[aarch64-port-dev ] RFR(M): 8209835: Aarch64: elide barriers on all volatile operations

Andrew Haley aph at redhat.com
Fri Oct 12 18:41:00 UTC 2018

On 10/05/2018 10:10 AM, Roland Westrelin wrote:
>>> http://cr.openjdk.java.net/~roland/8209835/webrev.00/
>>> This adds barrier elision support for all volatile operations that were
>>> not supported so far and extends the tests to cover all of them. I ran
>>> full jcstress successfully with this.
>> Yes, that looks good.
> Thanks for the review.
>> Did you also eyeball the generated code? I know jcstress ought to find
>> any bugs but it would be good to be doubly sure :-)
> I didn't eyeball the code (there's a lot to check!). I extended tests to
> cover all combination of atomic operations/argument types. So at least,
> tests should guarantee that the right variant in the ad file is
> picked. Then, of course, all variants must be correctly implemented. For
> that, I checked a couple times that the right boolean flag was passed.

I want to eyeball the code, but I just spent the last hour and a half
trying to figure out how to get real assembly code (not OptoAssembly)
out of jtreg. It seems incredibly difficult: everything is conspiring
to stop it from happening. If I edit the tests so that PrintAssembly
is passed, the tests fail.

In desperation I am about to edit HotSpot so that the assembly output
goes to a named pipe, but i can't help feeling that it really should
be easier than this.

Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671

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