Debugging info on # spills?

[Timothy J. Wood]

   I'm working on a fairly large Altivec function and on the of the main 
issues right now is that I need to reduce the number of registers I'm 
using to avoid spills in a tight inner loop (which is the entirety of 
this function, really).

   Is there some gcc option I can use that would allow me to determine 
how many 'extra' registers would be necessary to allow my function to 
run with zero spilling?  This would be useful so I can make plans about 
what sort of approach to use (i.e., if I know I need 6 'more' 
registers, I shouldn't settle on an approach that only frees up 4 
registers).

   Perhaps one of the debugging dumps?  I've tried dumping a few 
different things, but most look either not useful for this or pretty 
incomprehensible :)

-tim