diff --git a/src/main/java/com/android/tools/r8/graph/DexDebugEventBuilder.java b/src/main/java/com/android/tools/r8/graph/DexDebugEventBuilder.java
index 3d68ace..7020f4b 100644
--- a/src/main/java/com/android/tools/r8/graph/DexDebugEventBuilder.java
+++ b/src/main/java/com/android/tools/r8/graph/DexDebugEventBuilder.java
@@ -91,7 +91,7 @@
       // If this is the end of the block clear out the pending state.
       pendingLocals = null;
       pendingLocalChanges = false;
-    } else if (pc != emittedPc) {
+    } else if (pc != emittedPc && !instruction.isNop()) {
       // For non-exit / pc-advancing instructions emit any pending changes once possible.
       emitLocalChanges(pc);
     }
diff --git a/src/main/java/com/android/tools/r8/ir/code/BasicBlockInstructionIterator.java b/src/main/java/com/android/tools/r8/ir/code/BasicBlockInstructionIterator.java
index 40a4776..8a2de9b 100644
--- a/src/main/java/com/android/tools/r8/ir/code/BasicBlockInstructionIterator.java
+++ b/src/main/java/com/android/tools/r8/ir/code/BasicBlockInstructionIterator.java
@@ -108,6 +108,7 @@
       throw new IllegalStateException();
     }
     assert current.outValue() == null || !current.outValue().isUsed();
+    assert current.getDebugValues().isEmpty();
     for (int i = 0; i < current.inValues().size(); i++) {
       Value value = current.inValues().get(i);
       value.removeUser(current);
@@ -115,11 +116,28 @@
     for (Value value : current.getDebugValues()) {
       value.removeDebugUser(current);
     }
+    if (current.getLocalInfo() != null) {
+      for (Instruction user : current.outValue().debugUsers()) {
+        user.removeDebugValue(current.outValue());
+      }
+    }
     listIterator.remove();
     current = null;
   }
 
   @Override
+  public void removeOrReplaceByNop() {
+    if (current == null) {
+      throw new IllegalStateException();
+    }
+    if (current.getDebugValues().isEmpty()) {
+      remove();
+    } else {
+      replaceCurrentInstruction(new Nop());
+    }
+  }
+
+  @Override
   public void detach() {
     if (current == null) {
       throw new IllegalStateException();
diff --git a/src/main/java/com/android/tools/r8/ir/code/BasicBlockIterator.java b/src/main/java/com/android/tools/r8/ir/code/BasicBlockIterator.java
index d9ce088..74c2768 100644
--- a/src/main/java/com/android/tools/r8/ir/code/BasicBlockIterator.java
+++ b/src/main/java/com/android/tools/r8/ir/code/BasicBlockIterator.java
@@ -81,7 +81,8 @@
     // Remove all instructions from the block before removing the block.
     Iterator<Instruction> iterator = current.iterator();
     while (iterator.hasNext()) {
-      iterator.next();
+      Instruction instruction = iterator.next();
+      instruction.clearDebugValues();
       iterator.remove();
     }
     listIterator.remove();
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 f14d66a..de198c9 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
@@ -131,9 +131,19 @@
   }
 
   public void removeDebugValue(Value value) {
-    assert debugValues.contains(value);
-    value.removeDebugUser(this);
-    debugValues.remove(value);
+    assert value.getLocalInfo() != null;
+    if (debugValues != null) {
+      assert debugValues.contains(value);
+      debugValues.remove(value);
+      return;
+    }
+    assert false;
+  }
+
+  public void clearDebugValues() {
+    if (debugValues != null) {
+      debugValues.clear();
+    }
   }
 
