llvm-project

81a7b645 - [MLIR][LLVM] Recursion importer handle repeated self-references (#87295)

[MLIR][LLVM] Recursion importer handle repeated self-references (#87295) Followup to this discussion: https://github.com/llvm/llvm-project/pull/80251#discussion_r1535599920. The previous debug importer was correct but inefficient. For cases with mutual recursion that contain more than one back-edge, each back-edge would result in a new translated instance. This is because the previous implementation never caches any translated result with unbounded self-references. This means all translation inside a recursive context is performed from scratch, which will incur repeated run-time cost as well as repeated attribute sub-trees in the translated IR (differing only in their `recId`s). This PR refactors the importer to handle caching inside a recursive context. - In the presence of unbound self-refs, the translation result is cached in a separate cache that keeps track of the set of dependent unbound self-refs. - A dependent cache entry is valid only when all the unbound self-refs are in scope. Whenever a cached entry goes out of scope, it will be removed the next time it is looked up.