[llvm] [DA] runtime predicates for delinearization bounds checks (PR #170713)

[Sebastian Pop via llvm-commits]

sebpop wrote:

> I expect that actually making use of them will be quite challenging, because of the need to trade off the value of the transform with the probability of passing the runtime check and the code size increase of performing loop versioning

The decision to perform versioning is with the loop transform passes. DA is supposed to only provide a minimal list of predicates under which the DA result holds. Currently, when the info is missing, the result of DA is just "don't know" on which the LNO gives up with no choice.

Fewer runtime predicates will be generated with more info sent from the front-ends.

> * runtime predicates isn't a new concept, my understanding is that Polly also uses this.

Correct, both Polly and the vectorizer use runtime predicates to check for alias, dependences, and possible values of parameters.


https://github.com/llvm/llvm-project/pull/170713