/**

 * vim: set ts=4 :

 * ===============================================================

 * SourceMod, Copyright (C) 2004-2007 AlliedModders LLC. 

 * All rights reserved.

 * ===============================================================

 *

 *  This file is part of the SourceMod/SourcePawn SDK.  This file may only be 

 * used or modified under the Terms and Conditions of its License Agreement, 

 * which is found in public/licenses/LICENSE.txt.  As of this notice, derivative 

 * works must be licensed under the GNU General Public License (version 2 or 

 * greater).  A copy of the GPL is included under public/licenses/GPL.txt.

 * 

 * To view the latest information, see: http://www.sourcemod.net/license.php

 *

 * Version: $Id$

 */

#include <sm_platform.h>

#include "extension.h"

#include <jit_helpers.h>

#include <x86_macros.h>

#include "jit_call.h"

jit_uint32_t g_StackUsage = 0;

jit_uint32_t g_RegDecoder = 0;

/********************

 * Assembly Helpers *

 ********************/

inline jit_uint8_t _DecodeRegister3(jit_uint32_t val)

{

	switch (val % 3)

	{

	case 0:

		{

			return REG_EAX;

		}

	case 1:

		{

			return REG_EDX;

		}

	case 2:

		{

			return REG_ECX;

		}

	}

	/* Should never happen */

	return 0xFF;

}

/********************

 * Assembly Opcodes *

 ********************/

inline void Write_Execution_Prologue(JitWriter *jit, bool is_void, bool has_params)

{

	//push ebp

	//mov ebp, esp

	//if !is_void

	// push edi

	// mov edi, [ebp+12]

	//if has_params

	// push ebx

	// mov ebx, [ebp+8]

	IA32_Push_Reg(jit, REG_EBP);

	IA32_Mov_Reg_Rm(jit, REG_EBP, REG_ESP, MOD_REG);

	if (!is_void)

	{

		IA32_Push_Reg(jit, REG_EDI);

		IA32_Mov_Reg_Rm_Disp8(jit, REG_EDI, REG_EBP, 12);

	}

	if (has_params)

	{

		IA32_Push_Reg(jit, REG_EBX);

		IA32_Mov_Reg_Rm_Disp8(jit, REG_EBX, REG_EBP, 8);

	}

}

inline void Write_Function_Epilogue(JitWriter *jit, bool is_void, bool has_params)

{

	//if has_params

	// pop ebx

	//if !is_void

	// pop edi

	//mov esp, ebp

	//pop ebp

	//ret

	if (has_params)

	{

		IA32_Pop_Reg(jit, REG_EBX);

	}

	if (!is_void)

	{

		IA32_Pop_Reg(jit, REG_EDI);

	}

	IA32_Mov_Reg_Rm(jit, REG_ESP, REG_EBP, MOD_REG);

	IA32_Pop_Reg(jit, REG_EBP);

	IA32_Return(jit);

}

inline void Write_PushPOD(JitWriter *jit, const PassEncode *pEnc)

{

	jit_uint8_t reg = _DecodeRegister3(g_RegDecoder++);

	if (pEnc->info.flags & PASSFLAG_BYVAL)

	{

		switch (pEnc->info.size)

		{

		case 1:

			{

				//xor reg, reg

				//mov reg, BYTE PTR [ebx+<offset>]

				//push reg

				IA32_Xor_Reg_Rm(jit, reg, reg, MOD_REG);

				if (pEnc->offset < SCHAR_MAX)

				{

					IA32_Mov_Reg8_Rm8_Disp8(jit, reg, REG_EBX, (jit_int8_t)pEnc->offset);

				} else if (!pEnc->offset) {

					IA32_Mov_Reg8_Rm8(jit, reg, REG_EBX, MOD_MEM_REG);

				} else {

					IA32_Mov_Reg8_Rm8_Disp32(jit, reg, REG_EBX, pEnc->offset);

				}

				IA32_Push_Reg(jit, reg);

				g_StackUsage += 4;

				break;

			}

		case 2:

			{

				//xor reg, reg

				//mov reg, WORD PTR [ebx+<offset>]

