Re: [tree-ssa] must-alias analysis

[Jason Merrill <jason at redhat dot com>]

On Mon, 14 Jul 2003 12:04:25 -0600, law@redhat.com wrote:

>  >We currently do not propagate ADDR_EXPR values that have been type
>  >casted.  So, things like 'PTR = (type *)&VAR' are not propagated.  The
>  >problem with this is that we would need to fold instances of *PTR into
>  >(type)VAR, which would produce non-GIMPLE code and confuse the
>  >optimizers.  I'm not quite sure how to handle this one.  I think it's
>  >important because right now we are not handling code like this (from Joe
>  >Buck's sample code a while back):
> We've *REALLY* got to fix our handling of NOP_EXPRs.  REALLY REALLY REALLY.
>
> They're getting in the way far too often.  I really want to see someone
> tackle that problem.  I'm consistently running into cases where we either
> miss a redundancy, generate a useless copy, etc because of the way we
> handle NOP_EXPRs.

Yep.  As Nathanael was pointing out, most of the NOPs are, in fact, nops,
changing between pointer and reference or adjusting cv-quals.  In most
cases we should be able to remove them and just change the type of the
expression they wrap.  I'll work on such a change.

Jason