[C++20] [Modules] Handle initializer for Header Units

[ChuanqiXu]

Summary

Previously when we add module initializer, we forget to handle header units. This results that we couldn't compile a Hello World Example with Header Units. This patch tries to fix this.

[ChuanqiXu]

clang/lib/CodeGen/CodeGenModule.cpp

2524–2525

See the example about M.cppm.

[iains]

LGTM, one small point about the test,

clang/test/CodeGenCXX/module-initializer-header.cppm

5–7

you could use -triple %itanium_abi_triple which would increase the test coverage to other titanium platforms.

clang/lib/CodeGen/CGDeclCXX.cpp

void CodeGenModule::EmitCXXModuleInitFunc(Module *Primary) {
   for (auto I : Primary->Exports)
     AllImports.push_back(I.getPointer());
   // Ones that we only import.
   for (Module *M : Primary->Imports)
     AllImports.push_back(M);
 
   SmallVector<llvm::Function *, 8> ModuleInits;
   for (Module *M : AllImports) {
-    // No Itanium initializer in module map modules.
-    if (M->isModuleMapModule())
+    // No Itanium initializer in header like modules.
+    if (M->isHeaderLikeModule())
       continue; // TODO: warn of mixed use of module map modules and C++20?
     llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
     SmallString<256> FnName;
     {
       llvm::raw_svector_ostream Out(FnName);
       cast<ItaniumMangleContext>(getCXXABI().getMangleContext())
           .mangleModuleInitializer(M, Out);
     }

 CodeGenModule::EmitCXXGlobalInitFunc() {
   while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
     CXXGlobalInits.pop_back();
 
   // When we import C++20 modules, we must run their initializers first.
   SmallVector<llvm::Function *, 8> ModuleInits;
   if (CXX20ModuleInits)
     for (Module *M : ImportedModules) {
-      // No Itanium initializer in module map modules.
-      if (M->isModuleMapModule())
+      // No Itanium initializer in header like modules.
+      if (M->isHeaderLikeModule())
         continue;
       llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
       SmallString<256> FnName;
       {
         llvm::raw_svector_ostream Out(FnName);
         cast<ItaniumMangleContext>(getCXXABI().getMangleContext())
             .mangleModuleInitializer(M, Out);
       }

clang/lib/CodeGen/CodeGenModule.cpp

for (llvm::GlobalValue &GV : M.global_values()) {
     }
 
     GV.setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass);
   }
 }
 
 void CodeGenModule::Release() {
   Module *Primary = getContext().getModuleForCodeGen();
-  if (CXX20ModuleInits && Primary && !Primary->isModuleMapModule())
+  if (CXX20ModuleInits && Primary && !Primary->isHeaderLikeModule())
     EmitModuleInitializers(Primary);
   EmitDeferred();
   DeferredDecls.insert(EmittedDeferredDecls.begin(),
                        EmittedDeferredDecls.end());
   EmittedDeferredDecls.clear();
   EmitVTablesOpportunistically();
   applyGlobalValReplacements();
   applyReplacements();
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?");
+      if (isa<ImportDecl>(D))
+        continue;
+      assert(isa<VarDecl>(D) && "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)
+    if (isa<ImportDecl>(D))
       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?");
+      assert(isa<VarDecl>(D) && "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

clang/test/CodeGenCXX/module-initializer-header.cppm

+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -triple=x86_64-unknown-linux-gnu -xc++-user-header -emit-header-unit %t/header.h -o %t/header.pcm
+// RUN: %clang_cc1 -std=c++20 -triple=x86_64-unknown-linux-gnu -fmodule-file=%t/header.pcm %t/M.cppm -S -emit-llvm -o - | FileCheck %t/M.cppm
+// RUN: %clang_cc1 -std=c++20 -triple=x86_64-unknown-linux-gnu -fmodule-file=%t/header.pcm %t/Use.cpp -S -emit-llvm -o - | FileCheck %t/Use.cpp
+//
+//--- header.h
+int foo();
+int i = foo();
+
+//--- M.cppm
+module;
+import "header.h";
+export module M;
+
+// CHECK: @i = global i32 0
+// CHECK: void @__cxx_global_var_init()
+// CHECK-NEXT: entry:
+// CHECK-NEXT:  %call = call noundef i32 @_Z3foov()
+// CHECK-NEXT:  store i32 %call, ptr @i  
+
+//--- Use.cpp
+import "header.h";
+
+// CHECK: @i = global i32 0
+// CHECK: void @__cxx_global_var_init()
+// CHECK-NEXT: entry:
+// CHECK-NEXT:  %call = call noundef i32 @_Z3foov()
+// CHECK-NEXT:  store i32 %call, ptr @i