diff --git a/modules/libcom/src/osi/Makefile b/modules/libcom/src/osi/Makefile
index ce9dcc692..a0835d57b 100644
--- a/modules/libcom/src/osi/Makefile
+++ b/modules/libcom/src/osi/Makefile
@@ -65,6 +65,10 @@ INC += osdVME.h
 INC += epicsMMIO.h
 INC += epicsMMIODef.h
 
+INC_clang += epicsAtomicGCC.h
+INC_gcc   += epicsAtomicGCC.h
+INC += $(INC_$(CMPLR_CLASS))
+
 Com_SRCS += epicsThread.cpp
 Com_SRCS += epicsMutex.cpp
 Com_SRCS += epicsEvent.cpp
diff --git a/modules/libcom/src/osi/compiler/clang/epicsAtomicCD.h b/modules/libcom/src/osi/compiler/clang/epicsAtomicCD.h
index 019ce244c..081828ad5 100644
--- a/modules/libcom/src/osi/compiler/clang/epicsAtomicCD.h
+++ b/modules/libcom/src/osi/compiler/clang/epicsAtomicCD.h
@@ -17,8 +17,18 @@
 #ifndef epicsAtomicCD_h
 #define epicsAtomicCD_h
 
+#ifndef __clang__
+#   error this header is only for use with the Clang compiler
+#endif
+
 #define EPICS_ATOMIC_CMPLR_NAME "CLANG"
 
+#include <epicsAtomicGCC.h>
+
+/*
+ * if currently unavailable as intrinsics we
+ * will try for an os specific inline solution
+ */
 #include "epicsAtomicOSD.h"
 
 #endif /* epicsAtomicCD_h */
diff --git a/modules/libcom/src/osi/compiler/gcc/epicsAtomicCD.h b/modules/libcom/src/osi/compiler/gcc/epicsAtomicCD.h
index a7bcd8f3c..c770b363e 100644
--- a/modules/libcom/src/osi/compiler/gcc/epicsAtomicCD.h
+++ b/modules/libcom/src/osi/compiler/gcc/epicsAtomicCD.h
@@ -23,130 +23,7 @@
 
 #define EPICS_ATOMIC_CMPLR_NAME "GCC"
 
