Repost: RFA: re-instate struct_equiv code

[Bernd Schmidt]

Joern RENNECKE wrote:
> If we want to get more fancy, we can add some logic to set a flag when 
> we potentially miss optimization opportunities because of uncertainties 
> about the liveness of a register,
> which is again cleared at the start of every iteration of cleanup_cfg.  

I don't think "fancy" is the direction we should be going with this. 
I'd rather experiment with moving crossjumping out of the 
try_optimize_cfg loop, to a place where we know life information is 
up-to-date, and making sure we don't visit blocks more than once.


Bernd