[csa] Add Unreachable() and use it after throw sites

src/builtins/builtins-regexp.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/builtins/builtins-regexp.h"
 
 #include "src/builtins/builtins-constructor.h"
 #include "src/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
 #include "src/code-factory.h"
@@ skipping 380 matching lines @@
   {
     Node* const message_id = SmiConstant(Smi::FromInt(msg_template));
     Node* const method_name_str = HeapConstant(
         isolate()->factory()->NewStringFromAsciiChecked(method_name, TENURED));
 
     Callable callable = CodeFactory::ToString(isolate());
     Node* const value_str = CallStub(callable, context, maybe_receiver);
 
     CallRuntime(Runtime::kThrowTypeError, context, message_id, method_name_str,
                 value_str);
-    var_value_map.Bind(UndefinedConstant());
-    Goto(&out);  // Never reached.
+    Unreachable();
   }
 
   Bind(&out);
   return var_value_map.value();
 }
 
 Node* RegExpBuiltinsAssembler::IsInitialRegExpMap(Node* context, Node* map) {
   Node* const native_context = LoadNativeContext(context);
   Node* const regexp_fun =
       LoadContextElement(native_context, Context::REGEXP_FUNCTION_INDEX);
@@ skipping 670 matching lines @@
     }
 
     Bind(&if_isnotprototype);
     {
       Node* const message_id =
           SmiConstant(Smi::FromInt(MessageTemplate::kRegExpNonRegExp));
       Node* const method_name_str = HeapConstant(
           isolate->factory()->NewStringFromAsciiChecked(method_name));
       CallRuntime(Runtime::kThrowTypeError, context, message_id,
                   method_name_str);
-      Return(UndefinedConstant());  // Never reached.
+      Unreachable();
     }
   }
 }
 
 // ES6 21.2.5.4.
 TF_BUILTIN(RegExpPrototypeGlobalGetter, RegExpBuiltinsAssembler) {
   FlagGetter(JSRegExp::kGlobal, v8::Isolate::kRegExpPrototypeOldFlagGetter,
              "RegExp.prototype.global");
 }
 
@@ skipping 1462 matching lines @@
   Bind(&if_matched);
   {
     Node* result =
         ConstructNewResultFromMatchInfo(context, regexp, match_indices, string);
     Return(result);
   }
 }
 
 }  // namespace internal
 }  // namespace v8