-/* expands __GCC_HAVE_SYNC_COMPARE_AND_SWAP_ concatentating the numeric value __SIZEOF_*__ */
-#define GCC_ATOMIC_CONCAT( A, B ) GCC_ATOMIC_CONCATR(A,B)
-#define GCC_ATOMIC_CONCATR( A, B ) ( A ## B )
-
-/*
- * As of GCC 8, the __sync_synchronize() is inlined for all
- * known targets (aarch64, arm, i386, powerpc, and x86_64)
- * except for arm <=6.
- * Note that i386 inlines __sync_synchronize() but does not
- * define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_*
- */
-#define GCC_ATOMIC_INTRINSICS_AVAIL_SYNC \
-    defined(GCC_ATOMIC_INTRINSICS_AVAIL_INT_T) || defined(GCC_ATOMIC_INTRINSICS_AVAIL_SIZE_T) || defined(__i386)
-
-#define GCC_ATOMIC_INTRINSICS_AVAIL_INT_T \
-    GCC_ATOMIC_CONCAT ( \
-        __GCC_HAVE_SYNC_COMPARE_AND_SWAP_, \
-        __SIZEOF_INT__ )
-
-/* we assume __SIZEOF_POINTER__ == __SIZEOF_SIZE_T__ */
-#define GCC_ATOMIC_INTRINSICS_AVAIL_SIZE_T \
-    GCC_ATOMIC_CONCAT ( \
-        __GCC_HAVE_SYNC_COMPARE_AND_SWAP_, \
-        __SIZEOF_SIZE_T__ )
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#if GCC_ATOMIC_INTRINSICS_AVAIL_SYNC
-
-#ifndef EPICS_ATOMIC_READ_MEMORY_BARRIER
-#define EPICS_ATOMIC_READ_MEMORY_BARRIER
-EPICS_ATOMIC_INLINE void epicsAtomicReadMemoryBarrier (void)
-{
-    __sync_synchronize ();
-}
-#endif
-
-#ifndef EPICS_ATOMIC_WRITE_MEMORY_BARRIER
-#define EPICS_ATOMIC_WRITE_MEMORY_BARRIER
-EPICS_ATOMIC_INLINE void epicsAtomicWriteMemoryBarrier (void)
-{
-    __sync_synchronize ();
-}
-#endif
-
-#endif
-
-#if GCC_ATOMIC_INTRINSICS_AVAIL_INT_T
-
-#define EPICS_ATOMIC_INCR_INTT
-EPICS_ATOMIC_INLINE int epicsAtomicIncrIntT ( int * pTarget )
-{
-    return __sync_add_and_fetch ( pTarget, 1 );
-}
-
-#define EPICS_ATOMIC_DECR_INTT
-EPICS_ATOMIC_INLINE int epicsAtomicDecrIntT ( int * pTarget )
-{
-    return __sync_sub_and_fetch ( pTarget, 1 );
-}
-
-#define EPICS_ATOMIC_ADD_INTT
-EPICS_ATOMIC_INLINE int epicsAtomicAddIntT ( int * pTarget, int delta )
-{
-    return __sync_add_and_fetch ( pTarget, delta );
-}
-
-#define EPICS_ATOMIC_CAS_INTT
-EPICS_ATOMIC_INLINE int epicsAtomicCmpAndSwapIntT ( int * pTarget,
-                                        int oldVal, int newVal )
-{
-    return __sync_val_compare_and_swap ( pTarget, oldVal, newVal);
-}
-
-#endif
-
-#if GCC_ATOMIC_INTRINSICS_AVAIL_SIZE_T
-
-#define EPICS_ATOMIC_INCR_SIZET
-EPICS_ATOMIC_INLINE size_t epicsAtomicIncrSizeT ( size_t * pTarget )
-{
-    return __sync_add_and_fetch ( pTarget, 1u );
-}
-
-#define EPICS_ATOMIC_DECR_SIZET
-EPICS_ATOMIC_INLINE size_t epicsAtomicDecrSizeT ( size_t * pTarget )
-{
-    return __sync_sub_and_fetch ( pTarget, 1u );
-}
-
-#define EPICS_ATOMIC_ADD_SIZET
-EPICS_ATOMIC_INLINE size_t epicsAtomicAddSizeT ( size_t * pTarget, size_t delta )
-{
-    return __sync_add_and_fetch ( pTarget, delta );
-}
-
-#define EPICS_ATOMIC_SUB_SIZET
-EPICS_ATOMIC_INLINE size_t epicsAtomicSubSizeT ( size_t * pTarget, size_t delta )
-{
-    return __sync_sub_and_fetch ( pTarget, delta );
-}
-
-#define EPICS_ATOMIC_CAS_SIZET
-EPICS_ATOMIC_INLINE size_t epicsAtomicCmpAndSwapSizeT ( size_t * pTarget,
-                                        size_t oldVal, size_t newVal )
-{
-    return __sync_val_compare_and_swap ( pTarget, oldVal, newVal);
-}
-
-#define EPICS_ATOMIC_CAS_PTRT
-EPICS_ATOMIC_INLINE EpicsAtomicPtrT epicsAtomicCmpAndSwapPtrT (
-                            EpicsAtomicPtrT * pTarget,
-                            EpicsAtomicPtrT oldVal, EpicsAtomicPtrT newVal )
-{
-    return __sync_val_compare_and_swap ( pTarget, oldVal, newVal);
-}
-
-#endif
-
-#ifdef __cplusplus
-} /* end of extern "C" */
-#endif
+#include <epicsAtomicGCC.h>
 
