RFR(S): 8245047: PPC64 fails jcstress Unsafe (?) memory ordering tests due to C2 (?) bug

[Aleksey Shipilev]

On 5/15/20 6:21 PM, Doerr, Martin wrote:
> Aleksey has reported the issue:
> https://bugs.openjdk.java.net/browse/JDK-8245047

Well, I think it is a good idea to change the synopsis. I speculated in the provisional synopsis,
and thought "(?)" would prompt the edit :) Looks to me, it is "[PPC64] C2: ReverseBytes(U)S/Load(U)S
always match to unordered loads".

> Here’s my proposed fix:
> http://cr.openjdk.java.net/~mdoerr/8245047_ppc64_load_reversed_acquire/webrev.00/

Looks fine to me. It is a bit odd to me to see that "normal" loads are matched with isync, but it
seems to fit the rest of ppc64.ad that has two versions of loads, unordered/followed_by_acquire
explicitly excepted.

> I’d appreciate retesting, too, if possible.

I'll run a few jcstress tests here.

-- 
Thanks,
-Aleksey