[aarch64-port-dev ] RFR(s): AARCH64: 8147805: C1 segmentation fault due to inline Unsafe::getAndSetObject

[Andrew Haley]

On 01/20/2016 02:21 PM, Edward Nevill wrote:
> On Wed, 2016-01-20 at 21:30 +0800, Hui Shi wrote:
>> Hi All,
>>
>> Could some one help review this AArch64 C1 issue? Issue happens when inline
>> unsafe.getAndSet(data) in C1 and UseCompressedOops flag is true, register
>> is compressed for store, but it is not restored into decompressed form.
>> Later compressed result is used as reference address and goes wrong.
>>
>> Bug:  https://bugs.openjdk.java.net/browse/JDK-8147805
>> webrev: http://cr.openjdk.java.net/~hshi/8147805/webrev/
>> Small test case in http://cr.openjdk.java.net/~hshi/8147805/TestUnsafe.java
>> Crash can be reproduced by java -XX:TieredStopAtLevel=3
>> -XX:+TieredCompilation -Xms4G -Xmx4G TestUnsafe
> 
> Hi Hui Shi,
> 
> Thanks for finding this. Your change looks correct, but if I make suggest the following smaller change which achieves the same.
> 
> diff -r 46c1abd5c34d src/cpu/aarch64/vm/c1_LIRAssembler_aarch64.cpp
> --- a/src/cpu/aarch64/vm/c1_LIRAssembler_aarch64.cpp    Tue Jan 12 14:55:15 2016 +0000
> +++ b/src/cpu/aarch64/vm/c1_LIRAssembler_aarch64.cpp    Wed Jan 20 14:16:56 2016 +0000
> @@ -3169,7 +3169,8 @@
>        Register obj = as_reg(data);
>        Register dst = as_reg(dest);
>        if (is_oop && UseCompressedOops) {
> -        __ encode_heap_oop(obj);
> +        __ encode_heap_oop(rscratch1, obj);
> +        obj = rscratch1;
>        }
>        assert_different_registers(obj, addr.base(), tmp, rscratch2, dst);
>        Label again;

I agree.  I have tried this and it works well.  The patch is OK with
this change.

Andrew.