ioq3/code/qcommon/vm_x86.c

/*
===========================================================================
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) */
#if defined(__linux__) || defined(__FreeBSD__)
#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

*/

#define VMFREE_BUFFERS() do {Z_Free(buf); Z_Free(jused);} while(0)
static	byte	*buf = NULL;
static	byte	*jused = NULL;
static	int		jusedSize = 0;
static	int		compiledOfs = 0;
static	byte	*code = NULL;
static	int		pc = 0;

#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

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

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;

static void ErrJump( void ) 
{ 
	Com_Error( ERR_DROP, "program tried to execute code outside VM\n" ); 
	exit(1);
}

static void (*const errJumpPtr)(void) = ErrJump;

static int NextConstant4(void)
{
	return (code[pc] | (code[pc+1]<<8) | (code[pc+2]<<16) | (code[pc+3]<<24));
}

static int	Constant4( void ) {
	int		v;

	v = NextConstant4();
	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';
	}

	VMFREE_BUFFERS();
	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 ( jlabel ) {
		EmitString( "83 C7 04" );	//	add edi,4
		return;
	}
	if ( LastCommand == LAST_COMMAND_SUB_DI_4 ) 
	{	// sub edi, 4
		compiledOfs -= 3;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		return;
	}
	if ( LastCommand == LAST_COMMAND_SUB_DI_8 ) 
	{	// sub edi, 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 ( jlabel ) {
		EmitString( "8B 07" );		// mov eax, dword ptr [edi]
		return;
	}
	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]
}

void EmitMovECXEDI( vm_t *vm ) {
	if ( jlabel ) {
		EmitString( "8B 0F" );		// mov ecx, dword ptr [edi]
		return;
	}
	if ( LastCommand == LAST_COMMAND_MOV_EDI_EAX ) // mov [edi], eax
	{
		compiledOfs -= 2;
		vm->instructionPointers[ instruction-1 ] = compiledOfs;
		EmitString( "89 C1" );		// mov ecx, eax
		return;
	}
	if (pop1 == OP_DIVI || pop1 == OP_DIVU || pop1 == OP_MULI || pop1 == OP_MULU ||
		pop1 == OP_STORE4 || pop1 == OP_STORE2 || pop1 == OP_STORE1 ) 
	{	
		EmitString( "89 C1" );		// mov ecx, eax
		return;
	}
	EmitString( "8B 0F" );		    // mov ecx, dword ptr [edi]
}


qboolean EmitMovEBXEDI(vm_t *vm, int andit) {
	if ( jlabel ) {
		EmitString( "8B 1F" );		// mov ebx, dword ptr [edi]
		return qfalse;
	}
	if ( LastCommand == LAST_COMMAND_MOV_EDI_EAX ) 
	{	// mov dword ptr [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 dword ptr [edi], 0x12345678
		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;
}

#define JUSED(x) \
	do { \
		if (x < 0 || x >= jusedSize) { \
		        VMFREE_BUFFERS(); \
			Com_Error( ERR_DROP, \
					"VM_CompileX86: jump target out of range at offset %d", pc ); \
		} \
		jused[x] = 1; \
	} while(0)

#define SET_JMPOFS(x) do { buf[(x)] = compiledOfs - ((x) + 1); } while(0)

/*
=================
DoSyscall
Uses asm to retrieve arguments from registers to work around different calling conventions
=================
*/

static void DoSyscall(void)
{
        vm_t *savedVM;
	int *data;

	int syscallNum;
	int programStack;
	int *opStack;
	
#ifdef _MSC_VER
	__asm
	{
		mov		dword ptr syscallNum, eax
		mov		dword ptr programStack, esi
		mov		dword ptr opStack, edi
	}
#else
	__asm__ volatile(
		""
		: "=a" (syscallNum), "=S" (programStack), "=D" (opStack)
		:
		: "memory"
		);
#endif

	// save currentVM so as to allow for recursive VM entry
	savedVM = currentVM;
	data = (int *) (savedVM->dataBase + programStack + 4);

	// modify VM stack pointer for recursive VM entry
	savedVM->programStack = programStack - 4;
	*data = syscallNum;
	opStack[1] = savedVM->systemCall(data);

	currentVM = savedVM;
}

/*
=================
EmitCallProcedure
=================
*/

int EmitCallProcedure(vm_t *vm)
{
	int jmpSystemCall, jmpBadAddr;
	int retval;

