RFR: Restore Method pointer for every AOTCodeEntry [v4]

[Ashutosh Mehra]

On Tue, 12 Aug 2025 03:39:05 GMT, Ashutosh Mehra <asmehra at openjdk.org> wrote:

>> There was a recent commit [0] that included code to invalidate preload entry when invalidating a normal `AOTCodeEntry`. This is done by reaching out to the preload entry through the normal `AOTCodeEntry::_method`:
>> 
>> https://github.com/openjdk/leyden/blob/7b7648a4c9f67be509c6fccbcbc0502648388fdc/src/hotspot/share/code/aotCodeCache.cpp#L1056-L1070
>> 
>> But unfortunately `AOTCodeEntry::_method` is restored only for the entries marked for preload:
>> https://github.com/openjdk/leyden/blob/7b7648a4c9f67be509c6fccbcbc0502648388fdc/src/hotspot/share/code/aotCodeCache.cpp#L1938-L1939
>> 
>> This PR fixes this bug by restoring `AOTCodeEntry::_method` for all AOTCodeEntry-s. This is achieved by using AOTCache's pointer bitmap to track `AOTCodeEntry::_method`. It removes the need to store method offset separately in the AOTCodeEntry.
>> It also fixes a couple of related bugs:
>> 1. In `AOTCodeCache::finish_write()` it is possible that the AOTCodeEntry array is not properly aligned.
>> 2. When invalidating a preload entry, it is possible that the entry has not been loaded. This triggers the assert that expects an entry to be invalidated is always loaded.
>> 
>> [0] https://github.com/openjdk/leyden/commit/392fbbb1859cd71521cb915b601a65cf59ba495b
>
> Ashutosh Mehra has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Modify cpu feature name iteration code to avoid subtle bug like missing
>   i++ in get_missing_features_name()
>   
>   Signed-off-by: Ashutosh Mehra <asmehra at redhat.com>

This is passing the tests now. Integrating it.

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PR Comment: https://git.openjdk.org/leyden/pull/90#issuecomment-3179465532