On Mon, 4 Jul 2011, Ira Rosen wrote:
>
>
> Richard Guenther <rguent...@suse.de> wrote on 04/07/2011 02:38:50 PM:
>
> > Handling of negative steps broke one of the many asserts in
> > the vectorizer. The following patch drops one that I can't
> > make sense of. I think all asserts need comments - especially
> > this one would, as I can't see why using vf is correct to
> > test against and not nelements (and why <= vf and not < vf).
>
> There is an explanation 10 rows above the assert. It doesn't make sense to
> peel more than vf iterations (and not nelements, since for the case of
> multiple types it may help to align more data-refs - see the comment in the
> code). IIRC <= is for the case of aligned access, but I am not sure about
> that, so maybe you are right.
>
> I don't see how it is related to negative steps.
>
> I think that the real reason for this failure is that the loads are
> actually irrelevant (hence, vf=4 that doesn't take char loads into
> account), but we don't check that when we analyze data-refs. So, in my
> opinion, the proper fix will add such check.
The following also works for me:
Index: tree-vect-data-refs.c
===================================================================
--- tree-vect-data-refs.c (revision 175802)
+++ tree-vect-data-refs.c (working copy)
@@ -1495,6 +1495,9 @@ vect_enhance_data_refs_alignment (loop_v
stmt = DR_STMT (dr);
stmt_info = vinfo_for_stmt (stmt);
+ if (!STMT_VINFO_RELEVANT (stmt_info))
+ continue;
+
/* For interleaving, only the alignment of the first access
matters. */
if (STMT_VINFO_STRIDED_ACCESS (stmt_info)
does that look better or do you propose to clean the datarefs
vector from those references?
Thanks,
Richard.
