/*
===========================================================================
Copyright (C) 1999-2005 Id Software, Inc.

This file is part of Quake III Arena source code.

Quake III Arena source code 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; either version 2 of the License,
or (at your option) any later version.

Quake III Arena source code 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 for more details.

You should have received a copy of the GNU General Public License
along with Quake III Arena source code; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/
// vm_x86.c -- load time compiler and execution environment for x86

#include "vm_local.h"
#ifdef _WIN32
#include <windows.h>
#endif

#ifdef __FreeBSD__
#include <sys/types.h>
#endif

#ifndef _WIN32
#include <sys/mman.h> // for PROT_ stuff
#endif

/* need this on NX enabled systems (i386 with PAE kernel or
 * noexec32=on x86_64) */
#ifdef __linux__
#define VM_X86_MMAP
#endif

static void VM_Destroy_Compiled(vm_t* self);

/*

  eax	scratch
  ebx	scratch
  ecx	scratch (required for shifts)
  edx	scratch (required for divisions)
  esi	program stack
  edi	opstack

*/

static	byte	*buf = NULL;
static	byte	*jused = NULL;
static	int		compiledOfs = 0;
static	byte	*code = NULL;
static	int		pc = 0;

static	int		*instructionPointers = NULL;

#define FTOL_PTR

#ifdef _MSC_VER

#if defined( FTOL_PTR )
int _ftol( float );
static	int		ftolPtr = (int)_ftol;
#endif

#else // _MSC_VER

#if defined( FTOL_PTR )

int qftol( void );
int qftol027F( void );
int qftol037F( void );
int qftol0E7F( void );
int qftol0F7F( void );


static	int		ftolPtr = (int)qftol0F7F;
#endif // FTOL_PTR

#endif

void AsmCall(void);
static void (*const asmCallPtr)(void) = AsmCall;


static	int		callMask = 0;

static	int	instruction, pass;
static	int	lastConst = 0;
static	int	oc0, oc1, pop0, pop1;

typedef enum 
{
	LAST_COMMAND_NONE	= 0,
	LAST_COMMAND_MOV_EDI_EAX,
	LAST_COMMAND_SUB_DI_4,
	LAST_COMMAND_SUB_DI_8,
} ELastCommand;

static	ELastCommand	LastCommand;

/*
=================
AsmCall
=================
*/
#ifdef _MSC_VER
__declspec( naked ) void AsmCall( void ) {
int		programStack;
int		*opStack;
int		syscallNum;
vm_t*	savedVM;

__asm {
	mov		eax, dword ptr [edi]
	sub		edi, 4
	test	eax,eax
	jl		systemCall
	// calling another vm function
	shl		eax,2
	add		eax, dword ptr [instructionPointers]
	call	dword ptr [eax]
	mov		eax, dword ptr [edi]
	and		eax, [callMask]
	ret
systemCall:

	// convert negative num to system call number
	// and store right before the first arg
	not		eax

	push    ebp
	mov     ebp, esp
	sub     esp, __LOCAL_SIZE

	mov		dword ptr syscallNum, eax	// so C code can get at it
	mov		dword ptr programStack, esi	// so C code can get at it
	mov		dword ptr opStack, edi

	push	ecx
	push	esi							// we may call recursively, so the
	push	edi							// statics aren't guaranteed to be around
}

	savedVM = currentVM;

	// save the stack to allow recursive VM entry
	currentVM->programStack = programStack - 4;
	*(int *)((byte *)currentVM->dataBase + programStack + 4) = syscallNum;
//VM_LogSyscalls(  (int *)((byte *)currentVM->dataBase + programStack + 4) );
	*(opStack+1) = currentVM->systemCall( (int *)((byte *)currentVM->dataBase + programStack + 4) );

	currentVM = savedVM;

_asm {
	pop		edi
	pop		esi
	pop		ecx
	add		edi, 4		// we added the return value

	mov     esp, ebp
	pop     ebp

	ret
}

}

#else //!_MSC_VER

#if defined(__MINGW32__) || defined(MACOS_X) // _ is prepended to compiled symbols
#	define CMANG(sym) "_"#sym
#else
#	define CMANG(sym) #sym
#endif

static void __attribute__((cdecl, used)) CallAsmCall(int const syscallNum,
		int const programStack, int* const opStack)
{
	vm_t     *const vm   = currentVM;
	intptr_t *const data = (intptr_t*)(vm->dataBase + programStack + 4);

