diff --git a/src/compiler/control-reducer.cc b/src/compiler/control-reducer.cc
index 136064faa7..df84d525a4 100644
--- a/src/compiler/control-reducer.cc
+++ b/src/compiler/control-reducer.cc
@@ -507,8 +507,6 @@ class ControlReducerImpl {
       index++;
     }
 
-    if (live > 1 && live == node->InputCount()) return node;  // nothing to do.
-
     TRACE(("ReduceMerge: #%d:%s (%d live)\n", node->id(),
            node->op()->mnemonic(), live));
 
@@ -527,15 +525,46 @@ class ControlReducerImpl {
       return node->InputAt(live_index);
     }
 
-    // Edit phis in place, removing dead inputs and revisiting them.
-    for (Node* const phi : phis) {
-      TRACE(("  PhiInMerge: #%d:%s (%d live)\n", phi->id(),
-             phi->op()->mnemonic(), live));
-      RemoveDeadInputs(node, phi);
-      Revisit(phi);
+    DCHECK_LE(2, live);
+
+    if (live < node->InputCount()) {
+      // Edit phis in place, removing dead inputs and revisiting them.
+      for (Node* const phi : phis) {
+        TRACE(("  PhiInMerge: #%d:%s (%d live)\n", phi->id(),
+               phi->op()->mnemonic(), live));
+        RemoveDeadInputs(node, phi);
+        Revisit(phi);
+      }
+      // Edit the merge in place, removing dead inputs.
+      RemoveDeadInputs(node, node);
     }
-    // Edit the merge in place, removing dead inputs.
-    RemoveDeadInputs(node, node);
+
+    DCHECK_EQ(live, node->InputCount());
+
+    // Check if it's an unused diamond.
+    if (live == 2 && phis.empty()) {
+      Node* node0 = node->InputAt(0);
+      Node* node1 = node->InputAt(1);
+      if (((node0->opcode() == IrOpcode::kIfTrue &&
+            node1->opcode() == IrOpcode::kIfFalse) ||
+           (node0->opcode() == IrOpcode::kIfTrue &&
+            node1->opcode() == IrOpcode::kIfFalse)) &&
+          node0->OwnedBy(node) && node1->OwnedBy(node)) {
+        Node* branch0 = NodeProperties::GetControlInput(node0);
+        Node* branch1 = NodeProperties::GetControlInput(node1);
+        if (branch0 == branch1) {
+          // It's a dead diamond, i.e. neither the IfTrue nor the IfFalse nodes
+          // have users except for the Merge and the Merge has no Phi or
+          // EffectPhi uses, so replace the Merge with the control input of the
+          // diamond.
+          TRACE(("  DeadDiamond: #%d:%s #%d:%s #%d:%s\n", node0->id(),
+                 node0->op()->mnemonic(), node1->id(), node1->op()->mnemonic(),
+                 branch0->id(), branch0->op()->mnemonic()));
+          return NodeProperties::GetControlInput(branch0);
+        }
+      }
+    }
+
     return node;
   }
 
diff --git a/test/cctest/compiler/test-control-reducer.cc b/test/cctest/compiler/test-control-reducer.cc
index f0efb7ddcd..f6d354767e 100644
--- a/test/cctest/compiler/test-control-reducer.cc
+++ b/test/cctest/compiler/test-control-reducer.cc
@@ -694,9 +694,9 @@ TEST(CMergeReduce_none1) {
 TEST(CMergeReduce_none2) {
   ControlReducerTester R;
 
-  Node* t = R.graph.NewNode(R.common.IfTrue(), R.start);
-  Node* f = R.graph.NewNode(R.common.IfFalse(), R.start);
-  Node* merge = R.graph.NewNode(R.common.Merge(2), t, f);
+  Node* t1 = R.graph.NewNode(R.common.IfTrue(), R.start);
+  Node* t2 = R.graph.NewNode(R.common.IfTrue(), R.start);
+  Node* merge = R.graph.NewNode(R.common.Merge(2), t1, t2);
   R.ReduceMerge(merge, merge);
 }
 
@@ -744,7 +744,7 @@ TEST(CMergeReduce_dead_rm1b) {
   ControlReducerTester R;
 
   Node* t = R.graph.NewNode(R.common.IfTrue(), R.start);
-  Node* f = R.graph.NewNode(R.common.IfFalse(), R.start);
+  Node* f = R.graph.NewNode(R.common.IfTrue(), R.start);
   for (int i = 0; i < 2; i++) {
     Node* merge = R.graph.NewNode(R.common.Merge(3), R.dead, R.dead, R.dead);
     for (int j = i + 1; j < 3; j++) {
@@ -1118,7 +1118,7 @@ TEST(CChainedDiamondsReduce_x_false) {
   Diamond d2(R, R.zero);
   d2.chain(d1);
 
-  R.ReduceMergeIterative(d1.merge, d2.merge);
+  R.ReduceMergeIterative(R.start, d2.merge);
 }
 
 
@@ -1128,8 +1128,7 @@ TEST(CChainedDiamondsReduce_false_x) {
   Diamond d2(R, R.p0);
   d2.chain(d1);
 
-  R.ReduceMergeIterative(d2.merge, d2.merge);
-  CheckInputs(d2.branch, R.p0, R.start);
+  R.ReduceMergeIterative(R.start, d2.merge);
 }
 
 
@@ -1190,6 +1189,14 @@ TEST(CNestedDiamonds_xyz) {
 }
 
 
+TEST(CDeadDiamond) {
+  ControlReducerTester R;
+  // if (p0) { } else { }
+  Diamond d(R, R.p0);
+  R.ReduceMergeIterative(R.start, d.merge);
+}
+
+
 TEST(CDeadLoop1) {
   ControlReducerTester R;
 
@@ -1329,9 +1336,7 @@ TEST(Return_nested_diamonds1) {
 
   CheckInputs(ret, d1.phi, R.start, d1.merge);
   CheckInputs(d1.phi, R.one, R.zero, d1.merge);
-  CheckInputs(d1.merge, d2.merge, d3.merge);
-  CheckLiveDiamond(d2);
-  CheckLiveDiamond(d3);
+  CheckInputs(d1.merge, d1.if_true, d1.if_false);
 }
 
 
@@ -1348,11 +1353,7 @@ TEST(Return_nested_diamonds_true1) {
 
   R.ReduceGraph();  // d1 gets folded true.
 
-  CheckInputs(ret, R.one, R.start, d2.merge);
-  CheckInputs(d2.branch, R.p0, R.start);
-  CheckDeadDiamond(d1);
-  CheckLiveDiamond(d2);
-  CheckDeadDiamond(d3);
+  CheckInputs(ret, R.one, R.start, R.start);
 }
 
 
@@ -1369,11 +1370,7 @@ TEST(Return_nested_diamonds_false1) {
 
   R.ReduceGraph();  // d1 gets folded false.
 
-  CheckInputs(ret, R.zero, R.start, d3.merge);
-  CheckInputs(d3.branch, R.p0, R.start);
-  CheckDeadDiamond(d1);
-  CheckDeadDiamond(d2);
-  CheckLiveDiamond(d3);
+  CheckInputs(ret, R.zero, R.start, R.start);
 }