[Bug tree-optimization/68707] [6 Regression] testcase gcc.dg/vect/O3-pr36098.c vectorized using VEC_PERM_EXPR rather than VEC_LOAD_LANES

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68707

--- Comment #19 from rguenther at suse dot de <rguenther at suse dot de> ---
On December 16, 2015 8:24:49 PM GMT+01:00, "alalaw01 at gcc dot gnu.org"
<gcc-bugzilla@gcc.gnu.org> wrote:
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68707
>
>--- Comment #18 from alalaw01 at gcc dot gnu.org ---
>Well, we've seen this patch fix some of the vectorizer performance
>regressions
>we've had on some benchmarks.
>
>On SPEC...the "SLP cancelled" case triggers all over the place, but in
>most of
>those cases, doesn't lead to any codegen difference. (Presumably SLP
>would have
>failed anyway for some other reason, e.g. costs, and either we generate
>load/store-lanes either way, or we still *can't* generate
>load/store-lanes...).
>The only sub-benchmark where codegen changes is facerec, where we seem
>to
>*lose* st2 rather than gain....this needs more analysis.

Would be nice to have a reduced testcase for this one.