	EmitString("8B 07");		// mov eax, dword ptr [edi]
	EmitString("83 EF 04");		// sub edi, 4
	EmitString("85 C0");		// test eax, eax

	// Jump to syscall code
	EmitString("7C");		// jl systemCall
	jmpSystemCall = compiledOfs++;
		
	/************ Call inside VM ************/
	
	EmitString("81 F8");		// cmp eax, vm->instructionCount
	Emit4(vm->instructionCount);
		
	// Error jump if invalid jump target
	EmitString("73");		// jae badAddr
	jmpBadAddr = compiledOfs++;
		
	EmitString("FF 14 85");		// call dword ptr [vm->instructionPointers + eax * 4]
	Emit4((intptr_t) vm->instructionPointers);
	EmitString("8B 07");		// mov eax, dword ptr [edi]
	EmitString("C3");		// ret
		
	// badAddr:
	SET_JMPOFS(jmpBadAddr);
	EmitString("B8");		// mov eax, ErrJump
	Emit4((intptr_t) ErrJump);
	EmitString("FF D0");		// call eax

	/************ System Call ************/
	
	// systemCall:
	SET_JMPOFS(jmpSystemCall);
	retval = compiledOfs;

	EmitString("F7 D0");		// not eax
	// use edx register to store DoSyscall address
	EmitString("BA");		// mov edx, DoSyscall
	Emit4((intptr_t) DoSyscall);

	// align the stack pointer to a 16-byte-boundary
	EmitString("55");		// push ebp
	EmitString("89 E5");		// mov ebp, esp
	EmitString("83 E4 F0");		// and esp, 0xFFFFFFF0
			
	// call the syscall wrapper function
	EmitString("FF D2");		// call edx

	// reset the stack pointer to its previous value
	EmitString("89 EC");		// mov esp, ebp
	EmitString("5D");		// pop ebp

	// have opStack reg point at return value
	EmitString("83 C7 04");		// add edi, 4
	EmitString("C3");		// ret

	return retval;
}

void EmitCall(vm_t *vm, int sysCallOfs)
{
       	EmitString("8B 15");	// mov edx, [dword ptr vm->codeBase]
       	Emit4((intptr_t) &vm->codeBase);

       	if(sysCallOfs)
       	{
	       	if(sysCallOfs < 0x80 || sysCallOfs > 0x7f)
	       	{
		       	EmitString("83 C2");	// add edx, sysCallOfs
		       	Emit1(sysCallOfs);
		}
		else
		{
			EmitString("81 C2");	// add edx, sysCallOfs
			Emit4(sysCallOfs);
		}
	}

	EmitString("FF D2");	// call edx
}

/*
=================
EmitCallConst
=================
*/

void EmitCallConst(vm_t *vm, int cdest, int sysCallOfs)
{
	if(cdest < 0)
	{
		EmitString("B8");	// mov eax, cdest
		Emit4(cdest);

		EmitCall(vm, sysCallOfs);
	}
	else
	{
			JUSED(cdest);
			EmitString("FF 15");	// call dword ptr [vm->instructionPointers + cdest]
			Emit4((intptr_t) &vm->instructionPointers[cdest]);
	}
}


/*
=================
ConstOptimize
=================
*/
qboolean ConstOptimize(vm_t *vm, int sysCallOfs)
{
	int v, opt;
	int op1;

	// we can safely perform optimizations only in case if 
	// we are 100% sure that next instruction is not a jump label
	if (vm->jumpTableTargets && !jused[instruction])
		op1 = code[pc+4];
	else
		return qfalse;

	switch ( op1 ) {

	case 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;
		return qtrue;

	case 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_LOAD2
		instruction += 1;
		return qtrue;

	case 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_LOAD1
		instruction += 1;
		return qtrue;

	case 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;
		return qtrue;

	case 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_STORE2
		instruction += 1;
		return qtrue;

	case 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;
		return qtrue;

	case OP_ADD:
		v = Constant4();
		EmitMovEAXEDI( vm ); 
		if ( v >= 0 && v <= 127 ) {
			EmitString( "83 C0" );	// add eax, 0x7F
			Emit1( v );
		} else {
			EmitString( "05" );	    // add eax, 0x12345678
			Emit4( v );
		}
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc++;						// OP_ADD
		instruction += 1;
		return qtrue;

