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

test/cctest/heap/test-alloc.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 30 matching lines @@
 AllocationResult v8::internal::HeapTester::AllocateAfterFailures() {
   Heap* heap = CcTest::heap();
 
   // New space.
   heap->AllocateByteArray(100).ToObjectChecked();
   heap->AllocateFixedArray(100, NOT_TENURED).ToObjectChecked();
 
   // Make sure we can allocate through optimized allocation functions
   // for specific kinds.
   heap->AllocateFixedArray(100).ToObjectChecked();
-  heap->AllocateHeapNumber(0.42).ToObjectChecked();
+  heap->AllocateHeapNumber().ToObjectChecked();
   Object* object = heap->AllocateJSObject(
       *CcTest::i_isolate()->object_function()).ToObjectChecked();
   heap->CopyJSObject(JSObject::cast(object)).ToObjectChecked();
 
   // Old data space.
   heap::SimulateFullSpace(heap->old_space());
   heap->AllocateByteArray(100, TENURED).ToObjectChecked();
 
   // Old pointer space.
   heap::SimulateFullSpace(heap->old_space());
@@ skipping 181 matching lines @@
       code_range.FreeRawMemory(blocks[index].base, blocks[index].size);
       current_allocated -= blocks[index].size;
       if (index < blocks.length() - 1) {
         blocks[index] = blocks.RemoveLast();
       } else {
         blocks.RemoveLast();
       }
     }
   }
 }