RFR: 8328306: AArch64: MacOS lazy JIT "write xor execute" switching [v4]

[David Holmes]

On Tue, 19 Aug 2025 08:19:16 GMT, Andrew Haley <aph at openjdk.org> wrote:

> We change mode when we're _all but certain_ that we need to. That seems right to me. If the mode doesn't need changing because it's already set, that's OK. Why do you think this might be a problem?

My concern is that if we have code that needs a specific mode, but it is not obvious at that piece of code that this is the case, then things will work fine if somewhere on the path to that code we set the right mode. But if we introduce a new path to that code that might not be the case and so we will introduce a new place where we switch modes. That can lead to redundancy. The whole thing (as it has from day one) seems ad-hoc.

But if the proposed scheme performs better in general, and is not obviously "worse" from the ad-hoc perspective then ...

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PR Comment: https://git.openjdk.org/jdk/pull/26562#issuecomment-3208537749