	case OP_SUB:
		v = Constant4();
		EmitMovEAXEDI( vm );
		if ( v >= 0 && v <= 127 ) {
			EmitString( "83 E8" );	// sub eax, 0x7F
			Emit1( v );
		} else {
			EmitString( "2D" );		// sub eax, 0x12345678
			Emit4( v );
		}
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc++;						// OP_SUB
		instruction += 1;
		return qtrue;

	case OP_MULI:
		v = Constant4();
		EmitMovEAXEDI( vm );
		if ( v >= 0 && v <= 127 ) {
			EmitString( "6B C0" );	// imul eax, 0x7F
			Emit1( v );
		} else {
			EmitString( "69 C0" );	// imul eax, 0x12345678
			Emit4( v );
		}
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc++;						// OP_MULI
		instruction += 1;
		return qtrue;

	case OP_LSH:
		v = NextConstant4();
		if ( v < 0 || v > 31 )
			break;
		EmitMovEAXEDI( vm );
		EmitString( "C1 E0" );	// shl dword ptr [edi], 0x12
		Emit1( v );
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc += 5;				// CONST + OP_LSH
		instruction += 1;
		return qtrue;

	case OP_RSHI:
		v = NextConstant4();
		if ( v < 0 || v > 31 )
			break;
		EmitMovEAXEDI( vm );
		EmitString( "C1 F8" );	// sar eax, 0x12
		Emit1( v );
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc += 5;				// CONST + OP_RSHI
		instruction += 1;
		return qtrue;

	case OP_RSHU:
		v = NextConstant4();
		if ( v < 0 || v > 31 )
			break;
		EmitMovEAXEDI( vm );
		EmitString( "C1 E8" );	// shr eax, 0x12
		Emit1( v );
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc += 5;				// CONST + OP_RSHU
		instruction += 1;
		return qtrue;
	
	case OP_BAND:
		v = Constant4();
		EmitMovEAXEDI( vm );
		if ( v >= 0 && v <= 127 ) {
			EmitString( "83 E0" ); // and eax, 0x7F
			Emit1( v );
		} else {
			EmitString( "25" ); // and eax, 0x12345678
			Emit4( v );
		}
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc += 1;				   // OP_BAND
		instruction += 1;
		return qtrue;

	case OP_BOR:
		v = Constant4();
		EmitMovEAXEDI( vm );
		if ( v >= 0 && v <= 127 ) {
			EmitString( "83 C8" ); // or eax, 0x7F
			Emit1( v );
		} else {
			EmitString( "0D" );    // or eax, 0x12345678
			Emit4( v );
		}
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc += 1;				   // OP_BOR
		instruction += 1;
		return qtrue;

	case OP_BXOR:
		v = Constant4();
		EmitMovEAXEDI( vm );
		if ( v >= 0 && v <= 127 ) {
			EmitString( "83 F0" ); // xor eax, 0x7F
			Emit1( v );
		} else {
			EmitString( "35" );    // xor eax, 0x12345678
			Emit4( v );
		}
		EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
		pc += 1;				   // OP_BXOR
		instruction += 1;
		return qtrue;

	case OP_EQF:
	case OP_NEF:
		if ( NextConstant4() != 0 )
			break;
		pc += 5;				   // CONST + OP_EQF|OP_NEF
		EmitMovEAXEDI( vm );
		EmitCommand(LAST_COMMAND_SUB_DI_4);
		// floating point hack :)
		EmitString( "25" );        // and eax, 0x7FFFFFFF
		Emit4( 0x7FFFFFFF );
		if ( op1 == OP_EQF )
			EmitString( "75 06" ); // jnz +6
		else
			EmitString( "74 06" ); // jz +6
		EmitString( "FF 25" );	   // jmp [0x12345678]
		v = Constant4();
		JUSED(v);
		Emit4( (int)vm->instructionPointers + v*4 );
		instruction += 1;
		return qtrue;

	case OP_EQ:
	case OP_NE:
		v = Constant4();
		EmitMovEAXEDI( vm );
		EmitCommand(LAST_COMMAND_SUB_DI_4);
		if ( v == 0 ) {
			EmitString( "85 C0" ); // test eax, eax
		} else {
			EmitString( "3D" );    // cmp eax, 0x12345678
			Emit4( v );
		}
		pc += 1;				   // OP_EQ/OP_NE
		if ( op1 == OP_EQ )
			EmitString( "75 06" ); // jne +6
		else
			EmitString( "74 06" ); // je +6
		EmitString( "FF 25" );	   // jmp [0x12345678]
		v = Constant4();
		JUSED(v);
		Emit4( (int)vm->instructionPointers + v*4 );
		instruction += 1;
		return qtrue;

