RFR: 8345067: C2: enable implicit null checks for ZGC reads [v3]

[Roberto Castañeda Lozano]

On Thu, 15 May 2025 13:25:56 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> Two small nits/questions, but otherwise ready from my side :)

Thanks again for reviewing @eme64, I have addressed your questions now. And thanks also for your review @vnkozlov.

@stefank @fisk @xmas92 @jsikstro may I get a review from the GC side?

@RealFYang @TheRealMDoerr note that this PR also introduces implicit null check support for ZGC loads in RISC-V and PPC, but I cannot test it beyond GHA. May I ask you to test the changes on your respective platforms? (or let me know if you prefer to add the support in separate PRs).

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PR Comment: https://git.openjdk.org/jdk/pull/25066#issuecomment-2885960803