live variables

[Charles Martin <martin@chasm.org>]

I would like to follow up to the mailing list a series of posts on 
comp.lang.functional.  Jerome Vouillon explained that the native code 
compiler compiles

	let rec foldl f q = function
	| [] -> q
	| x :: xx -> foldl f (f q x) xx

as if it were written

	let rec foldl f q = function
	| [] -> q
	| l ->
	  let x = List.hd l in
	  let r = f q x in
	  let xx = List.tl l in
	  foldl f r xx

As Daniel Wang points out, this does not preserve the basic liveness 
properties of the original program.  As he asked on the newsgroup, is there 
a deep reason for this, or is this just a bug that has yet to be fixed?

Charles