RFC: integer division by multiply with invariant reciprocal

[Charles J. Tabony]

> So I think that the easiest way to integrate this with the rest of the
> compiler is to have a target hook that emits trees to compute SHIFT, INV1
> and INV2.

(define_tree_expand "name"
  <template>
  "condition"
  {
    preparation statements;
  }
)

:-)