C++: Reorder parameters to subEdge relations

This improves performance slightly by putting the parameters in the
order in which they'll be needed in `qlCFGSuccessor`.

Author: jbj

cpp/ql/src/semmle/code/cpp/controlflow/internal/CFG.qll

@@ -827,7 +827,8 @@ private predicate straightLineDense(Node scope, int rnk, Node nrnk, Spec spec) {
  * but most cases should be handled through one of the convenience predicates
  * as outlined in the comment at the top of this file.
  */
-private predicate subEdge(Node n1, Pos p1, Node n2, Pos p2) {
+// The parameters are ordered this way for performance.
+private predicate subEdge(Pos p1, Node n1, Node n2, Pos p2) {
   exists(Node scope, int rnk, Spec spec1, Spec spec2 |
     straightLineDense(scope, rnk, n1, spec1) and
     straightLineDense(scope, rnk + 1, n2, spec2) and
@@ -997,13 +998,13 @@ private predicate subEdge(Node n1, Pos p1, Node n2, Pos p2) {
  * predicate includes all sub-edges except those with true/false labels (see
  * `conditionJumps`).
  */
-private predicate subEdgeIncludingDestructors(Node n1, Pos p1, Node n2, Pos p2) {
-  subEdge(n1, p1, n2, p2)
+private predicate subEdgeIncludingDestructors(Pos p1, Node n1, Node n2, Pos p2) {
+  subEdge(p1, n1, n2, p2)
   or
   // If `n1` has sub-nodes to accomodate destructors, but there are none to be
   // called, connect the "before destructors" node directly to the "after
   // destructors" node. For performance, only do this when the nodes exist.
-  exists(Pos afterDtors | afterDtors.isAfterDestructors() | subEdge(n1, afterDtors, _, _)) and
+  exists(Pos afterDtors | afterDtors.isAfterDestructors() | subEdge(afterDtors, n1, _, _)) and
   not exists(getDestructorCallAfterNode(n1, 0)) and
   p1.nodeBeforeDestructors(n1, n1) and
   p2.nodeAfterDestructors(n2, n1)
@@ -1301,7 +1302,7 @@ private predicate normalGroupMember(Node memberNode, Pos memberPos, Node atNode)
   exists(Node succNode, Pos succPos |
     normalGroupMember(succNode, succPos, atNode) and
     not memberPos.isAt() and
-    subEdgeIncludingDestructors(memberNode, memberPos, succNode, succPos)
+    subEdgeIncludingDestructors(memberPos, memberNode, succNode, succPos)
   )
 }
 
@@ -1317,7 +1318,7 @@ private predicate precedesCondition(Node memberNode, Pos memberPos, Node test) {
   or
   exists(Node succNode, Pos succPos |
     precedesCondition(succNode, succPos, test) and
-    subEdgeIncludingDestructors(memberNode, memberPos, succNode, succPos) and
+    subEdgeIncludingDestructors(memberPos, memberNode, succNode, succPos) and
     // Unlike the similar TC in normalGroupMember we're here including the
     // At-node in the group. This should generalize better to the case where
     // the base case isn't always an After-node.
@@ -1355,7 +1356,7 @@ private module Cached {
   cached
   predicate qlCFGSuccessor(Node n1, Node n2) {
     exists(Node memberNode, Pos memberPos |
-      subEdgeIncludingDestructors(n1, any(Pos at | at.isAt()), memberNode, memberPos) and
+      subEdgeIncludingDestructors(any(Pos at | at.isAt()), n1, memberNode, memberPos) and
       normalGroupMember(memberNode, memberPos, n2)
     )
     or