[llvm-branch-commits] [CAS] Add ActionCache to LLVMCAS Library (PR #114097)

[Steven Wu via llvm-branch-commits]

https://github.com/cachemeifyoucan created https://github.com/llvm/llvm-project/pull/114097

ActionCache is used to store a mapping from CASID to CASID. The current
implementation of the ActionCache can only be used to associate the
key/value from the same hash context.

ActionCache has two operations: `put` to store the key/value and `get` to
lookup the key/value mapping. ActionCache uses the same TrieRawHashMap
data structure to store the mapping, where is CASID of the key is the
hash to index the map.

While CASIDs for key/value are often associcate with actual CAS
ObjectStore, it doesn't provide the guarantee of the existence of such
object in any ObjectStore.