--- a/src/hotspot/cpu/aarch64/gc/g1/g1BarrierSetAssembler_aarch64.cpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/g1/g1BarrierSetAssembler_aarch64.cpp	Mon Mar 25 19:49:32 2019 +0300
@@ -72,15 +72,12 @@
 }
 
 void G1BarrierSetAssembler::gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
-                                                             Register start, Register end, Register scratch, RegSet saved_regs) {
+                                                             Register start, Register count, Register scratch, RegSet saved_regs) {
   __ push(saved_regs, sp);
-  // must compute element count unless barrier set interface is changed (other platforms supply count)
-  assert_different_registers(start, end, scratch);
-  __ lea(scratch, Address(end, BytesPerHeapOop));
-  __ sub(scratch, scratch, start);               // subtract start to get #bytes
-  __ lsr(scratch, scratch, LogBytesPerHeapOop);  // convert to element count
+  assert_different_registers(start, count, scratch);
+  assert_different_registers(c_rarg0, count);
   __ mov(c_rarg0, start);
-  __ mov(c_rarg1, scratch);
+  __ mov(c_rarg1, count);
   __ call_VM_leaf(CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_array_post_entry), 2);
   __ pop(saved_regs, sp);
 }

--- a/src/hotspot/cpu/aarch64/gc/g1/g1BarrierSetAssembler_aarch64.hpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/g1/g1BarrierSetAssembler_aarch64.hpp	Mon Mar 25 19:49:32 2019 +0300
@@ -39,7 +39,7 @@
   void gen_write_ref_array_pre_barrier(MacroAssembler* masm, DecoratorSet decorators,
                                        Register addr, Register count, RegSet saved_regs);
   void gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
-                                        Register start, Register end, Register tmp, RegSet saved_regs);
+                                        Register start, Register count, Register tmp, RegSet saved_regs);
 
   void g1_write_barrier_pre(MacroAssembler* masm,
                             Register obj,

--- a/src/hotspot/cpu/aarch64/gc/shared/cardTableBarrierSetAssembler_aarch64.cpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/shared/cardTableBarrierSetAssembler_aarch64.cpp	Mon Mar 25 19:49:32 2019 +0300
@@ -62,18 +62,22 @@
 }
 
 void CardTableBarrierSetAssembler::gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
-                                                                    Register start, Register end, Register scratch, RegSet saved_regs) {
+                                                                    Register start, Register count, Register scratch, RegSet saved_regs) {
   BarrierSet* bs = BarrierSet::barrier_set();
   CardTableBarrierSet* ctbs = barrier_set_cast<CardTableBarrierSet>(bs);
   CardTable* ct = ctbs->card_table();
 
-  Label L_loop;
+  Label L_loop, L_done;
+  const Register end = count;
 
+  __ cbz(count, L_done); // zero count - nothing to do
+
+  __ lea(end, Address(start, count, Address::lsl(LogBytesPerHeapOop))); // end = start + count << LogBytesPerHeapOop
+  __ sub(end, end, BytesPerHeapOop); // last element address to make inclusive
   __ lsr(start, start, CardTable::card_shift);
   __ lsr(end, end, CardTable::card_shift);
-  __ sub(end, end, start); // number of bytes to copy
+  __ sub(count, end, start); // number of bytes to copy
 
-  const Register count = end; // 'end' register contains bytes count now
   __ load_byte_map_base(scratch);
   __ add(start, start, scratch);
   if (ct->scanned_concurrently()) {
@@ -83,6 +87,7 @@
   __ strb(zr, Address(start, count));
   __ subs(count, count, 1);
   __ br(Assembler::GE, L_loop);
+  __ bind(L_done);
 }
 
 void CardTableBarrierSetAssembler::oop_store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,

--- a/src/hotspot/cpu/aarch64/gc/shared/cardTableBarrierSetAssembler_aarch64.hpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/shared/cardTableBarrierSetAssembler_aarch64.hpp	Mon Mar 25 19:49:32 2019 +0300
@@ -33,7 +33,7 @@
   void store_check(MacroAssembler* masm, Register obj, Address dst);
 
   virtual void gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
-                                                Register start, Register end, Register tmp, RegSet saved_regs);
+                                                Register start, Register count, Register tmp, RegSet saved_regs);
   virtual void oop_store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
                             Address dst, Register val, Register tmp1, Register tmp2);
 

--- a/src/hotspot/cpu/aarch64/gc/shared/modRefBarrierSetAssembler_aarch64.cpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/shared/modRefBarrierSetAssembler_aarch64.cpp	Mon Mar 25 19:49:32 2019 +0300
@@ -37,10 +37,10 @@
 }
 
 void ModRefBarrierSetAssembler::arraycopy_epilogue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
-                                                   Register start, Register end, Register tmp,
+                                                   Register start, Register count, Register tmp,
                                                    RegSet saved_regs) {
   if (is_oop) {
-    gen_write_ref_array_post_barrier(masm, decorators, start, end, tmp, saved_regs);
+    gen_write_ref_array_post_barrier(masm, decorators, start, count, tmp, saved_regs);
   }
 }
 

