/**

 * $Id: armcore.c,v 1.20 2006-01-22 22:40:05 nkeynes Exp $

 * 

 * ARM7TDMI CPU emulation core.

 *

 * Copyright (c) 2005 Nathan Keynes.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */

#define MODULE aica_module

#include "dream.h"

#include "mem.h"

#include "aica/armcore.h"

#include "aica/aica.h"

#define STM_R15_OFFSET 12

struct arm_registers armr;

void arm_set_mode( int mode );

uint32_t arm_exceptions[][2] = {{ MODE_SVC, 0x00000000 },

				{ MODE_UND, 0x00000004 },

				{ MODE_SVC, 0x00000008 },

				{ MODE_ABT, 0x0000000C },

				{ MODE_ABT, 0x00000010 },

				{ MODE_IRQ, 0x00000018 },

				{ MODE_FIQ, 0x0000001C } };

#define EXC_RESET 0

#define EXC_UNDEFINED 1

#define EXC_SOFTWARE 2

#define EXC_PREFETCH_ABORT 3

#define EXC_DATA_ABORT 4

#define EXC_IRQ 5

#define EXC_FAST_IRQ 6

uint32_t arm_cpu_freq = ARM_BASE_RATE;

uint32_t arm_cpu_period = 1000 / ARM_BASE_RATE;

#define CYCLES_PER_SAMPLE ((ARM_BASE_RATE * 1000000) / AICA_SAMPLE_RATE)

static struct breakpoint_struct arm_breakpoints[MAX_BREAKPOINTS];

static int arm_breakpoint_count = 0;

void arm_set_breakpoint( uint32_t pc, int type )

{

    arm_breakpoints[arm_breakpoint_count].address = pc;

    arm_breakpoints[arm_breakpoint_count].type = type;

    arm_breakpoint_count++;

}

gboolean arm_clear_breakpoint( uint32_t pc, int type )

{

    int i;

    for( i=0; i<arm_breakpoint_count; i++ ) {

	if( arm_breakpoints[i].address == pc && 

	    arm_breakpoints[i].type == type ) {

	    while( ++i < arm_breakpoint_count ) {

		arm_breakpoints[i-1].address = arm_breakpoints[i].address;

		arm_breakpoints[i-1].type = arm_breakpoints[i].type;

	    }

	    arm_breakpoint_count--;

	    return TRUE;

	}

    }

    return FALSE;

}

int arm_get_breakpoint( uint32_t pc )

{

    int i;

    for( i=0; i<arm_breakpoint_count; i++ ) {

	if( arm_breakpoints[i].address == pc )

	    return arm_breakpoints[i].type;

    }

    return 0;

}

uint32_t arm_run_slice( uint32_t num_samples )

{

    int i,j,k;

    if( !armr.running )

	return num_samples;

    for( i=0; i<num_samples; i++ ) {

	for( j=0; j < CYCLES_PER_SAMPLE; j++ ) {

	    armr.icount++;

	    if( !arm_execute_instruction() )

		return i;

#ifdef ENABLE_DEBUG_MODE

	    for( k=0; k<arm_breakpoint_count; k++ ) {

		if( arm_breakpoints[k].address == armr.r[15] ) {

		    dreamcast_stop();

		    if( arm_breakpoints[k].type == BREAK_ONESHOT )

			arm_clear_breakpoint( armr.r[15], BREAK_ONESHOT );

		    return i;

		}

	    }

#endif	

	}

	k = MMIO_READ( AICA2, AICA_TCR );

	if( k & 0x40 ) {

	    uint8_t val = MMIO_READ( AICA2, AICA_TIMER );

	    val++;

	    if( val == 0 ) {

		aica_event( AICA_EVENT_TIMER );

		MMIO_WRITE( AICA2, AICA_TCR, k & ~0x40 );

	    }

	    MMIO_WRITE( AICA2, AICA_TIMER, val );

	}

	if( !dreamcast_is_running() )

	    break;

    }

    return i;

}

void arm_save_state( FILE *f )

{

    fwrite( &armr, sizeof(armr), 1, f );

}

int arm_load_state( FILE *f )

{

    fread( &armr, sizeof(armr), 1, f );

    return 0;

}

/* Exceptions */

void arm_reset( void )

{

    /* Wipe all processor state */

    memset( &armr, 0, sizeof(armr) );

    armr.cpsr = MODE_SVC | CPSR_I | CPSR_F;

    armr.r[15] = 0x00000000;

    armr.running = TRUE;

