[modules] Separately track whether an identifier's preprocessor information and

name lookup information have changed since deserialization. For a C++ modules
build, we do not need to re-emit the identifier into the serialized identifier
table if only the name lookup information has changed (and in all cases, we
don't need to re-emit the macro information if only the name lookup information
has changed).

llvm-svn: 259901

3 files changed, 7 insertions, 2 deletions

diff --git a/clang/lib/Basic/IdentifierTable.cpp b/clang/lib/Basic/IdentifierTable.cpp
index 67de1cb6fda..d6ad0f5c915 100644
--- a/clang/lib/Basic/IdentifierTable.cpp
+++ b/clang/lib/Basic/IdentifierTable.cpp
@@ -42,6 +42,7 @@ IdentifierInfo::IdentifierInfo() {
   NeedsHandleIdentifier = false;
   IsFromAST = false;
   ChangedAfterLoad = false;
+  FEChangedAfterLoad = false;
   RevertedTokenID = false;
   OutOfDate = false;
   IsModulesImport = false;
diff --git a/clang/lib/Sema/IdentifierResolver.cpp b/clang/lib/Sema/IdentifierResolver.cpp
index 53263bac546..0bdb19490bc 100644
--- a/clang/lib/Sema/IdentifierResolver.cpp
+++ b/clang/lib/Sema/IdentifierResolver.cpp
@@ -381,7 +381,7 @@ void IdentifierResolver::updatingIdentifier(IdentifierInfo &II) {
     PP.getExternalSource()->updateOutOfDateIdentifier(II);
   
   if (II.isFromAST())
-    II.setChangedSinceDeserialization();
+    II.setFETokenInfoChangedSinceDeserialization();
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 0b28a7aa673..3e153327923 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3162,6 +3162,8 @@ public:
         NeedDecls(!IsModule || !Writer.getLangOpts().CPlusPlus),
         InterestingIdentifierOffsets(InterestingIdentifierOffsets) {}
 
+  bool needDecls() const { return NeedDecls; }
+
   static hash_value_type ComputeHash(const IdentifierInfo* II) {
     return llvm::HashString(II->getName());
   }
@@ -3307,7 +3309,9 @@ void ASTWriter::WriteIdentifierTable(Preprocessor &PP,
       auto *II = const_cast<IdentifierInfo *>(IdentIDPair.first);
       IdentID ID = IdentIDPair.second;
       assert(II && "NULL identifier in identifier table");
-      if (!Chain || !II->isFromAST() || II->hasChangedSinceDeserialization())
+      if (!Chain || !II->isFromAST() || II->hasChangedSinceDeserialization() ||
+          (Trait.needDecls() &&
+           II->hasFETokenInfoChangedSinceDeserialization()))
         Generator.insert(II, ID, Trait);
     }