diff --git a/clang-tools-extra/clangd/Threading.cpp b/clang-tools-extra/clangd/Threading.cpp
--- a/clang-tools-extra/clangd/Threading.cpp
+++ b/clang-tools-extra/clangd/Threading.cpp
@@ -10,7 +10,7 @@
 #elif defined(__APPLE__)
 #include <sys/resource.h>
 #elif defined (_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 namespace clang {
diff --git a/clang/lib/Driver/ToolChains/MSVC.cpp b/clang/lib/Driver/ToolChains/MSVC.cpp
--- a/clang/lib/Driver/ToolChains/MSVC.cpp
+++ b/clang/lib/Driver/ToolChains/MSVC.cpp
@@ -35,7 +35,7 @@
   #ifndef NOMINMAX
     #define NOMINMAX
   #endif
-  #include <windows.h>
+  #include <Windows.h>
 #endif
 
 #ifdef _MSC_VER
diff --git a/clang/tools/libclang/CIndexer.cpp b/clang/tools/libclang/CIndexer.cpp
--- a/clang/tools/libclang/CIndexer.cpp
+++ b/clang/tools/libclang/CIndexer.cpp
@@ -31,7 +31,7 @@
 #endif
 
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #elif defined(_AIX)
 #include <errno.h>
 #include <sys/ldr.h>
diff --git a/compiler-rt/lib/BlocksRuntime/runtime.c b/compiler-rt/lib/BlocksRuntime/runtime.c
--- a/compiler-rt/lib/BlocksRuntime/runtime.c
+++ b/compiler-rt/lib/BlocksRuntime/runtime.c
@@ -46,7 +46,7 @@
 
 #elif defined(__WIN32__) || defined(_WIN32)
 #define _CRT_SECURE_NO_WARNINGS 1
-#include <windows.h>
+#include <Windows.h>
 
 static __inline bool OSAtomicCompareAndSwapLong(long oldl, long newl, long volatile *dst) {
     /* fixme barrier is overkill -- see objc-os.h */
diff --git a/compiler-rt/lib/asan/asan_win.cc b/compiler-rt/lib/asan/asan_win.cc
--- a/compiler-rt/lib/asan/asan_win.cc
+++ b/compiler-rt/lib/asan/asan_win.cc
@@ -14,7 +14,7 @@
 #include "sanitizer_common/sanitizer_platform.h"
 #if SANITIZER_WINDOWS
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 
 #include <stdlib.h>
 
diff --git a/compiler-rt/lib/asan/asan_win_dynamic_runtime_thunk.cc b/compiler-rt/lib/asan/asan_win_dynamic_runtime_thunk.cc
--- a/compiler-rt/lib/asan/asan_win_dynamic_runtime_thunk.cc
+++ b/compiler-rt/lib/asan/asan_win_dynamic_runtime_thunk.cc
@@ -24,7 +24,7 @@
 #define SANITIZER_IMPORT_INTERFACE 1
 #include "sanitizer_common/sanitizer_win_defs.h"
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 
 // Define weak alias for all weak functions imported from asan dll.
 #define INTERFACE_FUNCTION(Name)
diff --git a/compiler-rt/lib/builtins/emutls.c b/compiler-rt/lib/builtins/emutls.c
--- a/compiler-rt/lib/builtins/emutls.c
+++ b/compiler-rt/lib/builtins/emutls.c
@@ -123,7 +123,7 @@
 #include <assert.h>
 #include <malloc.h>
 #include <stdio.h>
-#include <windows.h>
+#include <Windows.h>
 
 static LPCRITICAL_SECTION emutls_mutex;
 static DWORD emutls_tls_index = TLS_OUT_OF_INDEXES;
diff --git a/compiler-rt/lib/builtins/enable_execute_stack.c b/compiler-rt/lib/builtins/enable_execute_stack.c
--- a/compiler-rt/lib/builtins/enable_execute_stack.c
+++ b/compiler-rt/lib/builtins/enable_execute_stack.c
@@ -19,7 +19,7 @@
 
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 #else
 #ifndef __APPLE__
 #include <unistd.h>
diff --git a/compiler-rt/lib/fuzzer/FuzzerIOWindows.cpp b/compiler-rt/lib/fuzzer/FuzzerIOWindows.cpp
--- a/compiler-rt/lib/fuzzer/FuzzerIOWindows.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerIOWindows.cpp
@@ -19,7 +19,7 @@
 #include <iterator>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <windows.h>
+#include <Windows.h>
 
 namespace fuzzer {
 
diff --git a/compiler-rt/lib/fuzzer/FuzzerUtilWindows.cpp b/compiler-rt/lib/fuzzer/FuzzerUtilWindows.cpp
--- a/compiler-rt/lib/fuzzer/FuzzerUtilWindows.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerUtilWindows.cpp
@@ -20,7 +20,7 @@
 #include <signal.h>
 #include <stdio.h>
 #include <sys/types.h>
-#include <windows.h>
+#include <Windows.h>
 
 // This must be included after windows.h.
 #include <psapi.h>
diff --git a/compiler-rt/lib/interception/interception_win.cc b/compiler-rt/lib/interception/interception_win.cc
--- a/compiler-rt/lib/interception/interception_win.cc
+++ b/compiler-rt/lib/interception/interception_win.cc
@@ -129,7 +129,7 @@
 #if SANITIZER_WINDOWS
 #include "sanitizer_common/sanitizer_platform.h"
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 
 namespace __interception {
 
diff --git a/compiler-rt/lib/interception/tests/interception_win_test.cc b/compiler-rt/lib/interception/tests/interception_win_test.cc
--- a/compiler-rt/lib/interception/tests/interception_win_test.cc
+++ b/compiler-rt/lib/interception/tests/interception_win_test.cc
@@ -19,7 +19,7 @@
 #if SANITIZER_WINDOWS
 
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 
 namespace __interception {
 namespace {
diff --git a/compiler-rt/lib/profile/CMakeLists.txt b/compiler-rt/lib/profile/CMakeLists.txt
--- a/compiler-rt/lib/profile/CMakeLists.txt
+++ b/compiler-rt/lib/profile/CMakeLists.txt
@@ -2,7 +2,7 @@
 CHECK_CXX_SOURCE_COMPILES("
 #ifdef _MSC_VER
 #include <Intrin.h> /* Workaround for PR19898. */
-#include <windows.h>
+#include <Windows.h>
 #endif
 int main() {
 #ifdef _MSC_VER
diff --git a/compiler-rt/lib/profile/GCDAProfiling.c b/compiler-rt/lib/profile/GCDAProfiling.c
--- a/compiler-rt/lib/profile/GCDAProfiling.c
+++ b/compiler-rt/lib/profile/GCDAProfiling.c
@@ -29,7 +29,7 @@
 
 #if defined(_WIN32)
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 #include "WindowsMMap.h"
 #else
 #include <sys/mman.h>
diff --git a/compiler-rt/lib/profile/InstrProfilingPort.h b/compiler-rt/lib/profile/InstrProfilingPort.h
--- a/compiler-rt/lib/profile/InstrProfilingPort.h
+++ b/compiler-rt/lib/profile/InstrProfilingPort.h
@@ -52,7 +52,7 @@
 
