llvm-project

29c89d72 - [VectorCombine] foldShuffleOfShuffles - fold "shuffle (shuffle x, y, m1), (shuffle y, x, m2)" -> "shuffle x, y, m3" (#120959)

[VectorCombine] foldShuffleOfShuffles - fold "shuffle (shuffle x, y, m1), (shuffle y, x, m2)" -> "shuffle x, y, m3" (#120959) foldShuffleOfShuffles currently only folds unary shuffles to ensure we don't end up with a merged shuffle with more than 2 sources, but this prevented cases where both shuffles were sharing sources. This patch generalizes the merge process to find up to 2 sources as it merges with the inner shuffles, it also moves the undef/poison handling stages into the merge loop as well. Fixes #120764