RFR: JDK-8203172: Primitive heap access for interpreter BarrierSetAssembler/aarch64

[Roman Kennke]

Hi Andrew,

> On 14/05/18 21:23, Roman Kennke wrote:
>> . . .
>> Can I please get a review?
> I have only one small question regarding this change in
> templateTable_aarch64.cpp:
> 
> @@ -2763,12 +2756,11 @@
> 
>    // ztos
>    {
>      __ pop(ztos);
>      if (!is_static) pop_and_check_object(obj);
> -    __ andw(r0, r0, 0x1);
> -    __ strb(r0, field);
> +    __ access_store_at(T_BOOLEAN, IN_HEAP, field, r0, noreg, noreg);
>      if (rc == may_rewrite) {
>        patch_bytecode(Bytecodes::_fast_zputfield, bc, r1, true, byte_no);
>      }
>      __ b(Done);
>    }
> 
> The implementation of access_store_at (when the call finally lands in in
> BarrierSetAssembler) for the T_BOOLEAN case simply does an strb. So, the
> andw(r0, r0, 0x1) in the original has been elided in the replacement.
> Was that definitely redundant in the original?

http://cr.openjdk.java.net/~rkennke/JDK-8203172/webrev.00/src/hotspot/cpu/aarch64/gc/shared/barrierSetAssembler_aarch64.cpp.udiff.html

+  case T_BOOLEAN:
+    __ andw(val, val, 0x1);  // boolean is true if LSB is 1
+    __ strb(val, dst);
+    break;

I think it does what you want?

Cheers, Roman