Introduce StackArgumentsAccessor class for X64

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index a823bf2e6d0ce6e7a919b271cda30a1a04accca5..ab1c5adb9d212abb3a65fff854771605cf021a0b 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -744,6 +744,28 @@ void Code::PatchPlatformCodeAge(byte* sequence,
 }
 
 
+Operand StackArgumentsAccessor::GetArgumentOperand(int index) {
+  ASSERT(index >= 0);
+  ASSERT(base_reg_.is(rsp) || base_reg_.is(rbp));
+  int receiver = (receiver_mode_ == ARGUMENTS_CONTAIN_RECEIVER) ? 1 : 0;
+  int displacement_to_last_argument = base_reg_.is(rsp) ?
+      kPCOnStackSize : kFPOnStackSize + kPCOnStackSize;
+  displacement_to_last_argument += extra_displacement_to_last_argument_;
+  if (argument_count_reg_.is(no_reg)) {
+    // argument[0] is at base_reg_ + displacement_to_last_argument +
+    // (argument_count_immediate_ + receiver - 1) * kPointerSize.
+    ASSERT(argument_count_immediate_ + receiver > 0);
+    return Operand(base_reg_, displacement_to_last_argument +
+        (argument_count_immediate_ + receiver - 1 - index) * kPointerSize);
+  } else {
+    // argument[0] is at base_reg_ + displacement_to_last_argument +
+    // argument_count_reg_ * times_pointer_size + (receiver - 1) * kPointerSize.
+    return Operand(base_reg_, argument_count_reg_, times_pointer_size,
+        displacement_to_last_argument + (receiver - 1 - index) * kPointerSize);
+  }
+}
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64