[LLVMbugs] [Bug 3040] New: DAGCombiner:: visitXOR transforms condition code without checking legality

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Mon Nov 10 18:12:59 PST 2008


           Summary: DAGCombiner::visitXOR transforms condition code without
                    checking legality
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sharparrow1 at yahoo.com
                CC: llvmbugs at cs.uiuc.edu

Per summary; the following code in DAGCombiner::visitXOR is wrong:

  // fold !(x cc y) -> (x !cc y)
  if (N1C && N1C->getAPIntValue() == 1 && isSetCCEquivalent(N0, LHS, RHS, CC))
    bool isInt = LHS.getValueType().isInteger();
    ISD::CondCode NotCC = ISD::getSetCCInverse(cast<CondCodeSDNode>(CC)->get(),
    if (N0.getOpcode() == ISD::SETCC)
      return DAG.getSetCC(VT, LHS, RHS, NotCC);
    if (N0.getOpcode() == ISD::SELECT_CC)
      return DAG.getSelectCC(LHS, RHS,
    assert(0 && "Unhandled SetCC Equivalent!");

This needs to check whether the inverse opcode is legal when this is running
post-legalize.  That said, this doesn't affect any existing backends as far as
I know.

It looks like combineSelectAndUse has the same issue, but a quick search
doesn't find any other places affected similarly.

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