Kenneth Zadeck <> writes:
> Richard,
> thanks, for doing the changes.    In particular, i did not really 
> understand how the target stuff was supposed to work.
> I have one issue with the changes that you made.
> I had actually decided that the speed/size decision was not relevant to 
> this patch.    The problem is that since this is a global optimization 
> which propagates the info across the entire web of moves, you really 
> want/need to use the same cost metric everywhere.  (of course, making 
> the speed/size decision on the global optimization level would be fine; 
> my issue is with the choice being at the bb level.)    So now you are 
> going to have some moves in a web saying yes while others saying no.    
> The ones that say no will dominate.   It is unlikely you will get what 
> you want (the important nodes really running fast) out of this, assuming 
> you have a target where the decision could go either way.

Yeah, I suppose that's true.  The problem is that both ways are wrong really.
If we just use the function-level speed setting, there'll be times where
a cold-only web will be optimised as hot.  But as you say, if we apply
the bb-level setting, cold blocks can hold back the hot blocks.
And I don't particularly relish the idea of trying to joust between
the two.

So yeah, applying it on a function-by-function basis is probably better.
Does anyone else have any thoughts before I make that change?


Reply via email to