llvm-project

f8eca64a - Reapply "[LV] Use ExtractLane(LastActiveLane, V) live outs when tail-folding. (#149042)"

Reapply "[LV] Use ExtractLane(LastActiveLane, V) live outs when tail-folding. (#149042)" This reverts commit a6edeedbfa308876d6f2b1648729d52970bb07e6. The following fixes have landed, addressing issues causing the original revert: * https://github.com/llvm/llvm-project/pull/169298 * https://github.com/llvm/llvm-project/pull/167897 * https://github.com/llvm/llvm-project/pull/168949 Original message: Building on top of https://github.com/llvm/llvm-project/pull/148817, introduce a new abstract LastActiveLane opcode that gets lowered to Not(Mask) → FirstActiveLane(NotMask) → Sub(result, 1). When folding the tail, update all extracts for uses outside the loop the extract the value of the last actice lane. See also https://github.com/llvm/llvm-project/issues/148603 PR: https://github.com/llvm/llvm-project/pull/149042