[llvm] [RFC][LV] VPlan-based cost model (PR #67647)

[Renato Golin via llvm-commits]

https://github.com/rengolin commented:

> > General idea seems sound, but this needs tests to convince me that LV behavior doesn't change with VPlan-based costing.
> 
> Indeed. Similar comment on the original Phab thread. Needs existing tests with flag to not change behaviour based on new cost model.

The cost model has moved inside the VPlan infrastructure and is no longer called from the same place in the same way. Please provide evidence that, even without the vplan-based cost model flag, the behaviour of the vectorizer hasn't changed.

Performance numbers on some benchmarks, traces on the test-suite showing what gets vectorized and what doesn't, etc.

If this is just about the migration, then it should behave in the same way as before without the optional flag.

https://github.com/llvm/llvm-project/pull/67647