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

[Viktoriia Bakalova via cfe-commits]

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

…-like friend function templates only if ` -fclang-abi-compat>=19`.

>From 5bdf3b5814f90b953a8638e6024cd081bc300e8b 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/lib/AST/ItaniumMangle.cpp          | 11 ++++++++++-
 clang/test/CodeGenCXX/mangle-concept.cpp |  4 ++++
 2 files changed, 14 insertions(+), 1 deletion(-)

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(