5d238c0c2c
This adds a little extra work, since now dominance is computed and blocks that don't just have then-return or else-return are looked at. However it means that nir_lower_returns can now keep phis up to date by inserting undefs without causing some phis to become non-trivial. This ends up obviating a couple of tests for lower_returns. Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22913>