				//push reg

				IA32_Xor_Reg_Rm(jit, reg, reg, MOD_REG);

				jit->write_ubyte(IA32_16BIT_PREFIX);

				if (pEnc->offset < SCHAR_MAX)

				{

					IA32_Mov_Reg_Rm_Disp8(jit, reg, REG_EBX, (jit_int8_t)pEnc->offset);

				} else if (!pEnc->offset) {

					IA32_Mov_Reg_Rm(jit, reg, REG_EBX, MOD_MEM_REG);

				} else {

					IA32_Mov_Reg_Rm_Disp32(jit, reg, REG_EBX, pEnc->offset);

				}

				IA32_Push_Reg(jit, reg);

				g_StackUsage += 4;

				break;

			}

		case 4:

			{

				//mov reg, DWORD PTR [ebx+<offset>]

				//push reg

				if (pEnc->offset < SCHAR_MAX)

				{

					IA32_Mov_Reg_Rm_Disp8(jit, reg, REG_EBX, (jit_int8_t)pEnc->offset);

				} else if (!pEnc->offset) {

					IA32_Mov_Reg_Rm(jit, reg, REG_EBX, MOD_MEM_REG);

				} else {

					IA32_Mov_Reg_Rm_Disp32(jit, reg, REG_EBX, pEnc->offset);

				}

				IA32_Push_Reg(jit, reg);

				g_StackUsage += 4;

				break;

			}

		case 8:

			{

				//mov reg, DWORD PTR [ebx+<offset>+4]

				//mov reg2, DWORD PTR [ebx+<offset>]

				//push reg

				//push reg2

				jit_uint8_t reg2 = _DecodeRegister3(g_RegDecoder++);

				if (pEnc->offset+4 < SCHAR_MAX)

				{

					IA32_Mov_Reg_Rm_Disp8(jit, reg, REG_EBX, (jit_int8_t)(pEnc->offset+4));

				} else {

					IA32_Mov_Reg_Rm_Disp32(jit, reg, REG_EBX, pEnc->offset+4);

				}

				if (pEnc->offset < SCHAR_MAX)

				{

					IA32_Mov_Reg_Rm_Disp8(jit, reg2, REG_EBX, (jit_int8_t)pEnc->offset);

				} else if (!pEnc->offset) {

					IA32_Mov_Reg_Rm(jit, reg, REG_EBX, MOD_MEM_REG);

				} else {

					IA32_Mov_Reg_Rm_Disp32(jit, reg2, REG_EBX, pEnc->offset);

				}

				IA32_Push_Reg(jit, reg);

				IA32_Push_Reg(jit, reg2);

				g_StackUsage += 8;

				break;

			}

		}

	} else if (pEnc->info.flags & PASSFLAG_BYREF) {

		//lea reg, [ebx+<offset>]

		//push reg

		if (!pEnc->offset)

		{

			IA32_Push_Reg(jit, REG_EBX);

			g_StackUsage += 4;

			return;

		}

		if (pEnc->offset < SCHAR_MAX)

		{

			IA32_Lea_DispRegImm8(jit, reg, REG_EBX, (jit_int8_t)pEnc->offset);

		} else {

			IA32_Lea_DispRegImm32(jit, reg, REG_EBX, pEnc->offset);

		}

		IA32_Push_Reg(jit, reg);

		g_StackUsage += 4;

	}

}

inline void Write_PushFloat(JitWriter *jit, const PassEncode *pEnc)

{

	if (pEnc->info.flags & PASSFLAG_BYVAL)

	{

		switch (pEnc->info.size)

		{

		case 4:

			{

				//fld DWORD PTR [ebx+<offset>]

				//push reg

				//fstp DWORD PTR [esp]

				if (pEnc->offset < SCHAR_MAX)

				{

					IA32_Fld_Mem32_Disp8(jit, REG_EBX, (jit_int8_t)pEnc->offset);

				} else {

					IA32_Fld_Mem32_Disp32(jit, REG_EBX, pEnc->offset);

				}

				IA32_Push_Reg(jit, _DecodeRegister3(g_RegDecoder++));

				IA32_Fstp_Mem32(jit, REG_ESP, REG_NOIDX, NOSCALE);

				g_StackUsage += 4;

				break;

