Richard Biener <[email protected]> writes: > On Thu, 20 Aug 2026, Richard Sandiford wrote: >> Richard Biener <[email protected]> writes: >> > SLP permute nodes (can) have no SLP_TREE_REPRESENTATIVE, avoid >> > leaving vertex weight (later used for costing) at zero but >> > assign weight based on the region entry block. >> >> That's better than 0 :) but is there a plan to make the choice of >> block more accurate in future? Using the entry block for something >> that actually ends up in a loop would defeat the speed-based costing. > > Well, permutes are invented by the vectorizer, so they do not have > a natural "block choice". One could assign a weigth based on the > weigth of the permuted operands (possibly recursively) or it's > uses. Or based on the place where we'd code generate it (which > is based on the operands places). But the processing doesn't walk > the graph in a particular oder, so that looked iffy to implement.
Maybe it could be another field in the SLP node, calculated separately? I think the situation would be worth a ??? comment, but otherwise the patch seems ok to me FWIW. Richard
