diff --git a/common/lib/libc/arch/aarch64/atomic/atomic_cas_16.S b/common/lib/libc/arch/aarch64/atomic/atomic_cas_16.S
index c45710461dc8..a499ff6dbef9 100644
--- a/common/lib/libc/arch/aarch64/atomic/atomic_cas_16.S
+++ b/common/lib/libc/arch/aarch64/atomic/atomic_cas_16.S
@@ -1,4 +1,4 @@
-/* $NetBSD: atomic_cas_16.S,v 1.2 2020/08/12 12:59:57 skrll Exp $ */
+/* $NetBSD: atomic_cas_16.S,v 1.3 2020/10/07 07:31:47 skrll Exp $ */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
 #include "atomic_op_asm.h"
 
 ENTRY_NP(_atomic_cas_16)
-	mov	x4, x0			/* we need r0 for return value */
+	mov	x4, x0			/* we need x0 for return value */
 1:	ldxrh	w0, [x4]		/* load old value */
 	cmp	w0, w1			/*   compare? */
 	b.ne	2f
diff --git a/common/lib/libc/arch/aarch64/atomic/atomic_cas_32.S b/common/lib/libc/arch/aarch64/atomic/atomic_cas_32.S
index f3f337c26ab4..ec538f16b70f 100644
--- a/common/lib/libc/arch/aarch64/atomic/atomic_cas_32.S
+++ b/common/lib/libc/arch/aarch64/atomic/atomic_cas_32.S
@@ -1,4 +1,4 @@
-/* $NetBSD: atomic_cas_32.S,v 1.2 2020/08/12 12:59:57 skrll Exp $ */
+/* $NetBSD: atomic_cas_32.S,v 1.3 2020/10/07 07:31:47 skrll Exp $ */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
 #include "atomic_op_asm.h"
 
 ENTRY_NP(_atomic_cas_32)
-	mov	x4, x0			/* we need r0 for return value */
+	mov	x4, x0			/* we need x0 for return value */
 1:	ldxr	w0, [x4]		/* load old value */
 	cmp	w0, w1			/*   compare? */
 	b.ne	2f			/*     return if different */
diff --git a/common/lib/libc/arch/aarch64/atomic/atomic_cas_64.S b/common/lib/libc/arch/aarch64/atomic/atomic_cas_64.S
index 914cbb8fb596..a46545dd050f 100644
--- a/common/lib/libc/arch/aarch64/atomic/atomic_cas_64.S
+++ b/common/lib/libc/arch/aarch64/atomic/atomic_cas_64.S
@@ -1,4 +1,4 @@
-/* $NetBSD: atomic_cas_64.S,v 1.4 2020/08/12 12:59:57 skrll Exp $ */
+/* $NetBSD: atomic_cas_64.S,v 1.5 2020/10/07 07:31:47 skrll Exp $ */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
 #include "atomic_op_asm.h"
 
 ENTRY_NP(_atomic_cas_64)
-	mov	x4, x0			/* we need r0 for return value */
+	mov	x4, x0			/* we need x0 for return value */
 1:	ldxr	x0, [x4]		/* load old value */
 	cmp	x0, x1			/*   compare? */
 	b.ne	2f			/*     return if different */
diff --git a/common/lib/libc/arch/aarch64/atomic/atomic_cas_8.S b/common/lib/libc/arch/aarch64/atomic/atomic_cas_8.S
index ab7a9ce4b820..939ff2a8db3a 100644
--- a/common/lib/libc/arch/aarch64/atomic/atomic_cas_8.S
+++ b/common/lib/libc/arch/aarch64/atomic/atomic_cas_8.S
@@ -1,4 +1,4 @@
-/* $NetBSD: atomic_cas_8.S,v 1.2 2020/08/12 12:59:57 skrll Exp $ */
+/* $NetBSD: atomic_cas_8.S,v 1.3 2020/10/07 07:31:47 skrll Exp $ */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
 #include "atomic_op_asm.h"
 
 ENTRY_NP(_atomic_cas_8)
-	mov	x4, x0			/* we need r0 for return value */
+	mov	x4, x0			/* we need x0 for return value */
 1:	ldxrb	w0, [x4]		/* load old value */
 	cmp	w0, w1			/*   compare? */
 	b.ne	2f
diff --git a/common/lib/libc/arch/aarch64/atomic/atomic_op_asm.h b/common/lib/libc/arch/aarch64/atomic/atomic_op_asm.h
index f31c43b3de3b..e63fcf599c47 100644
--- a/common/lib/libc/arch/aarch64/atomic/atomic_op_asm.h
+++ b/common/lib/libc/arch/aarch64/atomic/atomic_op_asm.h
@@ -1,4 +1,4 @@
-/* $NetBSD: atomic_op_asm.h,v 1.3 2019/02/08 06:56:56 ryo Exp $ */
+/* $NetBSD: atomic_op_asm.h,v 1.4 2020/10/07 07:34:29 skrll Exp $ */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -47,7 +47,7 @@ END(_atomic_##OP##_8)
 
 #define	ATOMIC_OP8_NV(OP, INSN)						\
 ENTRY_NP(_atomic_##OP##_8_nv)						;\
-	mov	x4, x0			/* need r0 for return value */	;\
+	mov	x4, x0			/* need x0 for return value */	;\
 1:	ldxrb	w0, [x4]		/* load old value */		;\
 	INSN	w0, w0, w1		/* calc new (return) value */	;\
 	stxrb	w3, w0, [x4]		/* try to store */		;\
@@ -69,7 +69,7 @@ END(_atomic_##OP##_16)
 
 #define	ATOMIC_OP16_NV(OP, INSN)					\
 ENTRY_NP(_atomic_##OP##_16_nv)						;\
-	mov	x4, x0			/* need r0 for return value */	;\
+	mov	x4, x0			/* need x0 for return value */	;\
 1:	ldxrh	w0, [x4]		/* load old value */		;\
 	INSN	w0, w0, w1		/* calc new (return) value */	;\
 	stxrh	w3, w0, [x4]		/* try to store */		;\
@@ -91,7 +91,7 @@ END(_atomic_##OP##_32)
 
 #define	ATOMIC_OP32_NV(OP, INSN)					\
 ENTRY_NP(_atomic_##OP##_32_nv)						;\
-	mov	x4, x0			/* need r0 for return value */	;\
+	mov	x4, x0			/* need x0 for return value */	;\
 1:	ldxr	w0, [x4]		/* load old value */		;\
 	INSN	w0, w0, w1		/* calc new (return) value */	;\
 	stxr	w3, w0, [x4]		/* try to store */		;\
@@ -113,7 +113,7 @@ END(_atomic_##OP##_64)
 
 #define	ATOMIC_OP64_NV(OP, INSN)					\
 ENTRY_NP(_atomic_##OP##_64_nv)						;\
-	mov	x4, x0			/* need r0 for return value */	;\
+	mov	x4, x0			/* need x0 for return value */	;\
 1:	ldxr	x0, [x4]		/* load old value */		;\
 	INSN	x0, x0, x1		/* calc new (return) value */	;\
 	stxr	w3, x0, [x4]		/* try to store */		;\