[SelectionDAG] Replace findGlueUse in SelectionDAGISel with SDNode::getGluedUser. NFC

SDNode::getGluedUser has a little bit different implemenetation,
but the effect should be the same.

  SDNode *getGluedUser() const {
    for (use_iterator UI = use_begin(), UE = use_end(); UI != UE; ++UI)
      if (UI.getUse().get().getValueType() == MVT::Glue)
        return *UI;
    return nullptr;
  }

Author: topperc

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@@ -2329,19 +2329,6 @@ void SelectionDAGISel::SelectInlineAsmMemoryOperands(std::vector<SDValue> &Ops,
     Ops.push_back(handle.getValue());
 }
 
-/// findGlueUse - Return use of MVT::Glue value produced by the specified
-/// SDNode.
-///
-static SDNode *findGlueUse(SDNode *N) {
-  unsigned FlagResNo = N->getNumValues()-1;
-  for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
-    SDUse &Use = I.getUse();
-    if (Use.getResNo() == FlagResNo)
-      return Use.getUser();
-  }
-  return nullptr;
-}
-
 /// findNonImmUse - Return true if "Def" is a predecessor of "Root" via a path
 /// beyond "ImmedUse".  We may ignore chains as they are checked separately.
 static bool findNonImmUse(SDNode *Root, SDNode *Def, SDNode *ImmedUse,
@@ -2445,7 +2432,7 @@ bool SelectionDAGISel::IsLegalToFold(SDValue N, SDNode *U, SDNode *Root,
   // glueged set.
   EVT VT = Root->getValueType(Root->getNumValues()-1);
   while (VT == MVT::Glue) {
-    SDNode *GU = findGlueUse(Root);
+    SDNode *GU = Root->getGluedUser();
     if (!GU)
       break;
     Root = GU;