diff --git a/openmp/runtime/src/CMakeLists.txt b/openmp/runtime/src/CMakeLists.txt
--- a/openmp/runtime/src/CMakeLists.txt
+++ b/openmp/runtime/src/CMakeLists.txt
@@ -60,6 +60,7 @@
 # Getting correct source files to build library
 set(LIBOMP_CXXFILES)
 set(LIBOMP_ASMFILES)
+set(LIBOMP_GNUASMFILES)
 if(STUBS_LIBRARY)
   set(LIBOMP_CXXFILES kmp_stub.cpp)
 else()
@@ -94,12 +95,15 @@
     libomp_append(LIBOMP_CXXFILES z_Windows_NT-586_util.cpp)
     if(${LIBOMP_ARCH} STREQUAL "i386" OR ${LIBOMP_ARCH} STREQUAL "x86_64")
       libomp_append(LIBOMP_ASMFILES z_Windows_NT-586_asm.asm) # Windows assembly file
+    elseif(${LIBOMP_ARCH} STREQUAL "aarch64" AND (NOT MSVC OR CMAKE_C_COMPILER_ID STREQUAL "Clang"))
+      # z_Linux_asm.S works for AArch64 Windows too.
+      libomp_append(LIBOMP_GNUASMFILES z_Linux_asm.S)
     endif()
   else()
     # Unix specific files
     libomp_append(LIBOMP_CXXFILES z_Linux_util.cpp)
     libomp_append(LIBOMP_CXXFILES kmp_gsupport.cpp)
-    libomp_append(LIBOMP_ASMFILES z_Linux_asm.S) # Unix assembly file
+    libomp_append(LIBOMP_GNUASMFILES z_Linux_asm.S) # Unix assembly file
   endif()
   libomp_append(LIBOMP_CXXFILES thirdparty/ittnotify/ittnotify_static.cpp LIBOMP_USE_ITT_NOTIFY)
   libomp_append(LIBOMP_CXXFILES kmp_debugger.cpp LIBOMP_USE_DEBUGGER)
@@ -115,7 +119,7 @@
 libomp_append(LIBOMP_CXXFILES ompt-general.cpp IF_TRUE LIBOMP_OMPT_SUPPORT)
 libomp_append(LIBOMP_CXXFILES ompd-specific.cpp IF_TRUE LIBOMP_OMPD_SUPPORT)
 
-set(LIBOMP_SOURCE_FILES ${LIBOMP_CXXFILES} ${LIBOMP_ASMFILES})
+set(LIBOMP_SOURCE_FILES ${LIBOMP_CXXFILES} ${LIBOMP_ASMFILES} ${LIBOMP_GNUASMFILES})
 # For Windows, there is a resource file (.rc -> .res) that is also compiled
 libomp_append(LIBOMP_SOURCE_FILES libomp.rc WIN32)
 
@@ -124,11 +128,9 @@
 libomp_get_asmflags(LIBOMP_CONFIGURED_ASMFLAGS)
 # Set the compiler flags for each type of source
 set_source_files_properties(${LIBOMP_CXXFILES} PROPERTIES COMPILE_FLAGS "${LIBOMP_CONFIGURED_CXXFLAGS}")
-set_source_files_properties(${LIBOMP_ASMFILES} PROPERTIES COMPILE_FLAGS "${LIBOMP_CONFIGURED_ASMFLAGS}")
-# Let the compiler handle the assembly files on Unix-like systems
-if(NOT WIN32)
-  set_source_files_properties(${LIBOMP_ASMFILES} PROPERTIES LANGUAGE C)
-endif()
+set_source_files_properties(${LIBOMP_ASMFILES} ${LIBOMP_GNUASMFILES} PROPERTIES COMPILE_FLAGS "${LIBOMP_CONFIGURED_ASMFLAGS}")
+# Let the compiler handle the GNU assembly files
+set_source_files_properties(${LIBOMP_GNUASMFILES} PROPERTIES LANGUAGE C)
 
 # Remove any cmake-automatic linking of the standard C++ library.
 # We neither need (nor want) the standard C++ library dependency even though we compile c++ files.
diff --git a/openmp/runtime/src/z_Linux_asm.S b/openmp/runtime/src/z_Linux_asm.S
--- a/openmp/runtime/src/z_Linux_asm.S
+++ b/openmp/runtime/src/z_Linux_asm.S
@@ -108,7 +108,7 @@
 # endif // KMP_OS_DARWIN
 #endif // KMP_ARCH_X86 || KMP_ARCH_x86_64
 
-#if (KMP_OS_LINUX || KMP_OS_DARWIN) && KMP_ARCH_AARCH64
+#if (KMP_OS_LINUX || KMP_OS_DARWIN || KMP_OS_WINDOWS) && KMP_ARCH_AARCH64
 
