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

src/heap/heap.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.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 1945 matching lines @@
       AllocationSite* allocation_site = NULL);
 
   // Allocates and initializes a new JavaScript object based on a map.
   // Passing an allocation site means that a memento will be created that
   // points to the site.
   MUST_USE_RESULT AllocationResult
   AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure = NOT_TENURED,
                           AllocationSite* allocation_site = NULL);
 
   // Allocates a HeapNumber from value.
-  MUST_USE_RESULT AllocationResult
-  AllocateHeapNumber(double value, MutableMode mode = IMMUTABLE,
-                     PretenureFlag pretenure = NOT_TENURED);
+  MUST_USE_RESULT AllocationResult AllocateHeapNumber(
+      MutableMode mode = IMMUTABLE, PretenureFlag pretenure = NOT_TENURED);
 
 // Allocates SIMD values from the given lane values.
 #define SIMD_ALLOCATE_DECLARATION(TYPE, Type, type, lane_count, lane_type) \
   AllocationResult Allocate##Type(lane_type lanes[lane_count],             \
                                   PretenureFlag pretenure = NOT_TENURED);
   SIMD128_TYPES(SIMD_ALLOCATE_DECLARATION)
 #undef SIMD_ALLOCATE_DECLARATION
 
   // Allocates a byte array of the specified length
   MUST_USE_RESULT AllocationResult
@@ skipping 717 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_