As is well known, the introduction of a ``loop header'' block facilitates the hoisting of loop-invariant code from a loop. But in a $lambda$-calculus intermediate representation, which has a notion of scope, this transformation is particularly useful. Loop headers with scope also solve an old problem with in-line expansion of recursive functions or loops: if done naively, only the first iteration is inlined. A loop header can encapsulate the loop or recursion for better in-line expansion. This optimization improves performance by about 5% in Standard ML of New Jersey.

This technical report has been published as

Loop Headers in Lambda-Calculus or CPS. Andrew W. Appel, Lisp and Symbolic Computation 7, 337-343, 1994.