http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49513
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |law at gcc dot gnu.org
Summary|PRE inhibits if-conversion |DOM inhibits if-conversion
|and vectorization |and vectorization
--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-06-23
12:58:44 UTC ---
(In reply to comment #2)
> thanks for the fast analysis.
>
> the code in question was there also to test what the vectorized code would do
> for x=0 and y=0 (it is extracted from a simplified version of atan2f that gcc
> can vectorize).
> Being a test, I can workaround (I've to test extreme conditions explicitely
> anyhow).
>
> In any case I think that any peeling will ruin alignmement.
>
> hoping gcc can find ways to avoid PRE and vectorization to clash.
I had a closer look and it is DOM jump-threading which creates this
rotated loop. CCin Jeff who was working in this area - PRE avoids
this kind of transformation. Jeff - can we avoid threading through
the loop header somehow?