}

#define SET_CPSR_CONTROL   0x00010000

#define SET_CPSR_EXTENSION 0x00020000

#define SET_CPSR_STATUS    0x00040000

#define SET_CPSR_FLAGS     0x00080000

uint32_t arm_get_cpsr( void )

{

    /* write back all flags to the cpsr */

    armr.cpsr = armr.cpsr & CPSR_COMPACT_MASK;

    if( armr.n ) armr.cpsr |= CPSR_N;

    if( armr.z ) armr.cpsr |= CPSR_Z;

    if( armr.c ) armr.cpsr |= CPSR_C;

    if( armr.v ) armr.cpsr |= CPSR_V;

    if( armr.t ) armr.cpsr |= CPSR_T;  

    return armr.cpsr;

}

/**

 * Return a pointer to the specified register in the user bank,

 * regardless of the active bank

 */

static uint32_t *arm_user_reg( int reg )

{

    if( IS_EXCEPTION_MODE() ) {

	if( reg == 13 || reg == 14 )

	    return &armr.user_r[reg-8];

	if( IS_FIQ_MODE() ) {

	    if( reg >= 8 || reg <= 12 )

		return &armr.user_r[reg-8];

	}

    }

    return &armr.r[reg];

}

#define USER_R(n) *arm_user_reg(n)

/**

 * Set the CPSR to the specified value.

 *

 * @param value values to set in CPSR

 * @param fields set of mask values to define which sections of the 

 *   CPSR to set (one of the SET_CPSR_* values above)

 */

void arm_set_cpsr( uint32_t value, uint32_t fields )

{

    if( IS_PRIVILEGED_MODE() ) {

	if( fields & SET_CPSR_CONTROL ) {

	    int mode = value & CPSR_MODE;

	    arm_set_mode( mode );

	    armr.t = ( value & CPSR_T ); /* Technically illegal to change */

	    armr.cpsr = (armr.cpsr & 0xFFFFFF00) | (value & 0x000000FF);

	}

	/* Middle 16 bits not currently defined */

    }

    if( fields & SET_CPSR_FLAGS ) {

	/* Break flags directly out of given value - don't bother writing

	 * back to CPSR 

	 */

	armr.n = ( value & CPSR_N );

	armr.z = ( value & CPSR_Z );

	armr.c = ( value & CPSR_C );

	armr.v = ( value & CPSR_V );

    }

}

void arm_set_spsr( uint32_t value, uint32_t fields )

{

    /* Only defined if we actually have an SPSR register */

    if( IS_EXCEPTION_MODE() ) {

	if( fields & SET_CPSR_CONTROL ) {

	    armr.spsr = (armr.spsr & 0xFFFFFF00) | (value & 0x000000FF);

	}

	/* Middle 16 bits not currently defined */

	if( fields & SET_CPSR_FLAGS ) {

	    armr.spsr = (armr.spsr & 0x00FFFFFF) | (value & 0xFF000000);

	}

    }

}

/**

 * Raise an ARM exception (other than reset, which uses arm_reset().

 * @param exception one of the EXC_* exception codes defined above.

 */

void arm_raise_exception( int exception )

{

    int mode = arm_exceptions[exception][0];

    uint32_t spsr = arm_get_cpsr();

    arm_set_mode( mode );

    armr.spsr = spsr;

    armr.r[14] = armr.r[15] + 4;

    armr.cpsr = (spsr & 0xFFFFFF00) | mode | CPSR_I; 

    if( mode == MODE_FIQ )

	armr.cpsr |= CPSR_F;

    armr.r[15] = arm_exceptions[exception][1];

}

void arm_restore_cpsr( void )

{

    int spsr = armr.spsr;

    int mode = spsr & CPSR_MODE;

    arm_set_mode( mode );

    armr.cpsr = spsr;

    armr.n = ( spsr & CPSR_N );

    armr.z = ( spsr & CPSR_Z );

    armr.c = ( spsr & CPSR_C );

    armr.v = ( spsr & CPSR_V );

    armr.t = ( spsr & CPSR_T );

}

/**

 * Change the current executing ARM mode to the requested mode.

 * Saves any required registers to banks and restores those for the

 * correct mode. (Note does not actually update CPSR at the moment).

