[compiler] Drop the CompareNilIC.

src/compiler/change-lowering.cc

Index: src/compiler/change-lowering.cc
diff --git a/src/compiler/change-lowering.cc b/src/compiler/change-lowering.cc
index e217f3786b02c43ee5278b1c2555108857d24832..907b36a93b7dd860c2a32e27a6b685444c9baf33 100644
--- a/src/compiler/change-lowering.cc
+++ b/src/compiler/change-lowering.cc
@@ -55,6 +55,8 @@ Reduction ChangeLowering::Reduce(Node* node) {
       return ObjectIsSmi(node);
     case IrOpcode::kObjectIsNumber:
       return ObjectIsNumber(node);
+    case IrOpcode::kObjectIsUndetectable:
+      return ObjectIsUndetectable(node);
     default:
       return NoChange();
   }
@@ -603,6 +605,13 @@ Node* ChangeLowering::LoadHeapObjectMap(Node* object, Node* control) {
       graph()->start(), control);
 }
 
+Node* ChangeLowering::LoadMapBitField(Node* map) {
+  return graph()->NewNode(
+      machine()->Load(MachineType::Uint8()), map,
+      jsgraph()->IntPtrConstant(Map::kBitFieldOffset - kHeapObjectTag),
+      graph()->start(), graph()->start());
+}
+
 Node* ChangeLowering::LoadMapInstanceType(Node* map) {
   return graph()->NewNode(
       machine()->Load(MachineType::Uint8()), map,
@@ -650,6 +659,31 @@ Reduction ChangeLowering::ObjectIsReceiver(Node* node) {
   return Changed(node);
 }
 
+Reduction ChangeLowering::ObjectIsUndetectable(Node* node) {
+  Node* input = NodeProperties::GetValueInput(node, 0);
+  // TODO(bmeurer): Optimize somewhat based on input type.
+  Node* check = IsSmi(input);
+  Node* branch = graph()->NewNode(common()->Branch(), check, graph()->start());
+  Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+  Node* vtrue = jsgraph()->Int32Constant(0);
+  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+  Node* vfalse = graph()->NewNode(
+      machine()->Word32Equal(),
+      graph()->NewNode(
+          machine()->Word32Equal(),
+          graph()->NewNode(machine()->Word32And(),
+                           jsgraph()->Uint32Constant(1 << Map::kIsUndetectable),
+                           LoadMapBitField(LoadHeapObjectMap(input, if_false))),
+          jsgraph()->Int32Constant(0)),
+      jsgraph()->Int32Constant(0));
+  Node* control = graph()->NewNode(common()->Merge(2), if_true, if_false);
+  node->ReplaceInput(0, vtrue);
+  node->AppendInput(graph()->zone(), vfalse);
+  node->AppendInput(graph()->zone(), control);
+  NodeProperties::ChangeOp(node, common()->Phi(MachineRepresentation::kBit, 2));
+  return Changed(node);
+}
+
 Reduction ChangeLowering::ObjectIsSmi(Node* node) {
   node->ReplaceInput(0,
                      graph()->NewNode(machine()->WordAnd(), node->InputAt(0),