Only generate addcarry node when it is legal.

[deadalnix]

Summary

As per title.

[chandlerc]

Ok, this seems like a trivial fix to a breakage, but please spell out in the patch description when you commit it what we discussed on IRC:

• This was uncovered during stage2 of a bootstrap by build bots
• The patch that introduced it has already had other patches land on top and so trying to avoid lots of revert churn
• Working on adding a reduced test case that covers this, but wanted to get the build bots back to green ASAP, will land a test case as soon as one is available.

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

SDValue DAGCombiner::visitADDLike(SDValue N0, SDValue N1, SDNode *LocReference) {
   }
 
   // (add X, (addcarry Y, 0, Carry)) -> (addcarry X, Y, Carry)
   if (N1.getOpcode() == ISD::ADDCARRY && isNullConstant(N1.getOperand(1)))
     return DAG.getNode(ISD::ADDCARRY, DL, N1->getVTList(),
                        N0, N1.getOperand(0), N1.getOperand(2));
 
   // (add X, Carry) -> (addcarry X, 0, Carry)
+  if (TLI.isOperationLegalOrCustom(ISD::ADDCARRY, VT))
     if (SDValue Carry = getAsCarry(TLI, N1))
       return DAG.getNode(ISD::ADDCARRY, DL,
                          DAG.getVTList(VT, Carry.getValueType()), N0,
                          DAG.getConstant(0, DL, VT), Carry);
 
   return SDValue();
 }
 
 SDValue DAGCombiner::visitADDC(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   EVT VT = N0.getValueType();
SDValue DAGCombiner::visitUADDO(SDNode *N) {
 
   if (SDValue Combined = visitUADDOLike(N1, N0, N))
     return Combined;
 
   return SDValue();
 }
 
 SDValue DAGCombiner::visitUADDOLike(SDValue N0, SDValue N1, SDNode *N) {
+  auto VT = N0.getValueType();
+
   // (uaddo X, (addcarry Y, 0, Carry)) -> (addcarry X, Y, Carry)
   // If Y + 1 cannot overflow.
   if (N1.getOpcode() == ISD::ADDCARRY && isNullConstant(N1.getOperand(1))) {
     SDValue Y = N1.getOperand(0);
     SDValue One = DAG.getConstant(1, SDLoc(N), Y.getValueType());
     if (DAG.computeOverflowKind(Y, One) == SelectionDAG::OFK_Never)
       return DAG.getNode(ISD::ADDCARRY, SDLoc(N), N->getVTList(), N0, Y,
                          N1.getOperand(2));
   }
 
   // (uaddo X, Carry) -> (addcarry X, 0, Carry)
+  if (TLI.isOperationLegalOrCustom(ISD::ADDCARRY, VT))
     if (SDValue Carry = getAsCarry(TLI, N1))
       return DAG.getNode(ISD::ADDCARRY, SDLoc(N), N->getVTList(), N0,
-                       DAG.getConstant(0, SDLoc(N), N0.getValueType()), Carry);
+                         DAG.getConstant(0, SDLoc(N), VT), Carry);
 
   return SDValue();
 }
 
 SDValue DAGCombiner::visitADDE(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   SDValue CarryIn = N->getOperand(2);