[modules] Stop trying to fake up a linear MacroDirective history.

Modules builds fundamentally have a non-linear macro history. In the interest
of better source fidelity, represent the macro definition information
faithfully: we have a linear macro directive history within each module, and at
any point we have a unique "latest" local macro directive and a collection of
visible imported directives. This also removes the attendent complexity of
attempting to create a correct MacroDirective history (which we got wrong
in the general case).

No functionality change intended.

llvm-svn: 236176

1 files changed, 6 insertions, 4 deletions

diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 92ab2af..cd00be8 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -73,8 +73,7 @@ Preprocessor::Preprocessor(IntrusiveRefCntPtr<PreprocessorOptions> PPOpts,
       ModuleImportExpectsIdentifier(false), CodeCompletionReached(0),
       MainFileDir(nullptr), SkipMainFilePreamble(0, true), CurPPLexer(nullptr),
       CurDirLookup(nullptr), CurLexerKind(CLK_Lexer), CurSubmodule(nullptr),
-      Callbacks(nullptr), MacroVisibilityGeneration(0),
-      MacroArgCache(nullptr), Record(nullptr),
+      Callbacks(nullptr), MacroArgCache(nullptr), Record(nullptr),
       MIChainHead(nullptr), DeserialMIChainHead(nullptr) {
   OwnsHeaderSearch = OwnsHeaders;
   
@@ -108,6 +107,9 @@ Preprocessor::Preprocessor(IntrusiveRefCntPtr<PreprocessorOptions> PPOpts,
 
   // We haven't read anything from the external source.
   ReadMacrosFromExternalSource = false;
+  // We might already have some macros from an imported module (via a PCH or
+  // preamble) if modules is enabled.
+  MacroVisibilityGeneration = LangOpts.Modules ? 1 : 0;
   
   // "Poison" __VA_ARGS__, which can only appear in the expansion of a macro.
   // This gets unpoisoned where it is allowed.
@@ -623,8 +625,8 @@ bool Preprocessor::HandleIdentifier(Token &Identifier) {
   }
 
   // If this is a macro to be expanded, do it.
-  if (MacroDirective *MD = getMacroDirective(&II)) {
-    MacroInfo *MI = MD->getMacroInfo();
+  if (MacroDefinition MD = getMacroDefinition(&II)) {
+    auto *MI = MD.getMacroInfo();
     if (!DisableMacroExpansion) {
       if (!Identifier.isExpandDisabled() && MI->isEnabled()) {
         // C99 6.10.3p10: If the preprocessing token immediately after the