[Bug tree-optimization/29680] [4.3 Regression] Misscompilation of spec2006 gcc

["dnovillo at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #33 from dnovillo at redhat dot com  2006-11-09 21:48 -------
Subject: Re:  [4.3 Regression] Misscompilation
 of spec2006 gcc

dberlin at dberlin dot org wrote on 11/09/06 16:28:

> Uh, LIM and store sinking are too.  Roughly all of our memory
> optimizations are.
> 
They are?  Really?  Can you show me where exactly?

> The changes i have to make to PRE (and to the other things) to
> account for this is actually to rebuild the non-mem-ssa-factored (IE
> the current factored) form out of the chains by seeing what symbols
> they really affect.
> 
OK, so how come you were so positive about the new interface?  I need to
understand what was the great difficulty you ran into that made you 
change your mind.  I need to see a specific example.

See, the UD chains you get in mem-ssa are neither incomplete nor wrong.
The symbols affected are right there in plain sight, so there is no
loss of any information.

> For at least all the opts i see us doing, it makes them more or less 
> useless without doing things (like reexpanding them) first. Because 
> this is true, I'm not sure it's a good idea at all, which is why i'm 
> still on the fence.
> 
But you still haven't *shown* me where the hardness or slowness comes 
in.  Granted, the work is still unfinished so we can't really do actual 
measurements.  But I need to understand where the difficulties will be 
so that I can accomodate the infrastructure.  It's obviously not my 
intent to make things harder to use.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29680