[turbofan] Eliminate checkpoints before return in common op reducer.

src/compiler/checkpoint-elimination.cc

 // Copyright 2016 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/checkpoint-elimination.h"
 
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 20 matching lines @@
 }  // namespace
 
 Reduction CheckpointElimination::ReduceCheckpoint(Node* node) {
   DCHECK_EQ(IrOpcode::kCheckpoint, node->opcode());
   if (IsRedundantCheckpoint(node)) {
     return Replace(NodeProperties::GetEffectInput(node));
   }
   return NoChange();
 }
 
-Reduction CheckpointElimination::ReduceReturn(Node* node) {
-  DCHECK_EQ(IrOpcode::kReturn, node->opcode());
-  Node* effect = NodeProperties::GetEffectInput(node);
-  if (effect->opcode() == IrOpcode::kCheckpoint) {
-    // Any {Return} node can never be used to insert a deoptimization point,
-    // hence checkpoints can be cut out of the effect chain flowing into it.
-    Node* replacement = NodeProperties::GetEffectInput(effect);
-    NodeProperties::ReplaceEffectInput(node, replacement);
-    return Changed(node);
-  }
-  return NoChange();
-}
-
 Reduction CheckpointElimination::Reduce(Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kCheckpoint:
       return ReduceCheckpoint(node);
-    case IrOpcode::kReturn:
-      return ReduceReturn(node);
     default:
       break;
   }
   return NoChange();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8