This is changes the interface of CodeBuffer to that of a partially persistent
data structure based on reference counting:
- Exactly one CodeBuffer is now designated as "active", which means data can
be *appended* to it
- Lossy modifications to the active CodeBuffer will not invalidate any data
in use by other threads, which enables save sharing across threads
- Instead, such lossy modifications trigger a new "version" of the data in
the modifying thread. Old versions of the CodeBuffer persist as read-only
data for use by the other threads.
- The other threads can update their version of the CodeBuffer. This will
decrease the reference count and eventually trigger deallocation of the
old version
This data isn't really a cache, since the JIT is directly responsible of
writing its contents. Instead it be considered the source to populate the
L1/L2 caches from.
Furthermore, splitting off this data allows it to be shared across threads
in the future without affecting L1/L2 caches.
It is not an external component, and it makes paths needlessly long.
Ryan seemed amenable to this when we discussed on IRC earlier.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Tony Wasserka