RFR: 8290892: C2: Intrinsify Reference.reachabilityFence [v11]

[Dean Long]

On Fri, 12 Sep 2025 13:39:03 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> src/hotspot/share/opto/callGenerator.cpp line 620:
>> 
>>> 618:     // Inlining logic doesn't expect any extra edges past debug info and fails with
>>> 619:     // an assert in SafePointNode::grow_stack.
>>> 620:     assert(endoff == call->req(), "reachability edges not supported");
>> 
>> Could we trip over this assert by modifying the reproducer, and add some method somewhere that gets inlined late?
>
> Could we also bail out here? Or what would happen now in production if there is a RF edge?

We also use this area past endoff() for storing the "ex_oop" (see for example GraphKit::has_saved_ex_oop()).  Are ex_oop and reachability edges mutually exclusive?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25315#discussion_r2350439892