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

[Renato Golin via llvm-commits]

rengolin wrote:

> 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.

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