[turbofan] Support for %_DoubleHi, %_DoubleLo and %_ConstructDouble.

src/base/bits.h

 // Copyright 2014 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_BASE_BITS_H_
 #define V8_BASE_BITS_H_
 
 #include <stdint.h>
 #include "src/base/macros.h"
 #if V8_CC_MSVC
@@ skipping 220 matching lines @@
   return rhs ? lhs / rhs : 0u;
 }
 
 
 // UnsignedMod32(lhs, rhs) divides |lhs| by |rhs| and returns the remainder
 // truncated to uint32. If |rhs| is zero, then zero is returned.
 inline uint32_t UnsignedMod32(uint32_t lhs, uint32_t rhs) {
   return rhs ? lhs % rhs : 0u;
 }
 
+
+// InsertElement64(val, elm, off) returns |val| with the 32 bits at |off|
+// replaced by |elm|. |off| must be either 0 or 1.
+uint64_t InsertElement64(uint64_t val, uint32_t elm, uint8_t off);
+
 }  // namespace bits
 }  // namespace base
 }  // namespace v8
 
 #endif  // V8_BASE_BITS_H_