Index: clang/lib/Headers/CMakeLists.txt
===================================================================
--- clang/lib/Headers/CMakeLists.txt
+++ clang/lib/Headers/CMakeLists.txt
@@ -310,6 +310,10 @@
   llvm_libc_wrappers/inttypes.h
 )
 
+set(zos_wrapper_files
+  zos_wrappers/builtins.h
+)
+
 include(GetClangResourceDir)
 get_clang_resource_dir(output_dir PREFIX ${LLVM_LIBRARY_OUTPUT_INTDIR}/.. SUBDIR include)
 set(out_files)
@@ -345,7 +349,7 @@
 
 # Copy header files from the source directory to the build directory
 foreach( f ${files} ${cuda_wrapper_files} ${cuda_wrapper_bits_files}
-           ${ppc_wrapper_files} ${openmp_wrapper_files} ${hlsl_files}
+           ${ppc_wrapper_files} ${openmp_wrapper_files} ${zos_wrapper_files} ${hlsl_files}
            ${llvm_libc_wrapper_files})
   copy_header_to_output_dir(${CMAKE_CURRENT_SOURCE_DIR} ${f})
 endforeach( f )
@@ -459,7 +463,7 @@
 add_header_target("ppc-resource-headers" "${ppc_files};${ppc_wrapper_files}")
 add_header_target("ppc-htm-resource-headers" "${ppc_htm_files}")
 add_header_target("riscv-resource-headers" "${riscv_files};${riscv_generated_files}")
-add_header_target("systemz-resource-headers" "${systemz_files}")
+add_header_target("systemz-resource-headers" "${systemz_files};${zos_wrapper_files}")
 add_header_target("ve-resource-headers" "${ve_files}")
 add_header_target("webassembly-resource-headers" "${webassembly_files}")
 add_header_target("x86-resource-headers" "${x86_files}")
@@ -506,6 +510,11 @@
   DESTINATION ${header_install_dir}/openmp_wrappers
   COMPONENT clang-resource-headers)
 
+install(
+  FILES ${zos_wrapper_files}
+  DESTINATION ${header_install_dir}/zos_wrappers
+  COMPONENT clang-resource-headers)
+
 #############################################################
 # Install rules for separate header lists
 install(
@@ -610,6 +619,12 @@
   EXCLUDE_FROM_ALL
   COMPONENT systemz-resource-headers)
 
+install(
+  FILES ${zos_wrapper_files}
+  DESTINATION  ${header_install_dir}/zos_wrappers
+  EXCLUDE_FROM_ALL
+  COMPONENT systemz-resource-headers)
+
 install(
   FILES ${ve_files}
   DESTINATION ${header_install_dir}
Index: clang/lib/Headers/builtins.h
===================================================================
--- clang/lib/Headers/builtins.h
+++ clang/lib/Headers/builtins.h
@@ -13,4 +13,7 @@
 #ifndef __BUILTINS_H
 #define __BUILTINS_H
 
+#if defined(__MVS__) && __has_include_next(<builtins.h>)
+#include_next <builtins.h>
+#endif /* __MVS__ */
 #endif /* __BUILTINS_H */
Index: clang/lib/Headers/float.h
===================================================================
--- clang/lib/Headers/float.h
+++ clang/lib/Headers/float.h
@@ -10,6 +10,10 @@
 #ifndef __CLANG_FLOAT_H
 #define __CLANG_FLOAT_H
 
+#if defined(__MVS__) && __has_include_next(<float.h>)
+#include_next <float.h>
+#else
+
 /* If we're on MinGW, fall back to the system's float.h, which might have
  * additional definitions provided for Windows.
  * For more details see http://msdn.microsoft.com/en-us/library/y0ybw9fy.aspx
@@ -165,4 +169,5 @@
 #  define FLT16_TRUE_MIN    __FLT16_TRUE_MIN__
 #endif /* __STDC_WANT_IEC_60559_TYPES_EXT__ */
 
