[clang] [C++20] [Modules] Fix the duplicated static initializer problem (PR #114193)

[Chuanqi Xu via cfe-commits]

https://github.com/ChuanqiXu9 created https://github.com/llvm/llvm-project/pull/114193

Reproducer:

```
//--- a.cppm
export module a;
int func();
static int a = func();

//--- a.cpp
import a;
```

The `func()` should only execute once. However, before this patch we will somehow import `static int a` from a.cppm incorrectly and initialize that again.

This is super bad and can introduce serious runtime behaviors.

And also surprisingly, it looks like the root cause of the problem is simply some oversight choosing APIs.

>From a0139db2a3be898f7d548e6796636419816dbca1 Mon Sep 17 00:00:00 2001
From: Chuanqi Xu <yedeng.yd at linux.alibaba.com>
Date: Wed, 30 Oct 2024 16:48:52 +0800
Subject: [PATCH] [C++20] [Modules] Fix the duplicated static initializer
 problem

Reproducer:

```
//--- a.cppm
export module a;
int func();
static int a = func();

//--- a.cpp
import a;
```

The `func()` should only execute once. However, before this patch
we will somehow import `static int a` from a.cppm incorrectly and
initialize that again.

This is super bad and can introduce serious runtime behaviors.

And also surprisingly, it looks like the root cause of the problem is
simply some oversight choosing APIs.
---
 clang/lib/CodeGen/CodeGenModule.cpp        |  4 ++--
 clang/test/Modules/static-initializer.cppm | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/Modules/static-initializer.cppm

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 2bcca5e85bdfeb..ba376f9ecfacde 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -7146,8 +7146,8 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
     // For C++ standard modules we are done - we will call the module
     // initializer for imported modules, and that will likewise call those for
     // any imports it has.
-    if (CXX20ModuleInits && Import->getImportedOwningModule() &&
-        !Import->getImportedOwningModule()->isModuleMapModule())
+    if (CXX20ModuleInits && Import->getImportedModule() &&
+        Import->getImportedModule()->isNamedModule())
       break;
 
     // For clang C++ module map modules the initializers for sub-modules are
diff --git a/clang/test/Modules/static-initializer.cppm b/clang/test/Modules/static-initializer.cppm
new file mode 100644
index 00000000000000..10d4854ee67fa6
--- /dev/null
+++ b/clang/test/Modules/static-initializer.cppm
@@ -0,0 +1,18 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/a.cppm -emit-module-interface -o %t/a.pcm
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/a.cpp -fmodule-file=a=%t/a.pcm -emit-llvm -o - | FileCheck %t/a.cpp
+
+//--- a.cppm
+export module a;
+int func();
+static int a = func();
+
+//--- a.cpp
+import a;
+
+// CHECK-NOT: internal global
+// CHECK-NOT: __cxx_global_var_init
+