RFR: 8329433: Reduce nmethod header size [v3]

[Dean Long]

On Tue, 16 Apr 2024 03:12:48 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> src/hotspot/share/code/nmethod.hpp line 282:
>> 
>>> 280:           _has_flushed_dependencies:1, // Used for maintenance of dependencies (under CodeCache_lock)
>>> 281:           _is_unlinked:1,              // mark during class unloading
>>> 282:           _load_reported:1;            // used by jvmti to track if an event has been posted for this nmethod
>> 
>> It seems like the type could be changed from uint8_t to bool.
>
> Is there difference in generated code when you use bool instead of uint8_t?
> I used uint8_t to easy change to uint16_t in a future if needed.

I don't think uint8_t vs uint16_t matters, only if it is signed, unsigned, or bool.  So if we have more than 8 individual :1 fields, it will expand to a 2nd byte.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18768#discussion_r1566814258