[Serialization] Avoid serializing source orders, trust deserialized decls in preserving such order. rdar://24610992

Thank Jordan for suggesting this.

Author: nkcsgexi

include/swift/AST/Decl.h

@@ -759,8 +759,6 @@ class alignas(1 << DeclAlignInBits) Decl {
 
   Optional<StringRef> getGroupName() const;
 
-  Optional<unsigned> getSourceOrder() const;
-
   /// \returns the brief comment attached to this declaration.
   StringRef getBriefComment() const;
 

include/swift/AST/Module.h

@@ -675,11 +675,6 @@ class FileUnit : public DeclContext {
     return None;
   }
 
-  virtual Optional<unsigned>
-  getSourceOrderForDecl(const Decl *D) const {
-    return None;
-  }
-
   virtual void collectAllGroups(std::vector<StringRef> &Names) const {}
 
   /// Returns an implementation-defined "discriminator" for \p D, which

include/swift/AST/RawComment.h

@@ -73,7 +73,6 @@ struct CommentInfo {
   StringRef Brief;
   RawComment Raw;
   uint32_t Group;
-  uint32_t SourceOrder;
 };
 
 } // namespace swift

include/swift/Serialization/ModuleFile.h

@@ -616,7 +616,6 @@ class ModuleFile : public LazyMemberLoader {
 
   Optional<StringRef> getGroupNameById(unsigned Id) const;
   Optional<StringRef> getGroupNameForDecl(const Decl *D) const;
-  Optional<unsigned> getSourceOrderForDecl(const Decl *D) const;
   void collectAllGroups(std::vector<StringRef> &Names) const;
   Optional<CommentInfo> getCommentForDecl(const Decl *D) const;
   Optional<CommentInfo> getCommentForDeclByUSR(StringRef USR) const;

include/swift/Serialization/SerializedModuleLoader.h

@@ -140,8 +140,6 @@ class SerializedASTFile final : public LoadedFile {
 
   Optional<StringRef> getGroupNameForDecl(const Decl *D) const override;
 
-  Optional<unsigned> getSourceOrderForDecl(const Decl *D) const override;
-
   void collectAllGroups(std::vector<StringRef> &Names) const override;
 
   virtual void getTopLevelDecls(SmallVectorImpl<Decl*> &results) const override;

lib/AST/RawComment.cpp

@@ -171,16 +171,6 @@ Optional<StringRef> Decl::getGroupName() const {
   return None;
 }
 
-Optional<unsigned> Decl::getSourceOrder() const {
-
-  // We can only get source orders from deserialized module files.
-  if (auto *Unit =
-      dyn_cast<FileUnit>(this->getDeclContext()->getModuleScopeContext())) {
-    return  Unit->getSourceOrderForDecl(this);
-  }
-  return None;
-}
-
 static StringRef extractBriefComment(ASTContext &Context, RawComment RC,
                                      const Decl *D) {
   PrettyStackTraceDecl StackTrace("extracting brief comment for", D);

lib/IDE/ModuleInterfacePrinting.cpp

@@ -347,28 +347,27 @@ void swift::ide::printSubmoduleInterface(
     return false;
   });
 