   /**
@@ -824,6 +834,14 @@
     return null;
   }
 
+  public boolean isNop() {
+    return false;
+  }
+
+  public Nop asNop() {
+    return null;
+  }
+
   public boolean canBeFolded() {
     return false;
   }
diff --git a/src/main/java/com/android/tools/r8/ir/code/InstructionListIterator.java b/src/main/java/com/android/tools/r8/ir/code/InstructionListIterator.java
index 97f1885..ef49910 100644
--- a/src/main/java/com/android/tools/r8/ir/code/InstructionListIterator.java
+++ b/src/main/java/com/android/tools/r8/ir/code/InstructionListIterator.java
@@ -60,6 +60,12 @@
   }
 
   /**
+   * Safe removal function that will insert a Nop to take over the debug values if any are assocated
+   * with the current instruction.
+   */
+  void removeOrReplaceByNop();
+
+  /**
    * Remove the current instruction (aka the {@link Instruction} returned by the previous call to
    * {@link #next}) without updating its def/use chains.
    * <p>
diff --git a/src/main/java/com/android/tools/r8/ir/code/Nop.java b/src/main/java/com/android/tools/r8/ir/code/Nop.java
new file mode 100644
index 0000000..dc378de
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/ir/code/Nop.java
@@ -0,0 +1,63 @@
+// Copyright (c) 2017, 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.errors.Unreachable;
+import com.android.tools.r8.graph.AppInfoWithSubtyping;
+import com.android.tools.r8.graph.DexType;
+import com.android.tools.r8.ir.conversion.DexBuilder;
+import com.android.tools.r8.ir.optimize.Inliner.Constraint;
+import com.android.tools.r8.utils.InternalOptions;
+
+public class Nop extends Instruction {
+
+  public Nop() {
+    super(null);
+  }
+
+  @Override
+  public boolean isNop() {
+    return true;
+  }
+
+  @Override
+  public Nop asNop() {
+    return this;
+  }
+
+  @Override
+  public void buildDex(DexBuilder builder) {
+    builder.addNop(this);
+  }
+
+  @Override
+  public boolean identicalNonValueParts(Instruction other) {
+    return true;
+  }
+
+  @Override
+  public int compareNonValueParts(Instruction other) {
+    return 0;
+  }
+
+  @Override
+  public int maxInValueRegister() {
+    throw new Unreachable();
+  }
+
+  @Override
+  public int maxOutValueRegister() {
+    throw new Unreachable();
+  }
+
+  @Override
+  public Constraint inliningConstraint(AppInfoWithSubtyping info, DexType holder) {
+    return Constraint.ALWAYS;
+  }
+
+  @Override
+  public boolean canBeDeadCode(IRCode code, InternalOptions options) {
+    return getDebugValues().isEmpty();
+  }
+}
diff --git a/src/main/java/com/android/tools/r8/ir/code/Value.java b/src/main/java/com/android/tools/r8/ir/code/Value.java
index 2880c87..0af8f63 100644
--- a/src/main/java/com/android/tools/r8/ir/code/Value.java
+++ b/src/main/java/com/android/tools/r8/ir/code/Value.java
@@ -260,9 +260,7 @@
   }
 
   public boolean isUsed() {
-    return !users.isEmpty()
-        || !phiUsers.isEmpty()
-        || ((debugData != null) && !debugData.users.isEmpty());
+    return !users.isEmpty() || !phiUsers.isEmpty() || numberOfAllDebugUsers() > 0;
   }
 
   public boolean usedInMonitorOperation() {
@@ -291,6 +289,7 @@
     uniquePhiUsers = null;
     if (debugData != null) {
       debugData.users.clear();
+      debugData.phiUsers.clear();
     }
   }
 
diff --git a/src/main/java/com/android/tools/r8/ir/conversion/DexBuilder.java b/src/main/java/com/android/tools/r8/ir/conversion/DexBuilder.java
index da067d8..b35c1a0 100644
--- a/src/main/java/com/android/tools/r8/ir/conversion/DexBuilder.java
+++ b/src/main/java/com/android/tools/r8/ir/conversion/DexBuilder.java
@@ -317,7 +317,8 @@
   }
 
   private boolean isNopInstruction(com.android.tools.r8.ir.code.Instruction instruction) {
-    return instruction.isDebugLocalsChange()
+    return instruction.isNop()
+        || instruction.isDebugLocalsChange()
         || (instruction.isConstNumber() && !instruction.outValue().needsRegister());
   }
 