	// save the stack to allow recursive VM entry
	vm->programStack = programStack - 4;
	*data = syscallNum;
	opStack[1] = vm->systemCall(data);

	currentVM = vm;
}

__asm__(
	".text\n\t"
	".p2align 4,,15\n\t"
#if defined __ELF__
	".type " CMANG(AsmCall) ", @function\n"
#endif
	CMANG(AsmCall) ":\n\t"
	"movl  (%edi), %eax\n\t"
	"subl  $4, %edi\n\t"
	"testl %eax, %eax\n\t"
	"jl    0f\n\t"
	"shll  $2, %eax\n\t"
	"addl  " CMANG(instructionPointers) ", %eax\n\t"
	"call  *(%eax)\n\t"
	"movl  (%edi), %eax\n\t"
	"andl  " CMANG(callMask) ", %eax\n\t"
	"ret\n"
	"0:\n\t" // system call
	"notl  %eax\n\t"
	"pushl %ecx\n\t"
	"pushl %edi\n\t" // opStack
	"pushl %esi\n\t" // programStack
	"pushl %eax\n\t" // syscallNum
	"call  " CMANG(CallAsmCall) "\n\t"
	"addl  $12, %esp\n\t"
	"popl  %ecx\n\t"
	"addl  $4, %edi\n\t"
	"ret\n\t"
#if defined __ELF__
	".size " CMANG(AsmCall)", .-" CMANG(AsmCall)
#endif
);

#endif

static int	Constant4( void ) {
	int		v;

	v = code[pc] | (code[pc+1]<<8) | (code[pc+2]<<16) | (code[pc+3]<<24);
	pc += 4;
	return v;
}

static int	Constant1( void ) {
	int		v;

	v = code[pc];
	pc += 1;
	return v;
}

static void Emit1( int v ) 
{
	buf[ compiledOfs ] = v;
	compiledOfs++;

	LastCommand = LAST_COMMAND_NONE;
}

#if 0
static void Emit2( int v ) {
	Emit1( v & 255 );
	Emit1( ( v >> 8 ) & 255 );
}
#endif

static void Emit4( int v ) {
	Emit1( v & 255 );
	Emit1( ( v >> 8 ) & 255 );
	Emit1( ( v >> 16 ) & 255 );
	Emit1( ( v >> 24 ) & 255 );
}

static int Hex( int c ) {
	if ( c >= 'a' && c <= 'f' ) {
		return 10 + c - 'a';
	}
	if ( c >= 'A' && c <= 'F' ) {
		return 10 + c - 'A';
	}
	if ( c >= '0' && c <= '9' ) {
		return c - '0';
	}

	Com_Error( ERR_DROP, "Hex: bad char '%c'", c );

	return 0;
}
static void EmitString( const char *string ) {
	int		c1, c2;
	int		v;

	while ( 1 ) {
		c1 = string[0];
		c2 = string[1];

		v = ( Hex( c1 ) << 4 ) | Hex( c2 );
		Emit1( v );

		if ( !string[2] ) {
			break;
		}
		string += 3;
	}
}



static void EmitCommand(ELastCommand command)
{
	switch(command)
	{
		case LAST_COMMAND_MOV_EDI_EAX:
			EmitString( "89 07" );		// mov dword ptr [edi], eax
			break;

		case LAST_COMMAND_SUB_DI_4:
			EmitString( "83 EF 04" );	// sub edi, 4
			break;

		case LAST_COMMAND_SUB_DI_8:
			EmitString( "83 EF 08" );	// sub edi, 8
			break;
		default:
			break;
	}
	LastCommand = command;
}

static void EmitAddEDI4(vm_t *vm) {
	if (LastCommand == LAST_COMMAND_SUB_DI_4 && jused[instruction-1] == 0) 
	{		// sub di,4
		compiledOfs -= 3;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		return;
	}
	if (LastCommand == LAST_COMMAND_SUB_DI_8 && jused[instruction-1] == 0) 
	{		// sub di,8
		compiledOfs -= 3;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		EmitString( "83 EF 04" );	//	sub edi,4
		return;
	}
	EmitString( "83 C7 04" );	//	add edi,4
}

static void EmitMovEAXEDI(vm_t *vm) {
	if (LastCommand == LAST_COMMAND_MOV_EDI_EAX) 
	{	// mov [edi], eax
		compiledOfs -= 2;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		return;
	}
	if (pop1 == OP_DIVI || pop1 == OP_DIVU || pop1 == OP_MULI || pop1 == OP_MULU ||
		pop1 == OP_STORE4 || pop1 == OP_STORE2 || pop1 == OP_STORE1 ) 
	{	
		return;
	}
	if (pop1 == OP_CONST && buf[compiledOfs-6] == 0xC7 && buf[compiledOfs-5] == 0x07 ) 
	{	// mov edi, 0x123456
		compiledOfs -= 6;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		EmitString( "B8" );			// mov	eax, 0x12345678
		Emit4( lastConst );
		return;
	}
	EmitString( "8B 07" );		// mov eax, dword ptr [edi]
}

