Serialization: Read and write the underscored bit for @cdecl

Author: xymus

lib/Serialization/Deserialization.cpp

@@ -5993,9 +5993,9 @@ llvm::Error DeclDeserializer::deserializeDeclCommon() {
 
       case decls_block::CDecl_DECL_ATTR: {
         bool isImplicit;
-        bool isUnderscored = false;
+        bool isUnderscored;
         serialization::decls_block::CDeclDeclAttrLayout::readRecord(
-            scratch, isImplicit); // TODO isUnderscored
+            scratch, isImplicit, isUnderscored);
         Attr = new (ctx) CDeclAttr(blobData, isImplicit, isUnderscored);
         break;
       }

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ 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 = 938; // custom AvailabilityDomains
+const uint16_t SWIFTMODULE_VERSION_MINOR = 939; // cdecl isUnderscored
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -2232,7 +2232,8 @@ namespace decls_block {
   using CDeclDeclAttrLayout = BCRecordLayout<
     CDecl_DECL_ATTR,
     BCFixed<1>, // implicit flag
-    BCBlob      // _silgen_name
+    BCFixed<1>, // underscored flag
+    BCBlob      // cname
   >;
 
   using ImplementsDeclAttrLayout = BCRecordLayout<

lib/Serialization/Serialization.cpp

@@ -2993,6 +2993,7 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
       auto abbrCode = S.DeclTypeAbbrCodes[CDeclDeclAttrLayout::Code];
       CDeclDeclAttrLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode,
                                       theAttr->isImplicit(),
+                                      theAttr->Underscored,
                                       theAttr->Name);
       return;
     }