 #if COMPILER_RT_HAS_ATOMICS == 1
 #ifdef _MSC_VER
-#include <windows.h>
+#include <Windows.h>
 #if _MSC_VER < 1900
 #define snprintf _snprintf
 #endif
diff --git a/compiler-rt/lib/profile/InstrProfilingUtil.c b/compiler-rt/lib/profile/InstrProfilingUtil.c
--- a/compiler-rt/lib/profile/InstrProfilingUtil.c
+++ b/compiler-rt/lib/profile/InstrProfilingUtil.c
@@ -9,7 +9,7 @@
 #ifdef _WIN32
 #include <direct.h>
 #include <process.h>
-#include <windows.h>
+#include <Windows.h>
 #include "WindowsMMap.h"
 #else
 #include <sys/stat.h>
diff --git a/compiler-rt/lib/profile/WindowsMMap.c b/compiler-rt/lib/profile/WindowsMMap.c
--- a/compiler-rt/lib/profile/WindowsMMap.c
+++ b/compiler-rt/lib/profile/WindowsMMap.c
@@ -20,7 +20,7 @@
 #include "WindowsMMap.h"
 
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 
 #include "InstrProfiling.h"
 
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_dbghelp.h b/compiler-rt/lib/sanitizer_common/sanitizer_dbghelp.h
--- a/compiler-rt/lib/sanitizer_common/sanitizer_dbghelp.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_dbghelp.h
@@ -19,7 +19,7 @@
 #endif
 
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 #include <dbghelp.h>
 
 namespace __sanitizer {
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_unwind_win.cc b/compiler-rt/lib/sanitizer_common/sanitizer_unwind_win.cc
--- a/compiler-rt/lib/sanitizer_common/sanitizer_unwind_win.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_unwind_win.cc
@@ -15,7 +15,7 @@
 
 #define WIN32_LEAN_AND_MEAN
 #define NOGDI
-#include <windows.h>
+#include <Windows.h>
 
 #include "sanitizer_dbghelp.h"  // for StackWalk64
 #include "sanitizer_stacktrace.h"
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_win.cc b/compiler-rt/lib/sanitizer_common/sanitizer_win.cc
--- a/compiler-rt/lib/sanitizer_common/sanitizer_win.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_win.cc
@@ -16,7 +16,7 @@
 
 #define WIN32_LEAN_AND_MEAN
 #define NOGDI
-#include <windows.h>
+#include <Windows.h>
 #include <io.h>
 #include <psapi.h>
 #include <stdlib.h>
diff --git a/compiler-rt/lib/sanitizer_common/tests/sanitizer_libc_test.cc b/compiler-rt/lib/sanitizer_common/tests/sanitizer_libc_test.cc
--- a/compiler-rt/lib/sanitizer_common/tests/sanitizer_libc_test.cc
+++ b/compiler-rt/lib/sanitizer_common/tests/sanitizer_libc_test.cc
@@ -18,7 +18,7 @@
 
 #if SANITIZER_WINDOWS
 #define NOMINMAX
-#include <windows.h>
+#include <Windows.h>
 #undef NOMINMAX
 #endif
 #if SANITIZER_POSIX
diff --git a/compiler-rt/lib/stats/stats_client.cc b/compiler-rt/lib/stats/stats_client.cc
--- a/compiler-rt/lib/stats/stats_client.cc
+++ b/compiler-rt/lib/stats/stats_client.cc
@@ -16,7 +16,7 @@
 
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 #else
 #include <dlfcn.h>
 #endif
diff --git a/compiler-rt/test/asan/TestCases/Windows/aligned_mallocs.cc b/compiler-rt/test/asan/TestCases/Windows/aligned_mallocs.cc
--- a/compiler-rt/test/asan/TestCases/Windows/aligned_mallocs.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/aligned_mallocs.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t
 
-#include <windows.h>
+#include <Windows.h>
 
 #define CHECK_ALIGNED(ptr,alignment) \
   do { \
diff --git a/compiler-rt/test/asan/TestCases/Windows/beginthreadex.cc b/compiler-rt/test/asan/TestCases/Windows/beginthreadex.cc
--- a/compiler-rt/test/asan/TestCases/Windows/beginthreadex.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/beginthreadex.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t
 
-#include <windows.h>
+#include <Windows.h>
 #include <process.h>
 
 unsigned WINAPI thread_proc(void *) {
diff --git a/compiler-rt/test/asan/TestCases/Windows/bind_io_completion_callback.cc b/compiler-rt/test/asan/TestCases/Windows/bind_io_completion_callback.cc
--- a/compiler-rt/test/asan/TestCases/Windows/bind_io_completion_callback.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/bind_io_completion_callback.cc
@@ -4,7 +4,7 @@
 // RUN: %clangxx_asan %s -o %t.exe
 // RUN: %run %t.exe 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 
 void ThrowAndCatch();
diff --git a/compiler-rt/test/asan/TestCases/Windows/bitfield.cc b/compiler-rt/test/asan/TestCases/Windows/bitfield.cc
--- a/compiler-rt/test/asan/TestCases/Windows/bitfield.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/bitfield.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t
 
-#include <windows.h>
+#include <Windows.h>
 
 typedef struct _S {
   unsigned int bf1:1;
diff --git a/compiler-rt/test/asan/TestCases/Windows/bitfield_uaf.cc b/compiler-rt/test/asan/TestCases/Windows/bitfield_uaf.cc
--- a/compiler-rt/test/asan/TestCases/Windows/bitfield_uaf.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/bitfield_uaf.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 typedef struct _S {
   unsigned int bf1:1;
diff --git a/compiler-rt/test/asan/TestCases/Windows/crash_read_write.cc b/compiler-rt/test/asan/TestCases/Windows/crash_read_write.cc
--- a/compiler-rt/test/asan/TestCases/Windows/crash_read_write.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/crash_read_write.cc
@@ -2,7 +2,7 @@
 // RUN: not %run %t       2>&1 | FileCheck %s --check-prefix=READ
 // RUN: not %run %t write 2>&1 | FileCheck %s --check-prefix=WRITE
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 
 static volatile int sink;
diff --git a/compiler-rt/test/asan/TestCases/Windows/dll_control_c.cc b/compiler-rt/test/asan/TestCases/Windows/dll_control_c.cc
--- a/compiler-rt/test/asan/TestCases/Windows/dll_control_c.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/dll_control_c.cc
@@ -7,7 +7,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <windows.h>
+#include <Windows.h>
 
 static void __declspec(noinline) CrashOnProcessDetach() {
   printf("CrashOnProcessDetach\n");
diff --git a/compiler-rt/test/asan/TestCases/Windows/dll_heap_allocation.cc b/compiler-rt/test/asan/TestCases/Windows/dll_heap_allocation.cc
--- a/compiler-rt/test/asan/TestCases/Windows/dll_heap_allocation.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/dll_heap_allocation.cc
@@ -8,7 +8,7 @@
 