qboolean EmitMovEBXEDI(vm_t *vm, int andit) {
	if (LastCommand == LAST_COMMAND_MOV_EDI_EAX) 
	{	// mov [edi], eax
		compiledOfs -= 2;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		EmitString( "8B D8");		// mov bx, eax
		return qfalse;
	}
	if (pop1 == OP_DIVI || pop1 == OP_DIVU || pop1 == OP_MULI || pop1 == OP_MULU ||
		pop1 == OP_STORE4 || pop1 == OP_STORE2 || pop1 == OP_STORE1 ) 
	{	
		EmitString( "8B D8");		// mov bx, eax
		return qfalse;
	}
	if (pop1 == OP_CONST && buf[compiledOfs-6] == 0xC7 && buf[compiledOfs-5] == 0x07 ) 
	{		// mov edi, 0x123456
		compiledOfs -= 6;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		EmitString( "BB" );			// mov	ebx, 0x12345678
		if (andit) {
			Emit4( lastConst & andit );
		} else {
			Emit4( lastConst );
		}
		return qtrue;
	}

	EmitString( "8B 1F" );		// mov ebx, dword ptr [edi]
	return qfalse;
}

/*
=================
VM_Compile
=================
*/
void VM_Compile( vm_t *vm, vmHeader_t *header ) {
	int		op;
	int		maxLength;
	int		v;
	int		i;
	qboolean opt;

	// allocate a very large temp buffer, we will shrink it later
	maxLength = header->codeLength * 8;
	buf = Z_Malloc( maxLength );
	jused = Z_Malloc(header->instructionCount + 2 );
	
	Com_Memset(jused, 0, header->instructionCount+2);

	// ensure that the optimisation pass knows about all the jump
	// table targets
	for( i = 0; i < vm->numJumpTableTargets; i++ ) {
		jused[ *(int *)(vm->jumpTableTargets + ( i * sizeof( int ) ) ) ] = 1;
	}

	for(pass=0;pass<2;pass++) {
	oc0 = -23423;
	oc1 = -234354;
	pop0 = -43435;
	pop1 = -545455;

	// translate all instructions
	pc = 0;
	instruction = 0;
	code = (byte *)header + header->codeOffset;
	compiledOfs = 0;

	LastCommand = LAST_COMMAND_NONE;

	while ( instruction < header->instructionCount ) {
		if ( compiledOfs > maxLength - 16 ) {
			Com_Error( ERR_FATAL, "VM_CompileX86: maxLength exceeded" );
		}

		vm->instructionPointers[ instruction ] = compiledOfs;
		instruction++;

		if ( pc > header->codeLength ) {
			Com_Error( ERR_FATAL, "VM_CompileX86: pc > header->codeLength" );
		}

