llvm-project

054e7c59 - [VectorCombine] foldInsExtVectorToShuffle - ignore shuffle costs for 'identity' insertion masks

[VectorCombine] foldInsExtVectorToShuffle - ignore shuffle costs for 'identity' insertion masks <u,1,u,u> 'inplace' single src shuffles can be treated as free identity shuffles - ignore any shuffle cost (similar to what we already do in other folds like foldShuffleOfShuffles) - eventually getShuffleCost should just return TCC_Free in these cases but in a lot of the targets' shuffle cost logic this currently ends up treated as a generic SK_PermuteSingleSrc. We still want to generate the shuffle as it will help further shuffle folds with the additional PoisonMaskElem 'undemanded' elements.