Merge pull request #8147 from erik-krogh/cacheReg

JS: cache RegExpCreationNode::getAReference

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

@@ -1684,5 +1684,9 @@ class RegExpCreationNode extends DataFlow::SourceNode {
   }
 
   /** Gets a data flow node referring to this regular expression. */
-  DataFlow::SourceNode getAReference() { result = this.getAReference(DataFlow::TypeTracker::end()) }
+  cached
+  DataFlow::SourceNode getAReference() {
+    Stages::FlowSteps::ref() and
+    result = this.getAReference(DataFlow::TypeTracker::end())
+  }
 }

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

@@ -238,6 +238,8 @@ module Stages {
       1 = 1
       or
       DataFlow::SharedFlowStep::step(_, _)
+      or
+      exists(any(DataFlow::RegExpCreationNode e).getAReference())
     }
   }