[Bug tree-optimization/45764] [4.6 Regression] wrong code -O2 vs -O3 (problem in vectorizer???)

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45764

--- Comment #10 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-10-21 
11:10:45 UTC ---
Author: rguenth
Date: Thu Oct 21 11:10:41 2010
New Revision: 165768

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=165768
Log:
2010-10-21  Richard Guenther  <rguent...@suse.de>
    Michael Matz  <m...@suse.de>

    PR tree-optimization/45764
    * tree-vect-data-refs.c (vect_compute_data_ref_alignment):
    Adjust initial misalignment for negative DR_STEP.
    (vect_find_same_alignment_drs): Two DRs with different DR_STEP
    do not have the same alignment over the whole iteration domain.

        * gcc.dg/torture/pr45764.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr45764.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-vect-data-refs.c