[Bug optimization/13751] New: PHI pruning misses obvious cases

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

For gcc.c-torture/compile/920625-1.c, compile with -O -fdump-tree-sra-vops.
Notice at the end of the first function,

  # SR.16_4 = PHI <SR.16_3(2), SR.16_75(3), SR.16_85(1)>;
  # SR.15_5 = PHI <SR.15_1(2), SR.15_74(3), SR.15_84(1)>;
  # SR.14_6 = PHI <SR.14_9(2), SR.14_12(3), SR.14_83(1)>;
  # SR.13_7 = PHI <SR.13_10(2), SR.13_11(3), SR.13_82(1)>;
  # MT.12_8 = PHI <MT.12_2(2), MT.12_80(3), MT.12_91(1)>;
<L3>:;
<L4>:;
  return;

None of those are needed.  Though of course it's the PHIs for real vars that's
more important that the PHI for the VDEF.

-- 
           Summary: PHI pruning misses obvious cases
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: optimization
        AssignedTo: dnovillo at gcc dot gnu dot org
        ReportedBy: rth at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13751