Review

finding-15

/mubench/checkouts/closure/319/build/src//com/google/javascript/jscomp/PureFunctionIdentifier.java

propagateSideEffects()

class PureFunctionIdentifier {
  /**
   * Propagate side effect information by building a graph based on
   * call site information stored in FunctionInformation and the
   * DefinitionProvider and then running GraphReachability to
   * determine the set of functions that have side effects.
   */
  private void propagateSideEffects() {
    // Nodes are function declarations; Edges are function call sites.
    DiGraph<FunctionInformation, Node> sideEffectGraph =
        LinkedDirectedGraph.createWithoutAnnotations();

    // create graph nodes
    for (FunctionInformation functionInfo : functionSideEffectMap.values()) {
      sideEffectGraph.createNode(functionInfo);
    }

    // add connections to called functions and side effect root.
    for (FunctionInformation functionInfo : functionSideEffectMap.values()) {
      if (!functionInfo.mayHaveSideEffects()) {
        continue;
      }

      for (Node callSite : functionInfo.getCallsInFunctionBody()) {
        Node callee = callSite.getFirstChild();
        Collection<Definition> defs =
            getCallableDefinitions(definitionProvider, callee);
        if (defs == null) {
          // Definition set is not complete or eligible.  Possible
          // causes include:
          //  * "callee" is not of type NAME or GETPROP.
          //  * One or more definitions are not functions.
          //  * One or more definitions are complex.
          //    (e.i. return value of a call that returns a function).
          functionInfo.setTaintsUnknown();
          break;
        }

        for (Definition def : defs) {
          Node defValue = def.getRValue();
          FunctionInformation dep = functionSideEffectMap.get(defValue);
          Preconditions.checkNotNull(dep);
          sideEffectGraph.connect(dep, callSite, functionInfo);
        }
      }
    }

    // Propagate side effect information to a fixed point.
    FixedPointGraphTraversal.newTraversal(new SideEffectPropagationCallback())
        .computeFixedPoint(sideEffectGraph);

    // Mark remaining functions "pure".
    for (FunctionInformation functionInfo : functionSideEffectMap.values()) {
      if (functionInfo.mayBePure()) {
        functionInfo.setIsPure();
      }
    }
  }

}