cgraph callees availability

[Paulo J. Matos]

On 01/07/11 10:31, Richard Guenther wrote:
>
> It is being done because the edges are not kept up-to-date.  There is
> no other way to find callees but to walk all statements.  I also do not
> see a good reason why you would want to use the number of callees
> of a function to decide whether to emit sibcalls from it.
>

Thanks for the input Richard. Makes sense. One way which seems to work 
is to obviously add a pass to rebuild the cgraph edges before 
pass_expand and remove them afterwards.

The reason why I need them is that I need know if a given register is 
live. I can check this when I expand_epilogue but not during expand 
(because RA has not been done). This special register is used for the 
return address of a function. So, if it is live it tells me that there 
was another function call besides the sibcall. If there was, it means I 
have to emit some extra instructions to do the sibcall. However, if I 
have to emit extra instructions then I don't actually want to do the 
sibcall cause I will be adding to the resulting size of the function 
which goes against our backend port policy.

By checking if there is more than 1 callee (an extra function called 
besides the sibcall) then I will know if I will need extra instructions 
or not and if I do, I say the function is _not_ ok for sibcall.

I guess if I don't want to add the extra passes before and after pass 
expand then I have to walk the statements. Sounds like it's the cleaner 
solution if I don't want to mess with the core.

Cheers,
-- 
PMatos