diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
index 0a66d0d8d..c6e0d43c2 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
@@ -48,7 +48,7 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
     @Override
     public char charAt(int index) {
         if (index < 0 || index >= characters.length) {
-            throw new TStringIndexOutOfBoundsException(null);
+            throw new TStringIndexOutOfBoundsException();
         }
         return characters[index];
     }
diff --git a/teavm-core/src/main/java/org/teavm/model/BasicBlock.java b/teavm-core/src/main/java/org/teavm/model/BasicBlock.java
index b88e20cd8..c1d1e2d31 100644
--- a/teavm-core/src/main/java/org/teavm/model/BasicBlock.java
+++ b/teavm-core/src/main/java/org/teavm/model/BasicBlock.java
@@ -47,7 +47,7 @@ public class BasicBlock  {
         @Override
         public void add(int index, Instruction e) {
             if (e.getBasicBlock() != null) {
-                throw new IllegalArgumentException("This instruction is some basic block");
+                throw new IllegalArgumentException("This instruction is in some basic block");
             }
             e.setBasicBlock(BasicBlock.this);
             instructions.add(index, e);
@@ -56,7 +56,7 @@ public class BasicBlock  {
         @Override
         public Instruction set(int index, Instruction element) {
             if (element.getBasicBlock() != null) {
-                throw new IllegalArgumentException("This instruction is some basic block");
+                throw new IllegalArgumentException("This instruction is in some basic block");
             }
             Instruction oldInsn = instructions.get(index);
             oldInsn.setBasicBlock(null);
diff --git a/teavm-core/src/main/java/org/teavm/model/Program.java b/teavm-core/src/main/java/org/teavm/model/Program.java
index e8334ddf1..96e03f41e 100644
--- a/teavm-core/src/main/java/org/teavm/model/Program.java
+++ b/teavm-core/src/main/java/org/teavm/model/Program.java
@@ -53,6 +53,7 @@ public class Program {
         variables.set(index, null);
         variable.setIndex(-1);
         variable.setProgram(null);
+        packed = false;
     }
 
     public boolean isPacked() {
@@ -75,9 +76,17 @@ public class Program {
             basicBlocks.remove(basicBlocks.size() - 1);
         }
         sz = 0;
-        for (int i = 0; i < basicBlocks.size(); ++i) {
-
+        for (int i = 0; i < variables.size(); ++i) {
+            Variable var = variables.get(i);
+            if (var != null) {
+                var.setIndex(sz);
+                variables.set(sz++, var);
+            }
         }
+        while (variables.size() > sz) {
+            variables.remove(variables.size() - 1);
+        }
+        packed = true;
     }
 
     public int variableCount() {
diff --git a/teavm-core/src/main/java/org/teavm/optimization/ClassSetOptimizer.java b/teavm-core/src/main/java/org/teavm/optimization/ClassSetOptimizer.java
index d21f4c72b..9e2144668 100644
--- a/teavm-core/src/main/java/org/teavm/optimization/ClassSetOptimizer.java
+++ b/teavm-core/src/main/java/org/teavm/optimization/ClassSetOptimizer.java
@@ -12,14 +12,16 @@ import org.teavm.model.MethodHolder;
  */
 public class ClassSetOptimizer {
     private List<MethodOptimization> optimizations = Arrays.<MethodOptimization>asList(
-            new UnusedVariableElimination());
+            new CommonSubexpressionElimination(), new UnusedVariableElimination());
 
     public void optimizeAll(ListableClassHolderSource classSource) {
         for (String className : classSource.getClassNames()) {
             ClassHolder cls = classSource.getClassHolder(className);
             for (MethodHolder method : cls.getMethods()) {
-                for (MethodOptimization optimization : optimizations) {
-                    optimization.optimize(method);
+                if (method.getProgram() != null && method.getProgram().basicBlockCount() > 0) {
+                    for (MethodOptimization optimization : optimizations) {
+                        optimization.optimize(method);
+                    }
                 }
             }
         }
diff --git a/teavm-core/src/main/java/org/teavm/optimization/CommonSubexpressionElimination.java b/teavm-core/src/main/java/org/teavm/optimization/CommonSubexpressionElimination.java
index 9e2a58623..b0dad1118 100644
--- a/teavm-core/src/main/java/org/teavm/optimization/CommonSubexpressionElimination.java
+++ b/teavm-core/src/main/java/org/teavm/optimization/CommonSubexpressionElimination.java
@@ -2,12 +2,10 @@ package org.teavm.optimization;
 
 import java.util.HashMap;
 import java.util.Map;
+import org.teavm.common.DominatorTree;
 import org.teavm.common.Graph;
 import org.teavm.common.GraphUtils;
-import org.teavm.model.BasicBlock;
-import org.teavm.model.Instruction;
-import org.teavm.model.MethodHolder;
-import org.teavm.model.Program;
+import org.teavm.model.*;
 import org.teavm.model.instructions.*;
 import org.teavm.model.util.ProgramUtils;
 
