https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94043
--- Comment #10 from Kewen Lin <linkw at gcc dot gnu.org> --- (In reply to Richard Biener from comment #9) > OK, so it's indeed vectorizable_live_operation not paying attention to > loop-closed SSA form. > > What it should do before building the lane extract is create a _new_ > loop-closed PHI node for the vectorized def (vec_lhs), and then > demote the loop-closed PHI node for the scalar def (lhs) which should > _always_ exist to a copy. So from > > > loop; > > # lhs' = PHI <lhs> > > > go to > > loop; > > # vec_lhs' = PHI <vec_lhs> > new_tree = BIT_FIELD_REF <vec_lhs', ...>; > lhs' = new_tree; > > I think you can assert that the block of the loop-closed PHI > (single_exit()->dest) always has a single predecessor, otherwise > things will be more complicated. > > Can you try rework the code in this way? If that's too much just tell > me and I'll take care of this. Thanks Richi, I'll give it a shot! I'd like to ensure my understanding: with the proposed fix, we ensure the single_exit()->dest should be the correct BB to be inserted, no chance like gimple_find_edge_insert_loc to get one new BB to be inserted, is it right?
