Re: What tree flags tell me a variable is local?

[Daniel Berlin <dberlin at dberlin dot org>]

On Saturday, June 14, 2003, at 03:09  PM, Geoff Keating wrote:

> Daniel Berlin <dberlin@dberlin.org> writes:
>
> > I know you can do it with decl_function_context, but I'm trying to
> > avoid using it, because it's too expensive in PTA due to call overhead
> > (Any time a query is made, we need to figure out whether they are
> > querying about a global or not, so we end up calling it millions of
> > times).
> >
> > Thus, i'm wondering if there is some combination of tree flags i can
> > rely on to always be correct.
> >
> > Currently, I check DECL_CONTEXT, and iff it's a FUNCTION_DECL, we say
> > it's local, otherwise, we call decl_function_context and see if it
> > returns NULL.
> >
> >
> > Is there a better way?
>
> I presume that by 'local' you mean 'inside a function scope', not
> 'file-local' or 'automatic'?

Right. More "local to a function" (IE extern variables declared extern 
inside a function aren't function-local in this sense)

> No, there's no better way.

> Why do you want to do this?
Because Points-to, and tree-ssa in general, currently globs all 
non-local variables to one variable named "GLOBAL_VAR", which is 
clobbered by most types of function calls.

Thus, to do Points-To Analysis properly (IE be able to say what 
points-to GLOBAL_VAR) , we need to differentiate between function 
locals and non-locals.