Introduce DropUnderReturnAddress for x64 port.

src/x64/macro-assembler-x64.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 2648 matching lines @@
 }
 
 
 void MacroAssembler::Drop(int stack_elements) {
   if (stack_elements > 0) {
     addp(rsp, Immediate(stack_elements * kPointerSize));
   }
 }
 
 
+void MacroAssembler::DropUnderReturnAddress(int stack_elements,
+                                            Register scratch) {
+  ASSERT(stack_elements > 0);
+  if (kPointerSize == kInt64Size && stack_elements == 1) {
+    popq(MemOperand(rsp, 0));
+    return;
+  }
+
+  PopReturnAddressTo(scratch);
+  Drop(stack_elements);
+  PushReturnAddressFrom(scratch);
+}
+
+
 void MacroAssembler::Push(Register src) {
   if (kPointerSize == kInt64Size) {
     pushq(src);
   } else {
     ASSERT(kPointerSize == kInt32Size);
     // x32 uses 64-bit push for rbp in the prologue.
     ASSERT(src.code() != rbp.code());
     leal(rsp, Operand(rsp, -4));
     movp(Operand(rsp, 0), src);
   }
@@ skipping 2524 matching lines @@
   if (ms.shift() > 0) sarl(rdx, Immediate(ms.shift()));
   movl(rax, dividend);
   shrl(rax, Immediate(31));
   addl(rdx, rax);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64