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Re: [tree-ssa]: Easy way to get default def of a variable?
- From: Andrew MacLeod <amacleod at redhat dot com>
- To: Daniel Berlin <dberlin at dberlin dot org>
- Cc: Diego Novillo <dnovillo at redhat dot com>,gcc mailing list <gcc at gcc dot gnu dot org>
- Date: 05 Jun 2003 07:21:36 -0400
- Subject: Re: [tree-ssa]: Easy way to get default def of a variable?
- References: <9E7F0DA6-970F-11D7-AD2F-000A95A34564@dberlin.org>
On Thu, 2003-06-05 at 00:38, Daniel Berlin wrote:
> >>
> >>
> > We now connect them to empty_stmt_expr. Do you want to connect them to
> > this table so that we can traverse that table to look for live-
> > on-entry
> > or uninitialized uses? I guess we could do that.
>
> Well, remember, i want the table because right now i have to take a
> use, and walk the entire def chain backwards, to get the default def's
> version.
> This is expensive.
>
Out of curiosity, why do you need the default def? ie, why do you care
that a_2 is live on entry when you have a_4 = a_3 + 2, and a_3 has a
def? we are suppose to be able to treat them like disjoint variables.
It just so happens we are going to try to merge them all into the same
memory location, but it may not happen that way. Its highly unlikely,
but there is no reason that every version of 'a' couldn't have a
different memory location and be unrelated.
Andrew