C++: Use new back-edge def. in range analysis

jbj · jbj · commit bb7369e84437 · 2019-01-23T11:40:13.000+01:00
By using this new definition of back edges, the range analysis should
work on code that uses unstructured `goto`s.
diff --git a/cpp/ql/src/semmle/code/cpp/rangeanalysis/RangeUtils.qll b/cpp/ql/src/semmle/code/cpp/rangeanalysis/RangeUtils.qll
@@ -81,6 +81,5 @@ predicate isReducibleCFG(Function f) {
 
 predicate backEdge(PhiInstruction phi, PhiOperand op) {
   phi.getAnOperand() = op and
-  phi.getBlock().dominates(op.getPredecessorBlock())
-  // TODO: identify backedges during IR construction
-}
+  phi.getBlock() = op.getPredecessorBlock().getBackEdgeSuccessor(_)
+}
