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diff --git a/src/common/abi.h b/src/common/abi.h
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+// Copyright (C) 2003 Dolphin Project.
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, version 2.0 or later versions.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License 2.0 for more details.
+
+// A copy of the GPL 2.0 should have been included with the program.
+// If not, see http://www.gnu.org/licenses/
+
+// Official SVN repository and contact information can be found at
+// http://code.google.com/p/dolphin-emu/
+
+#pragma once
+
+#include "common_types.h"
+
+// x86/x64 ABI:s, and helpers to help follow them when JIT-ing code.
+// All convensions return values in EAX (+ possibly EDX).
+
+// Linux 32-bit, Windows 32-bit (cdecl, System V):
+// * Caller pushes left to right
+// * Caller fixes stack after call
+// * function subtract from stack for local storage only.
+// Scratch:      EAX ECX EDX
+// Callee-save:  EBX ESI EDI EBP
+// Parameters:   -
+
+// 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
+
+#ifdef _M_IX86 // 32 bit calling convention, shared by all
+
+// 32-bit don't pass parameters in regs, but these are convenient to have anyway when we have to
+// choose regs to put stuff in.
+#define ABI_PARAM1 RCX
+#define ABI_PARAM2 RDX
+
+// There are no ABI_PARAM* here, since args are pushed.
+// 32-bit bog standard cdecl, shared between linux and windows
+// MacOSX 32-bit is same as System V with a few exceptions that we probably don't care much about.
+
+#elif _M_X86_64 // 64 bit calling convention
+
+#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
+
+#else  //64-bit Unix (hopefully MacOSX too)
+
+#define ABI_PARAM1 RDI
+#define ABI_PARAM2 RSI
+#define ABI_PARAM3 RDX
+#define ABI_PARAM4 RCX
+#define ABI_PARAM5 R8
+#define ABI_PARAM6 R9
+
+#endif // WIN32
+
+#endif // X86