+#endif /* __MVS__ */
 #endif /* __CLANG_FLOAT_H */
Index: clang/lib/Headers/inttypes.h
===================================================================
--- clang/lib/Headers/inttypes.h
+++ clang/lib/Headers/inttypes.h
@@ -13,6 +13,9 @@
 #if !defined(_AIX) || !defined(_STD_TYPES_T)
 #define __CLANG_INTTYPES_H
 #endif
+#if defined(__MVS__) && __has_include_next(<inttypes.h>)
+#include_next <inttypes.h>
+#else
 
 #if defined(_MSC_VER) && _MSC_VER < 1800
 #error MSVC does not have inttypes.h prior to Visual Studio 2013
@@ -94,4 +97,5 @@
 #define SCNxFAST32 "x"
 #endif
 
+#endif /* __MVS__ */
 #endif /* __CLANG_INTTYPES_H */
Index: clang/lib/Headers/iso646.h
===================================================================
--- clang/lib/Headers/iso646.h
+++ clang/lib/Headers/iso646.h
@@ -9,6 +9,9 @@
 
 #ifndef __ISO646_H
 #define __ISO646_H
+#if defined(__MVS__) && __has_include_next(<iso646.h>)
+#include_next <iso646.h>
+#else
 
 #ifndef __cplusplus
 #define and    &&
@@ -24,4 +27,5 @@
 #define xor_eq ^=
 #endif
 
+#endif /* __MVS__ */
 #endif /* __ISO646_H */
Index: clang/lib/Headers/limits.h
===================================================================
--- clang/lib/Headers/limits.h
+++ clang/lib/Headers/limits.h
@@ -9,6 +9,10 @@
 #ifndef __CLANG_LIMITS_H
 #define __CLANG_LIMITS_H
 
+#if defined(__MVS__) && __has_include_next(<limits.h>)
+#include_next <limits.h>
+#else
+
 /* The system's limits.h may, in turn, try to #include_next GCC's limits.h.
    Avert this #include_next madness. */
 #if defined __GNUC__ && !defined _GCC_LIMITS_H_
@@ -124,4 +128,5 @@
 #define ULONG_LONG_MAX (__LONG_LONG_MAX__*2ULL+1ULL)
 #endif
 
+#endif /* __MVS__ */
 #endif /* __CLANG_LIMITS_H */
Index: clang/lib/Headers/stdalign.h
===================================================================
--- clang/lib/Headers/stdalign.h
+++ clang/lib/Headers/stdalign.h
@@ -10,6 +10,10 @@
 #ifndef __STDALIGN_H
 #define __STDALIGN_H
 
+#if defined(__MVS__) && __has_include_next(<stdalign.h>)
+#include_next <stdalign.h>
+#else
+
 /* FIXME: This is using the placeholder dates Clang produces for these macros
    in C2x mode; switch to the correct values once they've been published. */
 #if defined(__cplusplus) ||                                                    \
@@ -23,4 +27,5 @@
 #define __alignof_is_defined 1
 #endif /* __STDC_VERSION__ */
 
+#endif /* __MVS__ */
 #endif /* __STDALIGN_H */
Index: clang/lib/Headers/stdarg.h
===================================================================
--- clang/lib/Headers/stdarg.h
+++ clang/lib/Headers/stdarg.h
@@ -8,6 +8,10 @@
  */
 
 #ifndef __STDARG_H
+#if defined(__MVS__) && __has_include_next(<stdarg.h>)
+#define __STDARG_H
+#include_next <stdarg.h>
+#else
 
 #ifndef __GNUC_VA_LIST
 #define __GNUC_VA_LIST
@@ -46,6 +50,7 @@
 #define va_copy(dest, src)  __builtin_va_copy(dest, src)
 #endif
 
-#endif /* __STDARG_H */
+#endif /* __STDC_VERSION__ */
 
+#endif /* __MVS__ */
 #endif /* not __STDARG_H */
Index: clang/lib/Headers/stdbool.h
===================================================================
--- clang/lib/Headers/stdbool.h
+++ clang/lib/Headers/stdbool.h
@@ -12,6 +12,10 @@
 
 #define __bool_true_false_are_defined 1
 
+#if defined(__MVS__) && __has_include_next(<stdbool.h>)
+#include_next <stdbool.h>
+#else
+
 #if defined(__STDC_VERSION__) && __STDC_VERSION__ > 201710L
 /* FIXME: We should be issuing a deprecation warning here, but cannot yet due
  * to system headers which include this header file unconditionally.
@@ -31,4 +35,5 @@
 #endif
 #endif
 
