Allocate the right amount of memory for this vector up front.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24252 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -409,6 +409,7 @@ void SelectionDAGLegalize::LegalizeDAG() {
   // node is only legalized after all of its operands are legalized.
   std::map<SDNode*, unsigned> Visited;
   std::vector<SDNode*> Order;
+  Order.reserve(DAG.allnodes_end()-DAG.allnodes_begin());
   
   // Compute ordering from all of the leaves in the graphs, those (like the
   // entry node) that have no operands.