[turbofan] Simply context specialization and fix for OSR.

src/compiler/control-reducer.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/common-operator.h"
 #include "src/compiler/control-reducer.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-marker.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 273 matching lines @@
         if (!marked.IsReachableFromEnd(use)) {
           TRACE(("DeadLink: #%d:%s(%d) -> #%d:%s\n", use->id(),
                  use->op()->mnemonic(), edge.index(), node->id(),
                  node->op()->mnemonic()));
           edge.UpdateTo(NULL);
         }
       }
     }
 #if DEBUG
     // Verify that no inputs to live nodes are NULL.
-    for (size_t j = 0; j < nodes.size(); j++) {
-      Node* node = nodes[j];
-      for (Node* const input : node->inputs()) {
-        CHECK(input);
+    for (Node* node : nodes) {
+      for (int index = 0; index < node->InputCount(); index++) {
+        Node* input = node->InputAt(index);
+        if (input == nullptr) {
+          std::ostringstream str;
+          str << "GraphError: node #" << node->id() << ":" << *node->op()
+              << "(input @" << index << ") == null";
+          FATAL(str.str().c_str());
+        }
+        if (input->opcode() == IrOpcode::kDead) {
+          std::ostringstream str;
+          str << "GraphError: node #" << node->id() << ":" << *node->op()
+              << "(input @" << index << ") == dead";
+          FATAL(str.str().c_str());
+        }
       }
-      for (Node* const use : node->uses()) {
+      for (Node* use : node->uses()) {
         CHECK(marked.IsReachableFromEnd(use));
       }
     }
 #endif
   }
 
   // Reduce the node on the top of the stack.
   // If an input {i} is not yet visited or needs to be revisited, push {i} onto
   // the stack and return. Otherwise, all inputs are visited, so apply
   // reductions for {node} and pop it off the stack.
@@ skipping 329 matching lines @@
       return impl.ReduceIfTrue(node);
     case IrOpcode::kIfFalse:
       return impl.ReduceIfFalse(node);
     default:
       return node;
   }
 }
 }
 }
 }  // namespace v8::internal::compiler