 #ifdef HEAP_LIBRARY
 #include <memory>
-#include <windows.h>
+#include <Windows.h>
 
 std::unique_ptr<int> __declspec(dllexport) myglobal(new int(42));
 BOOL WINAPI DllMain(PVOID h, DWORD reason, PVOID reserved) {
diff --git a/compiler-rt/test/asan/TestCases/Windows/dll_host.cc b/compiler-rt/test/asan/TestCases/Windows/dll_host.cc
--- a/compiler-rt/test/asan/TestCases/Windows/dll_host.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/dll_host.cc
@@ -43,7 +43,7 @@
 // REQUIRES: asan-static-runtime
 
 #include <stdio.h>
-#include <windows.h>
+#include <Windows.h>
 
 int main(int argc, char **argv) {
   if (argc != 2) {
diff --git a/compiler-rt/test/asan/TestCases/Windows/dll_report_globals_symbolization_at_startup.cc b/compiler-rt/test/asan/TestCases/Windows/dll_report_globals_symbolization_at_startup.cc
--- a/compiler-rt/test/asan/TestCases/Windows/dll_report_globals_symbolization_at_startup.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/dll_report_globals_symbolization_at_startup.cc
@@ -6,7 +6,7 @@
 // initialization failure.
 // REQUIRES: asan-dynamic-runtime
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 
 extern "C" {
diff --git a/compiler-rt/test/asan/TestCases/Windows/dll_seh.cc b/compiler-rt/test/asan/TestCases/Windows/dll_seh.cc
--- a/compiler-rt/test/asan/TestCases/Windows/dll_seh.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/dll_seh.cc
@@ -7,7 +7,7 @@
 // RUN: %clang_cl_asan -GS- -LD -O0 %s -Fe%t.dll
 // RUN: %run %t %t.dll
 
-#include <windows.h>
+#include <Windows.h>
 #include <assert.h>
 #include <stdio.h>
 
diff --git a/compiler-rt/test/asan/TestCases/Windows/dll_thread_stack_array_left_oob.cc b/compiler-rt/test/asan/TestCases/Windows/dll_thread_stack_array_left_oob.cc
--- a/compiler-rt/test/asan/TestCases/Windows/dll_thread_stack_array_left_oob.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/dll_thread_stack_array_left_oob.cc
@@ -2,7 +2,7 @@
 // RUN: %clang_cl_asan -LD -O0 %s -Fe%t.dll
 // RUN: not %run %t %t.dll 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <malloc.h>
 
 DWORD WINAPI thread_proc(void *context) {
diff --git a/compiler-rt/test/asan/TestCases/Windows/global_const_string.cc b/compiler-rt/test/asan/TestCases/Windows/global_const_string.cc
--- a/compiler-rt/test/asan/TestCases/Windows/global_const_string.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/global_const_string.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 
 int main(void) {
diff --git a/compiler-rt/test/asan/TestCases/Windows/global_const_string_oob.cc b/compiler-rt/test/asan/TestCases/Windows/global_const_string_oob.cc
--- a/compiler-rt/test/asan/TestCases/Windows/global_const_string_oob.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/global_const_string_oob.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 
 extern "C" const char *foo = "foobarspam";
diff --git a/compiler-rt/test/asan/TestCases/Windows/operator_array_new_right_oob.cc b/compiler-rt/test/asan/TestCases/Windows/operator_array_new_right_oob.cc
--- a/compiler-rt/test/asan/TestCases/Windows/operator_array_new_right_oob.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/operator_array_new_right_oob.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 int main() {
   char *buffer = new char[42];
diff --git a/compiler-rt/test/asan/TestCases/Windows/operator_array_new_uaf.cc b/compiler-rt/test/asan/TestCases/Windows/operator_array_new_uaf.cc
--- a/compiler-rt/test/asan/TestCases/Windows/operator_array_new_uaf.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/operator_array_new_uaf.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 int main() {
   char *buffer = new char[42];
diff --git a/compiler-rt/test/asan/TestCases/Windows/operator_delete_wrong_argument.cc b/compiler-rt/test/asan/TestCases/Windows/operator_delete_wrong_argument.cc
--- a/compiler-rt/test/asan/TestCases/Windows/operator_delete_wrong_argument.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/operator_delete_wrong_argument.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 int main() {
   int *x = new int[42];
diff --git a/compiler-rt/test/asan/TestCases/Windows/operator_new_left_oob.cc b/compiler-rt/test/asan/TestCases/Windows/operator_new_left_oob.cc
--- a/compiler-rt/test/asan/TestCases/Windows/operator_new_left_oob.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/operator_new_left_oob.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 int main() {
   char *buffer = new char;
diff --git a/compiler-rt/test/asan/TestCases/Windows/operator_new_right_oob.cc b/compiler-rt/test/asan/TestCases/Windows/operator_new_right_oob.cc
--- a/compiler-rt/test/asan/TestCases/Windows/operator_new_right_oob.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/operator_new_right_oob.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 int main() {
   char *buffer = new char;
diff --git a/compiler-rt/test/asan/TestCases/Windows/operator_new_uaf.cc b/compiler-rt/test/asan/TestCases/Windows/operator_new_uaf.cc
--- a/compiler-rt/test/asan/TestCases/Windows/operator_new_uaf.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/operator_new_uaf.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 int main() {
   char *buffer = new char;
diff --git a/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item.cc b/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item.cc
--- a/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item.cc
@@ -4,7 +4,7 @@
 // RUN: %clangxx_asan %s -o %t.exe
 // RUN: %run %t.exe 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 
 void ThrowAndCatch();
diff --git a/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item_report.cc b/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item_report.cc
--- a/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item_report.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/queue_user_work_item_report.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 HANDLE done;
 
diff --git a/compiler-rt/test/asan/TestCases/Windows/recalloc_sanity.cc b/compiler-rt/test/asan/TestCases/Windows/recalloc_sanity.cc
--- a/compiler-rt/test/asan/TestCases/Windows/recalloc_sanity.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/recalloc_sanity.cc
@@ -5,7 +5,7 @@
 
 #include <cassert>
 #include <stdio.h>
-#include <windows.h>
+#include <Windows.h>
 
 int main() {
   void *p = calloc(1, 100);
diff --git a/compiler-rt/test/asan/TestCases/Windows/report_after_syminitialize.cc b/compiler-rt/test/asan/TestCases/Windows/report_after_syminitialize.cc
--- a/compiler-rt/test/asan/TestCases/Windows/report_after_syminitialize.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/report_after_syminitialize.cc
@@ -1,7 +1,7 @@
 // RUN: %clangxx_asan -O0 %s -o %t
 // RUN: %env_asan_opts=external_symbolizer_path=asdf not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <dbghelp.h>
 
