Re: DECL_CALL_CLOBBERED tweek

[Diego Novillo <dnovillo at redhat dot com>]

Jan Hubicka wrote on 12/21/06 09:45:

> This is done by reset_cc_flags pass and I am now starting to wonder why
> it is needed at all?  What is the semantic of CALL_CLOBBERED on static
> variables and why it differs on individual functions?  (I can see that
> perhaps function that is known to never reach functions that might
> clobber the variable might want to have this flag clear unlike other
> function that does call something clobbering it.  But I am surprised we
> do that especially because I've temporarily disabled IPA AA passes for
> now)
It may be a case where one function f() calls no clobbering functions, 
while a second function g() does.  So the CC state for the same decl is 
considered different for f() and g().

> I will benchmark it on the testcase suggested and prepare version with
> inline functions unless we can come with better solution to this
> problem.  If this flag really needs to be local to functions I am
> affraid I don't have better answer than this patch even if it turns out
> to be costy :(
Well, perhaps this will give us another incentive to move to a global 
dense DECL_UID space.  But in the meantime, we may need to move to this. 
 Dan may have other ideas as he worked on this before.