Introduce MakeSureDoubleAlignedHelper for x64 port.

src/x64/macro-assembler-x64.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_X64_MACRO_ASSEMBLER_X64_H_
 #define V8_X64_MACRO_ASSEMBLER_X64_H_
 
 #include "assembler.h"
 #include "frames.h"
 #include "v8globals.h"
@@ skipping 1464 matching lines @@
   void LeaveExitFrameEpilogue(bool restore_context);
 
   // Allocation support helpers.
   // Loads the top of new-space into the result register.
   // Otherwise the address of the new-space top is loaded into scratch (if
   // scratch is valid), and the new-space top is loaded into result.
   void LoadAllocationTopHelper(Register result,
                                Register scratch,
                                AllocationFlags flags);
 
+  void MakeSureDoubleAlignedHelper(Register result,
+                                   Register scratch,
+                                   Label* gc_required,
+                                   AllocationFlags flags);
+
   // Update allocation top with value in result_end register.
   // If scratch is valid, it contains the address of the allocation top.
   void UpdateAllocationTopHelper(Register result_end,
                                  Register scratch,
                                  AllocationFlags flags);
 
   // Helper for implementing JumpIfNotInNewSpace and JumpIfInNewSpace.
   void InNewSpace(Register object,
                   Register scratch,
                   Condition cc,
@@ skipping 104 matching lines @@
     masm->popfq();                                                           \
   }                                                                          \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_