 #pragma comment(lib, "dbghelp")
diff --git a/compiler-rt/test/asan/TestCases/Windows/report_globals_reload_dll.cc b/compiler-rt/test/asan/TestCases/Windows/report_globals_reload_dll.cc
--- a/compiler-rt/test/asan/TestCases/Windows/report_globals_reload_dll.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/report_globals_reload_dll.cc
@@ -3,7 +3,7 @@
 // RUN: %clang_cl_asan -O0 -DEXE %s -Fe%te.exe
 // RUN: %env_asan_opts=report_globals=1 %run %te.exe %t.dll 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 #include <string.h>
 
diff --git a/compiler-rt/test/asan/TestCases/Windows/report_globals_vs_freelibrary.cc b/compiler-rt/test/asan/TestCases/Windows/report_globals_vs_freelibrary.cc
--- a/compiler-rt/test/asan/TestCases/Windows/report_globals_vs_freelibrary.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/report_globals_vs_freelibrary.cc
@@ -2,7 +2,7 @@
 // RUN: %clang_cl_asan -O0 -DEXE %s -Fe%te.exe
 // RUN: %env_asan_opts=report_globals=2 %run %te.exe %t.dll 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 #include <string.h>
 
diff --git a/compiler-rt/test/asan/TestCases/Windows/seh.cc b/compiler-rt/test/asan/TestCases/Windows/seh.cc
--- a/compiler-rt/test/asan/TestCases/Windows/seh.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/seh.cc
@@ -13,7 +13,7 @@
 // RUN: %clang_cl_asan %s -DCOMPILE_SEH -Fe%t.exe
 // RUN: %run %t.exe
 
-#include <windows.h>
+#include <Windows.h>
 #include <assert.h>
 #include <stdio.h>
 
diff --git a/compiler-rt/test/asan/TestCases/Windows/thread_simple.cc b/compiler-rt/test/asan/TestCases/Windows/thread_simple.cc
--- a/compiler-rt/test/asan/TestCases/Windows/thread_simple.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/thread_simple.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t
 
-#include <windows.h>
+#include <Windows.h>
 
 DWORD WINAPI thread_proc(void *) {
   volatile char stack_buffer[42];
diff --git a/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_left_oob.cc b/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_left_oob.cc
--- a/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_left_oob.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_left_oob.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 DWORD WINAPI thread_proc(void *) {
   int subscript = -1;
diff --git a/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_right_oob.cc b/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_right_oob.cc
--- a/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_right_oob.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/thread_stack_array_right_oob.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: not %run %t 2>&1 | FileCheck %s
 
-#include <windows.h>
+#include <Windows.h>
 
 DWORD WINAPI thread_proc(void *) {
   int subscript = 42;
diff --git a/compiler-rt/test/asan/TestCases/Windows/thread_stack_reuse.cc b/compiler-rt/test/asan/TestCases/Windows/thread_stack_reuse.cc
--- a/compiler-rt/test/asan/TestCases/Windows/thread_stack_reuse.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/thread_stack_reuse.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t
 
-#include <windows.h>
+#include <Windows.h>
 
 DWORD WINAPI thread_proc_1(void *) {
   volatile int x, y, z;
diff --git a/compiler-rt/test/asan/TestCases/Windows/thread_stress.cc b/compiler-rt/test/asan/TestCases/Windows/thread_stress.cc
--- a/compiler-rt/test/asan/TestCases/Windows/thread_stress.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/thread_stress.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t
 
-#include <windows.h>
+#include <Windows.h>
 
 DWORD WINAPI thread_proc(void *) {
   volatile char stack_buffer[42];
diff --git a/compiler-rt/test/asan/TestCases/Windows/thread_suspended.cc b/compiler-rt/test/asan/TestCases/Windows/thread_suspended.cc
--- a/compiler-rt/test/asan/TestCases/Windows/thread_suspended.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/thread_suspended.cc
@@ -1,7 +1,7 @@
 // RUN: %clang_cl_asan -O0 %s -Fe%t
 // RUN: %run %t
 
-#include <windows.h>
+#include <Windows.h>
 
 DWORD WINAPI thread_proc(void *) {
   volatile char stack_buffer[42];
diff --git a/compiler-rt/test/asan/TestCases/Windows/tls_init.cc b/compiler-rt/test/asan/TestCases/Windows/tls_init.cc
--- a/compiler-rt/test/asan/TestCases/Windows/tls_init.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/tls_init.cc
@@ -4,7 +4,7 @@
 // CHECK: my_thread_callback
 // CHECK: ran_before_main: 1
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 #include <string.h>
 
diff --git a/compiler-rt/test/asan/TestCases/Windows/user-exception.cc b/compiler-rt/test/asan/TestCases/Windows/user-exception.cc
--- a/compiler-rt/test/asan/TestCases/Windows/user-exception.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/user-exception.cc
@@ -13,7 +13,7 @@
 // ASAN: in main
 // ASAN: ERROR: AddressSanitizer: access-violation
 
-#include <windows.h>
+#include <Windows.h>
 #include <stdio.h>
 
 static long WINAPI SEHHandler(EXCEPTION_POINTERS *info) {
diff --git a/compiler-rt/test/asan/TestCases/Windows/windows_h.cc b/compiler-rt/test/asan/TestCases/Windows/windows_h.cc
--- a/compiler-rt/test/asan/TestCases/Windows/windows_h.cc
+++ b/compiler-rt/test/asan/TestCases/Windows/windows_h.cc
@@ -2,6 +2,6 @@
 // RUN: %run %t
 
 // Just make sure we can parse <windows.h>
-#include <windows.h>
+#include <Windows.h>
 
 int main() {}
diff --git a/compiler-rt/test/asan/TestCases/exitcode.cc b/compiler-rt/test/asan/TestCases/exitcode.cc
--- a/compiler-rt/test/asan/TestCases/exitcode.cc
+++ b/compiler-rt/test/asan/TestCases/exitcode.cc
@@ -10,7 +10,7 @@
 #include <stdio.h>
 
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 
 int spawn_child(char **argv) {
   // Set an environment variable to tell the child process to interrupt
diff --git a/compiler-rt/test/asan/TestCases/ill.cc b/compiler-rt/test/asan/TestCases/ill.cc
--- a/compiler-rt/test/asan/TestCases/ill.cc
+++ b/compiler-rt/test/asan/TestCases/ill.cc
@@ -5,7 +5,7 @@
 // REQUIRES: x86-target-arch
 
