[15u] RFR 8255065: Zero: accessor_entry misses the IRIW case

[Aleksey Shipilev]

Original bug:
   https://bugs.openjdk.java.net/browse/JDK-8255065
   https://git.openjdk.java.net/jdk/commit/bd45191f

Since cppInterpreter_zero.cpp was renamed to zeroInterpreter_zero.cpp in 16, this patch does not 
apply cleanly. So I had to apply the same hunk to the old location.

15u patch:

diff -r 96851120ae5c src/hotspot/cpu/zero/cppInterpreter_zero.cpp
--- a/src/hotspot/cpu/zero/cppInterpreter_zero.cpp      Thu Oct 08 08:10:55 2020 +0000
+++ b/src/hotspot/cpu/zero/cppInterpreter_zero.cpp      Fri Oct 23 13:10:38 2020 +0200
@@ -555,10 +555,13 @@
      stack->overflow_check(1, CHECK_0);
      stack->alloc(wordSize);
      break;
    }
    if (entry->is_volatile()) {
+    if (support_IRIW_for_not_multiple_copy_atomic_cpu) {
+      OrderAccess::fence();
+    }
      switch (entry->flag_state()) {
      case ctos:
        SET_LOCALS_INT(object->char_field_acquire(entry->f2_as_index()), 0);
        break;

Testing: Linux x86_64 Zero build

-- 
Thanks,
-Aleksey