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

[rguenth at gcc dot gnu.org]

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: unassig...@gcc.gnu.org

        ReportedBy: rgue...@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).