[MLton-devel] Re: PRE in MLton

[Tom Murphy]

Yes, and then even global CSE will hoist invariant code. But it might grow
the code quite a bit, because the body gets duplicated.

Better is to move the test at the beginning of the loop to both the
beginning and end:

F:
case n of
  0 => Ldone
  _ => Lhead
Lhead:
  ... here is where hoisted code goes ...
  GOTO Lbody

Lbody:
  ... body of loop ...
  n = n - 1
  case n of
    0 => Ldone
    _ => Lbody

 - Tom

> Isn't  the  transformation  to  handle  the  while vs. do-while simply one of
> unrolling recursive functions once.  I.e., all uses of f (except those in the
> body  of f) are replaced with calls to f'.  The definition of f' is identical
> to the definition of f.
>

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