Reland r22082 "Replace HeapNumber as doublebox with an explicit MutableHeapNumber."

src/heap.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/once.h"
 #include "src/base/utils/random-number-generator.h"
@@ skipping 2510 matching lines @@
     }
 
 #define ALLOCATE_VARSIZE_MAP(instance_type, field_name)                        \
     ALLOCATE_MAP(instance_type, kVariableSizeSentinel, field_name)
 
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, fixed_cow_array)
     ASSERT(fixed_array_map() != fixed_cow_array_map());
 
     ALLOCATE_VARSIZE_MAP(FIXED_ARRAY_TYPE, scope_info)
     ALLOCATE_MAP(HEAP_NUMBER_TYPE, HeapNumber::kSize, heap_number)
+    ALLOCATE_MAP(
+        MUTABLE_HEAP_NUMBER_TYPE, HeapNumber::kSize, mutable_heap_number)
     ALLOCATE_MAP(SYMBOL_TYPE, Symbol::kSize, symbol)
     ALLOCATE_MAP(FOREIGN_TYPE, Foreign::kSize, foreign)
 
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, the_hole);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, boolean);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, uninitialized);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, arguments_marker);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, no_interceptor_result_sentinel);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, exception);
     ALLOCATE_MAP(ODDBALL_TYPE, Oddball::kSize, termination_exception);
@@ skipping 104 matching lines @@
 
     TYPED_ARRAYS(ALLOCATE_EMPTY_FIXED_TYPED_ARRAY)
 #undef ALLOCATE_EMPTY_FIXED_TYPED_ARRAY
   }
   ASSERT(!InNewSpace(empty_fixed_array()));
   return true;
 }
 
 
 AllocationResult Heap::AllocateHeapNumber(double value,
+                                          MutableMode mode,
                                           PretenureFlag pretenure) {
   // Statically ensure that it is safe to allocate heap numbers in paged
   // spaces.
   int size = HeapNumber::kSize;
   STATIC_ASSERT(HeapNumber::kSize <= Page::kMaxRegularHeapObjectSize);
 
   AllocationSpace space = SelectSpace(size, OLD_DATA_SPACE, pretenure);
 
   HeapObject* result;
   { AllocationResult allocation = AllocateRaw(size, space, OLD_DATA_SPACE);
     if (!allocation.To(&result)) return allocation;
   }
 
-  result->set_map_no_write_barrier(heap_number_map());
+  Map* map = mode == MUTABLE ? mutable_heap_number_map() : heap_number_map();
+  HeapObject::cast(result)->set_map_no_write_barrier(map);
   HeapNumber::cast(result)->set_value(value);
   return result;
 }
 
 
 AllocationResult Heap::AllocateCell(Object* value) {
   int size = Cell::kSize;
   STATIC_ASSERT(Cell::kSize <= Page::kMaxRegularHeapObjectSize);
 
   HeapObject* result;
@@ skipping 85 matching lines @@
   // To workaround the problem, make separate functions without inlining.
   Heap::CreateJSEntryStub();
   Heap::CreateJSConstructEntryStub();
 }
 
 
 void Heap::CreateInitialObjects() {
   HandleScope scope(isolate());
   Factory* factory = isolate()->factory();
 
-  // The -0 value must be set before NumberFromDouble works.
-  set_minus_zero_value(*factory->NewHeapNumber(-0.0, TENURED));
+  // The -0 value must be set before NewNumber works.
+  set_minus_zero_value(*factory->NewHeapNumber(-0.0, IMMUTABLE, TENURED));
   ASSERT(std::signbit(minus_zero_value()->Number()) != 0);
 
-  set_nan_value(*factory->NewHeapNumber(base::OS::nan_value(), TENURED));
-  set_infinity_value(*factory->NewHeapNumber(V8_INFINITY, TENURED));
+  set_nan_value(
+      *factory->NewHeapNumber(base::OS::nan_value(), IMMUTABLE, TENURED));
+  set_infinity_value(*factory->NewHeapNumber(V8_INFINITY, IMMUTABLE, TENURED));
 
   // The hole has not been created yet, but we want to put something
   // predictable in the gaps in the string table, so lets make that Smi zero.
   set_the_hole_value(reinterpret_cast<Oddball*>(Smi::FromInt(0)));
 
   // Allocate initial string table.
   set_string_table(*StringTable::New(isolate(), kInitialStringTableSize));
 
   // Finish initializing oddballs after creating the string table.
   Oddball::Initialize(isolate(),
@@ skipping 3653 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal