RFR: 8290892: C2: Intrinsify Reference.reachabilityFence [v3]

[Emanuel Peter]

On Wed, 28 May 2025 19:35:09 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Right, nevermind about `DecodeNKlass` then. My question on heap loads still stands: do we actually get `reachabilityFence(someField)` from anywhere?
>
> Are you asking specifically about `ReachabilityFence -> DecodeN -> LoadN` shape? Yes, it's common, especially after inlining.

@iwanowww Can you add a code comment why this is safe to look through the ReachabilityFence?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25315#discussion_r2149517512