RFR: 8329597: C2: Intrinsify Reference.clear

[Aleksey Shipilev]

On Fri, 12 Jul 2024 11:57:56 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

> The runtime use of the Access API knows how to resolve an unknown oop ref strength using AccessBarrierSupport::resolve_unknown_oop_ref_strength. However, we do not have support for that in the C2 backend. In fact, it does not understand non-strong oop stores at all. 

Aw, nice usability landmine. I thought C2 barrier set would assert on me if it cannot deliver. Apparently not, I see it just does pre-barriers when it is not sure what strongness the store is. Hrmpf. OK, let me see what can be done here.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/20139#issuecomment-2225577027