llvm-project

26390f22 - [VectorCombine] foldShuffleOfShuffles - fold shuffle(shuffle(x,y),poison) length changing masks (#144690)

[VectorCombine] foldShuffleOfShuffles - fold shuffle(shuffle(x,y),poison) length changing masks (#144690) The shuffle merging code assumes that the shuffle sources are all the same type, which fails if we've changed length and don't have 2 inner shuffles. We already handle length-changing shuffles if we do have 2 inner shuffles. This patch creates a fake "all poison" shuffle mask and reuses the other shuffle's sources, which can be safely used with the existing merge code. The alternative was a considerable refactor of the merge code to account for different vector widths...... Fixes #144656