[clang] [clang][Itanium Mangle] Enable mangling of enclosing class for member… (PR #110503)

[Viktoriia Bakalova via cfe-commits]

https://github.com/VitaNuo updated https://github.com/llvm/llvm-project/pull/110503

>From f22108bcbe97365a29e134ecd496533641f901fb Mon Sep 17 00:00:00 2001
From: Viktoriia Bakalova <bakalova at google.com>
Date: Mon, 30 Sep 2024 12:50:09 +0000
Subject: [PATCH] [clang][Itanium Mangle] Enable mangling of enclosing class
 for member-like friend function templates only if ` -fclang-abi-compat>=19`.

---
 clang/docs/ReleaseNotes.rst              |  2 +-
 clang/include/clang/Basic/LangOptions.h  |  3 ++-
 clang/lib/AST/ItaniumMangle.cpp          | 11 ++++++++++-
 clang/test/CodeGenCXX/mangle-concept.cpp |  4 ++++
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 35c31452cef411..d824213d700905 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -104,6 +104,7 @@ ABI Changes in This Version
 
 - Fixed Microsoft name mangling of placeholder, auto and decltype(auto), return types for MSVC 1920+. This change resolves incompatibilities with code compiled by MSVC 1920+ but will introduce incompatibilities with code compiled by earlier versions of Clang unless such code is built with the compiler option -fms-compatibility-version=19.14 to imitate the MSVC 1914 mangling behavior.
 - Fixed the Itanium mangling of the construction vtable name. This change will introduce incompatibilities with code compiled by Clang 19 and earlier versions, unless the -fclang-abi-compat=19 option is used. (#GH108015)
+- Mangle friend function templates with a constraint that depends on a template parameter from an enclosing template as members of the enclosing class. (#GH110247, #GH110503)
 
 AST Dumping Potentially Breaking Changes
 ----------------------------------------
@@ -447,7 +448,6 @@ Bug Fixes to C++ Support
 - Fixed an assertion failure in debug mode, and potential crashes in release mode, when
   diagnosing a failed cast caused indirectly by a failed implicit conversion to the type of the constructor parameter.
 - Fixed an assertion failure by adjusting integral to boolean vector conversions (#GH108326)
-- Mangle friend function templates with a constraint that depends on a template parameter from an enclosing template as members of the enclosing class. (#GH110247)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
index 8c605f6852016e..f5fa1bd8df1967 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -241,8 +241,9 @@ class LangOptionsBase {
 
     /// Attempt to be ABI-compatible with code generated by Clang 19.0.x.
     /// This causes clang to:
-    ///   - Incorrectly mangles the 'base type' substitutions of the CXX
+    ///   - Incorrectly mangle the 'base type' substitutions of the CXX
     ///   construction vtable because it hasn't added 'type' as a substitution.
+    ///   - Skip mangling enclosing class templates of member-like friend function templates.
     Ver19,
 
     /// Conform to the underlying platform's C and C++ ABIs as closely
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 117255178eebb4..3d9d1e3f22f832 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -693,7 +693,7 @@ ItaniumMangleContextImpl::getEffectiveDeclContext(const Decl *D) {
     if (VD->isExternC())
       return getASTContext().getTranslationUnitDecl();
 
-  if (const auto *FD = D->getAsFunction()) {
+  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
     if (FD->isExternC())
       return getASTContext().getTranslationUnitDecl();
     // Member-like constrained friends are mangled as if they were members of
@@ -704,6 +704,15 @@ ItaniumMangleContextImpl::getEffectiveDeclContext(const Decl *D) {
       return D->getLexicalDeclContext()->getRedeclContext();
   }
 
+  if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(D)) {
+    // Member-like constrained friends are mangled as if they were members of
+    // the enclosing class.
+    if (FTD->getTemplatedDecl()->isMemberLikeConstrainedFriend() &&
+        getASTContext().getLangOpts().getClangABICompat() >
+            LangOptions::ClangABI::Ver19)
+      return D->getLexicalDeclContext()->getRedeclContext();
+  }
+
   return DC->getRedeclContext();
 }
 
diff --git a/clang/test/CodeGenCXX/mangle-concept.cpp b/clang/test/CodeGenCXX/mangle-concept.cpp
index 6053511c00a7b5..aa0940c35b237a 100644
--- a/clang/test/CodeGenCXX/mangle-concept.cpp
+++ b/clang/test/CodeGenCXX/mangle-concept.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -verify -std=c++20 -emit-llvm -triple %itanium_abi_triple -o - %s -fclang-abi-compat=latest | FileCheck %s
+// RUN: %clang_cc1 -verify -std=c++20 -emit-llvm -triple %itanium_abi_triple -o - %s -fclang-abi-compat=19 | FileCheck %s --check-prefix=CLANG19
 // RUN: %clang_cc1 -verify -std=c++20 -emit-llvm -triple %itanium_abi_triple -o - %s -fclang-abi-compat=17 | FileCheck %s --check-prefix=CLANG17
 // expected-no-diagnostics
 
@@ -59,18 +60,21 @@ namespace test2 {
     // CLANG17: call {{.*}}@_ZN5test21fEz(
     f(ai);
     // CHECK: call {{.*}}@_ZN5test21AIiEF1gIvEEvzQaa4TrueIT_E4TrueITL0__E(
+    // CLANG19: call {{.*}}@_ZN5test2F1gIvEEvzQaa4TrueIT_E4TrueITL0__E(
     // CLANG17: call {{.*}}@_ZN5test21gIvEEvz(
     g(ai);
     // CHECK: call {{.*}}@_ZN5test21hIvEEvzQ4TrueITL0__E(
     // CLANG17: call {{.*}}@_ZN5test21hIvEEvz(
     h(ai);
     // CHECK: call {{.*}}@_ZN5test21AIiEF1iIvQaa4TrueIT_E4TrueITL0__EEEvz(
+    // CLANG19: call {{.*}}@_ZN5test2F1iIvQaa4TrueIT_E4TrueITL0__EEEvz(
     // CLANG17: call {{.*}}@_ZN5test21iIvEEvz(
     i(ai);
     // CHECK: call {{.*}}@_ZN5test21jIvQ4TrueITL0__EEEvz(
     // CLANG17: call {{.*}}@_ZN5test21jIvEEvz(
     j(ai);
     // CHECK: call {{.*}}@_ZN5test21AIiEF1kITk4TruevQ4TrueIT_EEEvz(
+    // CLANG19: call {{.*}}@_ZN5test2F1kITk4TruevQ4TrueIT_EEEvz(
     // CLANG17: call {{.*}}@_ZN5test21kIvEEvz(
     k(ai);
     // CHECK: call {{.*}}@_ZN5test21lITk4TruevEEvz(