Richard Guenther <rguent...@suse.de> wrote on 04/07/2011 03:30:59 PM: > > > > 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?
Well, this is certainly enough to fix the PR. I am not sure if we can just remove these data-refs from the dependence checks. After that all the alignment and access checks are at least redundant. Thanks, Ira > > Thanks, > Richard.