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
index b698fc5..52c9eb4 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
@@ -50,9 +50,7 @@
 import com.android.tools.r8.ir.code.InvokeMethod;
 import com.android.tools.r8.ir.code.InvokeNewArray;
 import com.android.tools.r8.ir.code.InvokeVirtual;
-import com.android.tools.r8.ir.code.JumpInstruction;
 import com.android.tools.r8.ir.code.MemberType;
-import com.android.tools.r8.ir.code.Move;
 import com.android.tools.r8.ir.code.MoveType;
 import com.android.tools.r8.ir.code.NewArrayEmpty;
 import com.android.tools.r8.ir.code.NewArrayFilledData;
@@ -72,7 +70,6 @@
 import com.google.common.base.Equivalence.Wrapper;
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Maps;
@@ -423,7 +420,6 @@
     private int right;
     private BasicBlock target;
     private BasicBlock fallthrough;
-    private int blockNumber;
 
     public IfBuilder(IRCode code) {
       this.code = code;
@@ -483,7 +479,6 @@
 
     // Extract the information from the switch before removing it.
     Int2ReferenceSortedMap<BasicBlock> keyToTarget = theSwitch.getKeyToTargetMap();
-    Set<Value> originalDebugValues = ImmutableSet.copyOf(theSwitch.getDebugValues());
 
     // Keep track of the current fallthrough, starting with the original.
     BasicBlock fallthroughBlock = theSwitch.fallthroughBlock();
@@ -493,6 +488,8 @@
     BasicBlock originalSwitchBlock = iterator.split(code, blocksIterator);
     assert !originalSwitchBlock.hasCatchHandlers();
     assert originalSwitchBlock.getInstructions().size() == 1;
+    assert originalBlock.exit().isGoto();
+    theSwitch.moveDebugValues(originalBlock.exit());
     blocksIterator.remove();
     theSwitch.getBlock().detachAllSuccessors();
     BasicBlock block = theSwitch.getBlock().unlinkSinglePredecessor();
@@ -537,9 +534,6 @@
       fallthroughBlock = ifBlock;
     }
 
-    // Attach the debug values from the original switch to the first of the new instructions,
-    originalDebugValues.forEach(fallthroughBlock.exit()::addDebugValue);
-
     // Finally link the block before the original switch to the new block sequence.
     originalBlock.link(fallthroughBlock);
 
@@ -1770,16 +1764,15 @@
         Instruction current = iterator.next();
         if (current.isInvokeMethod()) {
           DexMethod invokedMethod = current.asInvokeMethod().getInvokedMethod();
-
           if (matchesMethodOfThrowable(invokedMethod, throwableMethods.addSuppressed)) {
             // Remove Throwable::addSuppressed(Throwable) call.
-            iterator.remove();
+            iterator.removeOrReplaceByNop();
           } else if (matchesMethodOfThrowable(invokedMethod, throwableMethods.getSuppressed)) {
             Value destValue = current.outValue();
             if (destValue == null) {
               // If the result of the call was not used we don't create
               // an empty array and just remove the call.
-              iterator.remove();
+              iterator.removeOrReplaceByNop();
               continue;
             }
 
diff --git a/src/test/java/com/android/tools/r8/ir/regalloc/RegisterMoveSchedulerTest.java b/src/test/java/com/android/tools/r8/ir/regalloc/RegisterMoveSchedulerTest.java
index 0e24dbd..8ab2de5 100644
--- a/src/test/java/com/android/tools/r8/ir/regalloc/RegisterMoveSchedulerTest.java
+++ b/src/test/java/com/android/tools/r8/ir/regalloc/RegisterMoveSchedulerTest.java
@@ -74,6 +74,11 @@
     }
 
     @Override
+    public void removeOrReplaceByNop() {
+      remove();
+    }
+
+    @Override
     public void detach() {
       remove();
     }