[turbofan] Make FindFrameStateBefore handle dead paths.

src/compiler/node-properties.cc

 // Copyright 2015 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/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/operator-properties.h"
@@ skipping 221 matching lines @@
 void NodeProperties::ChangeOp(Node* node, const Operator* new_op) {
   node->set_op(new_op);
   Verifier::VerifyNode(node);
 }
 
 
 // static
 Node* NodeProperties::FindFrameStateBefore(Node* node) {
   Node* effect = NodeProperties::GetEffectInput(node);
   while (effect->opcode() != IrOpcode::kCheckpoint) {
+    if (effect->opcode() == IrOpcode::kDead) return effect;
     DCHECK_EQ(1, effect->op()->EffectInputCount());
     effect = NodeProperties::GetEffectInput(effect);
   }
   Node* frame_state = GetFrameStateInput(effect, 0);
   return frame_state;
 }
 
 // static
 Node* NodeProperties::FindProjection(Node* node, size_t projection_index) {
   for (auto use : node->uses()) {
@@ skipping 172 matching lines @@
 // static
 bool NodeProperties::IsInputRange(Edge edge, int first, int num) {
   if (num == 0) return false;
   int const index = edge.index();
   return first <= index && index < first + num;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8