Retrieve the ABI name of the module, which is used for metadata and
+  /// mangling.
+  Identifier getABIName() const {
+    return ModuleABIName.empty() ? getName() : ModuleABIName;
+  }
+
+  /// Set the ABI name of the module;
+  void setABIName(Identifier name) {
+    ModuleABIName = name;
+  }
+
 private:
   /// A cache of this module's underlying module and required bystander if it's
   /// an underscored cross-import overlay.

include/swift/Frontend/FrontendOptions.h

@@ -48,9 +48,13 @@ class FrontendOptions {
   /// An Objective-C header to import and make implicitly visible.
   std::string ImplicitObjCHeaderPath;
 
-  /// The name of the module which the frontend is building.
+  /// The name of the module that the frontend is building.
   std::string ModuleName;
 
+  /// The ABI name of the module that the frontend is building, to be used in
+  /// mangling and metadata.
+  std::string ModuleABIName;
+
   /// The name of the library to link against when using this module.
   std::string ModuleLinkName;
 

include/swift/Option/Options.td

@@ -421,6 +421,9 @@ def module_link_name_EQ : Joined<["-"], "module-link-name=">,
 def autolink_force_load : Flag<["-"], "autolink-force-load">,
   Flags<[FrontendOption, ModuleInterfaceOption, HelpHidden]>,
   HelpText<"Force ld to link against this module even if no symbols are used">;
+def module_abi_name : Separate<["-"], "module-abi-name">,
+  Flags<[FrontendOption, ModuleInterfaceOption]>,
+  HelpText<"ABI name to use for the contents of this module">;
 
 def emit_module : Flag<["-"], "emit-module">,
   Flags<[FrontendOption, NoInteractiveOption, DoesNotAffectIncrementalBuild,

include/swift/Serialization/Validation.h

@@ -93,6 +93,7 @@ struct ValidationInfo {
 class ExtendedValidationInfo {
   SmallVector<StringRef, 4> ExtraClangImporterOpts;
   StringRef SDKPath;
+  StringRef ModuleABIName;
   struct {
     unsigned ArePrivateImportsEnabled : 1;
     unsigned IsSIB : 1;
@@ -145,6 +146,9 @@ class ExtendedValidationInfo {
   void setAllowModuleWithCompilerErrorsEnabled(bool val) {
     Bits.IsAllowModuleWithCompilerErrorsEnabled = val;
   }
+
+  StringRef getModuleABIName() const { return ModuleABIName; }
+  void setModuleABIName(StringRef name) { ModuleABIName = name; }
 };
 
 /// Returns info about the serialized AST in the given data.

lib/AST/ASTContext.cpp

@@ -164,6 +164,9 @@ struct ASTContext::Implementation {
   /// DenseMap.
   llvm::MapVector<Identifier, ModuleDecl *> LoadedModules;
 
+  /// The set of top-level modules we have loaded, indexed by ABI name.
+  llvm::MapVector<Identifier, ModuleDecl *> LoadedModulesByABIName;
+
   // FIXME: This is a StringMap rather than a StringSet because StringSet
   // doesn't allow passing in a pre-existing allocator.
   llvm::StringMap<Identifier::Aligner, llvm::BumpPtrAllocator&>

lib/AST/ASTMangler.cpp

@@ -2143,13 +2143,15 @@ void ASTMangler::appendModule(const ModuleDecl *module,
                               StringRef useModuleName) {
   assert(!module->getParent() && "cannot mangle nested modules!");
 
+  StringRef ModName =
+      DWARFMangling ? module->getName().str() : module->getABIName().str();
+
   // Try the special 'swift' substitution.
-  if (module->isStdlibModule()) {
+  if (ModName == STDLIB_NAME) {
     assert(useModuleName.empty());
     return appendOperator("s");
   }
 
-  StringRef ModName = module->getName().str();
   if (ModName == MANGLING_MODULE_OBJC) {
     assert(useModuleName.empty());
     return appendOperator("So");

lib/AST/Decl.cpp

@@ -638,6 +638,7 @@ StringRef Decl::getAlternateModuleName() const {
       }
     }
   }
+  
   for (auto *DC = getDeclContext(); DC; DC = DC->getParent()) {
     if (auto decl = DC->getAsDecl()) {
       if (decl == this)

lib/Driver/ToolChains.cpp

@@ -231,6 +231,7 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
   inputArgs.AddLastArg(arguments, options::OPT_import_underlying_module);
   inputArgs.AddLastArg(arguments, options::OPT_module_cache_path);
   inputArgs.AddLastArg(arguments, options::OPT_module_link_name);
+  inputArgs.AddLastArg(arguments, options::OPT_module_abi_name);
   inputArgs.AddLastArg(arguments, options::OPT_nostdimport);
   inputArgs.AddLastArg(arguments, options::OPT_parse_stdlib);
   inputArgs.AddLastArg(arguments, options::OPT_resource_dir);

