[turbofan] Insert sigma nodes for loop variable backedge.

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 1044 matching lines @@
       // (Object, elementtype) -> _|_
       // TODO(rossberg): activate once machine ops are typed.
       // CheckValueInputIs(node, 0, Type::Object());
       // CheckValueInputIs(node, 1, ElementAccessOf(node->op()).type));
       CheckNotTyped(node);
       break;
     case IrOpcode::kNumberSilenceNaN:
       CheckValueInputIs(node, 0, Type::Number());
       CheckUpperIs(node, Type::Number());
       break;
+    case IrOpcode::kSigma:
+      CheckUpperIs(node, SigmaTypeOf(node->op()));
+      break;
 
     // Machine operators
     // -----------------------
     case IrOpcode::kLoad:
     case IrOpcode::kStore:
     case IrOpcode::kStackSlot:
     case IrOpcode::kWord32And:
     case IrOpcode::kWord32Or:
     case IrOpcode::kWord32Xor:
     case IrOpcode::kWord32Shl:
@@ skipping 479 matching lines @@
          replacement->op()->EffectOutputCount() > 0);
   DCHECK(!NodeProperties::IsFrameStateEdge(edge) ||
          replacement->opcode() == IrOpcode::kFrameState);
 }
 
 #endif  // DEBUG
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8