@@ -16,16 +14,25 @@ import org.teavm.model.util.ProgramUtils;
  * @author Alexey Andreev
  */
 public class CommonSubexpressionElimination implements MethodOptimization {
-    private Map<String, Integer> knownValues = new HashMap<>();
-    private Instruction currentInsn;
+    private Map<String, KnownValue> knownValues = new HashMap<>();
+    private boolean eliminate;
     private int[] map;
     private Program program;
+    private int currentBlockIndex;
+    private DominatorTree domTree;
+
+    private static class KnownValue {
+        int value;
+        int location;
+    }
 
     @Override
     public void optimize(MethodHolder method) {
         program = method.getProgram();
+        knownValues.clear();
         Graph cfg = ProgramUtils.buildControlFlowGraph(method.getProgram());
-        Graph dom = GraphUtils.buildDominatorGraph(GraphUtils.buildDominatorTree(cfg), cfg.size());
+        domTree = GraphUtils.buildDominatorTree(cfg);
+        Graph dom = GraphUtils.buildDominatorGraph(domTree, cfg.size());
         map = new int[program.variableCount()];
         for (int i = 0; i < map.length; ++i) {
             map[i] = i;
@@ -40,30 +47,51 @@ public class CommonSubexpressionElimination implements MethodOptimization {
         }
         while (top > 0) {
             int v = stack[--top];
+            currentBlockIndex = v;
             BasicBlock block = program.basicBlockAt(v);
             for (int i = 0; i < block.getInstructions().size(); ++i) {
-                currentInsn = block.getInstructions().get(i);
+                Instruction currentInsn = block.getInstructions().get(i);
                 currentInsn.acceptVisitor(optimizer);
-                if (currentInsn != null) {
-                    block.getInstructions().set(i, currentInsn);
-                } else {
+                if (eliminate) {
                     block.getInstructions().remove(i--);
+                    eliminate = false;
                 }
             }
             for (int succ : dom.outgoingEdges(v)) {
                 stack[top++] = succ;
             }
         }
+        for (int v = 0; v < program.basicBlockCount(); ++v) {
+            BasicBlock block = program.basicBlockAt(v);
+            for (int i = 0; i < block.getPhis().size(); ++i) {
+                Phi phi = block.getPhis().get(i);
+                for (Incoming incoming : phi.getIncomings()) {
+                    int value = map[incoming.getValue().getIndex()];
+                    incoming.setValue(program.variableAt(value));
+                }
+            }
+        }
+
+        for (int i = 0; i < map.length; ++i) {
+            if (map[i] != i) {
+                program.deleteVariable(i);
+            }
+        }
+
         program.pack();
+        program = null;
     }
 
     private void bind(int var, String value) {
-        Integer known = knownValues.get(value);
-        if (known != null) {
-            currentInsn = null;
-            map[var] = known;
+        KnownValue known = knownValues.get(value);
+        if (known != null && domTree.dominates(known.location, currentBlockIndex)) {
+            eliminate = true;
+            map[var] = known.value;
         } else {
-            knownValues.put(value, var);
+            known = new KnownValue();
+            known.location = currentBlockIndex;
+            known.value = var;
+            knownValues.put(value, known);
         }
     }
 
@@ -160,34 +188,43 @@ public class CommonSubexpressionElimination implements MethodOptimization {
 
         @Override
         public void visit(AssignInstruction insn) {
-            map[insn.getReceiver().getIndex()] = insn.getAssignee().getIndex();
-            currentInsn = null;
+            map[insn.getReceiver().getIndex()] = map[insn.getAssignee().getIndex()];
+            eliminate = true;
         }
 
         @Override
         public void visit(CastInstruction insn) {
-            bind(insn.getReceiver().getIndex(), "@" + insn.getValue().getIndex() + " cast " +
-                    insn.getTargetType());
+            int a = map[insn.getValue().getIndex()];
+            insn.setValue(program.variableAt(a));
+            bind(insn.getReceiver().getIndex(), "@" + a + "::" + insn.getTargetType());
         }
 
         @Override
         public void visit(CastNumberInstruction insn) {
-            bind(insn.getReceiver().getIndex(), "@" + insn.getValue().getIndex() + " cast " +
-                    insn.getTargetType());
+            int a = map[insn.getValue().getIndex()];
+            insn.setValue(program.variableAt(a));
+            bind(insn.getReceiver().getIndex(), "@" + a + "::" + insn.getTargetType());
         }
 
