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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: "alalaw01 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 14 Dec 2015 15:44:13 +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 #13 from alalaw01 at gcc dot gnu.org ---
Hmmm, I realize a "definite" codegen improvement was maybe a bad choice of
wording. A "substantial" (albeit uncertain!) improvement, may have been more
accurate...
However, yes it looks like we want that patch (indeed, it still helps even when
we up the cost of permute operations and drop the -fno-vect-cost-model) - so
thanks, Richard. We'll clean up the testisms in due course.
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?