1 files changed, 53 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 56ed59d1e3f1..e282bc820255 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -136,6 +136,13 @@ CodeGenModule::CodeGenModule(ASTContext &C, const HeaderSearchOptions &HSO,
   GlobalsInt8PtrTy = Int8Ty->getPointerTo(DL.getDefaultGlobalsAddressSpace());
   ASTAllocaAddressSpace = getTargetCodeGenInfo().getASTAllocaAddressSpace();
 
+  // Build C++20 Module initializers.
+  // TODO: Add Microsoft here once we know the mangling required for the
+  // initializers.
+  CXX20ModuleInits =
+      LangOpts.CPlusPlusModules && getCXXABI().getMangleContext().getKind() ==
+                                       ItaniumMangleContext::MK_Itanium;
+
   RuntimeCC = getTargetCodeGenInfo().getABIInfo().getRuntimeCC();
 
   if (LangOpts.ObjC)
@@ -509,12 +516,18 @@ static void setVisibilityFromDLLStorageClass(const clang::LangOptions &LO,
 }
 
 void CodeGenModule::Release() {
+  Module *Primary = getContext().getModuleForCodeGen();
+  if (CXX20ModuleInits && Primary)
+    EmitModuleInitializers(Primary);
   EmitDeferred();
   EmitVTablesOpportunistically();
   applyGlobalValReplacements();
   applyReplacements();
   emitMultiVersionFunctions();
-  EmitCXXGlobalInitFunc();
+  if (CXX20ModuleInits && Primary && Primary->isInterfaceOrPartition())
+    EmitCXXModuleInitFunc(Primary);
+  else
+    EmitCXXGlobalInitFunc();
   EmitCXXGlobalCleanUpFunc();
   registerGlobalDtorsWithAtExit();
   EmitCXXThreadLocalInitFunc();
@@ -2491,6 +2504,31 @@ static void addLinkOptionsPostorder(CodeGenModule &CGM, Module *Mod,
   }
 }
 
+void CodeGenModule::EmitModuleInitializers(clang::Module *Primary) {
+  // Emit the initializers in the order that sub-modules appear in the
+  // source, first Global Module Fragments, if present.
+  if (auto GMF = Primary->getGlobalModuleFragment()) {
+    for (Decl *D : getContext().getModuleInitializers(GMF)) {
+      assert(D->getKind() == Decl::Var && "GMF initializer decl is not a var?");
+      EmitTopLevelDecl(D);
+    }
+  }
+  // Second any associated with the module, itself.
+  for (Decl *D : getContext().getModuleInitializers(Primary)) {
+    // Skip import decls, the inits for those are called explicitly.
+    if (D->getKind() == Decl::Import)
+      continue;
+    EmitTopLevelDecl(D);
+  }
+  // Third any associated with the Privat eMOdule Fragment, if present.
+  if (auto PMF = Primary->getPrivateModuleFragment()) {
+    for (Decl *D : getContext().getModuleInitializers(PMF)) {
+      assert(D->getKind() == Decl::Var && "PMF initializer decl is not a var?");
+      EmitTopLevelDecl(D);
+    }
+  }
+}
+
 void CodeGenModule::EmitModuleLinkOptions() {
   // Collect the set of all of the modules we want to visit to emit link
   // options, which is essentially the imported modules and all of their
@@ -2896,12 +2934,19 @@ bool CodeGenModule::MayBeEmittedEagerly(const ValueDecl *Global) {
       // explicitly instantiated, so they should not be emitted eagerly.
       return false;
   }
-  if (const auto *VD = dyn_cast<VarDecl>(Global))
+  if (const auto *VD = dyn_cast<VarDecl>(Global)) {
     if (Context.getInlineVariableDefinitionKind(VD) ==
         ASTContext::InlineVariableDefinitionKind::WeakUnknown)
       // A definition of an inline constexpr static data member may change
       // linkage later if it's redeclared outside the class.
       return false;
+    if (CXX20ModuleInits && VD->getOwningModule()) {
+      // For CXX20, module-owned initializers need to be deferred, since it is
+      // not known at this point if they will be run for the current module or
+      // as part of the initializer for an imported one.
+      return false;
+    }
+  }
   // If OpenMP is enabled and threadprivates must be generated like TLS, delay
   // codegen for global variables, because they may be marked as threadprivate.
   if (LangOpts.OpenMP && LangOpts.OpenMPUseTLS &&
@@ -6198,6 +6243,12 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
         DI->EmitImportDecl(*Import);
     }
 
+    // For CXX20 we are done - we will call the module initializer for the
+    // imported module, and that will likewise call those for any imports it
+    // has.
+    if (CXX20ModuleInits)
+      break;
+
     // Find all of the submodules and emit the module initializers.
     llvm::SmallPtrSet<clang::Module *, 16> Visited;
     SmallVector<clang::Module *, 16> Stack;