         @Override
         public void visit(CastIntegerInstruction insn) {
-            bind(insn.getReceiver().getIndex(), "@" + insn.getValue().getIndex() + " cast " +
-                    insn.getTargetType() + " " + insn.getDirection());
+            int a = map[insn.getValue().getIndex()];
+            insn.setValue(program.variableAt(a));
+            bind(insn.getReceiver().getIndex(), "@" + a + "::" + insn.getTargetType() + " " + insn.getDirection());
         }
 
         @Override
         public void visit(BranchingInstruction insn) {
+            int a = map[insn.getOperand().getIndex()];
+            insn.setOperand(program.variableAt(a));
         }
 
         @Override
         public void visit(BinaryBranchingInstruction insn) {
+            int a = map[insn.getFirstOperand().getIndex()];
+            int b = map[insn.getSecondOperand().getIndex()];
+            insn.setFirstOperand(program.variableAt(a));
+            insn.setSecondOperand(program.variableAt(b));
         }
 
         @Override
@@ -196,18 +233,28 @@ public class CommonSubexpressionElimination implements MethodOptimization {
 
         @Override
         public void visit(SwitchInstruction insn) {
+            int a = map[insn.getCondition().getIndex()];
+            insn.setCondition(program.variableAt(a));
         }
 
         @Override
         public void visit(ExitInstruction insn) {
+            if (insn.getValueToReturn() != null) {
+                int a = map[insn.getValueToReturn().getIndex()];
+                insn.setValueToReturn(program.variableAt(a));
+            }
         }
 
         @Override
         public void visit(RaiseInstruction insn) {
+            int a = map[insn.getException().getIndex()];
+            insn.setException(program.variableAt(a));
         }
 
         @Override
         public void visit(ConstructArrayInstruction insn) {
+            int a = map[insn.getSize().getIndex()];
+            insn.setSize(program.variableAt(a));
         }
 
         @Override
@@ -216,18 +263,35 @@ public class CommonSubexpressionElimination implements MethodOptimization {
 
         @Override
         public void visit(ConstructMultiArrayInstruction insn) {
+            for (int i = 0; i < insn.getDimensions().size(); ++i) {
+                int a = map[insn.getDimensions().get(i).getIndex()];
+                insn.getDimensions().set(i, program.variableAt(a));
+            }
         }
 
         @Override
         public void visit(GetFieldInstruction insn) {
+            if (insn.getInstance() != null) {
+                int instance = map[insn.getInstance().getIndex()];
+                insn.setInstance(program.variableAt(instance));
+            }
         }
 
         @Override
         public void visit(PutFieldInstruction insn) {
+            if (insn.getInstance() != null) {
+                int instance = map[insn.getInstance().getIndex()];
+                insn.setInstance(program.variableAt(instance));
+            }
+            int val = map[insn.getValue().getIndex()];
+            insn.setValue(program.variableAt(val));
         }
 
         @Override
         public void visit(ArrayLengthInstruction insn) {
+            int a = map[insn.getArray().getIndex()];
+            insn.setArray(program.variableAt(a));
+            bind(insn.getReceiver().getIndex(), "@" + a + ".length");
         }
 
         @Override
@@ -236,22 +300,46 @@ public class CommonSubexpressionElimination implements MethodOptimization {
 
         @Override
         public void visit(UnwrapArrayInstruction insn) {
+            int a = map[insn.getArray().getIndex()];
+            insn.setArray(program.variableAt(a));
+            bind(insn.getReceiver().getIndex(), "@" + a + ".data");
         }
 
         @Override
         public void visit(GetElementInstruction insn) {
+            int a = map[insn.getArray().getIndex()];
+            insn.setArray(program.variableAt(a));
+            int index = map[insn.getIndex().getIndex()];
+            insn.setIndex(program.variableAt(index));
         }
 
         @Override
         public void visit(PutElementInstruction insn) {
+            int a = map[insn.getArray().getIndex()];
+            insn.setArray(program.variableAt(a));
+            int index = map[insn.getIndex().getIndex()];
+            insn.setIndex(program.variableAt(index));
+            int val = map[insn.getValue().getIndex()];
+            insn.setValue(program.variableAt(val));
         }
 
         @Override
         public void visit(InvokeInstruction insn) {
+            if (insn.getInstance() != null) {
+                int instance = map[insn.getInstance().getIndex()];
+                insn.setInstance(program.variableAt(instance));
+            }
+            for (int i = 0; i < insn.getArguments().size(); ++i) {
+                int arg = map[insn.getArguments().get(i).getIndex()];
+                insn.getArguments().set(i, program.variableAt(arg));
+            }
         }
 
         @Override
         public void visit(IsInstanceInstruction insn) {
+            int val = map[insn.getValue().getIndex()];
+            insn.setValue(program.variableAt(val));
+            bind(insn.getReceiver().getIndex(), "@" + val + " :? " + insn.getType());
         }
     };
 }