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 int main(int argc, char **argv) {
diff --git a/compiler-rt/test/builtins/Unit/clear_cache_test.c b/compiler-rt/test/builtins/Unit/clear_cache_test.c
--- a/compiler-rt/test/builtins/Unit/clear_cache_test.c
+++ b/compiler-rt/test/builtins/Unit/clear_cache_test.c
@@ -14,7 +14,7 @@
 #include <string.h>
 #include <stdint.h>
 #if defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 static uintptr_t get_page_size() {
     SYSTEM_INFO si;
     GetSystemInfo(&si);
diff --git a/libcxx/src/chrono.cpp b/libcxx/src/chrono.cpp
--- a/libcxx/src/chrono.cpp
+++ b/libcxx/src/chrono.cpp
@@ -19,7 +19,7 @@
 #if defined(_LIBCPP_WIN32API)
 #define WIN32_LEAN_AND_MEAN
 #define VC_EXTRA_LEAN
-#include <windows.h>
+#include <Windows.h>
 #if _WIN32_WINNT >= _WIN32_WINNT_WIN8
 #include <winapifamily.h>
 #endif
diff --git a/libcxx/src/support/win32/thread_win32.cpp b/libcxx/src/support/win32/thread_win32.cpp
--- a/libcxx/src/support/win32/thread_win32.cpp
+++ b/libcxx/src/support/win32/thread_win32.cpp
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include <__threading_support>
-#include <windows.h>
+#include <Windows.h>
 #include <process.h>
 #include <fibersapi.h>
 
diff --git a/libcxx/src/thread.cpp b/libcxx/src/thread.cpp
--- a/libcxx/src/thread.cpp
+++ b/libcxx/src/thread.cpp
@@ -32,7 +32,7 @@
 #endif
 
 #if defined(_LIBCPP_WIN32API)
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
diff --git a/libcxx/utils/google-benchmark/src/colorprint.cc b/libcxx/utils/google-benchmark/src/colorprint.cc
--- a/libcxx/utils/google-benchmark/src/colorprint.cc
+++ b/libcxx/utils/google-benchmark/src/colorprint.cc
@@ -25,7 +25,7 @@
 #include "internal_macros.h"
 
 #ifdef BENCHMARK_OS_WINDOWS
-#include <windows.h>
+#include <Windows.h>
 #include <io.h>
 #else
 #include <unistd.h>
diff --git a/libcxx/utils/google-benchmark/src/sleep.cc b/libcxx/utils/google-benchmark/src/sleep.cc
--- a/libcxx/utils/google-benchmark/src/sleep.cc
+++ b/libcxx/utils/google-benchmark/src/sleep.cc
@@ -21,7 +21,7 @@
 #include "internal_macros.h"
 
 #ifdef BENCHMARK_OS_WINDOWS
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 namespace benchmark {
diff --git a/libcxx/utils/google-benchmark/src/sysinfo.cc b/libcxx/utils/google-benchmark/src/sysinfo.cc
--- a/libcxx/utils/google-benchmark/src/sysinfo.cc
+++ b/libcxx/utils/google-benchmark/src/sysinfo.cc
@@ -18,7 +18,7 @@
 #include <shlwapi.h>
 #undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
 #include <versionhelpers.h>
-#include <windows.h>
+#include <Windows.h>
 #include <codecvt>
 #else
 #include <fcntl.h>
diff --git a/libcxx/utils/google-benchmark/src/timers.cc b/libcxx/utils/google-benchmark/src/timers.cc
--- a/libcxx/utils/google-benchmark/src/timers.cc
+++ b/libcxx/utils/google-benchmark/src/timers.cc
@@ -19,7 +19,7 @@
 #include <shlwapi.h>
 #undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
 #include <versionhelpers.h>
-#include <windows.h>
+#include <Windows.h>
 #else
 #include <fcntl.h>
 #ifndef BENCHMARK_OS_FUCHSIA
diff --git a/libcxxabi/src/cxa_personality.cpp b/libcxxabi/src/cxa_personality.cpp
--- a/libcxxabi/src/cxa_personality.cpp
+++ b/libcxxabi/src/cxa_personality.cpp
@@ -23,7 +23,7 @@
 #include "unwind.h"
 
 #if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__)
-#include <windows.h>
+#include <Windows.h>
 #include <winnt.h>
 
 extern "C" EXCEPTION_DISPOSITION _GCC_specific_handler(PEXCEPTION_RECORD,
diff --git a/libunwind/include/unwind.h b/libunwind/include/unwind.h
--- a/libunwind/include/unwind.h
+++ b/libunwind/include/unwind.h
@@ -19,7 +19,7 @@
 #include <stddef.h>
 
 #if defined(__SEH__) && !defined(__USING_SJLJ_EXCEPTIONS__) && defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #include <ntverp.h>
 #endif
 
diff --git a/libunwind/src/AddressSpace.hpp b/libunwind/src/AddressSpace.hpp
--- a/libunwind/src/AddressSpace.hpp
+++ b/libunwind/src/AddressSpace.hpp
@@ -139,7 +139,7 @@
 #ifndef _WIN32
 #include <link.h>
 #else
-#include <windows.h>
+#include <Windows.h>
 #include <psapi.h>
 #endif
 #if !defined(ElfW)
diff --git a/libunwind/src/RWMutex.hpp b/libunwind/src/RWMutex.hpp
--- a/libunwind/src/RWMutex.hpp
+++ b/libunwind/src/RWMutex.hpp
@@ -14,7 +14,7 @@
 #define __RWMUTEX_HPP__
 
 #if defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #elif !defined(_LIBUNWIND_HAS_NO_THREADS)
 #include <pthread.h>
 #endif
diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
--- a/libunwind/src/UnwindCursor.hpp
+++ b/libunwind/src/UnwindCursor.hpp
@@ -17,7 +17,7 @@
 #include <unwind.h>
 
 #ifdef _WIN32
-  #include <windows.h>
+  #include <Windows.h>
   #include <ntverp.h>
 #endif
 #ifdef __APPLE__
diff --git a/lldb/include/lldb/Host/windows/windows.h b/lldb/include/lldb/Host/windows/windows.h
--- a/lldb/include/lldb/Host/windows/windows.h
+++ b/lldb/include/lldb/Host/windows/windows.h
@@ -16,7 +16,7 @@
 #define NOGDI
 #undef NOMINMAX // undef a previous definition to avoid warning
 #define NOMINMAX
-#include <windows.h>
+#include <Windows.h>
 #undef GetUserName
 #undef LoadImage
 #undef CreateProcess
diff --git a/lldb/packages/Python/lldbsuite/test/python_api/hello_world/main.c b/lldb/packages/Python/lldbsuite/test/python_api/hello_world/main.c
--- a/lldb/packages/Python/lldbsuite/test/python_api/hello_world/main.c
+++ b/lldb/packages/Python/lldbsuite/test/python_api/hello_world/main.c
@@ -1,6 +1,6 @@
 #include <stdio.h>
 #ifdef _MSC_VER
-#include <windows.h>
+#include <Windows.h>
 #define sleep(x) Sleep((x) * 1000)
 #else
 #include <unistd.h>
diff --git a/lldb/packages/Python/lldbsuite/test/python_api/signals/main.cpp b/lldb/packages/Python/lldbsuite/test/python_api/signals/main.cpp
--- a/lldb/packages/Python/lldbsuite/test/python_api/signals/main.cpp
+++ b/lldb/packages/Python/lldbsuite/test/python_api/signals/main.cpp
@@ -8,7 +8,7 @@
 #include <stdio.h>
 #include <sys/types.h>
 #if defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #else
 #include <unistd.h>
 #include <signal.h>
diff --git a/lldb/packages/Python/lldbsuite/test/tools/lldb-server/main.cpp b/lldb/packages/Python/lldbsuite/test/tools/lldb-server/main.cpp
--- a/lldb/packages/Python/lldbsuite/test/tools/lldb-server/main.cpp
+++ b/lldb/packages/Python/lldbsuite/test/tools/lldb-server/main.cpp
@@ -35,7 +35,7 @@
 #elif defined(__NetBSD__)
 #include <lwp.h>
 #elif defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 static const char *const RETVAL_PREFIX = "retval:";
diff --git a/lldb/source/Utility/Status.cpp b/lldb/source/Utility/Status.cpp
--- a/lldb/source/Utility/Status.cpp
+++ b/lldb/source/Utility/Status.cpp
@@ -27,7 +27,7 @@
 #endif
 
