http://llvm.org/bugs/show_bug.cgi?id=3040
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(),
isInt);
if (N0.getOpcode() == ISD::SETCC)
return DAG.getSetCC(VT, LHS, RHS, NotCC);
if (N0.getOpcode() == ISD::SELECT_CC)
return DAG.getSelectCC(LHS, RHS,
N0.getOperand(2),N0.getOperand(3),NotCC);
assert(0 && "Unhandled SetCC Equivalent!");
abort();
}
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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