[modules] Build a DAG of module macros for each identifier.

This graph will be used to determine the current set of active macros. This is
foundation work for getting macro visibility correct across submodules of the
current module. No functionality change for now.

llvm-svn: 235461

1 files changed, 40 insertions, 0 deletions

diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 3ceba05401a..4c6aa4e45ac 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -72,6 +72,46 @@ void Preprocessor::setLoadedMacroDirective(IdentifierInfo *II,
     II->setHasMacroDefinition(false);
 }
 
+ModuleMacro *Preprocessor::addModuleMacro(unsigned ModuleID, IdentifierInfo *II,
+                                          MacroInfo *Macro,
+                                          ArrayRef<ModuleMacro *> Overrides,
+                                          bool &New) {
+  llvm::FoldingSetNodeID ID;
+  ModuleMacro::Profile(ID, ModuleID, II);
+
+  void *InsertPos;
+  if (auto *MM = ModuleMacros.FindNodeOrInsertPos(ID, InsertPos)) {
+    New = false;
+    return MM;
+  }
+
+  auto *MM = ModuleMacro::create(*this, ModuleID, II, Macro, Overrides);
+  ModuleMacros.InsertNode(MM, InsertPos);
+
+  // Each overridden macro is now overridden by one more macro.
+  bool HidAny = false;
+  for (auto *O : Overrides) {
+    HidAny |= (O->NumOverriddenBy == 0);
+    ++O->NumOverriddenBy;
+  }
+
+  // If we were the first overrider for any macro, it's no longer a leaf.
+  auto &LeafMacros = LeafModuleMacros[II];
+  if (HidAny) {
+    LeafMacros.erase(std::remove_if(LeafMacros.begin(), LeafMacros.end(),
+                                    [](ModuleMacro *MM) {
+                                      return MM->NumOverriddenBy != 0;
+                                    }),
+                     LeafMacros.end());
+  }
+
+  // The new macro is always a leaf macro.
+  LeafMacros.push_back(MM);
+
+  New = true;
+  return MM;
+}
+
 /// RegisterBuiltinMacro - Register the specified identifier in the identifier
 /// table and mark it as a builtin macro to be expanded.
 static IdentifierInfo *RegisterBuiltinMacro(Preprocessor &PP, const char *Name){