		op = code[ pc ];
		pc++;
		switch ( op ) {
		case 0:
			break;
		case OP_BREAK:
			EmitString( "CC" );			// int 3
			break;
		case OP_ENTER:
			EmitString( "81 EE" );		// sub	esi, 0x12345678
			Emit4( Constant4() );
			break;
		case OP_CONST:
			if (code[pc+4] == OP_LOAD4) {
				EmitAddEDI4(vm);
				EmitString( "BB" );		// mov	ebx, 0x12345678
				Emit4( (Constant4()&vm->dataMask) + (int)vm->dataBase);
				EmitString( "8B 03" );		// mov	eax, dword ptr [ebx]
				EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
				pc++;						// OP_LOAD4
				instruction += 1;
				break;
			}
			if (code[pc+4] == OP_LOAD2) {
				EmitAddEDI4(vm);
				EmitString( "BB" );		// mov	ebx, 0x12345678
				Emit4( (Constant4()&vm->dataMask) + (int)vm->dataBase);
				EmitString( "0F B7 03" );	// movzx	eax, word ptr [ebx]
				EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
				pc++;						// OP_LOAD4
				instruction += 1;
				break;
			}
			if (code[pc+4] == OP_LOAD1) {
				EmitAddEDI4(vm);
				EmitString( "BB" );		// mov	ebx, 0x12345678
				Emit4( (Constant4()&vm->dataMask) + (int)vm->dataBase);
				EmitString( "0F B6 03" );	// movzx	eax, byte ptr [ebx]
				EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
				pc++;						// OP_LOAD4
				instruction += 1;
				break;
			}
			if (code[pc+4] == OP_STORE4) {
				opt = EmitMovEBXEDI(vm, (vm->dataMask & ~3));
				EmitString( "B8" );			// mov	eax, 0x12345678
				Emit4( Constant4() );
//				if (!opt) {
//					EmitString( "81 E3" );		// and ebx, 0x12345678
//					Emit4( vm->dataMask & ~3 );
//				}
				EmitString( "89 83" );		// mov dword ptr [ebx+0x12345678], eax
				Emit4( (int)vm->dataBase );
				EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
				pc++;						// OP_STORE4
				instruction += 1;
				break;
			}
			if (code[pc+4] == OP_STORE2) {
				opt = EmitMovEBXEDI(vm, (vm->dataMask & ~1));
				EmitString( "B8" );			// mov	eax, 0x12345678
				Emit4( Constant4() );
//				if (!opt) {
//					EmitString( "81 E3" );		// and ebx, 0x12345678
//					Emit4( vm->dataMask & ~1 );
//				}
				EmitString( "66 89 83" );	// mov word ptr [ebx+0x12345678], eax
				Emit4( (int)vm->dataBase );
				EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
				pc++;						// OP_STORE4
				instruction += 1;
				break;
			}
			if (code[pc+4] == OP_STORE1) {
				opt = EmitMovEBXEDI(vm, vm->dataMask);
				EmitString( "B8" );			// mov	eax, 0x12345678
				Emit4( Constant4() );
//				if (!opt) {
//					EmitString( "81 E3" );	// and ebx, 0x12345678
//					Emit4( vm->dataMask );
//				}
				EmitString( "88 83" );		// mov byte ptr [ebx+0x12345678], eax
				Emit4( (int)vm->dataBase );
				EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
				pc++;						// OP_STORE4
				instruction += 1;
				break;
			}
			if (code[pc+4] == OP_ADD) {
				EmitString( "81 07" );		// add dword ptr [edi], 0x1234567
				Emit4( Constant4() );
				pc++;						// OP_ADD
				instruction += 1;
				break;
			}
			if (code[pc+4] == OP_SUB) {
				EmitString( "81 2F" );		// sub dword ptr [edi], 0x1234567
				Emit4( Constant4() );
				pc++;						// OP_ADD
				instruction += 1;
				break;
			}
			EmitAddEDI4(vm);
			EmitString( "C7 07" );		// mov	dword ptr [edi], 0x12345678
			lastConst = Constant4();
			Emit4( lastConst );
			if (code[pc] == OP_JUMP) {
				jused[lastConst] = 1;
			}
			break;
		case OP_LOCAL:
			EmitAddEDI4(vm);
			EmitString( "8D 86" );		// lea eax, [0x12345678 + esi]
			oc0 = oc1;
			oc1 = Constant4();
			Emit4( oc1 );
			EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
			break;
		case OP_ARG:
			EmitMovEAXEDI(vm);			// mov	eax,dword ptr [edi]
			EmitString( "89 86" );		// mov	dword ptr [esi+database],eax
			// FIXME: range check
			Emit4( Constant1() + (int)vm->dataBase );
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_CALL:
			EmitString( "C7 86" );		// mov dword ptr [esi+database],0x12345678
			Emit4( (int)vm->dataBase );
			Emit4( pc );
			EmitString( "FF 15" );		// call asmCallPtr
			Emit4( (int)&asmCallPtr );
			break;
		case OP_PUSH:
			EmitAddEDI4(vm);
			break;
		case OP_POP:
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_LEAVE:
			v = Constant4();
			EmitString( "81 C6" );		// add	esi, 0x12345678
			Emit4( v );
			EmitString( "C3" );			// ret
			break;
		case OP_LOAD4:
			if (code[pc] == OP_CONST && code[pc+5] == OP_ADD && code[pc+6] == OP_STORE4) {
				if (oc0 == oc1 && pop0 == OP_LOCAL && pop1 == OP_LOCAL) {
					compiledOfs -= 11;
					vm->instructionPointers[ instruction-1 ] = compiledOfs;
				}
				pc++;						// OP_CONST
				v = Constant4();
				EmitMovEBXEDI(vm, vm->dataMask);
				if (v == 1 && oc0 == oc1 && pop0 == OP_LOCAL && pop1 == OP_LOCAL) {
					EmitString( "FF 83");		// inc dword ptr [ebx + 0x12345678]
					Emit4( (int)vm->dataBase );
				} else {
					EmitString( "8B 83" );		// mov	eax, dword ptr [ebx + 0x12345678]
					Emit4( (int)vm->dataBase );
					EmitString( "05"  );		// add eax, const
					Emit4( v );
					if (oc0 == oc1 && pop0 == OP_LOCAL && pop1 == OP_LOCAL) {
						EmitString( "89 83" );		// mov dword ptr [ebx+0x12345678], eax
						Emit4( (int)vm->dataBase );
					} else {
						EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
						EmitString( "8B 1F" );		// mov	ebx, dword ptr [edi]
						EmitString( "89 83" );		// mov dword ptr [ebx+0x12345678], eax
						Emit4( (int)vm->dataBase );
					}
				}
				EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
				pc++;						// OP_ADD
				pc++;						// OP_STORE
				instruction += 3;
				break;
			}

