DAG: Fix getNode dropping flags if there's a glue output

[arsenm]

Summary

The AMDGPU non-strict fdiv lowering needs to introduce an FP mode
switch in some cases, and has custom nodes to provide chain/glue for
the intermediate FP operations. We need to propagate nofpexcept here,
but getNode was dropping the flags.

Adding nofpexcept in the AMDGPU custom lowering is left to a future
patch.

Also fix a second case where flags were dropped, but in this case it
seems it just didn't handle this number of operands.

Test will be included in future AMDGPU patch.

[arsenm]

ping

[craig.topper]

LGTM

[arsenm]

836c7dcf1238683ff18882affac1dae5ae5c5f79

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

if (VT != MVT::Glue) {
     createOperands(N, Ops);
 
     CSEMap.InsertNode(N, IP);
   } else {
     N = newSDNode<SDNode>(Opcode, DL.getIROrder(), DL.getDebugLoc(), VTs);
     createOperands(N, Ops);
   }
 
+  N->setFlags(Flags);
   InsertNode(N);
   SDValue V(N, 0);
   NewSDValueDbgMsg(V, "Creating new node: ", this);
   return V;
 }
 
 SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL,
                               ArrayRef<EVT> ResultTys, ArrayRef<SDValue> Ops) {
#endif
   if (VTList.VTs[VTList.NumVTs-1] != MVT::Glue) {
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opcode, VTList, Ops);
     void *IP = nullptr;
     if (SDNode *E = FindNodeOrInsertPos(ID, DL, IP))
       return SDValue(E, 0);
 
     N = newSDNode<SDNode>(Opcode, DL.getIROrder(), DL.getDebugLoc(), VTList);
-    N->setFlags(Flags);
     createOperands(N, Ops);
     CSEMap.InsertNode(N, IP);
   } else {
     N = newSDNode<SDNode>(Opcode, DL.getIROrder(), DL.getDebugLoc(), VTList);
     createOperands(N, Ops);
   }
+
+  N->setFlags(Flags);
   InsertNode(N);
   SDValue V(N, 0);
   NewSDValueDbgMsg(V, "Creating new node: ", this);
   return V;
 }
 
 SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL,
                               SDVTList VTList) {