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[Bug tree-optimization/56612] New: basic-block vectorization does not replace all scalar uses


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56612

             Bug #: 56612
           Summary: basic-block vectorization does not replace all scalar
                    uses
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rguenth@gcc.gnu.org


When vectorizing stmts in a basic-block we do not verify that the SLP
instance covers all uses of the definitions the stmts in the SLP tree.
This can easily result in both the scalar and vectorized set of stmts
being kept live and executed.

See PR56608 for an example (trivial re-use of the SLP roots stored values).


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