Add a premature optimization.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@90532 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGVtable.cpp

@@ -832,6 +832,9 @@ bool VtableBuilder::OverrideMethod(GlobalDecl GD, llvm::Constant *m,
 }
 
 void VtableBuilder::AppendMethodsToVtable() {
+  // Reserve room for our new methods.
+  methods.reserve(methods.size() + Methods.size());
+
   for (unsigned i = 0, e = Methods.size(); i != e; ++i) {
     GlobalDecl GD = Methods[i];
     const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());