Access double fields in C++ as uint64_t fields to preserve signaling bit of a NaN.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 36034200a6d74a434839362ceaa9cb57902e1e92..5e77e06b35f4cc49e66a8cfc80c7ca2c85d77119 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2415,8 +2415,7 @@ bool Heap::CreateInitialMaps() {
   return true;
 }
 
-
-AllocationResult Heap::AllocateHeapNumber(double value, MutableMode mode,
+AllocationResult Heap::AllocateHeapNumber(MutableMode mode,
                                           PretenureFlag pretenure) {
   // Statically ensure that it is safe to allocate heap numbers in paged
   // spaces.
@@ -2433,7 +2432,6 @@ AllocationResult Heap::AllocateHeapNumber(double value, MutableMode mode,
 
   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;
 }
 
@@ -2600,8 +2598,11 @@ void Heap::CreateInitialObjects() {
 
   set_nan_value(*factory->NewHeapNumber(
       std::numeric_limits<double>::quiet_NaN(), IMMUTABLE, TENURED));
-  set_hole_nan_value(*factory->NewHeapNumber(bit_cast<double>(kHoleNanInt64),
-                                             IMMUTABLE, TENURED));
+  {
+    Handle<HeapNumber> value = factory->NewHeapNumber(0.0, IMMUTABLE, TENURED);
+    value->set_value_as_bits(kHoleNanInt64);
+    set_hole_nan_value(*value);
+  }
   set_infinity_value(*factory->NewHeapNumber(V8_INFINITY, IMMUTABLE, TENURED));
   set_minus_infinity_value(
       *factory->NewHeapNumber(-V8_INFINITY, IMMUTABLE, TENURED));