+#endif /* __MVS__ */
 #endif /* __STDBOOL_H */
Index: clang/lib/Headers/stddef.h
===================================================================
--- clang/lib/Headers/stddef.h
+++ clang/lib/Headers/stddef.h
@@ -11,6 +11,17 @@
     defined(__need_size_t) || defined(__need_wchar_t) ||                       \
     defined(__need_NULL) || defined(__need_wint_t)
 
+#if defined(__MVS__) && __has_include_next(<stddef.h>)
+#define __STDDEF_H
+#undef __need_ptrdiff_t
+#undef __need_size_t
+#undef __need_wchar_t
+#undef __need_NULL
+#undef __need_wint_t
+#include_next <stddef.h>
+
+#else
+
 #if !defined(__need_ptrdiff_t) && !defined(__need_size_t) &&                   \
     !defined(__need_wchar_t) && !defined(__need_NULL) &&                       \
     !defined(__need_wint_t)
@@ -130,4 +141,5 @@
 #undef __need_wint_t
 #endif /* __need_wint_t */
 
+#endif /* __MVS__ */
 #endif
Index: clang/lib/Headers/stdint.h
===================================================================
--- clang/lib/Headers/stdint.h
+++ clang/lib/Headers/stdint.h
@@ -14,6 +14,10 @@
 #define __CLANG_STDINT_H
 #endif
 
+#if defined(__MVS__) && __has_include_next(<stdint.h>)
+#include_next <stdint.h>
+#else
+
 /* If we're hosted, fall back to the system's stdint.h, which might have
  * additional definitions.
  */
@@ -976,4 +980,5 @@
 #endif
 
 #endif /* __STDC_HOSTED__ */
+#endif /* __MVS__ */
 #endif /* __CLANG_STDINT_H */
Index: clang/lib/Headers/stdnoreturn.h
===================================================================
--- clang/lib/Headers/stdnoreturn.h
+++ clang/lib/Headers/stdnoreturn.h
@@ -10,9 +10,15 @@
 #ifndef __STDNORETURN_H
 #define __STDNORETURN_H
 
+#if defined(__MVS__) && __has_include_next(<stdnoreturn.h>)
+#include_next <stdnoreturn.h>
+#else
+
 #define noreturn _Noreturn
 #define __noreturn_is_defined 1
 
+#endif /* __MVS__ */
+
 #if (defined(__STDC_VERSION__) && __STDC_VERSION__ > 201710L) &&               \
     !defined(_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS)
 /* The noreturn macro is deprecated in C2x. We do not mark it as such because
Index: clang/lib/Headers/varargs.h
===================================================================
--- clang/lib/Headers/varargs.h
+++ clang/lib/Headers/varargs.h
@@ -8,5 +8,9 @@
 */
 #ifndef __VARARGS_H
 #define __VARARGS_H
-  #error "Please use <stdarg.h> instead of <varargs.h>"
+#if defined(__MVS__) && __has_include_next(<varargs.h>)
+#include_next <varargs.h>
+#else
+#error "Please use <stdarg.h> instead of <varargs.h>"
+#endif /* __MVS__ */
 #endif
Index: clang/lib/Headers/zos_wrappers/builtins.h
===================================================================
--- /dev/null
+++ clang/lib/Headers/zos_wrappers/builtins.h
@@ -0,0 +1,18 @@
+/*===---- builtins.h - z/Architecture Builtin Functions --------------------===
+ *
+ * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+ * See https://llvm.org/LICENSE.txt for license information.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ *
+ *===-----------------------------------------------------------------------===
+ */
+
+#ifndef __ZOS_WRAPPERS_BUILTINS_H
+#define __ZOS_WRAPPERS_BUILTINS_H
+#if defined(__MVS__)
+#include_next <builtins.h>
+#if defined(__VEC__)
+#include <vecintrin.h>
+#endif
+#endif /* defined(__MVS__) */
+#endif /* __ZOS_WRAPPERS_BUILTINS_H */