	case OP_GEI:
	case OP_GTI:
		v = Constant4();
		EmitMovEAXEDI( vm );
		EmitCommand( LAST_COMMAND_SUB_DI_4 );
		EmitString( "3D" );        // cmp eax, 0x12345678
		Emit4( v );
		pc += 1;			       // OP_GEI|OP_GTI
		if ( op1 == OP_GEI )
			EmitString( "7C 06" ); // jl +6
		else
			EmitString( "7E 06" ); // jle +6
		EmitString( "FF 25" );     // jmp [0x12345678]
		v = Constant4();
		JUSED(v);
		Emit4( (int)vm->instructionPointers + v*4 );
		instruction += 1;
		return qtrue;

	case OP_LEI:
	case OP_LTI:
		v = Constant4();
		EmitMovEAXEDI( vm );
		EmitCommand( LAST_COMMAND_SUB_DI_4 );
		EmitString( "3D" );        // cmp eax, 0x12345678
		Emit4( v );
		pc += 1;			       // OP_GEI|OP_GTI
		if ( op1 == OP_LEI )
			EmitString( "7F 06" ); // jg +6
		else
			EmitString( "7D 06" ); // jge +6
		EmitString( "FF 25" );     // jmp [0x12345678]
		v = Constant4();
		JUSED(v);
		Emit4( (int)vm->instructionPointers + v*4 );
		instruction += 1;
		return qtrue;

	case OP_JUMP:
		v = Constant4();
		JUSED(v);
		EmitString( "FF 25" );    // jmp dword ptr [instructionPointers + 0x12345678]
		Emit4( (int)vm->instructionPointers + v*4 );
		pc += 1;                  // OP_JUMP
		instruction += 1;
		return qtrue;

	case OP_CALL:
		if ( NextConstant4() < 0 )
			break;
		v = Constant4();
		EmitCallConst(vm, v, sysCallOfs);

		pc += 1;                  // OP_CALL
		instruction += 1;
		return qtrue;

	default:
		break;
	}

	return qfalse;
}


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

	jusedSize = header->instructionCount + 2;

	// allocate a very large temp buffer, we will shrink it later
	maxLength = header->codeLength * 8;
	buf = Z_Malloc(maxLength);
	jused = Z_Malloc(jusedSize);
	code = Z_Malloc(header->codeLength+32);
	
	Com_Memset(jused, 0, jusedSize);
	Com_Memset(buf, 0, maxLength);

	// copy code in larger buffer and put some zeros at the end
	// so we can safely look ahead for a few instructions in it
	// without a chance to get false-positive because of some garbage bytes
	Com_Memset(code, 0, header->codeLength+32);
	Com_Memcpy(code, (byte *)header + header->codeOffset, header->codeLength );

	// 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;
	}

	// Start buffer with x86-VM specific procedures
	compiledOfs = 0;
	sysCallOfs = EmitCallProcedure(vm);
	vm->entryOfs = compiledOfs;

	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 = vm->entryOfs;

	LastCommand = LAST_COMMAND_NONE;

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

		vm->instructionPointers[ instruction ] = compiledOfs;

		if ( !vm->jumpTableTargets )
			jlabel = 1;
		else 
			jlabel = jused[ instruction ];

		instruction++;

		if(pc > header->codeLength)
		{
		        VMFREE_BUFFERS();
			Com_Error(ERR_DROP, "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(ConstOptimize(vm, sysCallOfs))
				break;

