This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [tree-ssa] patch suggestion: def_op vs vdef_ops
On Wed, 29 Jan 2003, Diego Novillo wrote:
> OTOH, vdef_ops mean that the variables are being modified in ways
> that the compiler doesn't know, or care. Mixing vdef_ops and
> def_op is not really possible without breaking the semantics of
> each one.
>
One more thing about vdef_ops that I forgot to add. They can be
used to follow def-def links. You'll see that a VDEF_EXPR is
both a definition and a use of a variable. You can from one
VDEF_EXPR go to the previous one, so that in a case like the
following:
1 ... = &a;
2 *p = 20;
3 ...
4 *q = 5;
5 ...
6 = a;
If *p and *q may alias a, you could determine that both *p and *q
can reach the use of a at line 6.
Diego.