fix performance by caching getArgument

Author: erik-krogh

javascript/ql/lib/semmle/javascript/dataflow/Nodes.qll

@@ -92,13 +92,20 @@ class InvokeNode extends DataFlow::SourceNode instanceof DataFlow::Impl::InvokeN
    * but the position of `z` cannot be determined, hence there are no first and second
    * argument nodes.
    */
-  DataFlow::Node getArgument(int i) { result = super.getArgument(i) }
+  cached
+  DataFlow::Node getArgument(int i) {
+    result = super.getArgument(i) and Stages::DataFlowStage::ref()
+  }
 
   /** Gets the data flow node corresponding to an argument of this invocation. */
-  DataFlow::Node getAnArgument() { result = super.getAnArgument() }
+  cached
+  DataFlow::Node getAnArgument() { result = super.getAnArgument() and Stages::DataFlowStage::ref() }
 
   /** Gets the data flow node corresponding to the last argument of this invocation. */
-  DataFlow::Node getLastArgument() { result = this.getArgument(this.getNumArgument() - 1) }
+  cached
+  DataFlow::Node getLastArgument() {
+    result = this.getArgument(this.getNumArgument() - 1) and Stages::DataFlowStage::ref()
+  }
 
   /**
    * Gets a data flow node corresponding to an array of values being passed as

javascript/ql/lib/semmle/javascript/internal/CachedStages.qll

@@ -145,6 +145,12 @@ module Stages {
       exists(any(DataFlow::PropRef ref).getBase())
       or
       exists(any(DataFlow::ClassNode cls))
+      or
+      exists(any(DataFlow::CallNode node).getArgument(_))
+      or
+      exists(any(DataFlow::CallNode node).getAnArgument())
+      or
+      exists(any(DataFlow::CallNode node).getLastArgument())
     }
   }