[Serialization] Omit local discrimiator from LocalDeclTableInfo

Local discriminators are emitted as a part of decl.

Author: rintaro

include/swift/Serialization/ModuleFormat.h

@@ -55,7 +55,7 @@ const uint16_t 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 VERSION_MINOR = 418; // Last change: add begin_access [builtin].
+const uint16_t VERSION_MINOR = 419; // Last change: Remove discriminator from LocalDeclTableInfo.
 
 using DeclIDField = BCFixed<31>;
 

lib/Serialization/ModuleFile.cpp

@@ -429,7 +429,7 @@ class ModuleFile::LocalDeclTableInfo {
 public:
   using internal_key_type = StringRef;
   using external_key_type = internal_key_type;
-  using data_type = std::pair<DeclID, unsigned>; // ID, local discriminator
+  using data_type = DeclID;
   using hash_value_type = uint32_t;
   using offset_type = unsigned;
 
@@ -447,7 +447,7 @@ class ModuleFile::LocalDeclTableInfo {
 
   static std::pair<unsigned, unsigned> ReadKeyDataLength(const uint8_t *&data) {
     unsigned keyLength = endian::readNext<uint16_t, little, unaligned>(data);
-    return { keyLength, sizeof(uint32_t) + sizeof(unsigned) };
+    return { keyLength, sizeof(uint32_t) };
   }
 
   static internal_key_type ReadKey(const uint8_t *data, unsigned length) {
@@ -456,9 +456,7 @@ class ModuleFile::LocalDeclTableInfo {
 
   static data_type ReadData(internal_key_type key, const uint8_t *data,
                             unsigned length) {
-    auto declID = endian::readNext<uint32_t, little, unaligned>(data);
-    auto discriminator = endian::readNext<unsigned, little, unaligned>(data);
-    return { declID, discriminator };
+    return endian::readNext<uint32_t, little, unaligned>(data);
   }
 };
 
@@ -1516,7 +1514,7 @@ TypeDecl *ModuleFile::lookupLocalType(StringRef MangledName) {
   if (iter == LocalTypeDecls->end())
     return nullptr;
 
-  return cast<TypeDecl>(getDecl((*iter).first));
+  return cast<TypeDecl>(getDecl(*iter));
 }
 
 TypeDecl *ModuleFile::lookupNestedType(Identifier name,
@@ -2021,11 +2019,8 @@ ModuleFile::getLocalTypeDecls(SmallVectorImpl<TypeDecl *> &results) {
   if (!LocalTypeDecls)
     return;
 
-  for (auto entry : LocalTypeDecls->data()) {
-    auto DeclID = entry.first;
+  for (auto DeclID : LocalTypeDecls->data()) {
     auto TD = cast<TypeDecl>(getDecl(DeclID));
-    assert(entry.second == TD->getLocalDiscriminator());
-//    TD->setLocalDiscriminator(entry.second);
     results.push_back(TD);
   }
 }

lib/Serialization/Serialization.cpp

@@ -228,7 +228,7 @@ namespace {
   public:
     using key_type = std::string;
     using key_type_ref = StringRef;
-    using data_type = std::pair<DeclID, unsigned>; // ID, local discriminator
+    using data_type = DeclID;
     using data_type_ref = const data_type &;
     using hash_value_type = uint32_t;
     using offset_type = unsigned;
@@ -242,7 +242,7 @@ namespace {
                                                     key_type_ref key,
                                                     data_type_ref data) {
       uint32_t keyLength = key.size();
-      uint32_t dataLength = sizeof(uint32_t) + sizeof(unsigned);
+      uint32_t dataLength = sizeof(uint32_t);
       endian::Writer<little> writer(out);
       writer.write<uint16_t>(keyLength);
       return { keyLength, dataLength };
@@ -256,8 +256,7 @@ namespace {
                   unsigned len) {
       static_assert(declIDFitsIn32Bits(), "DeclID too large");
       endian::Writer<little> writer(out);
-      writer.write<uint32_t>(data.first);
-      writer.write<unsigned>(data.second);
+      writer.write<uint32_t>(data);
     }
   };
 
@@ -4909,9 +4908,7 @@ void Serializer::writeAST(ModuleOrSourceFile DC,
       Mangle::ASTMangler Mangler;
       std::string MangledName = Mangler.mangleDeclAsUSR(TD, /*USRPrefix*/"");
       assert(!MangledName.empty() && "Mangled type came back empty!");
-      localTypeGenerator.insert(MangledName, {
-        addDeclRef(TD), TD->getLocalDiscriminator()
-      });
+      localTypeGenerator.insert(MangledName, addDeclRef(TD));
 
       if (auto IDC = dyn_cast<IterableDeclContext>(TD)) {
         collectInterestingNestedDeclarations(*this, IDC->getMembers(),