tree a6eec258ec65dbc2c3261d21ad44cbccad92e010
parent 7d572ef2dd9bf68d56c0fa3152c2dea2f778f147
author Simon Pilgrim <llvm-dev@redking.me.uk> 1585934753 +0100
committer Simon Pilgrim <llvm-dev@redking.me.uk> 1585934770 +0100

[X86][SSE] lowerShuffleWithPACK - extend to use chained PACKs for larger truncations

Extend lowerShuffleWithPACK/matchShuffleWithPACK/createPackShuffleMask to handle compaction style shuffle masks that can be lowered to chains of PACKSS/PACKUS if their inputs are suitably sign/zero extended.

This helps avoid PSHUFB (and its mask load) for short shuffle chains, shuffle combining will still replace with a PSHUFB if we have enough shuffles as getFauxShuffleMask should recognise the PACKSS/PACKUS chains.