truthful optimization

[Kent M Pitman <KMP@MIT-MC.ARPA>]

    Date: Wed, 17 Oct 84 12:51:41 EDT
    From: Chris Riesbeck <Riesbeck at YALE.ARPA>
    To:   T-Discussion at YALE.ARPA
    Re:   TRUE
    Message-Id: <8410171845.AA03035@YALE-BULLDOG.YALE.ARPA>

    Is (TRUE exp) a legitimate alternative to (BLOCK exp T)?
    Or is it intended that a compiler might optimize away the
    evaluation of the exp.

It seems to me that the definition of "optimization" precludes
anything which changes the semantics of an expression. ie, 
optimizations (in any language) only make sense when the compiler 
can prove that you'll never know the difference. If they're not
defined that way, they're not "optimizations", they're just "hacks".