[aarch64-port-dev ] RFR: 8243339: AArch64: Obsolete UseBarriersForVolatile option

[Ningsheng Jian]

I see CSR review and submit tests are clear, so I pushed.

Thanks,
Ningsheng

On 5/22/20 10:36 AM, Xiaohong Gong wrote:
> Hi Andrew,
> 
>> On 5/21/20 11:24 AM, Xiaohong Gong wrote:
>   > > I'v created a new patch to add the condition when inserting
>   > "DMBs"
>   > > before volatile load for C1/Interpreter.
>   > > The updated webrev:
>   > > http://cr.openjdk.java.net/~xgong/rfr/8243339/webrev.01/
>   > >
>   > > It adds a new function "is_c1_or_interpreter_only()" , which can
>   > > decide whether C2/JVMCI is used. Besides, since AOT also uses
>   > Graal
>   > > compiler as the codegen, it always return false if AOT mode is
>   > enabled.
>   >
>   > Looks good to me, thanks.
>   >
>   > As far as I remember, Graal does optimize volatile accesses to use
>   > ldar/stlr, or at least it will do so in the future, so if we're
>   > using AOT or JVMCI the safe thing to do is add the DMBs.
> 
> Yes, exactly! It has a patch in Graal github to do this optimization (https://github.com/oracle/graal/pull/1772).
> 
> Thanks,
> Xiaohong
> 
> -----Original Message-----
> From: Andrew Haley <aph at redhat.com>
> Sent: Thursday, May 21, 2020 10:06 PM
> To: Xiaohong Gong <Xiaohong.Gong at arm.com>; Andrew Dinn <adinn at redhat.com>; Derek White <derekw at marvell.com>; aarch64-port-dev at openjdk.java.net; hotspot-compiler-dev at openjdk.java.net
> Cc: nd <nd at arm.com>
> Subject: Re: [aarch64-port-dev ] RFR: 8243339: AArch64: Obsolete UseBarriersForVolatile option
> 
> On 5/21/20 11:24 AM, Xiaohong Gong wrote:
>> I'v created a new patch to add the condition when inserting "DMBs"
>> before volatile load for C1/Interpreter.
>> The updated webrev:
>> http://cr.openjdk.java.net/~xgong/rfr/8243339/webrev.01/
>>
>> It adds a new function "is_c1_or_interpreter_only()" , which can
>> decide whether C2/JVMCI is used. Besides, since AOT also uses Graal
>> compiler as the codegen, it always return false if AOT mode is enabled.
> 
> Looks good to me, thanks.
> 
> As far as I remember, Graal does optimize volatile accesses to use ldar/stlr, or at least it will do so in the future, so if we're using AOT or JVMCI the safe thing to do is add the DMBs.
> 
> --
> Andrew Haley  (he/him)
> Java Platform Lead Engineer
> Red Hat UK Ltd. <https://www.redhat.com> https://keybase.io/andrewhaley
> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
>