[turbofan] Avoid creating singleton state-values for the accumulator.

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 491 matching lines @@
         CHECK(NodeProperties::GetType(val)->Is(NodeProperties::GetType(node)));
       }
       break;
     }
     case IrOpcode::kFrameState: {
       // TODO(jarin): what are the constraints on these?
       CHECK_EQ(5, value_count);
       CHECK_EQ(0, control_count);
       CHECK_EQ(0, effect_count);
       CHECK_EQ(6, input_count);
-      for (int i = 0; i < 3; ++i) {
+      // Check that the parameters and registers are kStateValues or
+      // kTypedStateValues.
+      for (int i = 0; i < 2; ++i) {
         CHECK(NodeProperties::GetValueInput(node, i)->opcode() ==
                   IrOpcode::kStateValues ||
               NodeProperties::GetValueInput(node, i)->opcode() ==
                   IrOpcode::kTypedStateValues);
       }
+      // The accumulator (InputAt(2)) cannot be kStateValues, but it can be
+      // kTypedStateValues (to signal the type). Once AST graph builder
+      // is removed, we should check this here. Until then, AST graph
+      // builder can generate expression stack as InputAt(2), which can
+      // still be kStateValues.
       break;
     }
     case IrOpcode::kStateValues:
     case IrOpcode::kTypedStateValues:
     case IrOpcode::kArgumentsElementsState:
     case IrOpcode::kArgumentsLengthState:
     case IrOpcode::kObjectState:
     case IrOpcode::kTypedObjectState:
       // TODO(jarin): what are the constraints on these?
       break;
@@ skipping 1235 matching lines @@
          replacement->op()->EffectOutputCount() > 0);
   DCHECK(!NodeProperties::IsFrameStateEdge(edge) ||
          replacement->opcode() == IrOpcode::kFrameState);
 }
 
 #endif  // DEBUG
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8