Richard, First of all, I don't think that it is possible to write out test for outer-loop vectorization with zero-step reference because of possible loop-carried dependencies and run-time aliasing is not supported for outer-loop. If there are no such dependencies pre or pdse does hoisting (sinking) of such invariant references. So I add a check on it to accept zero-step references for outer loop marked with forc-vectorize flag to guarantee absence of loop-carried dependencies between inner-loop iterations. I included run-time test that checks vectorization correctness.
Update patch is attached. Yuri.. 2015-05-28 14:39 GMT+03:00 Richard Biener <richard.guent...@gmail.com>: > On Thu, May 28, 2015 at 1:00 PM, Yuri Rumyantsev <ysrum...@gmail.com> wrote: >> Hi All, >> >> Here is a simple patch which removes restriction on outer-loop >> vectorization - allow references in inner-loop with zero step. This >> case was found in one important benchmark. >> >> Bootstrap and regression testing did not show any new failures. >> Is it OK for trunk. >> >> ChangeLog: >> 2015-05-28 Yuri Rumyantsev <ysrum...@gmail.com> >> >> * tree-vect-data-refs.c (vect_analyze_data_ref_access): Allow >> consecutive accesses within outer-loop vectorization for references >> with zero step in inner-loop. >> >> gcc/testsuite/ChangeLog: >> * gcc.dg/vect/fast-math-vect-outer-1.c: New test. > > Can you please add a non-omp-simd testcase that triggers this as well and that > is a runtime testcase verifying the transform is correct? > > Also please don't add to the strange testcase-name machinery but just > use { dg-additional-options "-ffast-math" } > > Index: tree-vect-data-refs.c > =================================================================== > --- tree-vect-data-refs.c (revision 223653) > +++ tree-vect-data-refs.c (working copy) > @@ -2261,7 +2261,6 @@ > return true; > } > > - > /* Analyze the access pattern of the data-reference DR. > In case of non-consecutive accesses call vect_analyze_group_access() to > analyze groups of accesses. */ > > spurious white-space change > > > @@ -2291,14 +2290,8 @@ > if (loop_vinfo && integer_zerop (step)) > > Surely the comment before this needs updating now. > > { > GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL; > - if (nested_in_vect_loop_p (loop, stmt)) > - { > - if (dump_enabled_p ()) > - dump_printf_loc (MSG_NOTE, vect_location, > - "zero step in inner loop of nest\n"); > - return false; > - } > - return DR_IS_READ (dr); > + if (!nested_in_vect_loop_p (loop, stmt)) > + return DR_IS_READ (dr); > } > > if (loop && nested_in_vect_loop_p (loop, stmt)) > > so what happens after the patch? It would be nice to have a comment > explaining what happens in the nested_in_vect_loop_p case for > the case when the outer-loop step is zero and when it is not zero. > > In particular as you don't need any code generation changes - this hints > at that you may miss something ;) > > Otherwise of course the patch is ok - lifting restrictions is good. > > Thanks, > Richard.
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