diff --git a/src/main/java/com/android/tools/r8/ir/code/Dup.java b/src/main/java/com/android/tools/r8/ir/code/Dup.java
index 1f2e418..0932e62 100644
--- a/src/main/java/com/android/tools/r8/ir/code/Dup.java
+++ b/src/main/java/com/android/tools/r8/ir/code/Dup.java
@@ -36,12 +36,12 @@
 
   @Override
   public boolean identicalNonValueNonPositionParts(Instruction other) {
-    return false;
+    throw new Unreachable();
   }
 
   @Override
   public int compareNonValueParts(Instruction other) {
-    return 0;
+    throw new Unreachable();
   }
 
   @Override
@@ -61,10 +61,22 @@
   }
 
   @Override
-  public void insertLoadAndStores(InstructionListIterator it, LoadStoreHelper helper) {}
+  public void insertLoadAndStores(InstructionListIterator it, LoadStoreHelper helper) {
+    // Intentionally empty. Dup is a stack operation.
+  }
 
   @Override
   public boolean hasInvariantOutType() {
     return false;
   }
+
+  @Override
+  public boolean isDup() {
+    return true;
+  }
+
+  @Override
+  public Dup asDup() {
+    return this;
+  }
 }
diff --git a/src/main/java/com/android/tools/r8/ir/code/Instruction.java b/src/main/java/com/android/tools/r8/ir/code/Instruction.java
index 44a7a8e..90e8a6a 100644
--- a/src/main/java/com/android/tools/r8/ir/code/Instruction.java
+++ b/src/main/java/com/android/tools/r8/ir/code/Instruction.java
@@ -621,6 +621,14 @@
     return null;
   }
 
+  public boolean isDup() {
+    return false;
+  }
+
+  public Dup asDup() {
+    return null;
+  }
+
   public boolean isJumpInstruction() {
     return false;
   }
@@ -1052,6 +1060,14 @@
     return null;
   }
 
+  public boolean isSwap() {
+    return false;
+  }
+
+  public Swap asSwap() {
+    return null;
+  }
+
   public boolean isLoad() {
     return false;
   }
diff --git a/src/main/java/com/android/tools/r8/ir/code/Swap.java b/src/main/java/com/android/tools/r8/ir/code/Swap.java
new file mode 100644
index 0000000..494fbab
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/ir/code/Swap.java
@@ -0,0 +1,91 @@
+// Copyright (c) 2018, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.ir.code;
+
+import com.android.tools.r8.cf.LoadStoreHelper;
+import com.android.tools.r8.cf.code.CfStackInstruction;
+import com.android.tools.r8.cf.code.CfStackInstruction.Opcode;
+import com.android.tools.r8.errors.Unreachable;
+import com.android.tools.r8.graph.DexType;
+import com.android.tools.r8.ir.conversion.CfBuilder;
+import com.android.tools.r8.ir.conversion.DexBuilder;
+import com.android.tools.r8.ir.optimize.Inliner.ConstraintWithTarget;
+import com.android.tools.r8.ir.optimize.InliningConstraints;
+import java.util.Arrays;
+
+public class Swap extends Instruction {
+
+  public Swap(StackValues dest, StackValues src) {
+    super(dest, src.getStackValues());
+    assert src.getStackValues().size() == 2;
+    assert !(this.inValues.get(0).type.isWide() ^ this.inValues.get(1).type.isWide());
+  }
+
+  public Swap(StackValues dest, StackValue src1, StackValue src2) {
+    super(dest, Arrays.asList(src1, src2));
+    assert !(this.inValues.get(0).type.isWide() ^ !this.inValues.get(1).type.isWide());
+  }
+
+  @Override
+  public void buildDex(DexBuilder builder) {
+    throw new Unreachable("This classfile-specific IR should not be inserted in the Dex backend.");
+  }
+
+  @Override
+  public void buildCf(CfBuilder builder) {
+    if (this.inValues.get(0).type.isWide()) {
+      builder.add(new CfStackInstruction(Opcode.Dup2X2));
+      builder.add(new CfStackInstruction(Opcode.Pop2));
+    } else {
+      builder.add(new CfStackInstruction(Opcode.Swap));
+    }
+  }
+
+  @Override
+  public boolean identicalNonValueNonPositionParts(Instruction other) {
+    throw new Unreachable();
+  }
+
+  @Override
+  public int compareNonValueParts(Instruction other) {
+    throw new Unreachable();
+  }
+
+  @Override
+  public int maxInValueRegister() {
+    return 0;
+  }
+
+  @Override
+  public int maxOutValueRegister() {
+    throw new Unreachable();
+  }
+
+  @Override
+  public ConstraintWithTarget inliningConstraint(
+      InliningConstraints inliningConstraints, DexType invocationContext) {
+    return inliningConstraints.forSwap();
+  }
+
+  @Override
+  public void insertLoadAndStores(InstructionListIterator it, LoadStoreHelper helper) {
+    // Intentionally empty. Swap is a stack operation.
+  }
+
+  @Override
+  public boolean hasInvariantOutType() {
+    return false;
+  }
+
+  @Override
+  public boolean isSwap() {
+    return true;
+  }
+
+  @Override
+  public Swap asSwap() {
+    return this;
+  }
+}
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/InliningConstraints.java b/src/main/java/com/android/tools/r8/ir/optimize/InliningConstraints.java
index 7130516..cc85e39 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/InliningConstraints.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/InliningConstraints.java
@@ -237,6 +237,10 @@
     return ConstraintWithTarget.ALWAYS;
   }
 
+  public ConstraintWithTarget forSwap() {
+    return ConstraintWithTarget.ALWAYS;
+  }
+
   public ConstraintWithTarget forThrow() {
     return ConstraintWithTarget.ALWAYS;
   }