Debugging info on # spills?

[Michael Matz]

Hi,

On Tue, 6 Apr 2004, Timothy J. Wood wrote:

>   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?

Not really, no.  Solving it optimally is NP complete.  Solving this 
heuristically is possible, but GCC doesn't do it because the number of 
free registers is bounded by the hardware register for the target, i.e. is 
a compile time constant which can't be enlarged by any cmdline option.

You could possibly try to change the rs6000 machine description to provide 
something like 1000 hardregs, and then use the -ffixed-reg-... option to 
take some away, but that's obviously cumbersome.


Ciao,
Michael.