[llvm-branch-commits] [clang] release/21.x: [Clang][Cygwin] Use correct mangling rule (#158404) (PR #158442)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/158442

Backport 4abcbb053f8adaf48dbfff677e8ccda1f6d52b33

Requested by: @mstorsjo

>From f4907049285ca0875cc91770e3ceb3f162ec7c48 Mon Sep 17 00:00:00 2001
From: Tomohiro Kashiwada <kikairoya at gmail.com>
Date: Sun, 14 Sep 2025 06:40:12 +0900
Subject: [PATCH] [Clang][Cygwin] Use correct mangling rule (#158404)

In
https://github.com/llvm/llvm-project/commit/45ca613c135ea7b5fbc63bff003f20bf20f62081,
whether to mangle names based on calling conventions according to
Microsoft conventions was refactored to a bool in the TargetInfo. Cygwin
targets also require this mangling, but were missed, presumably due to
lack of test coverage of these targets. This commit enables the name
mangling for Cygwin, and also enables test coverage of this mangling on
Cygwin targets.

(cherry picked from commit 4abcbb053f8adaf48dbfff677e8ccda1f6d52b33)
---
 clang/lib/Basic/Targets/X86.h            | 2 ++
 clang/test/CodeGen/mangle-windows.c      | 6 ++++--
 clang/test/CodeGenCXX/mangle-windows.cpp | 3 +++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
index ebc59c92f4c24..a7be080695ed3 100644
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -649,6 +649,7 @@ class LLVM_LIBRARY_VISIBILITY CygwinX86_32TargetInfo : public X86_32TargetInfo {
       : X86_32TargetInfo(Triple, Opts) {
     this->WCharType = TargetInfo::UnsignedShort;
     this->WIntType = TargetInfo::UnsignedInt;
+    this->UseMicrosoftManglingForC = true;
     DoubleAlign = LongLongAlign = 64;
     resetDataLayout("e-m:x-p:32:32-p270:32:32-p271:32:32-p272:64:64-i64:64-"
                     "i128:128-f80:32-n8:16:32-a:0:32-S32",
@@ -986,6 +987,7 @@ class LLVM_LIBRARY_VISIBILITY CygwinX86_64TargetInfo : public X86_64TargetInfo {
       : X86_64TargetInfo(Triple, Opts) {
     this->WCharType = TargetInfo::UnsignedShort;
     this->WIntType = TargetInfo::UnsignedInt;
+    this->UseMicrosoftManglingForC = true;
   }
 
   void getTargetDefines(const LangOptions &Opts,
diff --git a/clang/test/CodeGen/mangle-windows.c b/clang/test/CodeGen/mangle-windows.c
index 046b1e8815a8a..e1b06e72a9635 100644
--- a/clang/test/CodeGen/mangle-windows.c
+++ b/clang/test/CodeGen/mangle-windows.c
@@ -1,8 +1,10 @@
 // RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-pc-win32 | FileCheck %s
-// RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-mingw32 | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-mingw32  | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-cygwin   | FileCheck %s
 // RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-pc-windows-msvc-elf | FileCheck %s --check-prefix=ELF32
 // RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-pc-win32 | FileCheck %s --check-prefix=X64
-// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-mingw32 | FileCheck %s --check-prefix=X64
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-mingw32  | FileCheck %s --check-prefix=X64
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-cygwin   | FileCheck %s --check-prefix=X64
 // RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-pc-windows-msvc-elf | FileCheck %s --check-prefix=ELF64
 
 // CHECK: target datalayout = "e-m:x-{{.*}}"
diff --git a/clang/test/CodeGenCXX/mangle-windows.cpp b/clang/test/CodeGenCXX/mangle-windows.cpp
index 3d5a1e9a868ef..737abcf6e3498 100644
--- a/clang/test/CodeGenCXX/mangle-windows.cpp
+++ b/clang/test/CodeGenCXX/mangle-windows.cpp
@@ -4,6 +4,9 @@
 // RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-mingw32 | \
 // RUN:     FileCheck --check-prefix=ITANIUM %s
 
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-cygwin | \
+// RUN:     FileCheck --check-prefix=ITANIUM %s
+
 void __stdcall f1(void) {}
 // WIN: define dso_local x86_stdcallcc void @"?f1@@YGXXZ"
 // ITANIUM: define dso_local x86_stdcallcc void @"\01__Z2f1v at 0"