Give CodeGenRegisterClass a real sorted member set.

Make the Elements vector private and expose an ArrayRef through
getOrder() instead. getOrder will eventually provide multiple
user-specified allocation orders.

Use the sorted member set for member and subclass tests. Clean up a lot
of ad hoc searches.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133040 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/InstrInfoEmitter.cpp b/utils/TableGen/InstrInfoEmitter.cpp
index 67cce0e..fc544ee 100644
--- a/utils/TableGen/InstrInfoEmitter.cpp
+++ b/utils/TableGen/InstrInfoEmitter.cpp
@@ -166,13 +166,13 @@
 
   for (unsigned i = 0, e = RCs.size(); i != e; ++i) {
     const CodeGenRegisterClass &RC = RCs[i];
-    unsigned NumRegs = RC.Elements.size();
-    if (NumRegs > NumDefs)
+    ArrayRef<Record*> Order = RC.getOrder();
+    if (Order.size() > NumDefs)
       continue; // Can't possibly clobber this RC.
 
     bool Clobber = true;
-    for (unsigned j = 0; j < NumRegs; ++j) {
-      Record *Reg = RC.Elements[j];
+    for (unsigned j = 0; j < Order.size(); ++j) {
+      Record *Reg = Order[j];
       if (!DefSet.count(Reg)) {
         Clobber = false;
         break;