[AST] Stop using side-table for local discriminators

Author: rintaro

include/swift/AST/Decl.h

@@ -2150,6 +2150,7 @@ class ValueDecl : public Decl {
   DeclName Name;
   SourceLoc NameLoc;
   llvm::PointerIntPair<Type, 3, OptionalEnum<AccessLevel>> TypeAndAccess;
+  unsigned LocalDiscriminator = 0;
 
 private:
     bool isUsableFromInline() const;

lib/AST/ASTContext.cpp

@@ -223,10 +223,6 @@ FOR_KNOWN_FOUNDATION_TYPES(CACHE_FOUNDATION_DECL)
   /// \brief Map from Swift declarations to brief comments.
   llvm::DenseMap<const Decl *, StringRef> BriefComments;
 
-  /// \brief Map from local declarations to their discriminators.
-  /// Missing entries implicitly have value 0.
-  llvm::DenseMap<const ValueDecl *, unsigned> LocalDiscriminators;
-
   /// \brief Map from declarations to foreign error conventions.
   /// This applies to both actual imported functions and to @objc functions.
   llvm::DenseMap<const AbstractFunctionDecl *,
@@ -1769,24 +1765,6 @@ void ASTContext::setBriefComment(const Decl *D, StringRef Comment) {
   Impl.BriefComments[D] = Comment;
 }
 
-unsigned ValueDecl::getLocalDiscriminator() const {
-  assert(getDeclContext()->isLocalContext());
-  auto &discriminators = getASTContext().Impl.LocalDiscriminators;
-  auto it = discriminators.find(this);
-  if (it == discriminators.end())
-    return 0;
-  return it->second;
-}
-
-void ValueDecl::setLocalDiscriminator(unsigned index) {
-  assert(getDeclContext()->isLocalContext());
-  if (!index) {
-    assert(!getASTContext().Impl.LocalDiscriminators.count(this));
-    return;
-  }
-  getASTContext().Impl.LocalDiscriminators.insert({this, index});
-}
-
 NormalProtocolConformance *
 ASTContext::getBehaviorConformance(Type conformingType,
                                    ProtocolDecl *protocol,
@@ -2031,7 +2009,6 @@ size_t ASTContext::getTotalMemory() const {
     llvm::capacity_in_bytes(Impl.ModuleLoaders) +
     llvm::capacity_in_bytes(Impl.RawComments) +
     llvm::capacity_in_bytes(Impl.BriefComments) +
-    llvm::capacity_in_bytes(Impl.LocalDiscriminators) +
     llvm::capacity_in_bytes(Impl.ModuleTypes) +
     llvm::capacity_in_bytes(Impl.GenericParamTypes) +
     // Impl.GenericFunctionTypes ?

lib/AST/Decl.cpp

@@ -1680,6 +1680,16 @@ bool ValueDecl::needsCapture() const {
   return !isa<TypeDecl>(this);
 }
 
+unsigned ValueDecl::getLocalDiscriminator() const {
+  return LocalDiscriminator;
+}
+
+void ValueDecl::setLocalDiscriminator(unsigned index) {
+  assert(getDeclContext()->isLocalContext());
+  assert(LocalDiscriminator == 0 && "LocalDiscriminator is set multiple times");
+  LocalDiscriminator = index;
+}
+
 ValueDecl *ValueDecl::getOverriddenDecl() const {
   if (auto fd = dyn_cast<FuncDecl>(this))
     return fd->getOverriddenDecl();

lib/Serialization/ModuleFile.cpp

@@ -2018,7 +2018,8 @@ ModuleFile::getLocalTypeDecls(SmallVectorImpl<TypeDecl *> &results) {
   for (auto entry : LocalTypeDecls->data()) {
     auto DeclID = entry.first;
     auto TD = cast<TypeDecl>(getDecl(DeclID));
-    TD->setLocalDiscriminator(entry.second);
+    assert(entry.second == TD->getLocalDiscriminator());
+//    TD->setLocalDiscriminator(entry.second);
     results.push_back(TD);
   }
 }