8350462: MethodTypeForm.LF_INTERPRET can cache the MemberName instead

[linzihao1999]

Modify the cache in MethodTypeForm that currently stores the LF_INTERPRET Lambda form. Instead of caching the entire LambdaForm, change it to store a SoftReference. This will avoid unnecessary memory usage.

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• JDK-8350462: MethodTypeForm.LF_INTERPRET can cache the MemberName instead (Enhancement - P4)

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[mlbridge]

Webrevs

• 01: Full - Incremental (3ce154ea)
• 00: Full (e70fb819)

[liach]

You can remove the LF_INTERPRET constant from this list.

[linzihao1999]

OK, removed it.

[liach]

Now the index 6 is left unused in the LF cache array - we can leave it empty and renumber the cache indices when we add a new entry to cache.

[liach]

I shall run hs-tier2 before approving, in case mainline leyden doesn't work with WeakReferences.