On Tue, 2 Jun 2026 02:15:35 GMT, Dean Long <[email protected]> wrote:
>> src/hotspot/share/opto/library_call.cpp line 7886:
>>
>>> 7884: Node* referent = argument(0);
>>> 7885: if (referent->is_InlineType()) {
>>> 7886: referent = referent->as_InlineType()->buffer(this);
>>
>> Please explain. The test doesn't trigger this code, so how do we test it?
>> I thought the whole point of reachabilityFence was to prevent a finalizer
>> from running too early, but what does that even mean for an InlineType that
>> might not be heap allocated? Wouldn't it be a no-op or even better, an
>> error, like trying to synchronize on a value object? Or are we now saying
>> that reachabilityFence on an inline type really means "do not scalarize,
>> make sure finalizer gets run, but not until we get here"?
>
> In other words, I think reachabilityFence() requires an identity object for
> correct semantics. I think there could be scenarios where buffering a copy
> is not enough. Does that mean that instead of the finalizer running exactly
> 1 time, now it will run once for every buffered copy?
A `reachabilityFence` keeps the object alive, which, in turn, keeps its fields
alive. We can implement this by looking at all of the oop fields of the
`InlineTypeNode` and keeping them alive instead. I decided to go for the
simplest solution, which is to ensure that the whole object is kept alive.
-------------
PR Review Comment:
https://git.openjdk.org/valhalla/pull/2496#discussion_r3338245864
