[aarch64-port-dev ] 8233839: aarch64: missing memory barrier in NewObjectArrayStub and NewTypeArrayStub

[Yangfei (Felix)]

Hi,

I witnessed random fail of one jcstress test on my 128-core aarch64 server: "org.openjdk.jcstress.tests.defaultValues.arrays.small.plain.StringTest"
Bug: https://bugs.openjdk.java.net/browse/JDK-8233839

I used the latest aarch64 jdk8u release build.  Please refer to the bugzilla for details and the analysis.
  I checked the assembler code emitted by LIR_Assembler::emit_alloc_array:
For the fast path, the StoreStore memory barrier is there.  But it’s not the case for the slow path.

  Patch adding the missing barrier for 14:

diff -r ad157fab6bf5 src/hotspot/cpu/aarch64/c1_Runtime1_aarch64.cpp
--- a/src/hotspot/cpu/aarch64/c1_Runtime1_aarch64.cpp   Thu Nov 07 16:26:57 2019 -0800
+++ b/src/hotspot/cpu/aarch64/c1_Runtime1_aarch64.cpp   Fri Nov 08 16:10:08 2019 +0800
@@ -840,6 +840,7 @@
           __ sub(arr_size, arr_size, t1);  // body length
           __ add(t1, t1, obj);       // body start
           __ initialize_body(t1, arr_size, 0, t2);
+          __ membar(Assembler::StoreStore);
           __ verify_oop(obj);

           __ ret(lr);

  JDK builds OK and passed tier1 test.

Thanks,
Felix