Subzero: Improve the use of NodeList objects.

src/IceTargetLoweringX8632.cpp

Index: src/IceTargetLoweringX8632.cpp
diff --git a/src/IceTargetLoweringX8632.cpp b/src/IceTargetLoweringX8632.cpp
index 999556ea7cef12a2bef88c06e4813039a192ae40..3c697b5a9e6d1ba2e2c5b25147cadd21fe82a708 100644
--- a/src/IceTargetLoweringX8632.cpp
+++ b/src/IceTargetLoweringX8632.cpp
@@ -4184,7 +4184,7 @@ void TargetX8632::lowerPhiAssignments(CfgNode *Node,
   assert(Node->getOutEdges().size() == 1);
   assert(Node->getInsts().empty());
   assert(Node->getPhis().empty());
-  CfgNode *Succ = Node->getOutEdges()[0];
+  CfgNode *Succ = Node->getOutEdges().front();
   getContext().init(Node);
   // Register set setup similar to regAlloc() and postLower().
   RegSetMask RegInclude = RegSet_All;