RFR: 8377339: Implement AOTCacheAccess::get_archived_object using heap roots

[Vladimir Kozlov]

On Fri, 6 Feb 2026 05:50:15 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> The API `oop AOTCacheAccess::get_archived_object(int)` is used by the AOT compiler to access heap objects in the AOT cache.
> 
>  Because the objects can move in the production run, there's currently a complicated way to keep them alive using OopHandles.
> 
> https://github.com/openjdk/leyden/blob/6ce1832147ef3f01602b8fac02160038422a77bf/src/hotspot/share/cds/heapShared.cpp#L545-L610
> 
> However, we already have a mechanism for this: `oop HeapShared::get_root(int index, ...)`
> 
> So we just need to make sure that all oops needed by the AOT compiler are all stored as heap roots.
> 
> This PR is intended to provide an acceptable solution in the short run to be used by the initial AOT compiler integration into the mainline.
> 
> The AOT compiler only needs the following objects
> 
> - a few common exception objects
> - class loaders
> - class mirrors
> - interned strings
> - method handles
> 
> Most of these objects are in the roots already. We just need to add interned strings and method handles into the heap roots.
> 
> (In the future, we should move the AOT compilation before we dump the heap. This way we know exactly what oops should be stored into the heap roots.)
> 
> Notes to reviewers
> - `HeapShared::archived_object_cache()` can now survive GCs that might happen during AOT compilation. I added a new function `HeapShared::archived_object_cache_hash()` with comments about how it uses `oop::identity_hash()`.
> - This code is added to make sure interned strings and method handles are roots
> 
>   if (AOTCodeCache::is_dumping_code() &&
>                (java_lang_invoke_MethodHandle::is_instance(obj) || is_interned_string(obj))) {
>       // Needed by AOT compiler.
>       append_root(obj);
>     }
> 
> - Also some clean up that's not necessary but nice to have:
>   - I removed the `DumpedInternedStrings` and replaced it with much simpler code.

@iklam note that `AOTCodeCache::is_dumping_code()` is true only after `AOTCodeCache::init2()` is called when we fully initialized everything for AOT code cache. It is called after `universe_init()` when some oops already been created I think.   May be we should use next which checks only flags when adding roots:

bool AOTCodeCache::maybe_dumping_code() {
  return AOTCodeCaching && CDSConfig::is_dumping_final_static_archive();
}


Or even next together with `CDSConfig::is_dumping_heap()`:

bool AOTCodeCache::is_caching_enabled() {
  return AOTCodeCaching || AOTStubCaching || AOTAdapterCaching;
}

-------------

PR Comment: https://git.openjdk.org/leyden/pull/108#issuecomment-3873020322