[C++20] [Modules] Skip ODR checks in implicit global modules

Previously we skipped the ODR checks in explicit global modules. And due
to similar reasons, we should skip the ODR checks in implicit global
modules too.

Author: ChuanqiXu9

clang/include/clang/AST/DeclBase.h

@@ -673,6 +673,9 @@ class alignas(8) Decl {
   /// Whether this declaration comes from explicit global module.
   bool isFromExplicitGlobalModule() const;
 
+  /// Whether this declaration comes from global module.
+  bool isFromGlobalModule() const;
+
   /// Whether this declaration comes from a named module.
   bool isInNamedModule() const;
 

clang/include/clang/Serialization/ASTReader.h

@@ -2478,7 +2478,7 @@ class BitsUnpacker {
 
 inline bool shouldSkipCheckingODR(const Decl *D) {
   return D->getASTContext().getLangOpts().SkipODRCheckInGMF &&
-         D->isFromExplicitGlobalModule();
+         D->isFromGlobalModule();
 }
 
 } // namespace clang

clang/lib/AST/DeclBase.cpp

@@ -1144,6 +1144,10 @@ bool Decl::isFromExplicitGlobalModule() const {
   return getOwningModule() && getOwningModule()->isExplicitGlobalModule();
 }
 
+bool Decl::isFromGlobalModule() const {
+  return getOwningModule() && getOwningModule()->isGlobalModule();
+}
+
 bool Decl::isInNamedModule() const {
   return getOwningModule() && getOwningModule()->isNamedModule();
 }

clang/test/Modules/skip-odr-check-in-gmf.cppm

@@ -35,22 +35,28 @@ module;
 export module a;
 export using ::func;
 
+export extern "C++" bool func1() { return true; }
+
 //--- b.cppm
 module;
 #include "func2.h"
 export module b;
 export using ::func;
 
+export extern "C++" bool func1() { return false; }
+
 //--- test.cc
 import a;
 import b;
 bool test() {
-    return func(1, 2);
+    return func(1, 2) && func1();
 }
 
 #ifdef IGNORE_ODR_VIOLATION
 // expected-no-diagnostics
 #else
 // [email protected]:1 {{'func' has different definitions in different modules;}}
 // [email protected]:1 {{but in 'a.<global>' found a different body}}
+// [email protected]:6 {{'func1' has different definitions in different modules; definition in module 'b.<implicit global>' first difference is function body}}
+// [email protected]:6 {{but in 'a.<implicit global>' found a different body}}
 #endif