Worth balancing the tree before scheduling?

[Geert Bosch]

On Nov 23, 2009, at 10:17, Ian Bolton wrote:

> Regardless of the architecture, I can't see how an unbalanced tree would
> ever be a good thing.  With a balanced tree, you can still choose to
> process it in either direction (broad versus deep) - whichever is better
> for your architecture - but, as far as I can see (bearing in mind that
> I'm very new to GCC development!), a tall lop-sided tree gives few
> scheduling options due to all the extra dependencies.  I guess I must
> be missing something?

Yes, a lop-sided tree often needs less registers.
For example, (((a+b)+c)+d)+e would only need 2 registers. 
Any more balanced tree would need at least one more.

  -Geert