Java: Fix performance issue in type flow library

Author: hvitved

java/ql/lib/semmle/code/java/dataflow/TypeFlow.qll

@@ -72,6 +72,35 @@ module FlowStepsInput implements UniversalFlow::UniversalFlowInput<Location> {
     }
   }
 
+  private class FlowNodeElement extends Element {
+    FlowNodeElement() {
+      this instanceof Field or
+      this instanceof Expr or
+      this instanceof Method
+    }
+  }
+
+  private predicate id(FlowNodeElement x, FlowNodeElement y) { x = y }
+
+  private predicate idOf(FlowNodeElement x, int y) = equivalenceRelation(id/2)(x, y)
+
+  int getFlowNodeId(FlowNode n) {
+    n =
+      rank[result](FlowNode n0, int a, int b |
+        a = 0 and
+        idOf(any(n0.asField()), b)
+        or
+        // no case for `n0.asSsa()`; here we rely on the built-in location-based ranking
+        a = 1 and
+        idOf(any(n0.asExpr()), b)
+        or
+        a = 2 and
+        idOf(any(n0.asMethod()), b)
+      |
+        n0 order by a, b
+      )
+  }
+
   private SrcCallable viableCallable_v1(Call c) {
     result = viableImpl_v1(c)
     or
@@ -165,6 +194,8 @@ private module Input implements TypeFlowInput<Location> {
 
   class TypeFlowNode = FlowNode;
 
+  predicate getTypeFlowNodeId = FlowStepsInput::getFlowNodeId/1;
+
   predicate isExcludedFromNullAnalysis = FlowStepsInput::isExcludedFromNullAnalysis/1;
 
   class Type = RefType;

java/ql/lib/semmle/code/java/security/ListOfConstantsSanitizer.qll

@@ -170,6 +170,8 @@ private class EmptyCollectionConstructor extends Constructor {
 private module CollectionFlowStepsInput implements UniversalFlow::UniversalFlowInput<Location> {
   import FlowStepsInput
 
+  predicate getFlowNodeId = FlowStepsInput::getFlowNodeId/1;
+
   /**
    * Holds if `n2` is a collection/array/constant whose value(s) are
    * determined completely from the range of `n1` nodes.

shared/typeflow/codeql/typeflow/TypeFlow.qll

@@ -29,6 +29,12 @@ signature module TypeFlowInput<LocationSig Location> {
     Location getLocation();
   }
 
+  /**
+   * Gets an identifier for node `n`, if any. When not implemented for a given node,
+   * the library will use location-based ranking.
+   */
+  default int getTypeFlowNodeId(TypeFlowNode n) { none() }
+
   /**
    * Holds if data can flow from `n1` to `n2` in one step.
    *

shared/typeflow/codeql/typeflow/UniversalFlow.qll

@@ -45,6 +45,12 @@ signature module UniversalFlowInput<LocationSig Location> {
     Location getLocation();
   }
 
+  /**
+   * Gets an identifier for node `n`, if any. When not implemented for a given node,
+   * the library will use location-based ranking.
+   */
+  default int getFlowNodeId(FlowNode n) { none() }
+
   /**
    * Holds if data can flow from `n1` to `n2` in one step.
    *
@@ -149,17 +155,40 @@ module Make<LocationSig Location, UniversalFlowInput<Location> I> {
   private module RankEdge<Edge E> implements RankedEdge<E::Node> {
     private import E
 
+    private int getFlowNodeIdByLoc(FlowNode n) {
+      n =
+        rank[result](FlowNode n0, string filePath, int startline, int startcolumn |
+          not exists(getFlowNodeId(n0)) and
+          n0.getLocation().hasLocationInfo(filePath, startline, startcolumn, _, _)
+        |
+          n0 order by filePath, startline, startcolumn
+        )
+    }
+
+    private int getFlowNodeIdExt(FlowNode n) {
+      n =
+        rank[result](FlowNode n0, int a, int b |
+          a = 0 and
+          b = getFlowNodeId(n0)
+          or
+          a = 1 and
+          b = getFlowNodeIdByLoc(n0)
+        |
+          n0 order by a, b
+        )
+    }
+
     /**
      * Holds if `r` is a ranking of the incoming edges `(n1,n2)` to `n2`. The used
      * ordering is not necessarily total, so the ranking may have gaps.
      */
     private predicate edgeRank1(int r, FlowNode n1, Node n2) {
       n1 =
-        rank[r](FlowNode n, int startline, int startcolumn |
+        rank[r](FlowNode n, int id |
           edge(n, n2) and
-          n.getLocation().hasLocationInfo(_, startline, startcolumn, _, _)
+          id = getFlowNodeIdExt(n)
         |
-          n order by startline, startcolumn
+          n order by id
         )
     }
 

shared/typeflow/codeql/typeflow/internal/TypeFlowImpl.qll

@@ -12,6 +12,8 @@ module TypeFlow<LocationSig Location, TypeFlowInput<Location> I> {
   private module UfInput implements UniversalFlow::UniversalFlowInput<Location> {
     class FlowNode = TypeFlowNode;
 
+    predicate getFlowNodeId = I::getTypeFlowNodeId/1;
+
     predicate step = I::step/2;
 
     predicate isNullValue = I::isNullValue/1;