Re: [tree-ssa vs lno] who is right?

[Andrew MacLeod <amacleod at redhat dot com>]

On Thu, 2004-03-25 at 20:32, Diego Novillo wrote:
> On Thu, 2004-03-25 at 20:29, Dale Johannesen wrote:
> 
> > ;; basic block 19, loop depth 0, count 0
> > ;; prev block 9, next block 20
> > ;; pred:       10 [100.0%]  (fallthru)
> > ;; succ:       28 [50.0%]  (true,exec) 29 [50.0%]  (false,exec)
> > # maxmin_Result_140 = PHI <1(10)>;
> > # maxmin_Result_142 = PHI <2(10)>;
> > # lsm_tmp.19_144 = PHI <lsm_tmp.19_84(10)>;
> > <L28>:;
> > if (m__10 == 0) goto <L26>; else goto <L27>;
> > 
> > Is that suppose to be a valid assumption?  The dup is created by 
> > copyrename, and
> > I see no code there that's intended to stop dups from being created (on 
> > the
> > contrary, but surely it's unusual for the live ranges to overlap).
> > 
> Are maxmin_Result the same variable?  Use -uid to find out.  If they
> both have the same UID, they're the same and that's a bug.  There should
> only be a single PHI node per variable in a basic block.

I dont see why we have to have that restriction... 

maxmin_Result_140 and maxmin_Result_142 should be treated as two
completely different variables. Why should we say its a bug to allow
that to happen? 

If the live range of SSA_NAMEs can overlap, why can't they overlap here?
What are the arguments for dissallowing it?

Andrew