Re: [tree-ssa] Minor code rearrangement

[law at redhat dot com]

In message <1065121453.5274.90.camel@p4>, Andrew MacLeod writes:
 >On Thu, 2003-10-02 at 14:53, law@redhat.com wrote:
 >> In message <m34qyrwlgv.fsf@averell.firstfloor.org>, Andi Kleen writes:
 >>  >law@redhat.com writes:
 >
 >> 
 >> I can also certainly envision at least one optimizer that is going to want
 >> to do a dominator tree walk, but which can not be merged with the existing
 >> walks.  Fundamentally, it can't co-exist with the existing dominator
 >> optimizer, but it wants to be able to use certain capabilities of the
 >> existing dominator optimizer.
 >> 
 >
 >There are a few things that would benefit from processing basic blocks
 >in dominator order too. So instead of 
 >  FOR_EACH_BB (bb) 
 >    {
 >      blah;
 >    }
 >
 >it would be cool to be able to do them something like:
 >
 >void blah_func ()
 >{
 >  blah;
 >}
 >
 >  for_each_bb_in_dominator_order (blah_func);
That's pretty easy with the scheme I'm looking at.  You just have to store
blah_func into the appropriate slot in the datastructure you pass to the
walker.

The appropriate slot of course determining if you want to call blah_func pre
or post-order.  You'd leave NULLs for the other callbacks.  


 >Then I know I will have visited as many predecessors as possible before
 >visiting each basic block. Initialization in CCP for instance.. One of
 >the big speedups was processing blocks in a breadth first manner instead
 >of the original depth_first manner.  Dominator order is even more ideal.
Yup.


 >I can think of other places I would like to do that sort of thing, as
 >long as its not much more time consuming than FOR_EACH_BB()...  In fact,
 >I even mentioned it to Diego a week ago ro so as something desirable :-)
Unsure if it'll be faster or slower than FOR_EACH_BB (OK, the base walker
will be slower, I'm assuming that we'll make up for some of that by doing
things in a better order).

If you're going to be doing a lot of dominator walks, you might just want
to get a list of the blocks in dominator order and iterate through them.

Or, hell, we might consider re-wiring the BBs so that FOR_EACH_BB presents
them in dominator order.  Dunno.

Jeff