diff --git a/clang/lib/AST/Mangle.cpp b/clang/lib/AST/Mangle.cpp
--- a/clang/lib/AST/Mangle.cpp
+++ b/clang/lib/AST/Mangle.cpp
@@ -212,6 +212,10 @@
   else
     mangleCXXName(GD, Out);
 
+  // do no produce @<number> suffix if it is regcall4
+  if (getASTContext().getLangOpts().RegCall4)
+    return;
+
   const FunctionDecl *FD = cast<FunctionDecl>(D);
   const FunctionType *FT = FD->getType()->castAs<FunctionType>();
   const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(FT);
diff --git a/clang/test/CodeGen/mangle-windows-regcall4.c b/clang/test/CodeGen/mangle-windows-regcall4.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/mangle-windows-regcall4.c
@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-pc-win32 -regcall4 | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-mingw32 -regcall4 | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=i386-pc-windows-msvc-elf -regcall4 | FileCheck %s --check-prefix=ELF32
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-pc-win32 -regcall4 | FileCheck %s --check-prefix=X64
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-mingw32 -regcall4 | FileCheck %s --check-prefix=X64
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-pc-windows-msvc-elf -regcall4 | FileCheck %s --check-prefix=ELF64
+
+// CHECK: target datalayout = "e-m:x-{{.*}}"
+// X64: target datalayout = "e-m:w-{{.*}}"
+// ELF32: target datalayout = "e-m:e-{{.*}}"
+// ELF64: target datalayout = "e-m:e-{{.*}}"
+
+void __regcall v1(void) {}
+// CHECK: define dso_local x86_regcallcc void @__regcall4__v1
+// X64: define dso_local x86_regcallcc void @__regcall4__v1
+// ELF32: define{{.*}} x86_regcallcc void @__regcall4__v1
+// ELF64: define{{.*}} x86_regcallcc void @__regcall4__v1
+
+void __regcall v2(char a) {}
+// CHECK: define dso_local x86_regcallcc void @__regcall4__v2
+// X64: define dso_local x86_regcallcc void @__regcall4__v2
+// ELF32: define{{.*}} x86_regcallcc void @__regcall4__v2
+// ELF64: define{{.*}} x86_regcallcc void @__regcall4__v2
+
+void __regcall v3(short a) {}
+// CHECK: define dso_local x86_regcallcc void @__regcall4__v3
+// X64: define dso_local x86_regcallcc void @__regcall4__v3
+
+void __regcall v4(int a) {}
+// CHECK: define dso_local x86_regcallcc void @__regcall4__v4
+// X64: define dso_local x86_regcallcc void @__regcall4__v4
+
+void __regcall v5(long long a) {}
+// CHECK: define dso_local x86_regcallcc void @__regcall4__v5
+// X64: define dso_local x86_regcallcc void @__regcall4__v5
+
+void __regcall v6(char a, char b) {}
+// CHECK: define dso_local x86_regcallcc void @__regcall4__v6(i8 inreg noundef signext %a, i8 inreg noundef signext %b)
+// X64: define dso_local x86_regcallcc void @__regcall4__v6(i8 noundef %a, i8 noundef %b)
+
+void __regcall v7(long long a, char b, char c, short d) {}
+// CHECK: define dso_local x86_regcallcc void @__regcall4__v7(i64 noundef %a, i8 inreg noundef signext %b, i8 inreg noundef signext %c, i16 inreg noundef signext %d)
+// X64: define dso_local x86_regcallcc void @__regcall4__v7(i64 noundef %a, i8 noundef %b, i8 noundef %c, i16 noundef %d)