Path: utzoo!attcan!uunet!cs.utexas.edu!yale!cmcl2!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.misc
Subject: Re: C's sins of commission
Message-ID: <65697@lanl.gov>
Date: 13 Oct 90 20:43:18 GMT
References: <PCG.90Oct13114804@odin.cs.aber.ac.uk>
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 21

From article <PCG.90Oct13114804@odin.cs.aber.ac.uk>, by pcg@cs.aber.ac.uk (Piercarlo Grandi):
> [...]
> I most strongly object to call this 'aggressive optimization'. It makes
> 'aggressive optimization' look respectable.
> 
> Aggressive optimization is where the optimizer rewrites your program in
> a supposedly similar form behind your back. [...]
> [...]
>-Piercarlo "Peter" Grandi     [...]

Grandi comes up with this one periodically.  I can never pin him down
on a meaning.  A compiler is a tool which  transforms one representation
of a program (the source) into a semantically equivalent form (the object
code) in another language.  If the compiler changes the semantics of the
program during this process, it is _BROKEN_.  The optimizer, as part of
the compiler, must obey this same constraint.  If the optimizer changes
the semantics of a code, it is _BROKEN_.  An optimizer may be as
"aggressive" as the compiler implementor wants to make it - as long
as it doesn't alter the semantics of the code it's translating.

J. Giles