[turbofan] Refactor IsSame into NodeProperties.

src/compiler/node-properties.cc

 // Copyright 2015 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/compiler/node-properties.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/operator-properties.h"
@@ skipping 294 matching lines @@
     DCHECK_NULL(projections[index]);
     projections[index] = use;
   }
 #ifdef DEBUG
   for (size_t index = 0; index < projection_count; ++index) {
     DCHECK_NOT_NULL(projections[index]);
   }
 #endif
 }
 
+// static
+bool NodeProperties::IsSame(Node* a, Node* b) {
+  for (;;) {
+    if (a->opcode() == IrOpcode::kCheckHeapObject) {
+      a = GetValueInput(a, 0);
+      continue;
+    }
+    if (b->opcode() == IrOpcode::kCheckHeapObject) {
+      b = GetValueInput(b, 0);
+      continue;
+    }
+    return a == b;
+  }
+}
 
 // static
 MaybeHandle<Context> NodeProperties::GetSpecializationContext(
     Node* node, MaybeHandle<Context> context) {
   switch (node->opcode()) {
     case IrOpcode::kHeapConstant:
       return Handle<Context>::cast(OpParameter<Handle<HeapObject>>(node));
     case IrOpcode::kParameter: {
       Node* const start = NodeProperties::GetValueInput(node, 0);
       DCHECK_EQ(IrOpcode::kStart, start->opcode());
@@ skipping 43 matching lines @@
 // static
 bool NodeProperties::IsInputRange(Edge edge, int first, int num) {
   if (num == 0) return false;
   int const index = edge.index();
   return first <= index && index < first + num;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8