[clang] [Clang][Cygwin] Use correct mangling rule (PR #158404)

[Tomohiro Kashiwada via cfe-commits]

https://github.com/kikairoya created https://github.com/llvm/llvm-project/pull/158404

follow-up to https://github.com/llvm/llvm-project/commit/45ca613c135ea7b5fbc63bff003f20bf20f62081

>From 3d88b0f56df2a269adcc46daf7b6dc437b15964e Mon Sep 17 00:00:00 2001
From: kikairoya <kikairoya at gmail.com>
Date: Sat, 13 Sep 2025 09:54:55 +0900
Subject: [PATCH 1/2] correct mangling rule

---
 clang/lib/Basic/Targets/X86.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
index 6e013c95dbf01..d159a7906854c 100644
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -646,6 +646,7 @@ 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",
@@ -983,6 +984,7 @@ 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,

>From 7c39b808652b9616b74c5567c89144faa60a3b09 Mon Sep 17 00:00:00 2001
From: kikairoya <kikairoya at gmail.com>
Date: Sat, 13 Sep 2025 09:55:06 +0900
Subject: [PATCH 2/2] test

---
 clang/test/CodeGen/mangle-windows.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

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-{{.*}}"