			if (code[pc] == OP_CONST && code[pc+5] == OP_SUB && code[pc+6] == OP_STORE4) {
				if (oc0 == oc1 && pop0 == OP_LOCAL && pop1 == OP_LOCAL) {
					compiledOfs -= 11;
					vm->instructionPointers[ instruction-1 ] = compiledOfs;
				}
				EmitMovEBXEDI(vm, vm->dataMask);
				EmitString( "8B 83" );		// mov	eax, dword ptr [ebx + 0x12345678]
				Emit4( (int)vm->dataBase );
				pc++;						// OP_CONST
				v = Constant4();
				if (v == 1 && oc0 == oc1 && pop0 == OP_LOCAL && pop1 == OP_LOCAL) {
					EmitString( "FF 8B");		// dec dword ptr [ebx + 0x12345678]
					Emit4( (int)vm->dataBase );
				} else {
					EmitString( "2D"  );		// sub eax, const
					Emit4( v );
					if (oc0 == oc1 && pop0 == OP_LOCAL && pop1 == OP_LOCAL) {
						EmitString( "89 83" );		// mov dword ptr [ebx+0x12345678], eax
						Emit4( (int)vm->dataBase );
					} else {
						EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
						EmitString( "8B 1F" );		// mov	ebx, dword ptr [edi]
						EmitString( "89 83" );		// mov dword ptr [ebx+0x12345678], eax
						Emit4( (int)vm->dataBase );
					}
				}
				EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
				pc++;						// OP_SUB
				pc++;						// OP_STORE
				instruction += 3;
				break;
			}

			if (buf[compiledOfs-2] == 0x89 && buf[compiledOfs-1] == 0x07) {
				compiledOfs -= 2;
				vm->instructionPointers[ instruction-1 ] = compiledOfs;
				EmitString( "8B 80");	// mov eax, dword ptr [eax + 0x1234567]
				Emit4( (int)vm->dataBase );
				EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
				break;
			}
			EmitMovEBXEDI(vm, vm->dataMask);
			EmitString( "8B 83" );		// mov	eax, dword ptr [ebx + 0x12345678]
			Emit4( (int)vm->dataBase );
			EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
			break;
		case OP_LOAD2:
			EmitMovEBXEDI(vm, vm->dataMask);
			EmitString( "0F B7 83" );	// movzx	eax, word ptr [ebx + 0x12345678]
			Emit4( (int)vm->dataBase );
			EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
			break;
		case OP_LOAD1:
			EmitMovEBXEDI(vm, vm->dataMask);
			EmitString( "0F B6 83" );	// movzx eax, byte ptr [ebx + 0x12345678]
			Emit4( (int)vm->dataBase );
			EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
			break;
		case OP_STORE4:
			EmitMovEAXEDI(vm);	
			EmitString( "8B 5F FC" );	// mov	ebx, dword ptr [edi-4]
//			if (pop1 != OP_CALL) {
//				EmitString( "81 E3" );		// and ebx, 0x12345678
//				Emit4( vm->dataMask & ~3 );
//			}
			EmitString( "89 83" );		// mov dword ptr [ebx+0x12345678], eax
			Emit4( (int)vm->dataBase );
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			break;
		case OP_STORE2:
			EmitMovEAXEDI(vm);	
			EmitString( "8B 5F FC" );	// mov	ebx, dword ptr [edi-4]
//			EmitString( "81 E3" );		// and ebx, 0x12345678
//			Emit4( vm->dataMask & ~1 );
			EmitString( "66 89 83" );	// mov word ptr [ebx+0x12345678], eax
			Emit4( (int)vm->dataBase );
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			break;
		case OP_STORE1:
			EmitMovEAXEDI(vm);	
			EmitString( "8B 5F FC" );	// mov	ebx, dword ptr [edi-4]
//			EmitString( "81 E3" );		// and ebx, 0x12345678
//			Emit4( vm->dataMask );
			EmitString( "88 83" );		// mov byte ptr [ebx+0x12345678], eax
			Emit4( (int)vm->dataBase );
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			break;