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #endif
 #include <stdint.h>
 
diff --git a/lldb/tools/lldb-mi/MICmnStreamStdin.cpp b/lldb/tools/lldb-mi/MICmnStreamStdin.cpp
--- a/lldb/tools/lldb-mi/MICmnStreamStdin.cpp
+++ b/lldb/tools/lldb-mi/MICmnStreamStdin.cpp
@@ -8,7 +8,7 @@
 
 // Third Party Headers
 #ifdef _MSC_VER
-#include <windows.h>
+#include <Windows.h>
 #endif
 #include <string.h>
 
diff --git a/lldb/tools/lldb-mi/MIUtilDebug.cpp b/lldb/tools/lldb-mi/MIUtilDebug.cpp
--- a/lldb/tools/lldb-mi/MIUtilDebug.cpp
+++ b/lldb/tools/lldb-mi/MIUtilDebug.cpp
@@ -8,7 +8,7 @@
 
 // Third party headers:
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 // In-house headers:
diff --git a/lldb/tools/lldb-vscode/IOStream.h b/lldb/tools/lldb-vscode/IOStream.h
--- a/lldb/tools/lldb-vscode/IOStream.h
+++ b/lldb/tools/lldb-vscode/IOStream.h
@@ -16,7 +16,7 @@
 // the JSON code we use also has methods named `GetObject()` and we conflict
 // against these.
 #define NOMINMAX
-#include <windows.h>
+#include <Windows.h>
 #else
 typedef int SOCKET;
 #endif
diff --git a/lldb/tools/lldb-vscode/lldb-vscode.cpp b/lldb/tools/lldb-vscode/lldb-vscode.cpp
--- a/lldb/tools/lldb-vscode/lldb-vscode.cpp
+++ b/lldb/tools/lldb-vscode/lldb-vscode.cpp
@@ -21,7 +21,7 @@
 // the JSON code we use also has methods named `GetObject()` and we conflict
 // against these.
 #define NOMINMAX
-#include <windows.h>
+#include <Windows.h>
 #undef GetObject
 #include <io.h>
 #else
diff --git a/llgo/third_party/gofrontend/libffi/src/dlmalloc.c b/llgo/third_party/gofrontend/libffi/src/dlmalloc.c
--- a/llgo/third_party/gofrontend/libffi/src/dlmalloc.c
+++ b/llgo/third_party/gofrontend/libffi/src/dlmalloc.c
@@ -445,7 +445,7 @@
 #endif  /* WIN32 */
 #ifdef WIN32
 #define WIN32_LEAN_AND_MEAN
-#include <windows.h>
+#include <Windows.h>
 #define HAVE_MMAP 1
 #define HAVE_MORECORE 0
 #define LACKS_UNISTD_H
diff --git a/llgo/third_party/gofrontend/libffi/src/x86/darwin_c.c b/llgo/third_party/gofrontend/libffi/src/x86/darwin_c.c
--- a/llgo/third_party/gofrontend/libffi/src/x86/darwin_c.c
+++ b/llgo/third_party/gofrontend/libffi/src/x86/darwin_c.c
@@ -31,7 +31,7 @@
 #if !defined(__x86_64__) || defined(_WIN64) || defined(__CYGWIN__)
 
 #ifdef _WIN64
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 #include <ffi.h>
diff --git a/llgo/third_party/gofrontend/libgo/go/runtime/crash_cgo_test.go b/llgo/third_party/gofrontend/libgo/go/runtime/crash_cgo_test.go
--- a/llgo/third_party/gofrontend/libgo/go/runtime/crash_cgo_test.go
+++ b/llgo/third_party/gofrontend/libgo/go/runtime/crash_cgo_test.go
@@ -444,7 +444,7 @@
 package main
 
 /*
-#include <windows.h>
+#include <Windows.h>
 
 DWORD getthread() {
 	return GetCurrentThreadId();
@@ -467,7 +467,7 @@
 /*
 #cgo CFLAGS: -mnop-fun-dllimport
 
-#include <windows.h>
+#include <Windows.h>
 
 DWORD agetthread() {
 	return GetCurrentThreadId();
diff --git a/llvm/cmake/modules/CheckAtomic.cmake b/llvm/cmake/modules/CheckAtomic.cmake
--- a/llvm/cmake/modules/CheckAtomic.cmake
+++ b/llvm/cmake/modules/CheckAtomic.cmake
@@ -81,7 +81,7 @@
 ## assumes C++11 <atomic> works.
 CHECK_CXX_SOURCE_COMPILES("
 #ifdef _MSC_VER
-#include <windows.h>
+#include <Windows.h>
 #endif
 int main() {
 #ifdef _MSC_VER
diff --git a/llvm/include/llvm/DebugInfo/PDB/DIA/DIASupport.h b/llvm/include/llvm/DebugInfo/PDB/DIA/DIASupport.h
--- a/llvm/include/llvm/DebugInfo/PDB/DIA/DIASupport.h
+++ b/llvm/include/llvm/DebugInfo/PDB/DIA/DIASupport.h
@@ -23,7 +23,7 @@
 
 // atlbase.h has to come before windows.h
 #include <atlbase.h>
-#include <windows.h>
+#include <Windows.h>
 
 // DIA headers must come after windows headers.
 #include <cvconst.h>
diff --git a/llvm/lib/ExecutionEngine/IntelJITEvents/ittnotify_config.h b/llvm/lib/ExecutionEngine/IntelJITEvents/ittnotify_config.h
--- a/llvm/lib/ExecutionEngine/IntelJITEvents/ittnotify_config.h
+++ b/llvm/lib/ExecutionEngine/IntelJITEvents/ittnotify_config.h
@@ -173,7 +173,7 @@
 
 /* OS communication functions */
 #if ITT_PLATFORM==ITT_PLATFORM_WIN
-#include <windows.h>
+#include <Windows.h>
 typedef HMODULE           lib_t;
 typedef DWORD             TIDT;
 typedef CRITICAL_SECTION  mutex_t;
diff --git a/llvm/lib/ExecutionEngine/IntelJITEvents/jitprofiling.c b/llvm/lib/ExecutionEngine/IntelJITEvents/jitprofiling.c
--- a/llvm/lib/ExecutionEngine/IntelJITEvents/jitprofiling.c
+++ b/llvm/lib/ExecutionEngine/IntelJITEvents/jitprofiling.c
@@ -18,7 +18,7 @@
 #include "ittnotify_config.h"
 