			}

		case 8:

			{

				//fld QWORD PTR [ebx+<offset>]

				//sub esp, 8

				//fstp QWORD PTR [esp]

				if (pEnc->offset < SCHAR_MAX)

				{

					IA32_Fld_Mem64_Disp8(jit, REG_EBX, (jit_int8_t)pEnc->offset);

				} else {

					IA32_Fld_Mem64_Disp32(jit, REG_EBX, pEnc->offset);

				}

				IA32_Sub_Rm_Imm8(jit, REG_ESP, 8, MOD_REG);

				IA32_Fstp_Mem64(jit, REG_ESP, REG_NOIDX, NOSCALE);

				g_StackUsage += 8;

				break;

			}

		}

	} else if (pEnc->info.flags & PASSFLAG_BYREF) {

		//lea reg, [ebx+<offset>]

		//push reg

		if (!pEnc->offset)

		{

			IA32_Push_Reg(jit, REG_EBX);

			g_StackUsage += 4;

			return;

		}

		jit_uint8_t reg = _DecodeRegister3(g_RegDecoder++);

		if (pEnc->offset < SCHAR_MAX)

		{

			IA32_Lea_DispRegImm8(jit, reg, REG_EBX, (jit_int8_t)pEnc->offset);

		} else {

			IA32_Lea_DispRegImm32(jit, reg, REG_EBX, pEnc->offset);

		}

		IA32_Push_Reg(jit, reg);

		g_StackUsage += 4;

	}

}

inline void Write_PushObject(JitWriter *jit, const PassEncode *pEnc)

{

	if (pEnc->info.flags & PASSFLAG_BYVAL)

	{

#ifdef PLATFORM_POSIX

		if (pEnc->info.flags & PASSFLAG_ODTOR)

		{

			goto push_byref;

		}

#endif

		jit_uint32_t dwords = pEnc->info.size >> 2;

		jit_uint32_t bytes = pEnc->info.size & 0x3;

		//sub esp, <size>

		//cld

		//push edi

		//push esi

		//lea edi, [esp+8]

		//lea esi, [ebx+<offs>]

		//if dwords

		// mov ecx, <dwords>

		// rep movsd

		//if bytes

		// mov ecx, <bytes>

		// rep movsb

		//pop esi

		//pop edi

		if (pEnc->info.size < SCHAR_MAX)

		{

			IA32_Sub_Rm_Imm8(jit, REG_ESP, (jit_int8_t)pEnc->info.size, MOD_REG);

		} else {

			IA32_Sub_Rm_Imm32(jit, REG_ESP, pEnc->info.size, MOD_REG);

		}

		IA32_Cld(jit);

		IA32_Push_Reg(jit, REG_EDI);

		IA32_Push_Reg(jit, REG_ESI);

		IA32_Lea_Reg_DispRegMultImm8(jit, REG_EDI, REG_NOIDX, REG_ESP, NOSCALE, 8);

		if (pEnc->offset < SCHAR_MAX)

		{

			IA32_Lea_DispRegImm8(jit, REG_ESI, REG_EBX, (jit_int8_t)pEnc->offset);

		} else if (!pEnc->offset) {

			IA32_Mov_Reg_Rm(jit, REG_ESI, REG_EBX, MOD_REG);

		} else {

			IA32_Lea_DispRegImm32(jit, REG_ESI, REG_EBX, pEnc->offset);

		}

		if (dwords)

		{

			IA32_Mov_Reg_Imm32(jit, REG_ECX, dwords);

			IA32_Rep(jit);

			IA32_Movsd(jit);

		}

		if (bytes)

		{

			IA32_Mov_Reg_Imm32(jit, REG_ECX, bytes);

			IA32_Rep(jit);

			IA32_Movsb(jit);

		}

		IA32_Pop_Reg(jit, REG_ESI);

		IA32_Pop_Reg(jit, REG_EDI);

		g_StackUsage += pEnc->info.size;

	} else if (pEnc->info.flags & PASSFLAG_BYREF) {

#ifdef PLATFORM_POSIX

push_byref:

#endif

		if (!pEnc->offset)

		{

			IA32_Push_Reg(jit, REG_EBX);

			g_StackUsage += 4;

			return;