--- a/src/hotspot/cpu/aarch64/gc/shared/modRefBarrierSetAssembler_aarch64.hpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/shared/modRefBarrierSetAssembler_aarch64.hpp	Mon Mar 25 19:49:32 2019 +0300
@@ -37,7 +37,7 @@
   virtual void gen_write_ref_array_pre_barrier(MacroAssembler* masm, DecoratorSet decorators,
                                                Register addr, Register count, RegSet saved_regs) {}
   virtual void gen_write_ref_array_post_barrier(MacroAssembler* masm, DecoratorSet decorators,
-                                                Register start, Register end, Register tmp, RegSet saved_regs) {}
+                                                Register start, Register count, Register tmp, RegSet saved_regs) {}
 
   virtual void oop_store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
                             Address dst, Register val, Register tmp1, Register tmp2) = 0;
@@ -46,7 +46,7 @@
   virtual void arraycopy_prologue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
                                   Register addr, Register count, RegSet saved_regs);
   virtual void arraycopy_epilogue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
-                                  Register start, Register end, Register tmp, RegSet saved_regs);
+                                  Register start, Register count, Register tmp, RegSet saved_regs);
   virtual void store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
                         Address dst, Register val, Register tmp1, Register tmp2);
 };

--- a/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.cpp	Mon Mar 25 19:49:32 2019 +0300
@@ -73,16 +73,13 @@
 }
 
 void ShenandoahBarrierSetAssembler::arraycopy_epilogue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
-                                                       Register start, Register end, Register scratch, RegSet saved_regs) {
+                                                       Register start, Register count, Register scratch, RegSet saved_regs) {
   if (is_oop) {
     __ push(saved_regs, sp);
-    // must compute element count unless barrier set interface is changed (other platforms supply count)
-    assert_different_registers(start, end, scratch);
-    __ lea(scratch, Address(end, BytesPerHeapOop));
-    __ sub(scratch, scratch, start);               // subtract start to get #bytes
-    __ lsr(scratch, scratch, LogBytesPerHeapOop);  // convert to element count
+    assert_different_registers(start, count, scratch);
+    assert_different_registers(c_rarg0, count);
     __ mov(c_rarg0, start);
-    __ mov(c_rarg1, scratch);
+    __ mov(c_rarg1, count);
     __ call_VM_leaf(CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_array_post_entry), 2);
     __ pop(saved_regs, sp);
   }

--- a/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.hpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/gc/shenandoah/shenandoahBarrierSetAssembler_aarch64.hpp	Mon Mar 25 19:49:32 2019 +0300
@@ -78,7 +78,7 @@
   virtual void arraycopy_prologue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
                                   Register addr, Register count, RegSet saved_regs);
   virtual void arraycopy_epilogue(MacroAssembler* masm, DecoratorSet decorators, bool is_oop,
-                                  Register start, Register end, Register tmp, RegSet saved_regs);
+                                  Register start, Register count, Register tmp, RegSet saved_regs);
   virtual void load_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,
                        Register dst, Address src, Register tmp1, Register tmp_thread);
   virtual void store_at(MacroAssembler* masm, DecoratorSet decorators, BasicType type,

--- a/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp	Mon Mar 25 09:07:55 2019 -0700
+++ b/src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp	Mon Mar 25 19:49:32 2019 +0300
@@ -1375,8 +1375,6 @@
       __ pop(RegSet::of(d, count), sp);
       if (VerifyOops)
         verify_oop_array(size, d, count, r16);
-      __ sub(count, count, 1); // make an inclusive end pointer
-      __ lea(count, Address(d, count, Address::lsl(exact_log2(size))));
     }
 
     bs->arraycopy_epilogue(_masm, decorators, is_oop, d, count, rscratch1, RegSet());
@@ -1448,8 +1446,6 @@
       __ pop(RegSet::of(d, count), sp);
       if (VerifyOops)
         verify_oop_array(size, d, count, r16);
-      __ sub(count, count, 1); // make an inclusive end pointer
-      __ lea(count, Address(d, count, Address::lsl(exact_log2(size))));
     }
     bs->arraycopy_epilogue(_masm, decorators, is_oop, d, count, rscratch1, RegSet());
     __ leave();
@@ -1842,8 +1838,7 @@
     __ br(Assembler::EQ, L_done_pop);
 
     __ BIND(L_do_card_marks);
-    __ add(to, to, -heapOopSize);         // make an inclusive end pointer
-    bs->arraycopy_epilogue(_masm, decorators, is_oop, start_to, to, rscratch1, wb_post_saved_regs);
+    bs->arraycopy_epilogue(_masm, decorators, is_oop, start_to, count_save, rscratch1, wb_post_saved_regs);
 
     __ bind(L_done_pop);
     __ pop(RegSet::of(r18, r19, r20, r21), sp);