[turbofan] Broaden checkpoint elimination on returns.

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 23 matching lines @@
   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 && effect->OwnedBy(node)) {
-    // Any checkpoint that is wholly owned by a {Return} node can never be used
-    // for an actual bailout and can hence be cut out of the effect chain.
+  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