> I can, but then I am giving lshift higher priority than every other > operation, not just rshift. And if I want to give (vec_select x 0) a > higher precedence than (vec_select x 1) but lower than (vec_select > (vec_concat a b) 1), the weights may become complicated, whereas the > comparison function could just recurse.
You cannot have both transitivity and fast-tracks in the comparison function. However it isn't clear (at least to me) if transitivity is really required. (vec_select x 0) and (vec_select x 1) are the same pattern so they shouldn't be distinguished here. > I wonder if those issues might in most cases be bugs in the back-ends > (optimizations missed depending on the order), that the canonicalization > would make more noticable (and thus easier to fix). There are certainly such issues in the back-ends (and even ??? comments about it) so sensible canonicalization is desirable. -- Eric Botcazou
