Re: [PATCH] Fix RTL fwprop compile-time for PR56113

[Michael Matz <matz at suse dot de>]

Hi,

On Wed, 30 Jan 2013, Richard Biener wrote:

> 483         {
> 484           redirect_immediate_dominators (CDI_DOMINATORS, bb, new_bb);
> 485           set_immediate_dominator (CDI_DOMINATORS, new_bb, bb);
> 486         }
> 
> but that doesn't set dominance info to DOM_OK again.  The
> iterate_fix_dominators doesn't do that either.
> 
> IMHO at least split_block () should be able to preserve fast queries?

I don't see how.  Fast queries rely on DFS in and out numbers of the 
dominance tree being correct.  If you insert a node in a tree the 
DFS numbers of all nodes after it need to change, i.e. updating fast 
queries for a single-block change is O(n_basic_blocks).


Ciao,
Michael.