		case OP_EQ:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "75 06" );		// jne +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_NE:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "74 06" );		// je +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LTI:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "7D 06" );		// jnl +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LEI:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "7F 06" );		// jnle +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GTI:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "7E 06" );		// jng +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GEI:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "7C 06" );		// jnge +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LTU:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "73 06" );		// jnb +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LEU:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "77 06" );		// jnbe +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GTU:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "76 06" );		// jna +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GEU:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "8B 47 04" );	// mov	eax, dword ptr [edi+4]
			EmitString( "3B 47 08" );	// cmp	eax, dword ptr [edi+8]
			EmitString( "72 06" );		// jnae +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_EQF:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "D9 47 04" );	// fld dword ptr [edi+4]
			EmitString( "D8 5F 08" );	// fcomp dword ptr [edi+8]
			EmitString( "DF E0" );		// fnstsw ax
			EmitString( "F6 C4 40" );	// test	ah,0x40
			EmitString( "74 06" );		// je +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;			
		case OP_NEF:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "D9 47 04" );	// fld dword ptr [edi+4]
			EmitString( "D8 5F 08" );	// fcomp dword ptr [edi+8]
			EmitString( "DF E0" );		// fnstsw ax
			EmitString( "F6 C4 40" );	// test	ah,0x40
			EmitString( "75 06" );		// jne +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;			
		case OP_LTF:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "D9 47 04" );	// fld dword ptr [edi+4]
			EmitString( "D8 5F 08" );	// fcomp dword ptr [edi+8]
			EmitString( "DF E0" );		// fnstsw ax
			EmitString( "F6 C4 01" );	// test	ah,0x01
			EmitString( "74 06" );		// je +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;			
		case OP_LEF:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "D9 47 04" );	// fld dword ptr [edi+4]
			EmitString( "D8 5F 08" );	// fcomp dword ptr [edi+8]
			EmitString( "DF E0" );		// fnstsw ax
			EmitString( "F6 C4 41" );	// test	ah,0x41
			EmitString( "74 06" );		// je +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;			
		case OP_GTF:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "D9 47 04" );	// fld dword ptr [edi+4]
			EmitString( "D8 5F 08" );	// fcomp dword ptr [edi+8]
			EmitString( "DF E0" );		// fnstsw ax
			EmitString( "F6 C4 41" );	// test	ah,0x41
			EmitString( "75 06" );		// jne +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;			
		case OP_GEF:
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "D9 47 04" );	// fld dword ptr [edi+4]
			EmitString( "D8 5F 08" );	// fcomp dword ptr [edi+8]
			EmitString( "DF E0" );		// fnstsw ax
			EmitString( "F6 C4 01" );	// test	ah,0x01
			EmitString( "75 06" );		// jne +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			jused[v] = 1;
			Emit4( (int)vm->instructionPointers + v*4 );
			break;			
		case OP_NEGI:
			EmitString( "F7 1F" );		// neg dword ptr [edi]
			break;
		case OP_ADD:
			EmitMovEAXEDI(vm);			// mov eax, dword ptr [edi]
			EmitString( "01 47 FC" );	// add dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_SUB:
			EmitMovEAXEDI(vm);			// mov eax, dword ptr [edi]
			EmitString( "29 47 FC" );	// sub dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_DIVI:
			EmitString( "8B 47 FC" );	// mov eax,dword ptr [edi-4]
			EmitString( "99" );			// cdq
			EmitString( "F7 3F" );		// idiv dword ptr [edi]
			EmitString( "89 47 FC" );	// mov dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_DIVU:
			EmitString( "8B 47 FC" );	// mov eax,dword ptr [edi-4]
			EmitString( "33 D2" );		// xor edx, edx
			EmitString( "F7 37" );		// div dword ptr [edi]
			EmitString( "89 47 FC" );	// mov dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_MODI:
			EmitString( "8B 47 FC" );	// mov eax,dword ptr [edi-4]
			EmitString( "99" );			// cdq
			EmitString( "F7 3F" );		// idiv dword ptr [edi]
			EmitString( "89 57 FC" );	// mov dword ptr [edi-4],edx
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_MODU:
			EmitString( "8B 47 FC" );	// mov eax,dword ptr [edi-4]
			EmitString( "33 D2" );		// xor edx, edx
			EmitString( "F7 37" );		// div dword ptr [edi]
			EmitString( "89 57 FC" );	// mov dword ptr [edi-4],edx
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_MULI:
			EmitString( "8B 47 FC" );	// mov eax,dword ptr [edi-4]
			EmitString( "F7 2F" );		// imul dword ptr [edi]
			EmitString( "89 47 FC" );	// mov dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_MULU:
			EmitString( "8B 47 FC" );	// mov eax,dword ptr [edi-4]
			EmitString( "F7 27" );		// mul dword ptr [edi]
			EmitString( "89 47 FC" );	// mov dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_BAND:
			EmitMovEAXEDI(vm);			// mov eax, dword ptr [edi]
			EmitString( "21 47 FC" );	// and dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_BOR:
			EmitMovEAXEDI(vm);			// mov eax, dword ptr [edi]
			EmitString( "09 47 FC" );	// or dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_BXOR:
			EmitMovEAXEDI(vm);			// mov eax, dword ptr [edi]
			EmitString( "31 47 FC" );	// xor dword ptr [edi-4],eax
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_BCOM:
			EmitString( "F7 17" );		// not dword ptr [edi]
			break;
		case OP_LSH:
			EmitString( "8B 0F" );		// mov ecx, dword ptr [edi]
			EmitString( "D3 67 FC" );	// shl dword ptr [edi-4], cl
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_RSHI:
			EmitString( "8B 0F" );		// mov ecx, dword ptr [edi]
			EmitString( "D3 7F FC" );	// sar dword ptr [edi-4], cl
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_RSHU:
			EmitString( "8B 0F" );		// mov ecx, dword ptr [edi]
			EmitString( "D3 6F FC" );	// shr dword ptr [edi-4], cl
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_NEGF:
			EmitString( "D9 07" );		// fld dword ptr [edi]
			EmitString( "D9 E0" );		// fchs
			EmitString( "D9 1F" );		// fstp dword ptr [edi]
			break;
		case OP_ADDF:
			EmitString( "D9 47 FC" );	// fld dword ptr [edi-4]
			EmitString( "D8 07" );		// fadd dword ptr [edi]
			EmitString( "D9 5F FC" );	// fstp dword ptr [edi-4]
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_SUBF:
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			EmitString( "D9 07" );		// fld dword ptr [edi]
			EmitString( "D8 67 04" );	// fsub dword ptr [edi+4]
			EmitString( "D9 1F" );		// fstp dword ptr [edi]
			break;
		case OP_DIVF:
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			EmitString( "D9 07" );		// fld dword ptr [edi]
			EmitString( "D8 77 04" );	// fdiv dword ptr [edi+4]
			EmitString( "D9 1F" );		// fstp dword ptr [edi]
			break;
		case OP_MULF:
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			EmitString( "D9 07" );		// fld dword ptr [edi]
			EmitString( "D8 4f 04" );	// fmul dword ptr [edi+4]
			EmitString( "D9 1F" );		// fstp dword ptr [edi]
			break;
		case OP_CVIF:
			EmitString( "DB 07" );		// fild dword ptr [edi]
			EmitString( "D9 1F" );		// fstp dword ptr [edi]
			break;
		case OP_CVFI:
#ifndef FTOL_PTR // WHENHELLISFROZENOVER
			// not IEEE complient, but simple and fast
			EmitString( "D9 07" );		// fld dword ptr [edi]
			EmitString( "DB 1F" );		// fistp dword ptr [edi]
#else // FTOL_PTR
			// call the library conversion function
			EmitString( "D9 07" );		// fld dword ptr [edi]
			EmitString( "FF 15" );		// call ftolPtr
			Emit4( (int)&ftolPtr );
			EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
#endif
			break;
		case OP_SEX8:
			EmitString( "0F BE 07" );	// movsx eax, byte ptr [edi]
			EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
			break;
		case OP_SEX16:
			EmitString( "0F BF 07" );	// movsx eax, word ptr [edi]
			EmitCommand(LAST_COMMAND_MOV_EDI_EAX);		// mov dword ptr [edi], eax
			break;