 */

void arm_set_mode( int targetMode )

{

    int currentMode = armr.cpsr & CPSR_MODE;

    if( currentMode == targetMode )

	return;

    switch( currentMode ) {

    case MODE_USER:

    case MODE_SYS:

	armr.user_r[5] = armr.r[13];

	armr.user_r[6] = armr.r[14];

	break;

    case MODE_SVC:

	armr.svc_r[0] = armr.r[13];

	armr.svc_r[1] = armr.r[14];

	armr.svc_r[2] = armr.spsr;

	break;

    case MODE_ABT:

	armr.abt_r[0] = armr.r[13];

	armr.abt_r[1] = armr.r[14];

	armr.abt_r[2] = armr.spsr;

	break;

    case MODE_UND:

	armr.und_r[0] = armr.r[13];

	armr.und_r[1] = armr.r[14];

	armr.und_r[2] = armr.spsr;

	break;

    case MODE_IRQ:

	armr.irq_r[0] = armr.r[13];

	armr.irq_r[1] = armr.r[14];

	armr.irq_r[2] = armr.spsr;

	break;

    case MODE_FIQ:

	armr.fiq_r[0] = armr.r[8];

	armr.fiq_r[1] = armr.r[9];

	armr.fiq_r[2] = armr.r[10];

	armr.fiq_r[3] = armr.r[11];

	armr.fiq_r[4] = armr.r[12];

	armr.fiq_r[5] = armr.r[13];

	armr.fiq_r[6] = armr.r[14];

	armr.fiq_r[7] = armr.spsr;

	armr.r[8] = armr.user_r[0];

	armr.r[9] = armr.user_r[1];

	armr.r[10] = armr.user_r[2];

	armr.r[11] = armr.user_r[3];

	armr.r[12] = armr.user_r[4];

	break;

    }

    switch( targetMode ) {

    case MODE_USER:

    case MODE_SYS:

	armr.r[13] = armr.user_r[5];

	armr.r[14] = armr.user_r[6];

	break;

    case MODE_SVC:

	armr.r[13] = armr.svc_r[0];

	armr.r[14] = armr.svc_r[1];

	armr.spsr = armr.svc_r[2];

	break;

    case MODE_ABT:

	armr.r[13] = armr.abt_r[0];

	armr.r[14] = armr.abt_r[1];

	armr.spsr = armr.abt_r[2];

	break;

    case MODE_UND:

	armr.r[13] = armr.und_r[0];

	armr.r[14] = armr.und_r[1];

	armr.spsr = armr.und_r[2];

	break;

    case MODE_IRQ:

	armr.r[13] = armr.irq_r[0];

	armr.r[14] = armr.irq_r[1];

	armr.spsr = armr.irq_r[2];

	break;

    case MODE_FIQ:

	armr.user_r[0] = armr.r[8];

	armr.user_r[1] = armr.r[9];

	armr.user_r[2] = armr.r[10];

	armr.user_r[3] = armr.r[11];

	armr.user_r[4] = armr.r[12];

	armr.r[8] = armr.fiq_r[0];

	armr.r[9] = armr.fiq_r[1];

	armr.r[10] = armr.fiq_r[2];

	armr.r[11] = armr.fiq_r[3];

	armr.r[12] = armr.fiq_r[4];

	armr.r[13] = armr.fiq_r[5];

	armr.r[14] = armr.fiq_r[6];

	armr.spsr = armr.fiq_r[7];

	break;

    }

}

/* Page references are as per ARM DDI 0100E (June 2000) */

#define MEM_READ_BYTE( addr ) arm_read_byte(addr)

#define MEM_READ_WORD( addr ) arm_read_word(addr)

#define MEM_READ_LONG( addr ) arm_read_long(addr)

#define MEM_WRITE_BYTE( addr, val ) arm_write_byte(addr, val)

#define MEM_WRITE_WORD( addr, val ) arm_write_word(addr, val)

#define MEM_WRITE_LONG( addr, val ) arm_write_long(addr, val)

#define IS_NOTBORROW( result, op1, op2 ) (op2 > op1 ? 0 : 1)

#define IS_CARRY( result, op1, op2 ) (result < op1 ? 1 : 0)

#define IS_SUBOVERFLOW( result, op1, op2 ) (((op1^op2) & (result^op1)) >> 31)

#define IS_ADDOVERFLOW( result, op1, op2 ) (((op1&op2) & (result^op1)) >> 31)

#define PC armr.r[15]

/* Instruction fields */

#define COND(ir) (ir>>28)

#define GRP(ir) ((ir>>26)&0x03)

#define OPCODE(ir) ((ir>>20)&0x1F)

#define IFLAG(ir) (ir&0x02000000)

#define SFLAG(ir) (ir&0x00100000)

#define PFLAG(ir) (ir&0x01000000)

#define UFLAG(ir) (ir&0x00800000)

#define BFLAG(ir) (ir&0x00400000)

#define WFLAG(ir) (ir&0x00200000)

#define LFLAG(ir) SFLAG(ir)

#define RN(ir) (armr.r[((ir>>16)&0x0F)] + (((ir>>16)&0x0F) == 0x0F ? 4 : 0))

#define RD(ir) (armr.r[((ir>>12)&0x0F)] + (((ir>>12)&0x0F) == 0x0F ? 4 : 0))

#define RDn(ir) ((ir>>12)&0x0F)

#define RS(ir) (armr.r[((ir>>8)&0x0F)] + (((ir>>8)&0x0F) == 0x0F ? 4 : 0))

#define RM(ir) (armr.r[(ir&0x0F)] + (((ir&0x0F) == 0x0F ? 4 : 0)) )

#define LRN(ir) armr.r[((ir>>16)&0x0F)]

#define LRD(ir) armr.r[((ir>>12)&0x0F)]

#define LRS(ir) armr.r[((ir>>8)&0x0F)]

#define LRM(ir) armr.r[(ir&0x0F)]

#define IMM8(ir) (ir&0xFF)

#define IMM12(ir) (ir&0xFFF)

#define SHIFTIMM(ir) ((ir>>7)&0x1F)

#define IMMROT(ir) ((ir>>7)&0x1E)

#define ROTIMM12(ir) ROTATE_RIGHT_LONG(IMM8(ir),IMMROT(ir))

#define SIGNEXT24(n) ((n&0x00800000) ? (n|0xFF000000) : (n&0x00FFFFFF))

#define SHIFT(ir) ((ir>>4)&0x07)

#define DISP24(ir) ((ir&0x00FFFFFF))

#define UNDEF(ir) do{ arm_raise_exception( EXC_UNDEFINED ); return TRUE; } while(0)

#define UNIMP(ir) do{ PC-=4; ERROR( "Halted on unimplemented instruction at %08x, opcode = %04x", PC, ir ); dreamcast_stop(); return FALSE; }while(0)

/**

 * Determine the value of the shift-operand for a data processing instruction,

 * without determing a value for shift_C (optimized form for instructions that

 * don't require shift_C ).

 * @see s5.1 Addressing Mode 1 - Data-processing operands (p A5-2, 218)

 */

static uint32_t arm_get_shift_operand( uint32_t ir )

{

	uint32_t operand, tmp;

	if( IFLAG(ir) == 0 ) {

		operand = RM(ir);

		switch(SHIFT(ir)) {

		case 0: /* (Rm << imm) */

			operand = operand << SHIFTIMM(ir);

			break;

		case 1: /* (Rm << Rs) */

			tmp = RS(ir)&0xFF;

			if( tmp > 31 ) operand = 0;

			else operand = operand << tmp;

			break;

		case 2: /* (Rm >> imm) */

			operand = operand >> SHIFTIMM(ir);

			break;

		case 3: /* (Rm >> Rs) */

			tmp = RS(ir) & 0xFF;

			if( tmp > 31 ) operand = 0;

			else operand = operand >> ir;

			break;

		case 4: /* (Rm >>> imm) */

			tmp = SHIFTIMM(ir);

			if( tmp == 0 ) operand = ((int32_t)operand) >> 31;

			else operand = ((int32_t)operand) >> tmp;

			break;

		case 5: /* (Rm >>> Rs) */

			tmp = RS(ir) & 0xFF;

			if( tmp > 31 ) operand = ((int32_t)operand) >> 31;

			else operand = ((int32_t)operand) >> tmp;

			break;

		case 6:

			tmp = SHIFTIMM(ir);

			if( tmp == 0 ) /* RRX aka rotate with carry */

				operand = (operand >> 1) | (armr.c<<31);

			else

				operand = ROTATE_RIGHT_LONG(operand,tmp);

			break;

		case 7:

			tmp = RS(ir)&0x1F;

			operand = ROTATE_RIGHT_LONG(operand,tmp);

			break;

		}

	} else {

		operand = IMM8(ir);

		tmp = IMMROT(ir);

		operand = ROTATE_RIGHT_LONG(operand, tmp);

	}

	return operand;

}

/**

 * Determine the value of the shift-operand for a data processing instruction,

 * and set armr.shift_c accordingly.