 # if KMP_OS_DARWIN
 #  define KMP_PREFIX_UNDERSCORE(x) _##x  // extra underscore for OS X* symbols
@@ -117,6 +117,9 @@
 .macro ALIGN
 	.align $0
 .endmacro
+.macro COMMON name, size, align_power
+	.comm \name, \size
+.endm
 
 .macro DEBUG_INFO
 /* Not sure what .size does in icc, not sure if we need to do something
@@ -129,7 +132,28 @@
 	.globl KMP_PREFIX_UNDERSCORE($0)
 KMP_PREFIX_UNDERSCORE($0):
 .endmacro
-# else // KMP_OS_DARWIN
+# elif KMP_OS_WINDOWS
+#  define KMP_PREFIX_UNDERSCORE(x) x  // no extra underscore for Windows/ARM64 symbols
+// Format labels so that they don't override function names in gdb's backtraces
+#  define KMP_LABEL(x) .L_##x         // local label hidden from backtraces
+
+.macro ALIGN size
+	.align 1<<(\size)
+.endm
+.macro COMMON name, size, align_power
+	.comm \name, \size, \align_power
+.endm
+
+.macro DEBUG_INFO proc
+	ALIGN 2
+.endm
+
+.macro PROC proc
+	ALIGN 2
+	.globl KMP_PREFIX_UNDERSCORE(\proc)
+KMP_PREFIX_UNDERSCORE(\proc):
+.endm
+# else // KMP_OS_DARWIN || KMP_OS_WINDOWS
 #  define KMP_PREFIX_UNDERSCORE(x) x  // no extra underscore for Linux* OS symbols
 // Format labels so that they don't override function names in gdb's backtraces
 #  define KMP_LABEL(x) .L_##x         // local label hidden from backtraces
@@ -137,6 +161,9 @@
 .macro ALIGN size
 	.align 1<<(\size)
 .endm
+.macro COMMON name, size, align_power
+	.comm \name, \size, (1<<(\align_power))
+.endm
 
 .macro DEBUG_INFO proc
 	.cfi_endproc
@@ -154,7 +181,7 @@
 .endm
 # endif // KMP_OS_DARWIN
 
-#endif // (KMP_OS_LINUX || KMP_OS_DARWIN) && KMP_ARCH_AARCH64
+#endif // (KMP_OS_LINUX || KMP_OS_DARWIN || KMP_OS_WINDOWS) && KMP_ARCH_AARCH64
 
 // -----------------------------------------------------------------------
 // data
@@ -1204,7 +1231,7 @@
 #endif /* KMP_ARCH_X86_64 */
 
 // '
-#if (KMP_OS_LINUX || KMP_OS_DARWIN) && KMP_ARCH_AARCH64
+#if (KMP_OS_LINUX || KMP_OS_DARWIN || KMP_OS_WINDOWS) && KMP_ARCH_AARCH64
 
 //------------------------------------------------------------------------
 // int
@@ -1328,7 +1355,7 @@
 	DEBUG_INFO __kmp_invoke_microtask
 // -- End  __kmp_invoke_microtask
 
-#endif /* (KMP_OS_LINUX || KMP_OS_DARWIN) && KMP_ARCH_AARCH64 */
+#endif /* (KMP_OS_LINUX || KMP_OS_DARWIN || KMP_OS_WINDOWS) && KMP_ARCH_AARCH64 */
 
 #if KMP_ARCH_PPC64
 
@@ -1885,7 +1912,7 @@
 
 #if KMP_ARCH_ARM || KMP_ARCH_MIPS
     .data
-    .comm .gomp_critical_user_,32,8
+    COMMON .gomp_critical_user_, 32, 3
     .data
     .align 4
     .global __kmp_unnamed_critical_addr
@@ -1899,7 +1926,7 @@
 # define KMP_PREFIX_UNDERSCORE(x) x
 #endif
     .data
-    .comm .gomp_critical_user_,32,8
+    COMMON .gomp_critical_user_, 32, 3
     .data
     .align 8
     .global KMP_PREFIX_UNDERSCORE(__kmp_unnamed_critical_addr)
diff --git a/openmp/runtime/src/z_Windows_NT-586_util.cpp b/openmp/runtime/src/z_Windows_NT-586_util.cpp
--- a/openmp/runtime/src/z_Windows_NT-586_util.cpp
+++ b/openmp/runtime/src/z_Windows_NT-586_util.cpp
@@ -134,7 +134,9 @@
   return old_value;
 }
 
-#if KMP_ARCH_AARCH64
+#if KMP_ARCH_AARCH64 && KMP_COMPILER_MSVC
+// For !KMP_COMPILER_MSVC, this function is provided in assembly form
+// by z_Linux_asm.S.
 int __kmp_invoke_microtask(microtask_t pkfn, int gtid, int tid, int argc,
                            void *p_argv[]
 #if OMPT_SUPPORT