[Bug tree-optimization/33245] Missed opportunities for vectorization due to invariant condition

["dorit at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from dorit at gcc dot gnu dot org  2007-08-31 14:18 -------
(In reply to comment #2)
> Subject: Re:  Missed opportunities for vectorization due to invariant condition
> > Looks like -fno-tree-pre is not enough, because if PRE doesn't do it, then sink
> > does it. When I use "-O3 -ftree-vectorize -msse2 -fno-tree-pre -fno-tree-sink"
> > I get the dataref problem you report below, without manual modifications to the
> > code
> >
> Apparently this is sink is triggered on -O3, Daniel also warned yesterday
> about the fact that it's not PRE specific.
> Actually, can't we move that code back in the loop body when
> the vectorizer detects that code in the latch bb?

here's a related discussion from a couple years ago:
http://gcc.gnu.org/ml/gcc-patches/2005-11/msg02045.html

(and also a somewhat related PR - PR28643) 

> I'm thinking that it is not really difficult to consider these scalars
> as arrays with a single element, and then just pass these to the rest
> of data deps.  I'll try to figure out a patch for this problem that would
> bring us more vectorized cases.

great.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33245