[turbofan] Drop the obsolete TypeGuard operator.

src/compiler/verifier.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/verifier.h"
 
 #include <algorithm>
 #include <deque>
 #include <queue>
 #include <sstream>
@@ skipping 399 matching lines @@
     }
     case IrOpcode::kEffectPhi: {
       // EffectPhi input count matches parent control node.
       CHECK_EQ(0, value_count);
       CHECK_EQ(1, control_count);
       Node* control = NodeProperties::GetControlInput(node, 0);
       CHECK_EQ(effect_count, control->op()->ControlInputCount());
       CHECK_EQ(input_count, 1 + effect_count);
       break;
     }
-    case IrOpcode::kTypeGuard:
-      // TODO(bmeurer): what are the constraints on these?
-      break;
     case IrOpcode::kCheckpoint:
       // Type is empty.
       CheckNotTyped(node);
       break;
     case IrOpcode::kBeginRegion:
       // TODO(rossberg): what are the constraints on these?
       break;
     case IrOpcode::kFinishRegion: {
       // TODO(rossberg): what are the constraints on these?
       // Type must be subsumed by input type.
@@ skipping 1060 matching lines @@
          replacement->op()->EffectOutputCount() > 0);
   DCHECK(!NodeProperties::IsFrameStateEdge(edge) ||
          replacement->opcode() == IrOpcode::kFrameState);
 }
 
 #endif  // DEBUG
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8