 #if ITT_PLATFORM==ITT_PLATFORM_WIN
-#include <windows.h>
+#include <Windows.h>
 #pragma optimize("", off)
 #else  /* ITT_PLATFORM==ITT_PLATFORM_WIN */
 #include <dlfcn.h>
diff --git a/llvm/lib/Support/Atomic.cpp b/llvm/lib/Support/Atomic.cpp
--- a/llvm/lib/Support/Atomic.cpp
+++ b/llvm/lib/Support/Atomic.cpp
@@ -19,7 +19,7 @@
 #include <intrin.h>
 
 // We must include windows.h after intrin.h.
-#include <windows.h>
+#include <Windows.h>
 #undef MemoryFence
 #endif
 
diff --git a/llvm/lib/Support/CodeGenCoverage.cpp b/llvm/lib/Support/CodeGenCoverage.cpp
--- a/llvm/lib/Support/CodeGenCoverage.cpp
+++ b/llvm/lib/Support/CodeGenCoverage.cpp
@@ -22,7 +22,7 @@
 #if LLVM_ON_UNIX
 #include <unistd.h>
 #elif defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 using namespace llvm;
diff --git a/llvm/lib/Support/LockFileManager.cpp b/llvm/lib/Support/LockFileManager.cpp
--- a/llvm/lib/Support/LockFileManager.cpp
+++ b/llvm/lib/Support/LockFileManager.cpp
@@ -24,7 +24,7 @@
 #include <system_error>
 #include <tuple>
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #endif
 #if LLVM_ON_UNIX
 #include <unistd.h>
diff --git a/llvm/lib/Support/Windows/WindowsSupport.h b/llvm/lib/Support/Windows/WindowsSupport.h
--- a/llvm/lib/Support/Windows/WindowsSupport.h
+++ b/llvm/lib/Support/Windows/WindowsSupport.h
@@ -44,7 +44,7 @@
 #include <cassert>
 #include <string>
 #include <system_error>
-#include <windows.h>
+#include <Windows.h>
 
 // Must be included after windows.h
 #include <wincrypt.h>
diff --git a/llvm/unittests/Support/CrashRecoveryTest.cpp b/llvm/unittests/Support/CrashRecoveryTest.cpp
--- a/llvm/unittests/Support/CrashRecoveryTest.cpp
+++ b/llvm/unittests/Support/CrashRecoveryTest.cpp
@@ -13,7 +13,7 @@
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
 #define NOGDI
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 using namespace llvm;
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -26,7 +26,7 @@
 #ifdef _WIN32
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/Chrono.h"
-#include <windows.h>
+#include <Windows.h>
 #include <winerror.h>
 #endif
 
diff --git a/llvm/unittests/Support/ProcessTest.cpp b/llvm/unittests/Support/ProcessTest.cpp
--- a/llvm/unittests/Support/ProcessTest.cpp
+++ b/llvm/unittests/Support/ProcessTest.cpp
@@ -10,7 +10,7 @@
 #include "gtest/gtest.h"
 
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 namespace {
diff --git a/llvm/unittests/Support/ProgramTest.cpp b/llvm/unittests/Support/ProgramTest.cpp
--- a/llvm/unittests/Support/ProgramTest.cpp
+++ b/llvm/unittests/Support/ProgramTest.cpp
@@ -27,7 +27,7 @@
   sleep(seconds);
 }
 #elif defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 void sleep_for(unsigned int seconds) {
   Sleep(seconds * 1000);
 }
diff --git a/llvm/unittests/Support/TimerTest.cpp b/llvm/unittests/Support/TimerTest.cpp
--- a/llvm/unittests/Support/TimerTest.cpp
+++ b/llvm/unittests/Support/TimerTest.cpp
@@ -10,7 +10,7 @@
 #include "gtest/gtest.h"
 
 #if _WIN32
-#include <windows.h>
+#include <Windows.h>
 #else
 #include <time.h>
 #endif
diff --git a/llvm/utils/KillTheDoctor/KillTheDoctor.cpp b/llvm/utils/KillTheDoctor/KillTheDoctor.cpp
--- a/llvm/utils/KillTheDoctor/KillTheDoctor.cpp
+++ b/llvm/utils/KillTheDoctor/KillTheDoctor.cpp
@@ -51,7 +51,7 @@
 #include <system_error>
 
 // These includes must be last.
-#include <windows.h>
+#include <Windows.h>
 #include <winerror.h>
 #include <dbghelp.h>
 #include <psapi.h>
diff --git a/llvm/utils/benchmark/src/colorprint.cc b/llvm/utils/benchmark/src/colorprint.cc
--- a/llvm/utils/benchmark/src/colorprint.cc
+++ b/llvm/utils/benchmark/src/colorprint.cc
@@ -25,7 +25,7 @@
 #include "internal_macros.h"
 
 #ifdef BENCHMARK_OS_WINDOWS
-#include <windows.h>
+#include <Windows.h>
 #include <io.h>
 #else
 #include <unistd.h>
diff --git a/llvm/utils/benchmark/src/sleep.cc b/llvm/utils/benchmark/src/sleep.cc
--- a/llvm/utils/benchmark/src/sleep.cc
+++ b/llvm/utils/benchmark/src/sleep.cc
@@ -21,7 +21,7 @@
 #include "internal_macros.h"
 
 #ifdef BENCHMARK_OS_WINDOWS
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 namespace benchmark {
diff --git a/llvm/utils/benchmark/src/sysinfo.cc b/llvm/utils/benchmark/src/sysinfo.cc
--- a/llvm/utils/benchmark/src/sysinfo.cc
+++ b/llvm/utils/benchmark/src/sysinfo.cc
@@ -18,7 +18,7 @@
 #include <shlwapi.h>
 #undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
 #include <versionhelpers.h>
-#include <windows.h>
+#include <Windows.h>
 #else
 #include <fcntl.h>
 #ifndef BENCHMARK_OS_FUCHSIA
diff --git a/llvm/utils/benchmark/src/timers.cc b/llvm/utils/benchmark/src/timers.cc
--- a/llvm/utils/benchmark/src/timers.cc
+++ b/llvm/utils/benchmark/src/timers.cc
@@ -19,7 +19,7 @@
 #include <shlwapi.h>
 #undef StrCat  // Don't let StrCat in string_util.h be renamed to lstrcatA
 #include <versionhelpers.h>
-#include <windows.h>
+#include <Windows.h>
 #else
 #include <fcntl.h>
 #ifndef BENCHMARK_OS_FUCHSIA
diff --git a/openmp/runtime/src/kmp.h b/openmp/runtime/src/kmp.h
--- a/openmp/runtime/src/kmp.h
+++ b/openmp/runtime/src/kmp.h
@@ -594,7 +594,7 @@
 #pragma warning(push)
 #pragma warning(disable : 271 310)
 #endif
-#include <windows.h>
+#include <Windows.h>
 #if KMP_MSVC_COMPAT
 #pragma warning(pop)
 #endif
diff --git a/openmp/runtime/src/kmp_environment.cpp b/openmp/runtime/src/kmp_environment.cpp
--- a/openmp/runtime/src/kmp_environment.cpp
+++ b/openmp/runtime/src/kmp_environment.cpp
@@ -65,7 +65,7 @@
 extern char **environ;
 #endif
 #elif KMP_OS_WINDOWS
-#include <windows.h> // GetEnvironmentVariable, SetEnvironmentVariable,
+#include <Windows.h> // GetEnvironmentVariable, SetEnvironmentVariable,
 // GetLastError.
 #else
 #error Unknown or unsupported OS.
diff --git a/openmp/runtime/src/kmp_i18n.cpp b/openmp/runtime/src/kmp_i18n.cpp
--- a/openmp/runtime/src/kmp_i18n.cpp
+++ b/openmp/runtime/src/kmp_i18n.cpp
@@ -219,7 +219,7 @@
 #define KMP_I18N_OK
 