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -217,6 +217,9 @@ bool ArgsToFrontendOptionsConverter::convert(
     return true;
   }
 
+  if (const Arg *A = Args.getLastArg(OPT_module_abi_name))
+    Opts.ModuleABIName = A->getValue();
+
   if (const Arg *A = Args.getLastArg(OPT_module_link_name))
     Opts.ModuleLinkName = A->getValue();
 

lib/Frontend/Frontend.cpp

@@ -925,7 +925,10 @@ ModuleDecl *CompilerInstance::getMainModule() const {
       MainModule->setPrivateImportsEnabled();
     if (Invocation.getFrontendOptions().EnableImplicitDynamic)
       MainModule->setImplicitDynamicEnabled();
-
+    if (!Invocation.getFrontendOptions().ModuleABIName.empty()) {
+      MainModule->setABIName(getASTContext().getIdentifier(
+          Invocation.getFrontendOptions().ModuleABIName));
+    }
     if (Invocation.getFrontendOptions().EnableLibraryEvolution)
       MainModule->setResilienceStrategy(ResilienceStrategy::Resilient);
 

lib/IDE/CompletionInstance.cpp

@@ -464,6 +464,7 @@ bool CompletionInstance::performCachedOperationIfPossible(
     auto &Ctx = oldM->getASTContext();
     auto *newM = ModuleDecl::createMainModule(Ctx, oldM->getName(),
                                               oldM->getImplicitImportInfo());
+    newM->setABIName(oldM->getABIName());
     auto *newSF = new (Ctx) SourceFile(*newM, SourceFileKind::Main, newBufferID,
                                        oldSF->getParsingOptions());
     newM->addFile(*newSF);

lib/IRGen/GenMeta.cpp

@@ -492,7 +492,7 @@ namespace {
     }
 
     void addName() {
-      B.addRelativeAddress(IGM.getAddrOfGlobalString(M->getName().str(),
+      B.addRelativeAddress(IGM.getAddrOfGlobalString(M->getABIName().str(),
                                            /*willBeRelativelyAddressed*/ true));
     }
 

lib/Serialization/ModuleFile.h

@@ -433,6 +433,11 @@ class ModuleFile
     return Core->Name;
   }
 
+  /// The ABI name of the module.
+  StringRef getModuleABIName() const {
+    return Core->ModuleABIName;
+  }
+
   /// The Swift compatibility version in use when this module was built.
   const version::Version &getCompatibilityVersion() const {
     return Core->CompatibilityVersion;

lib/Serialization/ModuleFileSharedCore.cpp

@@ -148,6 +148,9 @@ static bool readOptionsBlock(llvm::BitstreamCursor &cursor,
     case options_block::IS_ALLOW_MODULE_WITH_COMPILER_ERRORS_ENABLED:
       extendedInfo.setAllowModuleWithCompilerErrorsEnabled(true);
       break;
+    case options_block::MODULE_ABI_NAME:
+      extendedInfo.setModuleABIName(blobData);
+      break;
     default:
       // Unknown options record, possibly for use by a future version of the
       // module format.
@@ -1177,6 +1180,7 @@ ModuleFileSharedCore::ModuleFileSharedCore(
       Bits.IsAllowModuleWithCompilerErrorsEnabled =
           extInfo.isAllowModuleWithCompilerErrorsEnabled();
       MiscVersion = info.miscVersion;
+      ModuleABIName = extInfo.getModuleABIName();
 
       hasValidControlBlock = true;
       break;

lib/Serialization/ModuleFileSharedCore.h

@@ -73,6 +73,9 @@ class ModuleFileSharedCore {
   /// include the version string of the compiler that built the module.
   StringRef MiscVersion;
 
