[clang][modules] Serialize `Module::DefinitionLoc`

This is a prep patch for avoiding the quadratic number of calls to `HeaderSearch::lookupModule()` in `ASTReader` for each (transitively) loaded PCM file. (Specifically in the context of `clang-scan-deps`).

This patch explicitly serializes `Module::DefinitionLoc` so that we can stop relying on it being filled by the module map parser. This change also required change to the module map parser, where we used the absence of `DefinitionLoc` to determine whether a file came from a PCM file. We also need to make sure we consider the "containing" module map affecting when writing a PCM, so that it's not stripped during serialization, which ensures `DefinitionLoc` still ends up pointing to the correct offset. This is intended to be a NFC change.

Reviewed By: benlangmuir

Differential Revision: https://reviews.llvm.org/D150292

1 files changed, 5 insertions, 3 deletions

diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index c480719..c97642e 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -2016,10 +2016,12 @@ void ModuleMapParser::parseModuleDecl() {
   Module *ShadowingModule = nullptr;
   if (Module *Existing = Map.lookupModuleQualified(ModuleName, ActiveModule)) {
     // We might see a (re)definition of a module that we already have a
-    // definition for in two cases:
+    // definition for in three cases:
     //  - If we loaded one definition from an AST file and we've just found a
     //    corresponding definition in a module map file, or
-    bool LoadedFromASTFile = Existing->DefinitionLoc.isInvalid();
+    bool LoadedFromASTFile = Existing->IsFromModuleFile;
+    //  - If we previously inferred this module from different module map file.
+    bool Inferred = Existing->IsInferred;
     //  - If we're building a (preprocessed) module and we've just loaded the
     //    module map file from which it was created.
     bool ParsedAsMainInput =
@@ -2027,7 +2029,7 @@ void ModuleMapParser::parseModuleDecl() {
         Map.LangOpts.CurrentModule == ModuleName &&
         SourceMgr.getDecomposedLoc(ModuleNameLoc).first !=
             SourceMgr.getDecomposedLoc(Existing->DefinitionLoc).first;
-    if (!ActiveModule && (LoadedFromASTFile || ParsedAsMainInput)) {
+    if (!ActiveModule && (LoadedFromASTFile || Inferred || ParsedAsMainInput)) {
       // Skip the module definition.
       skipUntil(MMToken::RBrace);
       if (Tok.is(MMToken::RBrace))