Remove SMI length check from Builtins::Generate_ArrayIndexOf

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 2003 matching lines @@
   len_var.Bind(intptr_zero);
 
   // Take slow path if not a JSArray, if retrieving elements requires
   // traversing prototype, or if access checks are required.
   assembler.BranchIfFastJSArray(
       array, context, CodeStubAssembler::FastJSArrayAccessMode::INBOUNDS_READ,
       &init_len, &call_runtime);
 
   assembler.Bind(&init_len);
   {
-    // Handle case where JSArray length is not an Smi in the runtime
-    Node* len = assembler.LoadObjectField(array, JSArray::kLengthOffset);
-    assembler.GotoIfNot(assembler.TaggedIsSmi(len), &call_runtime);
+    // JSArray length is always an Smi for fast arrays.
+    CSA_ASSERT(&assembler, assembler.TaggedIsSmi(assembler.LoadObjectField(
+                               array, JSArray::kLengthOffset)));
+    Node* len =
+        assembler.LoadAndUntagObjectField(array, JSArray::kLengthOffset);
 
-    len_var.Bind(assembler.SmiToWord(len));
+    len_var.Bind(len);
     assembler.Branch(assembler.WordEqual(len_var.value(), intptr_zero),
                      &return_not_found, &init_k);
   }
 
   assembler.Bind(&init_k);
   {
     Label done(&assembler), init_k_smi(&assembler), init_k_heap_num(&assembler),
         init_k_zero(&assembler), init_k_n(&assembler);
     Node* tagged_n = assembler.ToInteger(context, start_from);
 
@@ skipping 810 matching lines @@
   {
     Node* message = assembler.SmiConstant(MessageTemplate::kDetachedOperation);
     assembler.CallRuntime(Runtime::kThrowTypeError, context, message,
                           assembler.HeapConstant(operation));
     assembler.Unreachable();
   }
 }
 
 }  // namespace internal
 }  // namespace v8