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

src/builtins/builtins-array.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.h"
 #include "src/builtins/builtins-utils.h"
 
 #include "src/code-factory.h"
 #include "src/code-stub-assembler.h"
 #include "src/contexts.h"
@@ skipping 634 matching lines @@
     Bind(&after_loop);
     Return(UndefinedConstant());
   }
 
   Bind(&throw_null_undefined_exception);
   {
     CallRuntime(Runtime::kThrowTypeError, context,
                 SmiConstant(MessageTemplate::kCalledOnNullOrUndefined),
                 HeapConstant(isolate()->factory()->NewStringFromAsciiChecked(
                     "Array.prototype.forEach")));
-    Return(UndefinedConstant());
+    Unreachable();
   }
 
   Bind(&type_exception);
   {
     CallRuntime(Runtime::kThrowTypeError, context,
                 SmiConstant(MessageTemplate::kCalledNonCallable), callbackfn);
-    Return(UndefinedConstant());
+    Unreachable();
   }
 }
 
 BUILTIN(ArraySlice) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
   int len = -1;
   int relative_start = 0;
   int relative_end = 0;
 
@@ skipping 2156 matching lines @@
     assembler.StoreObjectFieldNoWriteBarrier(
         result, JSIteratorResult::kValueOffset, var_value.value());
     assembler.StoreObjectFieldNoWriteBarrier(
         result, JSIteratorResult::kDoneOffset, var_done.value());
     assembler.Return(result);
   }
 
   assembler.Bind(&throw_bad_receiver);
   {
     // The {receiver} is not a valid JSArrayIterator.
-    Node* result = assembler.CallRuntime(
-        Runtime::kThrowIncompatibleMethodReceiver, context,
-        assembler.HeapConstant(operation), iterator);
-    assembler.Return(result);
+    assembler.CallRuntime(Runtime::kThrowIncompatibleMethodReceiver, context,
+                          assembler.HeapConstant(operation), iterator);
+    assembler.Unreachable();
   }
 
   assembler.Bind(&if_isdetached);
   {
     Node* message = assembler.SmiConstant(MessageTemplate::kDetachedOperation);
-    Node* result =
-        assembler.CallRuntime(Runtime::kThrowTypeError, context, message,
-                              assembler.HeapConstant(operation));
-    assembler.Return(result);
+    assembler.CallRuntime(Runtime::kThrowTypeError, context, message,
+                          assembler.HeapConstant(operation));
+    assembler.Unreachable();
   }
 }
 
 }  // namespace internal
 }  // namespace v8