-  std::sort(SwiftDecls.begin(), SwiftDecls.end(),
-            [&](Decl *LHS, Decl *RHS) -> bool {
-    auto *LHSValue = dyn_cast<ValueDecl>(LHS);
-    auto *RHSValue = dyn_cast<ValueDecl>(RHS);
-
-    // If group is specified, we order the decls by their source order.
-    if (GroupName && LHS->getSourceOrder() && RHS->getSourceOrder()) {
-      return LHS->getSourceOrder().getValue() < RHS->getSourceOrder().getValue();
-    }
-
-    if (LHSValue && RHSValue) {
-      StringRef LHSName = LHSValue->getName().str();
-      StringRef RHSName = RHSValue->getName().str();
-      if (int Ret = LHSName.compare(RHSName))
-        return Ret < 0;
-      // FIXME: this is not sufficient to establish a total order for overloaded
-      // decls.
-      return LHS->getKind() < RHS->getKind();
-    }
+  // If the group name is specified, we sort them according to their source order,
+  // which is the order preserved by getTopLeveDecls.
+  if (!GroupName) {
+    std::sort(SwiftDecls.begin(), SwiftDecls.end(),
+      [&](Decl *LHS, Decl *RHS) -> bool {
+        auto *LHSValue = dyn_cast<ValueDecl>(LHS);
+        auto *RHSValue = dyn_cast<ValueDecl>(RHS);
+
+        if (LHSValue && RHSValue) {
+          StringRef LHSName = LHSValue->getName().str();
+          StringRef RHSName = RHSValue->getName().str();
+          if (int Ret = LHSName.compare(RHSName))
+            return Ret < 0;
+          // FIXME: this is not sufficient to establish a total order for overloaded
+          // decls.
+          return LHS->getKind() < RHS->getKind();
+        }
 
-    return LHS->getKind() < RHS->getKind();
-  });
+        return LHS->getKind() < RHS->getKind();
+      });
+  }
 
   ASTPrinter *PrinterToUse = &Printer;
 

lib/Serialization/ModuleFile.cpp

@@ -597,7 +597,6 @@ class ModuleFile::DeclCommentTableInfo {
     }
     result.Raw = RawComment(Comments);
     result.Group = endian::readNext<uint32_t, little, unaligned>(data);
-    result.SourceOrder = endian::readNext<uint32_t, little, unaligned>(data);
     return result;
   }
 };
@@ -1557,15 +1556,6 @@ Optional<StringRef> ModuleFile::getGroupNameForDecl(const Decl *D) const {
   return getGroupNameById(Triple.getValue().Group);
 }
 
-Optional<unsigned>
-ModuleFile::getSourceOrderForDecl(const Decl *D) const {
-  auto Triple = getCommentForDecl(D);
-  if (!Triple.hasValue()) {
-    return None;
-  }
-  return Triple.getValue().SourceOrder;
-}
-
 void ModuleFile::collectAllGroups(std::vector<StringRef> &Names) const {
   if (!GroupNamesMap)
     return;

lib/Serialization/Serialization.cpp

@@ -3415,7 +3415,6 @@ struct DeclCommentTableData {
   StringRef Brief;
   RawComment Raw;
   uint32_t Group;
-  uint32_t Order;
 };
 
 class DeclCommentTableInfo {
@@ -3448,9 +3447,6 @@ class DeclCommentTableInfo {
 
     // Group Id.
     dataLength += numLen;
-
-    // Source order.
-    dataLength += numLen;
     endian::Writer<little> writer(out);
     writer.write<uint32_t>(keyLength);
     writer.write<uint32_t>(dataLength);
@@ -3473,7 +3469,6 @@ class DeclCommentTableInfo {
       out << C.RawText;
     }
     writer.write<uint32_t>(data.Group);
-    writer.write<uint32_t>(data.Order);
   }
 };
 
@@ -3580,8 +3575,7 @@ static void writeDeclCommentTable(
 
       generator.insert(copyString(USRBuffer.str()),
                        { VD->getBriefComment(), Raw,
-                         GroupContext.getGroupSequence(VD),
-                         SourceOrder ++ });
+                         GroupContext.getGroupSequence(VD) });
       return true;
     }
   };

lib/Serialization/SerializedModuleLoader.cpp

@@ -494,11 +494,6 @@ SerializedASTFile::getGroupNameForDecl(const Decl *D) const {
   return File.getGroupNameForDecl(D);
 }
 
-Optional<unsigned>
-SerializedASTFile::getSourceOrderForDecl(const Decl *D) const {
-  return File.getSourceOrderForDecl(D);
-}
-
 void
 SerializedASTFile::collectAllGroups(std::vector<StringRef> &Names) const {
   File.collectAllGroups(Names);