RFR: 8262256: C2 intrinsincs should not modify IR when bailing out

[Roland Westrelin]

On Mon, 1 Mar 2021 08:30:49 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> While investigating [JDK-8262231](https://bugs.openjdk.java.net/browse/JDK-8262231) in project Valhalla, I've noticed that the unsafe access C2 intrinsics sometimes emit code before then bailing out, leaving control flow before the slow call that might lead to deoptimization or an inconsistent JVMState. I've added an assert to catch this and fixed the corresponding intrinsic code (in that case null checks in `make_unsafe_address` are the culprit).
> 
> Thanks,
> Tobias

Looks good to me

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

Marked as reviewed by roland (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2775