		case OP_BLOCK_COPY:
			// FIXME: range check
			EmitString( "56" );			// push esi
			EmitString( "57" );			// push edi
			EmitString( "8B 37" );		// mov esi,[edi] 
			EmitString( "8B 7F FC" );	// mov edi,[edi-4] 
			EmitString( "B9" );			// mov ecx,0x12345678
			Emit4( Constant4() >> 2 );
			EmitString( "B8" );			// mov eax, datamask
			Emit4( vm->dataMask );
			EmitString( "BB" );			// mov ebx, database
			Emit4( (int)vm->dataBase );
			EmitString( "23 F0" );		// and esi, eax
			EmitString( "03 F3" );		// add esi, ebx
			EmitString( "23 F8" );		// and edi, eax
			EmitString( "03 FB" );		// add edi, ebx
			EmitString( "F3 A5" );		// rep movsd
			EmitString( "5F" );			// pop edi
			EmitString( "5E" );			// pop esi
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			break;

		case OP_JUMP:
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			EmitString( "8B 47 04" );	// mov eax,dword ptr [edi+4]
			// FIXME: range check
			EmitString( "FF 24 85" );	// jmp dword ptr [instructionPointers + eax * 4]
			Emit4( (int)vm->instructionPointers );
			break;
		default:
			Com_Error( ERR_DROP, "VM_CompileX86: bad opcode %i at offset %i", op, pc );
		}
		pop0 = pop1;
		pop1 = op;
	}
	}

