[turbofan] Handle impossible types (Type::None()) in the backend.

src/bailout-reason.h

 // 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.
 
 #ifndef V8_BAILOUT_REASON_H_
 #define V8_BAILOUT_REASON_H_
 
 namespace v8 {
 namespace internal {
 
@@ skipping 248 matching lines @@
   V(kVariableResolvedToWithContext, "Variable resolved to with context")       \
   V(kWeShouldNotHaveAnEmptyLexicalContext,                                     \
     "We should not have an empty lexical context")                             \
   V(kWithStatement, "WithStatement")                                           \
   V(kWrongFunctionContext, "Wrong context passed to function")                 \
   V(kWrongAddressOrValuePassedToRecordWrite,                                   \
     "Wrong address or value passed to RecordWrite")                            \
   V(kWrongArgumentCountForInvokeIntrinsic,                                     \
     "Wrong number of arguments for intrinsic")                                 \
   V(kShouldNotDirectlyEnterOsrFunction,                                        \
-    "Should not directly enter OSR-compiled function")
+    "Should not directly enter OSR-compiled function")                         \
+  V(kConversionFromImpossibleValue,                                            \
+    "Reached conversion from value with empty type (i.e., impossible type)")
 
 #define ERROR_MESSAGES_CONSTANTS(C, T) C,
 enum BailoutReason {
   ERROR_MESSAGES_LIST(ERROR_MESSAGES_CONSTANTS) kLastErrorMessage
 };
 #undef ERROR_MESSAGES_CONSTANTS
 
 
 const char* GetBailoutReason(BailoutReason reason);
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_BAILOUT_REASON_H_