Re: [PATCH 1/2] Assign vertex weight to all nodes

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