Index: lib/Basic/Targets/AArch64.cpp
===================================================================
--- lib/Basic/Targets/AArch64.cpp
+++ lib/Basic/Targets/AArch64.cpp
@@ -474,7 +474,6 @@
 void MicrosoftARM64TargetInfo::getVisualStudioDefines(
     const LangOptions &Opts, MacroBuilder &Builder) const {
   WindowsTargetInfo<AArch64leTargetInfo>::getVisualStudioDefines(Opts, Builder);
-  Builder.defineMacro("_WIN32", "1");
   Builder.defineMacro("_WIN64", "1");
   Builder.defineMacro("_M_ARM64", "1");
 }
@@ -494,10 +493,7 @@
 void MinGWARM64TargetInfo::getTargetDefines(const LangOptions &Opts,
                                             MacroBuilder &Builder) const {
   WindowsTargetInfo::getTargetDefines(Opts, Builder);
-  Builder.defineMacro("_WIN32", "1");
   Builder.defineMacro("_WIN64", "1");
-  Builder.defineMacro("WIN32", "1");
-  Builder.defineMacro("WIN64", "1");
   addMinGWDefines(Opts, Builder);
 }
 
Index: test/Preprocessor/predefined-macros.c
===================================================================
--- test/Preprocessor/predefined-macros.c
+++ test/Preprocessor/predefined-macros.c
@@ -204,8 +204,6 @@
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-ARM64-MINGW
 
 // CHECK-ARM64-MINGW-NOT: #define _M_ARM64 1
-// CHECK-ARM64-MINGW: #define WIN32 1
-// CHECK-ARM64-MINGW: #define WIN64 1
 // CHECK-ARM64-MINGW: #define _WIN32 1
 // CHECK-ARM64-MINGW: #define _WIN64 1
 // CHECK-ARM64-MINGW: #define __aarch64__ 1