--- old/src/hotspot/cpu/aarch64/aarch64.ad	2018-10-24 13:34:55.670847482 +0200
+++ new/src/hotspot/cpu/aarch64/aarch64.ad	2018-10-24 13:34:47.021827404 +0200
@@ -8341,8 +8341,7 @@
     "cmpxchg $res = $mem, $oldval, $newval\t# (byte, weak) if $mem == $oldval then $mem <-- $newval"
   %}
   ins_encode %{
-    __ uxtbw(rscratch2, $oldval$$Register);
-    __ cmpxchg($mem$$Register, rscratch2, $newval$$Register,
+    __ cmpxchg($mem$$Register, $oldval$$Register, $newval$$Register,
                Assembler::byte, /*acquire*/ false, /*release*/ true,
                /*weak*/ false, $res$$Register);
     __ sxtbw($res$$Register, $res$$Register);
@@ -8358,8 +8357,7 @@
     "cmpxchg $res = $mem, $oldval, $newval\t# (short, weak) if $mem == $oldval then $mem <-- $newval"
   %}
   ins_encode %{
-    __ uxthw(rscratch2, $oldval$$Register);
-    __ cmpxchg($mem$$Register, rscratch2, $newval$$Register,
+    __ cmpxchg($mem$$Register, $oldval$$Register, $newval$$Register,
                Assembler::halfword, /*acquire*/ false, /*release*/ true,
                /*weak*/ false, $res$$Register);
     __ sxthw($res$$Register, $res$$Register);
@@ -8436,8 +8434,7 @@
     "csetw $res, EQ\t# $res <-- (EQ ? 1 : 0)"
   %}
   ins_encode %{
-    __ uxtbw(rscratch2, $oldval$$Register);
-    __ cmpxchg($mem$$Register, rscratch2, $newval$$Register,
+    __ cmpxchg($mem$$Register, $oldval$$Register, $newval$$Register,
                Assembler::byte, /*acquire*/ false, /*release*/ true,
                /*weak*/ true, noreg);
     __ csetw($res$$Register, Assembler::EQ);
@@ -8454,8 +8451,7 @@
     "csetw $res, EQ\t# $res <-- (EQ ? 1 : 0)"
   %}
   ins_encode %{
-    __ uxthw(rscratch2, $oldval$$Register);
-    __ cmpxchg($mem$$Register, rscratch2, $newval$$Register,
+    __ cmpxchg($mem$$Register, $oldval$$Register, $newval$$Register,
                Assembler::halfword, /*acquire*/ false, /*release*/ true,
                /*weak*/ true, noreg);
     __ csetw($res$$Register, Assembler::EQ);