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

src/crankshaft/hydrogen-instructions.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_CRANKSHAFT_HYDROGEN_INSTRUCTIONS_H_
 #define V8_CRANKSHAFT_HYDROGEN_INSTRUCTIONS_H_
 
 #include <cstring>
 #include <iosfwd>
 
@@ skipping 3070 matching lines @@
   }
   bool HasSmiValue() const { return HasSmiValueField::decode(bit_field_); }
   bool HasDoubleValue() const {
     return HasDoubleValueField::decode(bit_field_);
   }
   double DoubleValue() const {
     DCHECK(HasDoubleValue());
     return double_value_;
   }
   uint64_t DoubleValueAsBits() const {
-    uint64_t bits;
     DCHECK(HasDoubleValue());
-    STATIC_ASSERT(sizeof(bits) == sizeof(double_value_));
-    std::memcpy(&bits, &double_value_, sizeof(bits));
-    return bits;
+    return bit_cast<uint64_t>(double_value_);
   }
   bool IsTheHole() const {
     if (HasDoubleValue() && DoubleValueAsBits() == kHoleNanInt64) {
       return true;
     }
     return object_.IsInitialized() &&
            object_.IsKnownGlobal(isolate()->heap()->the_hole_value());
   }
   bool HasNumberValue() const { return HasDoubleValue(); }
   int32_t NumberValueAsInteger32() const {
@@ skipping 3653 matching lines @@
   bool IsDeletable() const override { return true; }
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CRANKSHAFT_HYDROGEN_INSTRUCTIONS_H_