		}

		//lea reg, [ebx+<offset>]

		//push reg

		jit_uint8_t reg = _DecodeRegister3(g_RegDecoder++);

		if (pEnc->offset < SCHAR_MAX)

		{

			IA32_Lea_DispRegImm8(jit, reg, REG_EBX, (jit_int8_t)pEnc->offset);

		} else {

			IA32_Lea_DispRegImm32(jit, reg, REG_EBX, pEnc->offset);

		}

		IA32_Push_Reg(jit, reg);

		g_StackUsage += 4;

	}

}

inline void Write_PushThisPtr(JitWriter *jit)

{

#ifdef PLATFORM_POSIX

	//mov reg, [ebx]

	//push reg

	jit_uint8_t reg = _DecodeRegister3(g_RegDecoder++);

	IA32_Mov_Reg_Rm(jit, reg, REG_EBX, MOD_MEM_REG);

	IA32_Push_Reg(jit, reg);

	g_StackUsage += 4;

#elif defined PLATFORM_WINDOWS

	//mov ecx, [ebx]

	IA32_Mov_Reg_Rm(jit, REG_ECX, REG_EBX, MOD_MEM_REG);

#endif

}

inline void Write_PushRetBuffer(JitWriter *jit)

{

	//push edi

	IA32_Push_Reg(jit, REG_EDI);

}

inline void Write_CallFunction(JitWriter *jit, FuncAddrMethod method, CallWrapper *pWrapper)

{

	if (method == FuncAddr_Direct)

	{

		//call <addr>

		jitoffs_t call = IA32_Call_Imm32(jit, 0);

		IA32_Write_Jump32_Abs(jit, call, pWrapper->m_Addrs[ADDR_CALLEE]);

	} else if (method == FuncAddr_VTable) {

		//*(this + thisOffs + vtblOffs)[vtblIdx]

		//mov edx, [ebx]

		//mov eax, [edx+<thisOffs>+<vtblOffs>]

		//mov edx, [eax+<vtblIdx>*4]

		//call edx

		jit_uint32_t total_offs = pWrapper->m_VtInfo.thisOffs + pWrapper->m_VtInfo.vtblOffs;

		jit_uint32_t vfunc_pos = pWrapper->m_VtInfo.vtblIdx * 4;

		IA32_Mov_Reg_Rm(jit, REG_EDX, REG_EBX, MOD_MEM_REG);

		if (total_offs < SCHAR_MAX)

		{

			IA32_Mov_Reg_Rm_Disp8(jit, REG_EAX, REG_EDX, (jit_int8_t)total_offs);

		} else if (!total_offs) {

			IA32_Mov_Reg_Rm(jit, REG_EAX, REG_EDX, MOD_MEM_REG);

		} else {

			IA32_Mov_Reg_Rm_Disp32(jit, REG_EAX, REG_EDX, total_offs);

		}

		if (vfunc_pos < SCHAR_MAX)

		{

			IA32_Mov_Reg_Rm_Disp8(jit, REG_EDX, REG_EAX, (jit_int8_t)vfunc_pos);

		} else if (!vfunc_pos) {

			IA32_Mov_Reg_Rm(jit, REG_EDX, REG_EAX, MOD_MEM_REG);

		} else {

			IA32_Mov_Reg_Rm_Disp32(jit, REG_EDX, REG_EAX, vfunc_pos);

		}

		IA32_Call_Reg(jit, REG_EDX);

	}

}

inline void Write_RectifyStack(JitWriter *jit, jit_uint32_t value)

{

	//add esp, <value>

	if (value < SCHAR_MAX)

	{

		IA32_Add_Rm_Imm8(jit, REG_ESP, (jit_int8_t)value, MOD_REG);

	} else {

		IA32_Add_Rm_Imm32(jit, REG_ESP, value, MOD_REG);

	}

}

inline void Write_MovRet2Buf(JitWriter *jit, const PassInfo *pRet)

{

	if (pRet->type == PassType_Float)

	{

		switch (pRet->size)

		{

		case 4:

			{

				//fstp DWORD PTR [edi]

