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diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/bytecodeAnalysis/asm/RichControlFlow.java b/java/java-analysis-impl/src/com/intellij/codeInspection/bytecodeAnalysis/asm/RichControlFlow.java
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+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/bytecodeAnalysis/asm/RichControlFlow.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2000-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.codeInspection.bytecodeAnalysis.asm;
+
+import com.intellij.codeInspection.bytecodeAnalysis.asm.ControlFlowGraph.Edge;
+
+import gnu.trove.TIntArrayList;
+import gnu.trove.TIntHashSet;
+import gnu.trove.TIntIterator;
+
+/**
+ * @author lambdamix
+ */
+public final class RichControlFlow {
+  public final ControlFlowGraph controlFlow;
+  public final DFSTree dfsTree;
+
+  public RichControlFlow(ControlFlowGraph controlFlow, DFSTree dfsTree) {
+    this.controlFlow = controlFlow;
+    this.dfsTree = dfsTree;
+  }
+
+  // Tarjan. Testing flow graph reducibility.
+  // Journal of Computer and System Sciences 9.3 (1974): 355-365.
+  public boolean reducible() {
+    if (dfsTree.back.isEmpty()) {
+      return true;
+    }
+    int size = controlFlow.transitions.length;
+    boolean[] loopEnters = dfsTree.loopEnters;
+    TIntHashSet[] cycleIncomings = new TIntHashSet[size];
+    // really this may be array, since dfs already ensures no duplicates
+    TIntArrayList[] nonCycleIncomings = new TIntArrayList[size];
+    int[] collapsedTo = new int[size];
+    int[] queue = new int[size];
+    int top;
+    for (int i = 0; i < size; i++) {
+      if (loopEnters[i]) {
+        cycleIncomings[i] = new TIntHashSet();
+      }
+      nonCycleIncomings[i] = new TIntArrayList();
+      collapsedTo[i] = i;
+    }
+
+    // from whom back connections
+    for (Edge edge : dfsTree.back) {
+      cycleIncomings[edge.to].add(edge.from);
+    }
+    // from whom ordinary connections
+    for (Edge edge : dfsTree.nonBack) {
+      nonCycleIncomings[edge.to].add(edge.from);
+    }
+
+    for (int w = size - 1; w >= 0 ; w--) {
+      top = 0;
+      // NB - it is modified later!
+      TIntHashSet p = cycleIncomings[w];
+      if (p == null) {
+        continue;
+      }
+      TIntIterator iter = p.iterator();
+      while (iter.hasNext()) {
+        queue[top++] = iter.next();
+      }
+
+      while (top > 0) {
+        int x = queue[--top];
+        TIntArrayList incoming = nonCycleIncomings[x];
+        for (int i = 0; i < incoming.size(); i++) {
+          int y1 = collapsedTo[incoming.getQuick(i)];
+          if (!dfsTree.isDescendant(y1, w)) {
+            return false;
+          }
+          if (y1 != w && p.add(y1)) {
+            queue[top++] = y1;
+          }
+        }
+      }
+
+      iter = p.iterator();
+      while (iter.hasNext()) {
+        collapsedTo[iter.next()] = w;
+      }
+    }
+
+    return true;
+  }
+}