[IRGen] Prepare to emit prespecializations.

Author: nate-chandler

lib/IRGen/GenDecl.cpp

@@ -1150,6 +1150,7 @@ void IRGenerator::emitLazyDefinitions() {
       CanType type = LazySpecializedTypeMetadataRecords.pop_back_val();
       auto *nominal = type->getNominalOrBoundGenericNominal();
       CurrentIGMPtr IGM = getGenModule(nominal->getDeclContext());
+      emitLazySpecializedGenericTypeMetadata(*IGM.get(), type);
     }
     while (!LazyTypeContextDescriptors.empty()) {
       NominalTypeDecl *type = LazyTypeContextDescriptors.pop_back_val();

lib/IRGen/GenMeta.cpp

@@ -1834,6 +1834,11 @@ void irgen::emitLazyTypeMetadata(IRGenModule &IGM, NominalTypeDecl *type) {
   }
 }
 
+void irgen::emitLazySpecializedGenericTypeMetadata(IRGenModule &IGM,
+                                                   CanType type) {
+  emitSpecializedGenericStructMetadata(IGM, type);
+}
+
 llvm::Constant *
 IRGenModule::getAddrOfSharedContextDescriptor(LinkEntity entity,
                                               ConstantInit definition,
@@ -3678,6 +3683,10 @@ void irgen::emitStructMetadata(IRGenModule &IGM, StructDecl *structDecl) {
                          init.finishAndCreateFuture());
 }
 
+/// Emit the type metadata or metadata template for a struct.
+void irgen::emitSpecializedGenericStructMetadata(IRGenModule &IGM,
+                                                 CanType type) {}
+
 // Enums
 
 static Optional<Size> getConstantPayloadSize(IRGenModule &IGM,

lib/IRGen/GenMeta.h

@@ -71,6 +71,7 @@ namespace irgen {
   /// generated definitions.
   void emitLazyTypeMetadata(IRGenModule &IGM, NominalTypeDecl *type);
 
+  void emitLazySpecializedGenericTypeMetadata(IRGenModule &IGM, CanType type);
 
   /// Emit metadata for a foreign struct, enum or class.
   void emitForeignTypeMetadata(IRGenModule &IGM, NominalTypeDecl *decl);
@@ -81,6 +82,8 @@ namespace irgen {
   /// Emit the metadata associated with the given enum declaration.
   void emitEnumMetadata(IRGenModule &IGM, EnumDecl *theEnum);
 
+  void emitSpecializedGenericStructMetadata(IRGenModule &IGM, CanType type);
+
   /// Get what will be the index into the generic type argument array at the end
   /// of a nominal type's metadata.
   int32_t getIndexOfGenericArgument(IRGenModule &IGM,