------- Comment #4 from rguenther at suse dot de 2009-01-16 09:36 -------
Subject: Re: missing FRE with
VIEW_CONVERT_EXPR
On Fri, 16 Jan 2009, pinskia at gcc dot gnu dot org wrote:
> ------- Comment #2 from pinskia at gcc dot gnu dot org 2009-01-16 02:33
> -------
> Mine. Simple patch which implements it in vn_reference_lookup, Since VCE is
> both a reference and really a bit-wise cast, we can do the normal lookup and
> then do a lookup if the VCE was not there. I have not seen if this improves
> any testcases yet though but I thought I remembering seeing code like this in
> the benchmark we have internally.
Can you use the same trick as for union loads/stores and adjust
how we record V_C_Es instead and use the needs_insertion stuff?
Richard.
> Index: tree-ssa-sccvn.c
> ===================================================================
> --- tree-ssa-sccvn.c (revision 143413)
> +++ tree-ssa-sccvn.c (working copy)
> @@ -1041,6 +1041,19 @@ vn_reference_lookup (tree op, VEC (tree,
> vr1.operands = valueize_refs (shared_reference_ops_from_ref (op));
> vr1.hashcode = vn_reference_compute_hash (&vr1);
> result = vn_reference_lookup_1 (&vr1, vnresult);
> +
> + /* If we don't get the result right away for a VIEW_CONVERT_EXPR, try again
> + with the original expression. */
> + if (!result && TREE_CODE (op) == VIEW_CONVERT_EXPR)
> + {
> + vr1.vuses = valueize_vuses (vuses);
> + vr1.operands = valueize_refs (shared_reference_ops_from_ref
> (TREE_OPERAND (op, 0)));
> + vr1.hashcode = vn_reference_compute_hash (&vr1);
> + result = vn_reference_lookup_1 (&vr1, vnresult);
> + /* Convert it back to the original type */
> + if (result)
> + fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (op), result);
> + }
>
> /* If there is a single defining statement for all virtual uses, we can
> use that, following virtual use-def chains. */
>
>
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38865
