Jeethru said:


> > Detecting and Adjusting references is one of the most basic things an
> > optimizer should be capable of doing. This is especially true on a PIC
> > since there are only 2 instructions capable of directly modifying the
> > program counter, CALL and GOTO. And there might also be instructions
> > which add/move/subtract(i've never seen this) to the PCL register.
> > This should be no trouble detecting.

Olin responded:

> I think we're going in circles here.  A few posts ago I should, as an
> example, a MOVLW instruction that might or might not need to be adjusted
> depending on the program intent.  The problem is that there is no way to
> know that intent by just looking at the final instructions.  It's not just
> instructions that modify the program counter that matter.  Any reference
to
> a program memory address needs to be adjusted, and there is no way to find
> all the instructions that do this.
>
> I've been trying to say basically the same thing for several posts in a
row.
> Maybe I'm not explaining this well, but either way I'm getting tired of
it.
> Perhaps others can jump in here, I'm done responding to this issue.
Believe
> what you like.  Go ahead and try it.

I add:

Olin is 100% right. Object code is not the place to start doing these
optimizations. In general, it is IMPOSSIBLE to determine the intent of a
specific instruction like his MOVLW's.

As he said -- if you think you can do it go ahead and try. But I will be
_highly_ surprised if you succeed.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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