[14] RFR (XS): 8234403: C2: Enable CallSite.target updates in constructors

[Paul Sandoz]

+1

Paul.

> On Nov 19, 2019, at 9:18 AM, Vladimir Ivanov <vladimir.x.ivanov at oracle.com> wrote:
> 
> http://cr.openjdk.java.net/~vlivanov/8234403/webrev.00/
> https://bugs.openjdk.java.net/browse/JDK-8234403
> 
> Direct CallSite.target updates are not supported in C2, because in general the JVM has to invalidate all nmethod dependency before performing the update (handled by MethodHandleNatives.setCallSiteTargetNormal/Volatile).
> 
> But it's not the case for initializing stores during CallSite instance construction.
> 
> Proposed fix assumes all raw updates happen on not-yet-published instances (so no nmethod dependencies) and treats CallSite.target updates inside ctors as an ordinary field.
> 
> Considering the changes proposed for 8234401 [1], all direct updates in CallSite ctors are safe to be treated as ordinary field updates.
> 
> Testing: tier1-4
> 
> Best regards,
> Vladimir Ivanov
> 
> [1] https://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2019-November/036019.html