//==- W65816CallingConv.td - Calling Conventions for W65816 -*- tablegen -*-==//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// This describes the calling conventions for the W65816 architecture.
//
// The 65816 standard C calling convention passes parameters on the stack and
// returns values in the accumulator.  Tool-call and interrupt ABIs will be
// added in a later change; only the skeleton is defined here.
//===----------------------------------------------------------------------===//

//===----------------------------------------------------------------------===//
// W65816 Return Value Calling Convention
//===----------------------------------------------------------------------===//
def RetCC_W65816 : CallingConv<[
  // i8 values are returned in the 8-bit accumulator.
  CCIfType<[i8],  CCAssignToReg<[A]>>,
  // i16 values are returned in A; for a split i32 (legalizer produces
  // two i16 returns), the second slot lands in X.  LowerReturn /
  // LowerCall hardcode the same A,X order — keep them in sync.
  CCIfType<[i16], CCAssignToReg<[A, X]>>
]>;

//===----------------------------------------------------------------------===//
// W65816 Argument Calling Convention
//===----------------------------------------------------------------------===//
def CC_W65816 : CallingConv<[
  // Pass byval aggregates on the stack.
  CCIfByVal<CCPassByVal<2, 1>>,

  // Promote i8 arguments to i16 when passed on the stack.
  CCIfType<[i8], CCPromoteToType<i16>>,

  // Integer arguments occupy 2-byte stack slots with 1-byte alignment.
  CCIfType<[i16], CCAssignToStack<2, 1>>
]>;