[aarch64-port-dev ] jdk1 Fix for hotspot/test/gc/g1/TestJNIWeakG1/TestJNIWeakG1.java

[Andrew Dinn]

On 16/08/17 18:34, Stuart Monteith wrote:
> Ok,
>   The assert I added to g1_write_barrier_post was tripping - we were
> passing rscratch1 and using it locally. I could just change it to
> rscratch2, but if we are passing temporary registers as parameters,
> I'd argue we shouldn't be using rscratch1, etc, hardcoded in those
> routines. In other platforms we are passing more than two temporary
> registers. I'll have a look at a more extensive change.

First, regarding the asserts:

As you say, there is no need for to separate the cases to make two
different calls to assert_different_registers. However, it is nice that
the current code recognises the possibility that obj == noreg, albeit at
the cost of some branching. You could maybe use this:

  assert_different_registers(obj, pre_val, tmp, rscratch1);
  assert(pre_val != noreg &&  tmp != noreg, "expecting a register");

Second, the rscratch1 conflict in g1_write_barrier_post is best solved
by changing the calling code in templateTable_aarch64.cpp to pass
rscratch2 (that is the only call) i.e.

        } else {
          // G1 barrier needs uncompressed oop for region cross check.
          Register new_val = val;
          if (UseCompressedOops) {
-             new_val = rscratch1;
+             new_val = rscratch2;
            __ mov(new_val, val);
          }
          __ store_heap_oop(Address(r3, 0), val);
          __ g1_write_barrier_post(r3 /* store_adr */,
                                   new_val /* new_val */,
                                   rthread /* thread */,
                                   r10 /* tmp */,
                                   r1 /* tmp2 */);
        }

That should be enough to allow a similar assert to be used in
g1_write_barrier_post. In this latter case obj cannot be noreg so you
need to include that in the second assert for g1_write_barrier_post.

regards,


Andrew Dinn
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