			EmitAddEDI4(vm);
			EmitString( "C7 07" );		// mov	dword ptr [edi], 0x12345678
			lastConst = Constant4();
			Emit4( lastConst );
			if (code[pc] == OP_JUMP) {
				JUSED(lastConst);
			}
			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
			Emit4((Constant1() & vm->dataMask & 0xFF) + (int) vm->dataBase);
			EmitCommand(LAST_COMMAND_SUB_DI_4);		// sub edi, 4
			break;
		case OP_CALL:
			EmitCall(vm, 0);
			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:
			EmitMovEAXEDI( vm );
			EmitCommand( LAST_COMMAND_SUB_DI_8 );	// sub edi, 8
			EmitString( "3B 47 04" );				// cmp	eax, dword ptr [edi+4]
			EmitString( "75 06" );		// jne +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_NE:
			EmitMovEAXEDI( vm );
			EmitCommand( LAST_COMMAND_SUB_DI_8 );	// sub edi, 8
			EmitString( "3B 47 04" );	// cmp	eax, dword ptr [edi+4]
			EmitString( "74 06" );		// je +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LTI:
			EmitMovEAXEDI( vm );	
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	dword ptr [edi+4], eax
			EmitString( "7D 06" );		// jnl +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LEI:
			EmitMovEAXEDI( vm );
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	dword ptr [edi+4], eax
			EmitString( "7F 06" );		// jnle +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GTI:
			EmitMovEAXEDI( vm );
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	eax, dword ptr [edi+4]
			EmitString( "7E 06" );		// jng +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GEI:
			EmitMovEAXEDI( vm );	
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	eax, dword ptr [edi+4]
			EmitString( "7C 06" );		// jnge +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LTU:
			EmitMovEAXEDI( vm );	
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	eax, dword ptr [edi+4]
			EmitString( "73 06" );		// jnb +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_LEU:
			EmitMovEAXEDI( vm );	
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	eax, dword ptr [edi+4]
			EmitString( "77 06" );		// jnbe +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GTU:
			EmitMovEAXEDI( vm );	
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	eax, dword ptr [edi+4]
			EmitString( "76 06" );		// jna +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;
		case OP_GEU:
			EmitMovEAXEDI( vm );	
			EmitCommand(LAST_COMMAND_SUB_DI_8);		// sub edi, 8
			EmitString( "39 47 04" );	// cmp	eax, dword ptr [edi+4]
			EmitString( "72 06" );		// jnae +6
			EmitString( "FF 25" );		// jmp	[0x12345678]
			v = Constant4();
			JUSED(v);
			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);
			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);
			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);
			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);
			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);
			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);
			Emit4( (int)vm->instructionPointers + v*4 );
			break;			
		case OP_NEGI:
			EmitMovEAXEDI( vm );
			EmitString( "F7 D8" );		// neg eax
			EmitCommand( LAST_COMMAND_MOV_EDI_EAX );
			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]
			EmitMovECXEDI( vm );
			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]
			EmitMovECXEDI( vm );
			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]
			EmitMovECXEDI( vm );
			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]
			EmitString("81 F8");			// cmp eax, vm->instructionCount
			Emit4(vm->instructionCount);
			EmitString( "73 07" );			// jae +7
			EmitString( "FF 24 85" );		// jmp dword ptr [instructionPointers + eax * 4]
			Emit4((intptr_t) vm->instructionPointers);
			EmitString( "FF 15" );			// call errJumpPtr
			Emit4((intptr_t) &errJumpPtr);
			break;
		default:
		        VMFREE_BUFFERS();
			Com_Error(ERR_DROP, "VM_CompileX86: bad opcode %i at offset %i", op, pc);
		}
		pop0 = pop1;
		pop1 = op;
	}
	}

	// copy to an exact sized buffer with the appropriate permission bits
	vm->codeLength = compiledOfs;
#ifdef VM_X86_MMAP
	vm->codeBase = mmap(NULL, compiledOfs, PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
	if(vm->codeBase == MAP_FAILED)
		Com_Error(ERR_FATAL, "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_FATAL, "VM_CompileX86: VirtualAlloc failed");
#else
	vm->codeBase = malloc(compiledOfs);
	if(!vm->codeBase)
	        Com_Error(ERR_FATAL, "VM_CompileX86: malloc failed");
#endif

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

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

	Z_Free( code );
	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;

	currentVM = vm;

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

	// 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 + vm->entryOfs;

		__asm {
			pushad
			mov    esi, programStack
			mov    edi, opStack
			call   entryPoint
			mov    programStack, esi
			mov    opStack, edi
			popad
		}
#else
		__asm__ volatile(
		        "pushal\r\n"
		        "movl %0, %%esi\r\n"
		        "movl %1, %%edi\r\n"
			"call *%2\r\n"
			"movl %%edi, %1\r\n"
			"movl %%esi, %0\r\n"
			"popal\r\n"
			: "+g" (programStack), "+g" (opStack)
			: "g" (vm->codeBase + vm->entryOfs)
			: "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;

	return *(int *)opStack;
}