				IA32_Fstp_Mem32(jit, REG_EDI, REG_NOIDX, NOSCALE);

				break;

			}

		case 8:

			{

				//fstp QWORD PTR [edi]

				IA32_Fstp_Mem64(jit, REG_EDI, REG_NOIDX, NOSCALE);

				break;

			}

		}

		return;

	}

	switch (pRet->size)

	{

	case 1:

		{

			//mov BYTE PTR [edi], al

			IA32_Mov_Rm8_Reg8(jit, REG_EDI, REG_EAX, MOD_MEM_REG);

			break;

		}

	case 2:

		{

			//mov WORD PTR [edi], ax

			jit->write_ubyte(IA32_16BIT_PREFIX);

			IA32_Mov_Rm_Reg(jit, REG_EDI, REG_EAX, MOD_MEM_REG);

			break;

		}

	case 4:

		{

			//mov DWORD PTR [edi], eax

			IA32_Mov_Rm_Reg(jit, REG_EDI, REG_EAX, MOD_MEM_REG);

			break;

		}

	case 8:

		{

			//mov DWORD PTR [edi], eax

			//mov DWORD PTR [edi+4], edx

			IA32_Mov_Rm_Reg(jit, REG_EDI, REG_EAX, MOD_MEM_REG);

			IA32_Mov_Rm_Reg_Disp8(jit, REG_EDI, REG_EDX, 4);

			break;

		}

	}

}

/******************************

 * Assembly Compiler Function *

 ******************************/

void JIT_Compile(CallWrapper *pWrapper, FuncAddrMethod method)

{

	JitWriter writer;

	JitWriter *jit = &writer;

	jit_uint32_t CodeSize = 0;

	bool Needs_Retbuf = false;

	CallConvention Convention = pWrapper->GetCallConvention();

	jit_uint32_t ParamCount = pWrapper->GetParamCount();

	const PassInfo *pRet = pWrapper->GetReturnInfo();

	writer.outbase = NULL;

	writer.outptr = NULL;

jit_rewind:

	/* Write function prologue */

	Write_Execution_Prologue(jit, (pRet) ? false : true, (ParamCount) ? true : false);

	/* Write parameter push code */

	for (jit_int32_t i=ParamCount-1; i>=0; i--)

	{

		const PassEncode *pEnc = pWrapper->GetParamInfo(i);

		switch (pEnc->info.type)

		{

		case PassType_Basic:

			{

				Write_PushPOD(jit, pEnc);

				break;

			}

		case PassType_Float:

			{

				Write_PushFloat(jit, pEnc);

				break;

			}

		case PassType_Object:

			{

				Write_PushObject(jit, pEnc);

				break;

			}

		}

	}

	/* Prepare the this ptr if applicable */

	if (Convention == CallConv_ThisCall)

	{

		Write_PushThisPtr(jit);

	}

	/* Skip the return buffer stuff if this is a void function */

	if (!pRet)

	{

		goto skip_retbuffer;

	}

	if ((pRet->type == PassType_Object) && (pRet->flags & PASSFLAG_BYVAL))

	{

#ifdef PLATFORM_POSIX

		Needs_Retbuf = true;

#elif defined PLATFORM_WINDOWS

		if ((Convention == CallConv_ThisCall) ||

			((Convention == CallConv_Cdecl) &&

			((pRet->size > 8) || (pRet->flags & PASSFLAG_ODTOR|PASSFLAG_OCTOR|PASSFLAG_OASSIGNOP))))

		{

			Needs_Retbuf = true;

		}

#endif

	}

	/* Prepare the return buffer in case we are returning objects by value. */

	if (Needs_Retbuf)

	{

		Write_PushRetBuffer(jit);

	}

skip_retbuffer:

	/* Write the calling code */

	Write_CallFunction(jit, method, pWrapper);

	/* Clean up the calling stack */

#ifdef PLATFORM_WINDOWS

	if ((ParamCount || Needs_Retbuf) && (Convention == CallConv_Cdecl))

	{

		/* Pop all parameters from the stack + hidden return pointer */

		jit_uint32_t total = (Needs_Retbuf) ? g_StackUsage + sizeof(void *) : g_StackUsage;

		Write_RectifyStack(jit, total);