 /*
  * if currently unavailable as gcc intrinsics we
diff --git a/modules/libcom/src/osi/epicsAtomicGCC.h b/modules/libcom/src/osi/epicsAtomicGCC.h
new file mode 100644
index 000000000..006d6a27e
--- /dev/null
+++ b/modules/libcom/src/osi/epicsAtomicGCC.h
@@ -0,0 +1,156 @@
+/*************************************************************************\
+* Copyright (c) 2011 LANS LLC, as Operator of
+*     Los Alamos National Laboratory.
+* Copyright (c) 2021 UChicago Argonne LLC, as Operator of Argonne
+*     National Laboratory.
+* SPDX-License-Identifier: EPICS
+* EPICS BASE is distributed subject to a Software License Agreement found
+* in file LICENSE that is included with this distribution.
+\*************************************************************************/
+
+/*
+ *  Author Jeffrey O. Hill
+ *  johill@lanl.gov
+ */
+
+/*
+ * These implementations are the same for both GCC and Clang
+ */
+
+#ifndef INC_epicsAtomicGCC_H
+#define INC_epicsAtomicGCC_H
+
+/* expands __GCC_HAVE_SYNC_COMPARE_AND_SWAP_ concatentating
+ * the numeric value __SIZEOF_*__
+ */
+#define GCC_ATOMIC_CONCAT( A, B ) GCC_ATOMIC_CONCATR(A,B)
+#define GCC_ATOMIC_CONCATR( A, B ) ( A ## B )
+
+#define GCC_ATOMIC_INTRINSICS_AVAIL_INT_T \
+    GCC_ATOMIC_CONCAT ( \
+        __GCC_HAVE_SYNC_COMPARE_AND_SWAP_, \
+        __SIZEOF_INT__ )
+
+/* we assume __SIZEOF_POINTER__ == __SIZEOF_SIZE_T__ */
+#define GCC_ATOMIC_INTRINSICS_AVAIL_SIZE_T \
+    GCC_ATOMIC_CONCAT ( \
+        __GCC_HAVE_SYNC_COMPARE_AND_SWAP_, \
+        __SIZEOF_SIZE_T__ )
+
+/*
+ * As of GCC 8, the __sync_synchronize() is inlined for all
+ * known targets (aarch64, arm, i386, powerpc, and x86_64)
+ * except for arm <=6.
+ * Note that i386 inlines __sync_synchronize() but does not
+ * define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_*
+ */
+#if GCC_ATOMIC_INTRINSICS_AVAIL_INT_T || \
+    GCC_ATOMIC_INTRINSICS_AVAIL_SIZE_T || \
+    defined(__i386)
+#define GCC_ATOMIC_INTRINSICS_AVAIL_SYNC 1
+#else
+#define GCC_ATOMIC_INTRINSICS_AVAIL_SYNC 0
+#endif
+/* The above macro is also used in epicsAtomicTest.cpp */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if GCC_ATOMIC_INTRINSICS_AVAIL_SYNC
+
+#ifndef EPICS_ATOMIC_READ_MEMORY_BARRIER
+#define EPICS_ATOMIC_READ_MEMORY_BARRIER
+EPICS_ATOMIC_INLINE void epicsAtomicReadMemoryBarrier (void)
+{
+    __sync_synchronize ();
+}
+#endif
+
+#ifndef EPICS_ATOMIC_WRITE_MEMORY_BARRIER
+#define EPICS_ATOMIC_WRITE_MEMORY_BARRIER
+EPICS_ATOMIC_INLINE void epicsAtomicWriteMemoryBarrier (void)
+{
+    __sync_synchronize ();
+}
+#endif
+
+#endif
+
+#if GCC_ATOMIC_INTRINSICS_AVAIL_INT_T
+
+#define EPICS_ATOMIC_INCR_INTT
+EPICS_ATOMIC_INLINE int epicsAtomicIncrIntT ( int * pTarget )
+{
+    return __sync_add_and_fetch ( pTarget, 1 );
+}
+
+#define EPICS_ATOMIC_DECR_INTT
+EPICS_ATOMIC_INLINE int epicsAtomicDecrIntT ( int * pTarget )
+{
+    return __sync_sub_and_fetch ( pTarget, 1 );
+}
+
+#define EPICS_ATOMIC_ADD_INTT
+EPICS_ATOMIC_INLINE int epicsAtomicAddIntT ( int * pTarget, int delta )
+{
+    return __sync_add_and_fetch ( pTarget, delta );
+}
+
+#define EPICS_ATOMIC_CAS_INTT
+EPICS_ATOMIC_INLINE int epicsAtomicCmpAndSwapIntT ( int * pTarget,
+                                        int oldVal, int newVal )
+{
+    return __sync_val_compare_and_swap ( pTarget, oldVal, newVal);
+}
+
+#endif
+
+#if GCC_ATOMIC_INTRINSICS_AVAIL_SIZE_T
+
+#define EPICS_ATOMIC_INCR_SIZET
+EPICS_ATOMIC_INLINE size_t epicsAtomicIncrSizeT ( size_t * pTarget )
+{
+    return __sync_add_and_fetch ( pTarget, 1u );
+}
+
+#define EPICS_ATOMIC_DECR_SIZET
+EPICS_ATOMIC_INLINE size_t epicsAtomicDecrSizeT ( size_t * pTarget )
+{
+    return __sync_sub_and_fetch ( pTarget, 1u );
+}
+
+#define EPICS_ATOMIC_ADD_SIZET
+EPICS_ATOMIC_INLINE size_t epicsAtomicAddSizeT ( size_t * pTarget, size_t delta )
+{
+    return __sync_add_and_fetch ( pTarget, delta );
+}
+
+#define EPICS_ATOMIC_SUB_SIZET
+EPICS_ATOMIC_INLINE size_t epicsAtomicSubSizeT ( size_t * pTarget, size_t delta )
+{
+    return __sync_sub_and_fetch ( pTarget, delta );
+}
+
+#define EPICS_ATOMIC_CAS_SIZET
+EPICS_ATOMIC_INLINE size_t epicsAtomicCmpAndSwapSizeT ( size_t * pTarget,
+                                        size_t oldVal, size_t newVal )
+{
+    return __sync_val_compare_and_swap ( pTarget, oldVal, newVal);
+}
+
+#define EPICS_ATOMIC_CAS_PTRT
+EPICS_ATOMIC_INLINE EpicsAtomicPtrT epicsAtomicCmpAndSwapPtrT (
+                            EpicsAtomicPtrT * pTarget,
+                            EpicsAtomicPtrT oldVal, EpicsAtomicPtrT newVal )
+{
+    return __sync_val_compare_and_swap ( pTarget, oldVal, newVal);
+}
+
+#endif
+
+#ifdef __cplusplus
+} /* end of extern "C" */
+#endif
+
+#endif /* INC_epicsAtomicGCC_H */