Use signaling NaN for holes in fixed double arrays.

src/objects-inl.h

 // Copyright 2012 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 1305 matching lines @@
 
 #define WRITE_UINT32_FIELD(p, offset, value) \
   (*reinterpret_cast<uint32_t*>(FIELD_ADDR(p, offset)) = value)
 
 #define READ_INT32_FIELD(p, offset) \
   (*reinterpret_cast<const int32_t*>(FIELD_ADDR_CONST(p, offset)))
 
 #define WRITE_INT32_FIELD(p, offset, value) \
   (*reinterpret_cast<int32_t*>(FIELD_ADDR(p, offset)) = value)
 
+#define READ_UINT64_FIELD(p, offset) \
+  (*reinterpret_cast<const uint64_t*>(FIELD_ADDR_CONST(p, offset)))
+
+#define WRITE_UINT64_FIELD(p, offset, value) \
+  (*reinterpret_cast<uint64_t*>(FIELD_ADDR(p, offset)) = value)
+
 #define READ_INT64_FIELD(p, offset) \
   (*reinterpret_cast<const int64_t*>(FIELD_ADDR_CONST(p, offset)))
 
 #define WRITE_INT64_FIELD(p, offset, value) \
   (*reinterpret_cast<int64_t*>(FIELD_ADDR(p, offset)) = value)
 
 #define READ_SHORT_FIELD(p, offset) \
   (*reinterpret_cast<const uint16_t*>(FIELD_ADDR_CONST(p, offset)))
 
 #define WRITE_SHORT_FIELD(p, offset, value) \
@@ skipping 945 matching lines @@
 void FixedArray::set(int index, Object* value) {
   DCHECK_NE(GetHeap()->fixed_cow_array_map(), map());
   DCHECK_EQ(FIXED_ARRAY_TYPE, map()->instance_type());
   DCHECK(index >= 0 && index < this->length());
   int offset = kHeaderSize + index * kPointerSize;
   WRITE_FIELD(this, offset, value);
   WRITE_BARRIER(GetHeap(), this, offset, value);
 }
 
 
-inline bool FixedDoubleArray::is_the_hole_nan(double value) {
-  return bit_cast<uint64_t, double>(value) == kHoleNanInt64;
-}
-
-
-inline double FixedDoubleArray::hole_nan_as_double() {
-  return bit_cast<double, uint64_t>(kHoleNanInt64);
-}
-
-
-inline double FixedDoubleArray::canonical_not_the_hole_nan_as_double() {
-  DCHECK(bit_cast<uint64_t>(base::OS::nan_value()) != kHoleNanInt64);
-  DCHECK((bit_cast<uint64_t>(base::OS::nan_value()) >> 32) != kHoleNanUpper32);
-  return base::OS::nan_value();
-}
-
-
 double FixedDoubleArray::get_scalar(int index) {
   DCHECK(map() != GetHeap()->fixed_cow_array_map() &&
          map() != GetHeap()->fixed_array_map());
   DCHECK(index >= 0 && index < this->length());
-  double result = READ_DOUBLE_FIELD(this, kHeaderSize + index * kDoubleSize);
-  DCHECK(!is_the_hole_nan(result));
-  return result;
+  DCHECK(!is_the_hole(index));
+  return READ_DOUBLE_FIELD(this, kHeaderSize + index * kDoubleSize);
 }
 
-int64_t FixedDoubleArray::get_representation(int index) {
+
+uint64_t FixedDoubleArray::get_representation(int index) {
   DCHECK(map() != GetHeap()->fixed_cow_array_map() &&
          map() != GetHeap()->fixed_array_map());
   DCHECK(index >= 0 && index < this->length());
-  return READ_INT64_FIELD(this, kHeaderSize + index * kDoubleSize);
+  int offset = kHeaderSize + index * kDoubleSize;
+  return READ_UINT64_FIELD(this, offset);
 }
 
 
 Handle<Object> FixedDoubleArray::get(Handle<FixedDoubleArray> array,
                                      int index) {
   if (array->is_the_hole(index)) {
     return array->GetIsolate()->factory()->the_hole_value();
   } else {
     return array->GetIsolate()->factory()->NewNumber(array->get_scalar(index));
   }
 }
 
 
 void FixedDoubleArray::set(int index, double value) {
   DCHECK(map() != GetHeap()->fixed_cow_array_map() &&
          map() != GetHeap()->fixed_array_map());
   int offset = kHeaderSize + index * kDoubleSize;
-  if (std::isnan(value)) value = canonical_not_the_hole_nan_as_double();
-  WRITE_DOUBLE_FIELD(this, offset, value);
+  if (std::isnan(value)) {
+    WRITE_UINT64_FIELD(this, offset, V8_UINT64_C(0xFFFFFFFFFFFFFFFF));
+  } else {
+    WRITE_DOUBLE_FIELD(this, offset, value);
+  }
+  DCHECK(!is_the_hole(index));
 }
 
 
 void FixedDoubleArray::set_the_hole(int index) {
   DCHECK(map() != GetHeap()->fixed_cow_array_map() &&
          map() != GetHeap()->fixed_array_map());
   int offset = kHeaderSize + index * kDoubleSize;
-  WRITE_DOUBLE_FIELD(this, offset, hole_nan_as_double());
+  WRITE_UINT64_FIELD(this, offset, kHoleNanInt64);
 }
 
 
 bool FixedDoubleArray::is_the_hole(int index) {
-  int offset = kHeaderSize + index * kDoubleSize;
-  return is_the_hole_nan(READ_DOUBLE_FIELD(this, offset));
+  return get_representation(index) == kHoleNanInt64;
 }
 
 
 double* FixedDoubleArray::data_start() {
   return reinterpret_cast<double*>(FIELD_ADDR(this, kHeaderSize));
 }
 
 
 void FixedDoubleArray::FillWithHoles(int from, int to) {
   for (int i = from; i < to; i++) {
@@ skipping 5142 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_