From 79fa0ec8c4bfeeb21f7b44ebd9a66e7ec9781798 Mon Sep 17 00:00:00 2001
From: Chuanqi Xu <yedeng.yd@linux.alibaba.com>
Date: Tue, 13 Sep 2022 13:03:34 +0800
Subject: [PATCH] [C++20] [Modules] Make member functions with a in-class
 definition in HU implicitly inline

According to [dcl.inline]p7/note4,

> In the global module, a function defined within a class definition is
> implicitly inline.

And the declarations in the header unit are attached to the global
module fragment. So the function defined within a class definition in
header units should be implicitly inline too.

This fixes https://github.com/llvm/llvm-project/issues/57571.
---
 clang/lib/Sema/SemaDecl.cpp                        |  2 +-
 .../header-unit-friend-within-class-linkage.cpp    | 27 ++++++++++++++
 .../CodeGenCXX/header-unit-member-func-linkage.cpp | 24 ++++++++++++
 clang/unittests/AST/DeclTest.cpp                   | 43 ++++++++++++++++++++++
 4 files changed, 95 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CodeGenCXX/header-unit-friend-within-class-linkage.cpp
 create mode 100644 clang/test/CodeGenCXX/header-unit-member-func-linkage.cpp

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 9d0e676..b1c4539 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -9503,7 +9503,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     bool ImplicitInlineCXX20 = !getLangOpts().CPlusPlusModules ||
                                !NewFD->getOwningModule() ||
                                NewFD->getOwningModule()->isGlobalModule() ||
-                               NewFD->getOwningModule()->isModuleMapModule();
+                               NewFD->getOwningModule()->isHeaderLikeModule();
     bool isInline = D.getDeclSpec().isInlineSpecified();
     bool isVirtual = D.getDeclSpec().isVirtualSpecified();
     bool hasExplicit = D.getDeclSpec().hasExplicitSpecifier();
diff --git a/clang/test/CodeGenCXX/header-unit-friend-within-class-linkage.cpp b/clang/test/CodeGenCXX/header-unit-friend-within-class-linkage.cpp
new file mode 100644
index 0000000..cfee317
--- /dev/null
+++ b/clang/test/CodeGenCXX/header-unit-friend-within-class-linkage.cpp
@@ -0,0 +1,27 @@
+// Tests that the friend function with-in an class definition in the header unit is still implicit inline.
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -xc++-user-header -emit-header-unit %t/foo.h -o %t/foo.pcm
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -fmodule-file=%t/foo.pcm %t/user.cpp \
+// RUN:   -S -emit-llvm -disable-llvm-passes -o - | FileCheck %t/user.cpp
+
+//--- foo.h
+class foo {
+    int value;
+public:
+    foo(int v) : value(v) {}
+
+    friend int getFooValue(foo f) {
+        return f.value;
+    }
+};
+
+//--- user.cpp
+import "foo.h";
+int use() {
+    foo f(43);
+    return getFooValue(f);
+}
+
+// CHECK: define{{.*}}linkonce_odr{{.*}}@_Z11getFooValue3foo
diff --git a/clang/test/CodeGenCXX/header-unit-member-func-linkage.cpp b/clang/test/CodeGenCXX/header-unit-member-func-linkage.cpp
new file mode 100644
index 0000000..5ab15df
--- /dev/null
+++ b/clang/test/CodeGenCXX/header-unit-member-func-linkage.cpp
@@ -0,0 +1,24 @@
+// Tests that the member function with-in an class definition in the header unit is still implicit inline.
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -xc++-user-header -emit-header-unit %t/foo.h -o %t/foo.pcm
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple -fmodule-file=%t/foo.pcm %t/user.cpp \
+// RUN:   -S -emit-llvm -disable-llvm-passes -o - | FileCheck %t/user.cpp
+
+//--- foo.h
+class foo {
+public:
+    int getValue() {
+        return 43;
+    }
+};
+
+//--- user.cpp
+import "foo.h";
+int use() {
+    foo f;
+    return f.getValue();
+}
+
+// CHECK: define{{.*}}linkonce_odr{{.*}}@_ZN3foo8getValueEv
diff --git a/clang/unittests/AST/DeclTest.cpp b/clang/unittests/AST/DeclTest.cpp
index 7fe715db..43a3798 100644
--- a/clang/unittests/AST/DeclTest.cpp
+++ b/clang/unittests/AST/DeclTest.cpp
@@ -311,3 +311,46 @@ TEST(Decl, MemberFunctionInModules) {
   EXPECT_TRUE(bar->isInlined());
 }
 
+TEST(Decl, MemberFunctionInHeaderUnit) {
+  llvm::Annotations Code(R"(
+    class foo {
+    public:
+      int memFn() {
+        return 43;
+      }
+    };
+    )");
+
+  auto AST = tooling::buildASTFromCodeWithArgs(
+      Code.code(), {"-std=c++20", " -xc++-user-header ", "-emit-header-unit"});
+  ASTContext &Ctx = AST->getASTContext();
+
+  auto *memFn = selectFirst<FunctionDecl>(
+      "memFn", match(functionDecl(hasName("memFn")).bind("memFn"), Ctx));
+
+  EXPECT_TRUE(memFn->isInlined());
+}
+
+TEST(Decl, FriendFunctionWithinClassInHeaderUnit) {
+  llvm::Annotations Code(R"(
+    class foo {
+      int value;
+    public:
+      foo(int v) : value(v) {}
+
+      friend int getFooValue(foo f) {
+        return f.value;
+      }
+    };
+    )");
+
+  auto AST = tooling::buildASTFromCodeWithArgs(
+      Code.code(), {"-std=c++20", " -xc++-user-header ", "-emit-header-unit"});
+  ASTContext &Ctx = AST->getASTContext();
+
+  auto *getFooValue = selectFirst<FunctionDecl>(
+      "getFooValue",
+      match(functionDecl(hasName("getFooValue")).bind("getFooValue"), Ctx));
+
+  EXPECT_TRUE(getFooValue->isInlined());
+}
-- 
2.7.4