 * @see s5.1 Addressing Mode 1 - Data-processing operands (p A5-2, 218)

 */

static uint32_t arm_get_shift_operand_s( uint32_t ir )

{

	uint32_t operand, tmp;

	if( IFLAG(ir) == 0 ) {

		operand = RM(ir);

		switch(SHIFT(ir)) {

		case 0: /* (Rm << imm) */

			tmp = SHIFTIMM(ir);

			if( tmp == 0 ) { /* Rm */

				armr.shift_c = armr.c;

			} else { /* Rm << imm */

				armr.shift_c = (operand >> (32-tmp)) & 0x01;

				operand = operand << tmp;

			}

			break;

		case 1: /* (Rm << Rs) */

			tmp = RS(ir)&0xFF;

			if( tmp == 0 ) {

				armr.shift_c = armr.c;

			} else {

				if( tmp <= 32 )

					armr.shift_c = (operand >> (32-tmp)) & 0x01;

				else armr.shift_c = 0;

				if( tmp < 32 )

					operand = operand << tmp;

				else operand = 0;

			}

			break;

		case 2: /* (Rm >> imm) */

			tmp = SHIFTIMM(ir);

			if( tmp == 0 ) {

				armr.shift_c = operand >> 31;

				operand = 0;

			} else {

				armr.shift_c = (operand >> (tmp-1)) & 0x01;

				operand = RM(ir) >> tmp;

			}

			break;

		case 3: /* (Rm >> Rs) */

			tmp = RS(ir) & 0xFF;

			if( tmp == 0 ) {

				armr.shift_c = armr.c;

			} else {

				if( tmp <= 32 )

					armr.shift_c = (operand >> (tmp-1))&0x01;

				else armr.shift_c = 0;

				if( tmp < 32 )

					operand = operand >> tmp;

				else operand = 0;

			}

			break;

		case 4: /* (Rm >>> imm) */

			tmp = SHIFTIMM(ir);

			if( tmp == 0 ) {

				armr.shift_c = operand >> 31;

				operand = -armr.shift_c;

			} else {

				armr.shift_c = (operand >> (tmp-1)) & 0x01;

				operand = ((int32_t)operand) >> tmp;

			}

			break;

		case 5: /* (Rm >>> Rs) */

			tmp = RS(ir) & 0xFF;

			if( tmp == 0 ) {

				armr.shift_c = armr.c;

			} else {

				if( tmp < 32 ) {

					armr.shift_c = (operand >> (tmp-1))&0x01;

					operand = ((int32_t)operand) >> tmp;

				} else {

					armr.shift_c = operand >> 31;

					operand = ((int32_t)operand) >> 31;

				}

			}

			break;

		case 6:

			tmp = SHIFTIMM(ir);

			if( tmp == 0 ) { /* RRX aka rotate with carry */

				armr.shift_c = operand&0x01;

				operand = (operand >> 1) | (armr.c<<31);

			} else {

				armr.shift_c = operand>>(tmp-1);

				operand = ROTATE_RIGHT_LONG(operand,tmp);

			}

			break;

		case 7:

			tmp = RS(ir)&0xFF;

			if( tmp == 0 ) {

				armr.shift_c = armr.c;

			} else {

				tmp &= 0x1F;

				if( tmp == 0 ) {

					armr.shift_c = operand>>31;

				} else {

					armr.shift_c = (operand>>(tmp-1))&0x1;

					operand = ROTATE_RIGHT_LONG(operand,tmp);

				}

			}

			break;

		}

	} else {

		operand = IMM8(ir);

		tmp = IMMROT(ir);

		if( tmp == 0 ) {

			armr.shift_c = armr.c;

		} else {

			operand = ROTATE_RIGHT_LONG(operand, tmp);

			armr.shift_c = operand>>31;

		}

	}

	return operand;

}

/**

 * Another variant of the shifter code for index-based memory addressing.

 * Distinguished by the fact that it doesn't support register shifts, and

 * ignores the I flag (WTF do the load/store instructions use the I flag to

 * mean the _exact opposite_ of what it means for the data processing 

 * instructions ???)

