[printing] Fix DCHECK failure when printing FAST_HOLEY_DOUBLE_ELEMENTS

This CL fixes %DebugPrint for FAST_HOLEY_DOUBLE_ELEMENTS and now properly
distinguishes TheHole and NaN values.

BUG=

Review-Url: https://codereview.chromium.org/2294913004
Cr-Commit-Position: refs/heads/master@{#39293}

src/objects-printer.cc

@@ -318,18 +318,37 @@ void JSObject::PrintProperties(std::ostream& os) {  // NOLINT
   }
 }
 
+namespace {
+
+template <class T>
+double GetScalarElement(T* array, int index) {
+  return array->get_scalar(index);
+}
+
+double GetScalarElement(FixedDoubleArray* array, int index) {
+  if (array->is_the_hole(index)) return bit_cast<double>(kHoleNanInt64);
+  return array->get_scalar(index);
+}
+
+bool is_the_hole(double maybe_hole) {
+  return bit_cast<uint64_t>(maybe_hole) == kHoleNanInt64;
+}
+
+}  // namespace
+
 template <class T, bool print_the_hole>
 static void DoPrintElements(std::ostream& os, Object* object) {  // NOLINT
   T* array = T::cast(object);
   if (array->length() == 0) return;
   int previous_index = 0;
-  double previous_value = array->get_scalar(0);
+  double previous_value = GetScalarElement(array, 0);
   double value = 0.0;
   int i;
   for (i = 1; i <= array->length(); i++) {
-    if (i < array->length()) value = array->get_scalar(i);
+    if (i < array->length()) value = GetScalarElement(array, i);
     bool values_are_nan = std::isnan(previous_value) && std::isnan(value);
-    if ((previous_value == value || values_are_nan) && i != array->length()) {
+    if (i != array->length() && (previous_value == value || values_are_nan) &&
+        is_the_hole(previous_value) == is_the_hole(value)) {
       continue;
     }
     os << "\n";
@@ -339,8 +358,7 @@ static void DoPrintElements(std::ostream& os, Object* object) {  // NOLINT
       ss << '-' << (i - 1);
     }
     os << std::setw(12) << ss.str() << ": ";
-    if (print_the_hole &&
-        FixedDoubleArray::cast(object)->is_the_hole(previous_index)) {
+    if (print_the_hole && is_the_hole(previous_value)) {
       os << "<the_hole>";
     } else {
       os << previous_value;

test/mjsunit/debug-print.js

+// 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.
+
+// Flags: --allow-natives-syntax
+
+// Make sure printing different element kinds doesn't crash.
+
+var array;
+var obj = {};
+
+array = [];
+%DebugPrint(array);
+
+// FAST_SMI_ELEMENTS
+array = [1, 2, 3];
+%DebugPrint(array);
+
+// FAST_HOLEY_SMI_ELEMENTS
+array[10] = 100;
+array[11] = 100;
+%DebugPrint(array);
+
+// FAST_ELEMENTS
+array = [1, obj, obj];
+%DebugPrint(array);
+
+// FAST_HOLEY_ELEMENTS
+array[100] = obj;
+array[101] = obj;
+%DebugPrint(array);
+
+// FAST_DOUBLE_ELEMENTS
+array = [1.1, 2.2, 3.3, 3.3, 3.3, NaN];
+%DebugPrint(array);
+array.push(NaN);
+array.push(NaN);
+%DebugPrint(array);
+
+// FAST_HOLEY_DOUBLE_ELEMENTS
+array[100] = 1.2;
+array[101] = 1.2;
+%DebugPrint(array);
+
+// DICTIONARY_ELEMENTS
+%NormalizeElements(array);
+%DebugPrint(array);