	// copy to an exact size buffer on the hunk
	vm->codeLength = compiledOfs;
#ifdef VM_X86_MMAP
	vm->codeBase = mmap(NULL, compiledOfs, PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
	if(vm->codeBase == (void*)-1)
		Com_Error(ERR_DROP, "VM_CompileX86: can't mmap memory");
#elif _WIN32
	// allocate memory with EXECUTE permissions under windows.
	vm->codeBase = VirtualAlloc(NULL, compiledOfs, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
	if(!vm->codeBase)
		Com_Error(ERR_DROP, "VM_CompileX86: VirtualAlloc failed");
#else
	vm->codeBase = malloc(compiledOfs);
#endif

	Com_Memcpy( vm->codeBase, buf, compiledOfs );

#ifdef VM_X86_MMAP
	if(mprotect(vm->codeBase, compiledOfs, PROT_READ|PROT_EXEC))
		Com_Error(ERR_DROP, "VM_CompileX86: mprotect failed");
#elif _WIN32
	{
		DWORD oldProtect = 0;
		
		// remove write permissions.
		if(!VirtualProtect(vm->codeBase, compiledOfs, PAGE_EXECUTE_READ, &oldProtect))
			Com_Error(ERR_DROP, "VM_CompileX86: VirtualProtect failed");
	}
#endif

	Z_Free( buf );
	Z_Free( jused );
	Com_Printf( "VM file %s compiled to %i bytes of code\n", vm->name, compiledOfs );

	vm->destroy = VM_Destroy_Compiled;

	// offset all the instruction pointers for the new location
	for ( i = 0 ; i < header->instructionCount ; i++ ) {
		vm->instructionPointers[i] += (int)vm->codeBase;
	}
}

void VM_Destroy_Compiled(vm_t* self)
{
#ifdef VM_X86_MMAP
	munmap(self->codeBase, self->codeLength);
#elif _WIN32
	VirtualFree(self->codeBase, 0, MEM_RELEASE);
#else
	free(self->codeBase);
#endif
}

/*
==============
VM_CallCompiled

This function is called directly by the generated code
==============
*/
int	VM_CallCompiled( vm_t *vm, int *args ) {
	int		stack[1024];
	int		programCounter;
	int		programStack;
	int		stackOnEntry;
	byte	*image;
	void	*opStack;
	int		*oldInstructionPointers;

	oldInstructionPointers = instructionPointers;

	currentVM = vm;
	instructionPointers = vm->instructionPointers;

	// interpret the code
	vm->currentlyInterpreting = qtrue;

	callMask = vm->dataMask;

	// we might be called recursively, so this might not be the very top
	programStack = vm->programStack;
	stackOnEntry = programStack;

	// set up the stack frame 
	image = vm->dataBase;

	programCounter = 0;

	programStack -= 48;

	*(int *)&image[ programStack + 44] = args[9];
	*(int *)&image[ programStack + 40] = args[8];
	*(int *)&image[ programStack + 36] = args[7];
	*(int *)&image[ programStack + 32] = args[6];
	*(int *)&image[ programStack + 28] = args[5];
	*(int *)&image[ programStack + 24] = args[4];
	*(int *)&image[ programStack + 20] = args[3];
	*(int *)&image[ programStack + 16] = args[2];
	*(int *)&image[ programStack + 12] = args[1];
	*(int *)&image[ programStack + 8 ] = args[0];
	*(int *)&image[ programStack + 4 ] = 0;	// return stack
	*(int *)&image[ programStack ] = -1;	// will terminate the loop on return

	// off we go into generated code...
	opStack = &stack;

	{
#ifdef _MSC_VER
		void *entryPoint = vm->codeBase;

		__asm {
			pushad
			mov    esi, programStack
			mov    edi, opStack
			call   entryPoint
			mov    programStack, esi
			mov    opStack, edi
			popad
		}
#else
		/* These registers are used as scratch registers and are destroyed after the
		 * call.  Do not use clobber, so they can be used as input for the asm. */
		unsigned eax;
		unsigned ebx;
		unsigned ecx;
		unsigned edx;

		__asm__ volatile(
			"call *%6"
			: "+S" (programStack), "+D" (opStack),
			  "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
			: "mr" (vm->codeBase)
			: "cc", "memory"
		);
#endif
	}

	if ( opStack != &stack[1] ) {
		Com_Error( ERR_DROP, "opStack corrupted in compiled code" );
	}
	if ( programStack != stackOnEntry - 48 ) {
		Com_Error( ERR_DROP, "programStack corrupted in compiled code" );
	}

	vm->programStack = stackOnEntry;

	// in case we were recursively called by another vm
	instructionPointers = oldInstructionPointers;

	return *(int *)opStack;
}

