[modules] Add -fmodules-local-submodule-visibility flag.

This flag specifies that the normal visibility rules should be used even for
local submodules (submodules of the currently-being-built module). Thus names
will only be visible if a header / module that declares them has actually been
included / imported, and not merely because a submodule that happened to be
built earlier declared those names. This also removes the need to modularize
bottom-up: textually-included headers will be included into every submodule
that includes them, since their include guards will not leak between modules.

So far, this only governs visibility of macros, not of declarations, so is not
ready for real use yet.

llvm-svn: 236350

1 files changed, 17 insertions, 28 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 8a3b9d5163f..7ea50e5003f 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2019,37 +2019,23 @@ void ASTWriter::WritePreprocessor(const Preprocessor &PP, bool IsModule) {
   // Loop over all the macro directives that are live at the end of the file,
   // emitting each to the PP section.
 
-  // Construct the list of macro directives that need to be serialized.
-  typedef std::pair<const IdentifierInfo *, MacroDirective *> MacroChain;
-  SmallVector<MacroChain, 2> MacroDirectives;
-  for (Preprocessor::macro_iterator
-         I = PP.macro_begin(/*IncludeExternalMacros=*/false),
-         E = PP.macro_end(/*IncludeExternalMacros=*/false);
-       I != E; ++I) {
-    MacroDirectives.push_back(std::make_pair(I->first, I->second.getLatest()));
-  }
-
+  // Construct the list of identifiers with macro directives that need to be
+  // serialized.
+  SmallVector<const IdentifierInfo *, 128> MacroIdentifiers;
+  for (auto &Id : PP.getIdentifierTable())
+    if (Id.second->hadMacroDefinition() &&
+        (!Id.second->isFromAST() ||
+         Id.second->hasChangedSinceDeserialization()))
+      MacroIdentifiers.push_back(Id.second);
   // Sort the set of macro definitions that need to be serialized by the
   // name of the macro, to provide a stable ordering.
-  int (*Cmp)(const MacroChain*, const MacroChain*) =
-    [](const MacroChain *A, const MacroChain *B) -> int {
-      return A->first->getName().compare(B->first->getName());
-    };
-  llvm::array_pod_sort(MacroDirectives.begin(), MacroDirectives.end(), Cmp);
+  std::sort(MacroIdentifiers.begin(), MacroIdentifiers.end(),
+            llvm::less_ptr<IdentifierInfo>());
 
   // Emit the macro directives as a list and associate the offset with the
   // identifier they belong to.
-  for (auto &Chain : MacroDirectives) {
-    const IdentifierInfo *Name = Chain.first;
-    MacroDirective *MD = Chain.second;
-
-    // If the macro or identifier need no updates, don't write the macro history
-    // for this one.
-    // FIXME: Chain the macro history instead of re-writing it.
-    if (MD && MD->isFromPCH() &&
-        Name->isFromAST() && !Name->hasChangedSinceDeserialization())
-      continue;
-
+  for (const IdentifierInfo *Name : MacroIdentifiers) {
+    MacroDirective *MD = PP.getLocalMacroDirectiveHistory(Name);
     auto StartOffset = Stream.GetCurrentBitNo();
 
     // Emit the macro directives in reverse source order.
@@ -2069,6 +2055,7 @@ void ASTWriter::WritePreprocessor(const Preprocessor &PP, bool IsModule) {
     }
 
     // Write out any exported module macros.
+    bool EmittedModuleMacros = false;
     if (IsModule) {
       auto Leafs = PP.getLeafModuleMacros(Name);
       SmallVector<ModuleMacro*, 8> Worklist(Leafs.begin(), Leafs.end());
@@ -2079,7 +2066,7 @@ void ASTWriter::WritePreprocessor(const Preprocessor &PP, bool IsModule) {
         // Emit a record indicating this submodule exports this macro.
         ModuleMacroRecord.push_back(
             getSubmoduleID(Macro->getOwningModule()));
-        ModuleMacroRecord.push_back(getMacroID(Macro->getMacroInfo()));
+        ModuleMacroRecord.push_back(getMacroRef(Macro->getMacroInfo(), Name));
         for (auto *M : Macro->overrides())
           ModuleMacroRecord.push_back(getSubmoduleID(M->getOwningModule()));
 
@@ -2090,10 +2077,12 @@ void ASTWriter::WritePreprocessor(const Preprocessor &PP, bool IsModule) {
         for (auto *M : Macro->overrides())
           if (++Visits[M] == M->getNumOverridingMacros())
             Worklist.push_back(M);
+
+        EmittedModuleMacros = true;
       }
     }
 
-    if (Record.empty())
+    if (Record.empty() && !EmittedModuleMacros)
       continue;
 
     IdentMacroDirectivesOffsetMap[Name] = StartOffset;