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[Bug tree-optimization/68707] [6 Regression] testcase gcc.dg/vect/O3-pr36098.c vectorized using VEC_PERM_EXPR rather than VEC_LOAD_LANES
- From: "rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 14 Dec 2015 20:35:52 +0000
- Subject: [Bug tree-optimization/68707] [6 Regression] testcase gcc.dg/vect/O3-pr36098.c vectorized using VEC_PERM_EXPR rather than VEC_LOAD_LANES
- Auto-submitted: auto-generated
- References: <bug-68707-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68707
--- Comment #17 from rguenther at suse dot de <rguenther at suse dot de> ---
On December 14, 2015 4:44:13 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 #13 from alalaw01 at gcc dot gnu.org ---
>In the longer term, is the issue here, that we aren't comparing costs
>of SLP vs
>load-lanes, right? We merely compare the cost of whichever of those
>vectorization strategies we favour, permutes et al, vs leaving it in
>scalar
>code?
Correct. And the cost of using SLP is not comparable to the cost of
interleaving/load-lanes or rather it would almost always favor the latter.
BTW, for the patch can you do a compare with SPEC or another benchmark you are
usually testing for vectorizer performance?