8059780: SPECjvm2008-MPEG performance regressions on x64 platforms

Summary: Back-out 8052081 changes made in lcm.cpp.
Reviewed-by: iveresov, roland

src/share/vm/opto/lcm.cpp

@@ -484,9 +484,7 @@ Node* PhaseCFG::select(Block* block, Node_List &worklist, GrowableArray<int> &re
         iop == Op_CreateEx ||   // Create-exception must start block
         iop == Op_CheckCastPP
         ) {
-      // select the node n
-      // remove n from worklist and retain the order of remaining nodes
-      worklist.remove((uint)i);
+      worklist.map(i,worklist.pop());
       return n;
     }
 
@@ -572,9 +570,7 @@ Node* PhaseCFG::select(Block* block, Node_List &worklist, GrowableArray<int> &re
   assert(idx >= 0, "index should be set");
   Node *n = worklist[(uint)idx];      // Get the winner
 
-  // select the node n
-  // remove n from worklist and retain the order of remaining nodes
-  worklist.remove((uint)idx);
+  worklist.map((uint)idx, worklist.pop());     // Compress worklist
   return n;
 }