[turbofan] Use reference equal to zero instead of a smi check.

test/unittests/compiler/js-typed-lowering-unittest.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/code-factory.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/machine-operator.h"
@@ skipping 900 matching lines @@
                           FeedbackVectorICSlot::Invalid());
   for (int i = 0; i < DynamicGlobalAccess::kMaxCheckDepth; ++i) {
     uint32_t bitset = 1 << i;  // Only single check.
     Reduction r = Reduce(graph()->NewNode(
         javascript()->LoadDynamicGlobal(name, bitset, feedback, NOT_CONTEXTUAL),
         context, context, frame_state, frame_state, effect, control));
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(
         r.replacement(),
         IsPhi(kMachAnyTagged, _, _,
-              IsMerge(IsIfTrue(IsBranch(
-                          IsObjectIsSmi(IsLoadContext(
+              IsMerge(
+                  IsIfTrue(IsBranch(
+                      IsReferenceEqual(
+                          Type::Tagged(),
+                          IsLoadContext(
                               ContextAccess(i, Context::EXTENSION_INDEX, false),
-                              context)),
-                          control)),
-                      _)));
+                              context),
+                          IsNumberConstant(BitEq(0.0))),
+                      control)),
+                  _)));
   }
 }
 
 #if V8_TURBOFAN_TARGET
 
 // -----------------------------------------------------------------------------
 // JSAdd
 
 
 TEST_F(JSTypedLoweringTest, JSAddWithString) {
@@ skipping 112 matching lines @@
   EXPECT_THAT(r.replacement(),
               IsFinish(IsAllocate(IsNumberConstant(Context::SizeFor(
                                       Context::MIN_CONTEXT_SLOTS)),
                                   effect, control),
                        _));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8