+  /// The module ABI name.
+  StringRef ModuleABIName;
+
   /// \c true if this module has incremental dependency information.
   bool HasIncrementalInfo = false;
 

lib/Serialization/ModuleFormat.h

@@ -56,7 +56,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 602; // noasync apply
+const uint16_t SWIFTMODULE_VERSION_MINOR = 603; // module ABI name
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -790,7 +790,8 @@ namespace options_block {
     RESILIENCE_STRATEGY,
     ARE_PRIVATE_IMPORTS_ENABLED,
     IS_IMPLICIT_DYNAMIC_ENABLED,
-    IS_ALLOW_MODULE_WITH_COMPILER_ERRORS_ENABLED
+    IS_ALLOW_MODULE_WITH_COMPILER_ERRORS_ENABLED,
+    MODULE_ABI_NAME,
   };
 
   using SDKPathLayout = BCRecordLayout<
@@ -828,6 +829,11 @@ namespace options_block {
   using IsAllowModuleWithCompilerErrorsEnabledLayout = BCRecordLayout<
     IS_ALLOW_MODULE_WITH_COMPILER_ERRORS_ENABLED
   >;
+
+  using ModuleABINameLayout = BCRecordLayout<
+    MODULE_ABI_NAME,
+    BCBlob
+  >;
 }
 
 /// The record types within the input block.

lib/Serialization/Serialization.cpp

@@ -814,6 +814,7 @@ void Serializer::writeBlockInfoBlock() {
   BLOCK_RECORD(options_block, ARE_PRIVATE_IMPORTS_ENABLED);
   BLOCK_RECORD(options_block, RESILIENCE_STRATEGY);
   BLOCK_RECORD(options_block, IS_ALLOW_MODULE_WITH_COMPILER_ERRORS_ENABLED);
+  BLOCK_RECORD(options_block, MODULE_ABI_NAME);
 
   BLOCK(INPUT_BLOCK);
   BLOCK_RECORD(input_block, IMPORTED_MODULE);
@@ -1001,6 +1002,11 @@ void Serializer::writeHeader(const SerializationOptions &options) {
         AllowErrors.emit(ScratchRecord);
       }
 
+      if (M->getABIName() != M->getName()) {
+        options_block::ModuleABINameLayout ABIName(Out);
+        ABIName.emit(ScratchRecord, M->getABIName().str());
+      }
+
       if (options.SerializeOptionsForDebugging) {
         options_block::SDKPathLayout SDKPath(Out);
         options_block::XCCLayout XCC(Out);

lib/Serialization/SerializedModuleLoader.cpp

@@ -723,6 +723,8 @@ LoadedFile *SerializedModuleLoaderBase::loadAST(
       M.setImplicitDynamicEnabled();
     if (loadedModuleFile->hasIncrementalInfo())
       M.setHasIncrementalInfo();
+    if (!loadedModuleFile->getModuleABIName().empty())
+      M.setABIName(Ctx.getIdentifier(loadedModuleFile->getModuleABIName()));
 
     auto diagLocOrInvalid = diagLoc.getValueOr(SourceLoc());
     loadInfo.status = loadedModuleFile->associateWithFileContext(

test/IRGen/module_abi_name.swift

@@ -0,0 +1,19 @@
+// RUN: %target-swift-frontend -module-name=Hello -module-abi-name Goodbye -emit-ir %s | %FileCheck %s
+
+// CHECK-NOT: {{(5|")Hello}}
+
+// CHECK-DAG: [[MODULE_NAME:@.*]] = private constant [8 x i8] c"Goodbye\00"
+// CHECK-DAG: @"$s7GoodbyeMXM" = {{.*}} [[MODULE_NAME]]
+
+// CHECK-DAG: @"$s7Goodbye8GreetingCMm" =
+public class Greeting { }
+
+// CHECK-NOT: {{(5|")Hello}}
+// CHECK: define swiftcc void @"$s7Goodbye8functionyyF"()
+@inlinable public func function() { }
+
+func callFunction() {
+  function()
+}
+
+// CHECK-NOT: {{(5|")Hello}}

test/ModuleInterface/module_abi_name.swift

@@ -0,0 +1,5 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -emit-module-interface-path %t/Hello.swiftinterface -module-name Hello -module-abi-name Goodbye %s
+// RUN: %FileCheck %s < %t/Hello.swiftinterface
+
+// CHECK: -module-abi-name Goodbye

test/Serialization/Inputs/def_module_abi_name.swift

@@ -0,0 +1,3 @@
+public class Greeting { }
+
+@inlinable public func function() { }

test/Serialization/module_abi_name.swift

@@ -0,0 +1,12 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -o %t %S/Inputs/def_module_abi_name.swift -module-abi-name Goodbye
+// RUN: %target-swift-frontend -module-name ModuleABIName -emit-sil -I %t %s | %FileCheck %s
+
+import def_module_abi_name
+
+func callFunction() {
+  // CHECK: function_ref @$s7Goodbye8functionyyF
+  def_module_abi_name.function()
+}
+
+// CHECK: sil [serialized] @$s7Goodbye8functionyyF : $@convention(thin) () -> ()