 #include "kmp_environment.h"
-#include <windows.h>
+#include <Windows.h>
 
 #define KMP_I18N_NULLCAT NULL
 static HMODULE cat = KMP_I18N_NULLCAT; // !!! Shall it be volatile?
diff --git a/openmp/runtime/src/kmp_io.cpp b/openmp/runtime/src/kmp_io.cpp
--- a/openmp/runtime/src/kmp_io.cpp
+++ b/openmp/runtime/src/kmp_io.cpp
@@ -30,7 +30,7 @@
 #pragma warning(push)
 #pragma warning(disable : 271 310)
 #endif
-#include <windows.h>
+#include <Windows.h>
 #if KMP_MSVC_COMPAT
 #pragma warning(pop)
 #endif
diff --git a/openmp/runtime/src/kmp_os.h b/openmp/runtime/src/kmp_os.h
--- a/openmp/runtime/src/kmp_os.h
+++ b/openmp/runtime/src/kmp_os.h
@@ -268,7 +268,7 @@
 #endif
 
 #if KMP_OS_WINDOWS
-#include <windows.h>
+#include <Windows.h>
 
 static inline int KMP_GET_PAGE_SIZE(void) {
   SYSTEM_INFO si;
diff --git a/openmp/runtime/src/kmp_stub.cpp b/openmp/runtime/src/kmp_stub.cpp
--- a/openmp/runtime/src/kmp_stub.cpp
+++ b/openmp/runtime/src/kmp_stub.cpp
@@ -20,7 +20,7 @@
 #include "kmp_stub.h"
 
 #if KMP_OS_WINDOWS
-#include <windows.h>
+#include <Windows.h>
 #else
 #include <sys/time.h>
 #endif
diff --git a/openmp/runtime/src/thirdparty/ittnotify/ittnotify_config.h b/openmp/runtime/src/thirdparty/ittnotify/ittnotify_config.h
--- a/openmp/runtime/src/thirdparty/ittnotify/ittnotify_config.h
+++ b/openmp/runtime/src/thirdparty/ittnotify/ittnotify_config.h
@@ -215,7 +215,7 @@
 
 /* OS communication functions */
 #if ITT_PLATFORM==ITT_PLATFORM_WIN
-#include <windows.h>
+#include <Windows.h>
 typedef HMODULE           lib_t;
 typedef DWORD             TIDT;
 typedef CRITICAL_SECTION  mutex_t;
diff --git a/openmp/runtime/test/affinity/format/fields_values.c b/openmp/runtime/test/affinity/format/fields_values.c
--- a/openmp/runtime/test/affinity/format/fields_values.c
+++ b/openmp/runtime/test/affinity/format/fields_values.c
@@ -18,7 +18,7 @@
   }
 
 #if defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #define getpid _getpid
 typedef int pid_t;
 #define gettid GetCurrentThreadId
diff --git a/openmp/runtime/test/ompt/ompt-signal.h b/openmp/runtime/test/ompt/ompt-signal.h
--- a/openmp/runtime/test/ompt/ompt-signal.h
+++ b/openmp/runtime/test/ompt/ompt-signal.h
@@ -1,5 +1,5 @@
 #if defined(WIN32) || defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #define delay() Sleep(1);
 #else
 #include <unistd.h>
diff --git a/openmp/runtime/test/tasking/omp50_task_depend_mtx.c b/openmp/runtime/test/tasking/omp50_task_depend_mtx.c
--- a/openmp/runtime/test/tasking/omp50_task_depend_mtx.c
+++ b/openmp/runtime/test/tasking/omp50_task_depend_mtx.c
@@ -18,7 +18,7 @@
 #include <omp.h>
 
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #define mysleep(n) Sleep(n)
 #else
 #include <unistd.h>
diff --git a/openmp/runtime/test/tasking/omp50_task_depend_mtx2.c b/openmp/runtime/test/tasking/omp50_task_depend_mtx2.c
--- a/openmp/runtime/test/tasking/omp50_task_depend_mtx2.c
+++ b/openmp/runtime/test/tasking/omp50_task_depend_mtx2.c
@@ -18,7 +18,7 @@
 #include <omp.h>
 
 #ifdef _WIN32
-#include <windows.h>
+#include <Windows.h>
 #define mysleep(n) Sleep(n)
 #else
 #include <unistd.h>
diff --git a/openmp/runtime/test/worksharing/for/kmp_sch_simd_guided.c b/openmp/runtime/test/worksharing/for/kmp_sch_simd_guided.c
--- a/openmp/runtime/test/worksharing/for/kmp_sch_simd_guided.c
+++ b/openmp/runtime/test/worksharing/for/kmp_sch_simd_guided.c
@@ -9,7 +9,7 @@
 #include <omp.h>
 
 #if defined(WIN32) || defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #define delay() Sleep(1);
 #else
 #include <unistd.h>
diff --git a/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_api.c b/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_api.c
--- a/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_api.c
+++ b/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_api.c
@@ -8,7 +8,7 @@
 #include <omp.h>
 
 #if defined(WIN32) || defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #define delay() Sleep(1);
 #define seten(a,b,c) _putenv_s((a),(b))
 #else
diff --git a/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_guided.c b/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_guided.c
--- a/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_guided.c
+++ b/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_guided.c
@@ -15,7 +15,7 @@
 #include <omp.h>
 
 #if defined(WIN32) || defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #define delay() Sleep(1);
 #define seten(a,b,c) _putenv_s((a),(b))
 #else
diff --git a/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_static.c b/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_static.c
--- a/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_static.c
+++ b/openmp/runtime/test/worksharing/for/kmp_sch_simd_runtime_static.c
@@ -9,7 +9,7 @@
 #include <omp.h>
 
 #if defined(WIN32) || defined(_WIN32)
-#include <windows.h>
+#include <Windows.h>
 #define delay() Sleep(1);
 #define seten(a,b,c) _putenv_s((a),(b))
 #else