dolphin/Source/Core/Common/x64ABI.h

// Copyright 2008 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#pragma once

#include "Common/BitSet.h"
#include "Common/x64Reg.h"

// x64 ABI:s, and helpers to help follow them when JIT-ing code.
// All convensions return values in EAX (+ possibly EDX).

// Windows 64-bit
// * 4-reg "fastcall" variant, very new-skool stack handling
// * Callee moves stack pointer, to make room for shadow regs for the biggest function _it itself
// calls_
// * Parameters passed in RCX, RDX, ... further parameters are MOVed into the allocated stack space.
// Scratch:      RAX RCX RDX R8 R9 R10 R11
// Callee-save:  RBX RSI RDI RBP R12 R13 R14 R15
// Parameters:   RCX RDX R8 R9, further MOV-ed

// Linux 64-bit
// * 6-reg "fastcall" variant, old skool stack handling (parameters are pushed)
// Scratch:      RAX RCX RDX RSI RDI R8 R9 R10 R11
// Callee-save:  RBX RBP R12 R13 R14 R15
// Parameters:   RDI RSI RDX RCX R8 R9

#define ABI_ALL_FPRS BitSet32(0xffff0000)
#define ABI_ALL_GPRS BitSet32(0x0000ffff)

#ifdef _WIN32  // 64-bit Windows - the really exotic calling convention

#define ABI_PARAM1 RCX
#define ABI_PARAM2 RDX
#define ABI_PARAM3 R8
#define ABI_PARAM4 R9

// xmm0-xmm15 use the upper 16 bits in the functions that push/pop registers.
#define ABI_ALL_CALLER_SAVED                                                                       \
  (BitSet32{RAX, RCX, RDX, R8, R9, R10, R11, XMM0 + 16, XMM1 + 16, XMM2 + 16, XMM3 + 16,           \
            XMM4 + 16, XMM5 + 16})
#else  // 64-bit Unix / OS X

#define ABI_PARAM1 RDI
#define ABI_PARAM2 RSI
#define ABI_PARAM3 RDX
#define ABI_PARAM4 RCX
#define ABI_PARAM5 R8
#define ABI_PARAM6 R9

// FIXME: avoid pushing all 16 XMM registers when possible? most functions we call probably
// don't actually clobber them.
#define ABI_ALL_CALLER_SAVED (BitSet32{RAX, RCX, RDX, RDI, RSI, R8, R9, R10, R11} | ABI_ALL_FPRS)
#endif  // _WIN32

#define ABI_ALL_CALLEE_SAVED (~ABI_ALL_CALLER_SAVED)

#define ABI_RETURN RAX