[NFC] [C++20] [Modules] Refactor the warning to '-fmodule-file=<BMIPath>' for C++20 modules

Previous implementation of the warning to use `-fmodule-file=<BMIPath>`
for C++20 Modules is not straightforward and it is problematic in case
we read the BMIPath by writing tools based clang components. This patch
refactors it with a simple and direct style.

3 files changed, 18 insertions, 13 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index e500675..49c1d8e 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1717,7 +1717,8 @@ void CompilerInstance::createASTReader() {
     Listener->attachToASTReader(*TheASTReader);
 }
 
-bool CompilerInstance::loadModuleFile(StringRef FileName) {
+bool CompilerInstance::loadModuleFile(
+    StringRef FileName, serialization::ModuleFile *&LoadedModuleFile) {
   llvm::Timer Timer;
   if (FrontendTimerGroup)
     Timer.init("preloading." + FileName.str(), "Preloading " + FileName.str(),
@@ -1743,7 +1744,8 @@ bool CompilerInstance::loadModuleFile(StringRef FileName) {
   // Try to load the module file.
   switch (TheASTReader->ReadAST(
       FileName, serialization::MK_ExplicitModule, SourceLocation(),
-      ConfigMismatchIsRecoverable ? ASTReader::ARR_ConfigurationMismatch : 0)) {
+      ConfigMismatchIsRecoverable ? ASTReader::ARR_ConfigurationMismatch : 0,
+      &LoadedModuleFile)) {
   case ASTReader::Success:
     // We successfully loaded the module file; remember the set of provided
     // modules so that we don't try to load implicit modules for them.
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 2da25be..e016b94 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -1023,10 +1023,16 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
   }
 
   // If we were asked to load any module files, do so now.
-  for (const auto &ModuleFile : CI.getFrontendOpts().ModuleFiles)
-    if (!CI.loadModuleFile(ModuleFile))
+  for (const auto &ModuleFile : CI.getFrontendOpts().ModuleFiles) {
+    serialization::ModuleFile *Loaded = nullptr;
+    if (!CI.loadModuleFile(ModuleFile, Loaded))
       return false;
 
+    if (Loaded && Loaded->StandardCXXModule)
+      CI.getDiagnostics().Report(
+          diag::warn_eagerly_load_for_standard_cplusplus_modules);
+  }
+
   // If there is a layout overrides file, attach an external AST source that
   // provides the layouts from that file.
   if (!CI.getFrontendOpts().OverrideRecordLayoutsFile.empty() &&
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index faeea66..8ece979 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -4311,10 +4311,10 @@ static bool SkipCursorToBlock(BitstreamCursor &Cursor, unsigned BlockID) {
   }
 }
 
-ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
-                                            ModuleKind Type,
+ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName, ModuleKind Type,
                                             SourceLocation ImportLoc,
-                                            unsigned ClientLoadCapabilities) {
+                                            unsigned ClientLoadCapabilities,
+                                            ModuleFile **NewLoadedModuleFile) {
   llvm::TimeTraceScope scope("ReadAST", FileName);
 
   llvm::SaveAndRestore SetCurImportLocRAII(CurrentImportLoc, ImportLoc);
@@ -4344,6 +4344,9 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
     return ReadResult;
   }
 
+  if (NewLoadedModuleFile && !Loaded.empty())
+    *NewLoadedModuleFile = Loaded.back().Mod;
+
   // Here comes stuff that we only do once the entire chain is loaded. Do *not*
   // remove modules from this point. Various fields are updated during reading
   // the AST block and removing the modules would result in dangling pointers.
@@ -5709,12 +5712,6 @@ llvm::Error ASTReader::ReadSubmoduleBlock(ModuleFile &F,
       if (DeserializationListener)
         DeserializationListener->ModuleRead(GlobalID, CurrentModule);
 
-      // If we're loading a module before we initialize the sema, it implies
-      // we're performing eagerly loading.
-      if (!getSema() && CurrentModule->isModulePurview() &&
-          !getContext().getLangOpts().isCompilingModule())
-        Diag(clang::diag::warn_eagerly_load_for_standard_cplusplus_modules);
-
       SubmodulesLoaded[GlobalIndex] = CurrentModule;
 
       // Clear out data that will be replaced by what is in the module file.