RFR: 8328306: AArch64: MacOS lazy JIT "write xor execute" switching [v2]

[Dean Long]

On Tue, 12 Aug 2025 10:22:00 GMT, Andrew Dinn <adinn at openjdk.org> wrote:

>>> Why plant the WXEnable before the thread transition here when it is placed after the thread transition in the NO_ASYNC macro? Why not after in both?
>> 
>> OK.
>> 
>>> Likewise in later occurrences what governs the placement?
>> 
>> The process of discovering the sweet spots we entirely empirical, not analytical.
>
> I don't believe the order is going to matter (tell me if I am wrong) but I think it would be better to order them consistently, not just because I am a 'typical computer programmer' but because someone might be puzzled as to whether the re-ordering is significant (ok, yes, I guess that 'someone' would be a 'typical computer programmer' or maybe just me). I suggested both after because the async thread transition has a bail out and we might as well bail early . . .

I like having the mode change after the thread state change.  In my experiements, I tried to assert that we only change thread state when we are in Exec mode, but ended up relaxing that for Compiler and GC threads.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26562#discussion_r2274744437