Richard Biener <rguent...@suse.de> writes: > On Thu, 10 Sep 2020, Richard Sandiford wrote: > >> Richard Biener <rguent...@suse.de> writes: >> > This avoids unsharing the SLP tree when optimizing load permutations >> > for reductions but there is no actual permute taking place. >> > >> > Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed. >> > >> > 2020-09-09 Richard Biener <rguent...@suse.de> >> > >> > * tree-vect-slp.c (vect_attempt_slp_rearrange_stmts): Do >> > nothing when the permutation doesn't permute. >> >> Drive-by comment, sorry for not looking in more detail first, but: >> is there a difference in semantics between an identity load_permutation >> and a null load_permutation? Seems like it would be good to have >> a canonical form. > > Well, yes - an identity load_permutation will become non-identity > if there's a GROUP_GAP and we end up with a VF > 1. We're simply > postponing figuring this out until we have VF fixed (and > vect_attempt_slp_rearrange_stmts is quite legacy now and at an > odd place - sth I hope to address). So with GROUP_GAP == 1 > and an identity permute the permute should be NULL. > > I've run into this during development of other stuff but decided > to push this fix since it might as well happen for the SLP > reduction case. It's probably a regression from when I pushed > permute validity check to vectorizable_load.
Ah, OK, thanks. Richard
