Re: Help Me Please :)

[Robert Dewar <robert_dewar@my-deja.com>]

In article <38ECEB56.8FD7596E@gecm.com>,
  Simon Pilgrim <simon.pilgrim@gecm.com> wrote:

> > Finally, 11.6 is about optimization, it is almost always the
> > case that you want *no* optimization for SC code. Why?
> > Because
> > you want the best possible correspondence between source
> > code and object code.
>
> Not true for the PFC.  We have a lot of code to squeeze into
> that frame.

Well "no optimization" is a relative term here, none of the
compilers you used had particularly strong optimizers by
modern standards. Certainly none of them took full
advantage of 11.6, which was the specific point of
this discussion.

Actually when the safety-critical crowd asks for no
optimization, they are making the usual mistake of
specifying a solution to their problem, rather than
stating the problem.

The problem is to make the examination of the object code
as easy as possible.

Certain types of optimization assist in this goal. For example,
with gnat, we usually find that -O1 assembly code is far easier
to follow than -O0 code, simply because there is so much less
of it.

On the other hand, if you have really fierce optimization,
involving high level algorithm substitution, propagation
of information all around the place, including erroneous
situations, massive restructuring of code, etc, then the
resulting object code can become quite complex to read.


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