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[Bug tree-optimization/51499] vectorizer missing simple case


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51499

--- Comment #10 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-12-12 11:24:22 UTC ---
Hmm.  But we are vectorizing

  sum += a[i]
  sum += a[i+1]

the same as

  sum += a[i+1]
  sum += a[i]

no?  Thus you have to check whether the summation occours in "memory order"?


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