 */

static uint32_t arm_get_address_index( uint32_t ir )

{

	uint32_t operand = RM(ir);

	uint32_t tmp;

	switch(SHIFT(ir)) {

	case 0: /* (Rm << imm) */

		operand = operand << SHIFTIMM(ir);

		break;

	case 2: /* (Rm >> imm) */

		operand = operand >> SHIFTIMM(ir);

		break;

	case 4: /* (Rm >>> imm) */

		tmp = SHIFTIMM(ir);

		if( tmp == 0 ) operand = ((int32_t)operand) >> 31;

		else operand = ((int32_t)operand) >> tmp;

		break;

	case 6:

		tmp = SHIFTIMM(ir);

		if( tmp == 0 ) /* RRX aka rotate with carry */

			operand = (operand >> 1) | (armr.c<<31);

		else

			operand = ROTATE_RIGHT_LONG(operand,tmp);

		break;

	default: UNIMP(ir);

	}

	return operand;	

}

/**

 * Determine the address operand of a load/store instruction, including

 * applying any pre/post adjustments to the address registers.

 * @see s5.2 Addressing Mode 2 - Load and Store Word or Unsigned Byte

 * @param The instruction word.

 * @return The calculated address

 */

static uint32_t arm_get_address_operand( uint32_t ir )

{

	uint32_t addr;

	/* I P U . W */

	switch( (ir>>21)&0x1D ) {

	case 0: /* Rn -= imm offset (post-indexed) [5.2.8 A5-28] */

	case 1:

		addr = RN(ir);

		LRN(ir) = addr - IMM12(ir);

		break;

	case 4: /* Rn += imm offsett (post-indexed) [5.2.8 A5-28] */

	case 5:

		addr = RN(ir);

		LRN(ir) = addr + IMM12(ir);

		break;

	case 8: /* Rn - imm offset  [5.2.2 A5-20] */

		addr = RN(ir) - IMM12(ir);

		break;

	case 9: /* Rn -= imm offset (pre-indexed)  [5.2.5 A5-24] */

		addr = RN(ir) - IMM12(ir);

		LRN(ir) = addr;

		break;

	case 12: /* Rn + imm offset  [5.2.2 A5-20] */

		addr = RN(ir) + IMM12(ir);

		break;

	case 13: /* Rn += imm offset  [5.2.5 A5-24 ] */

		addr = RN(ir) + IMM12(ir);

		LRN(ir) = addr;

		break;

	case 16: /* Rn -= Rm (post-indexed)  [5.2.10 A5-32 ] */

	case 17:

		addr = RN(ir);

		LRN(ir) = addr - arm_get_address_index(ir);

		break;

	case 20: /* Rn += Rm (post-indexed)  [5.2.10 A5-32 ] */

	case 21:

		addr = RN(ir);

		LRN(ir) = addr - arm_get_address_index(ir);

		break;

	case 24: /* Rn - Rm  [5.2.4 A5-23] */

		addr = RN(ir) - arm_get_address_index(ir);

		break;

	case 25: /* RN -= Rm (pre-indexed)  [5.2.7 A5-26] */

		addr = RN(ir) - arm_get_address_index(ir);

		LRN(ir) = addr;

		break;

	case 28: /* Rn + Rm  [5.2.4 A5-23] */

		addr = RN(ir) + arm_get_address_index(ir);

		break;

	case 29: /* RN += Rm (pre-indexed) [5.2.7 A5-26] */

		addr = RN(ir) + arm_get_address_index(ir);

		LRN(ir) = addr;

		break;

	}

	return addr;

}

gboolean arm_execute_instruction( void ) 

{

    uint32_t pc;

    uint32_t ir;

    uint32_t operand, operand2, tmp, tmp2, cond;

    int i;

    tmp = armr.int_pending & (~armr.cpsr);

    if( tmp ) {

	if( tmp & CPSR_F ) {

	    arm_raise_exception( EXC_FAST_IRQ );

	} else {

	    arm_raise_exception( EXC_IRQ );

	}

    }

    ir = MEM_READ_LONG(PC);

    pc = PC + 4;

    PC = pc;

    /** 

     * Check the condition bits first - if the condition fails return 

     * immediately without actually looking at the rest of the instruction.

     */

    switch( COND(ir) ) {

    case 0: /* EQ */ 

	cond = armr.z;

	break;

    case 1: /* NE */

	cond = !armr.z;

	break;

    case 2: /* CS/HS */

	cond = armr.c;

	break;

    case 3: /* CC/LO */

	cond = !armr.c;

	break;

    case 4: /* MI */

	cond = armr.n;

	break;

    case 5: /* PL */

	cond = !armr.n;

	break;

    case 6: /* VS */

	cond = armr.v;

	break;

    case 7: /* VC */

	cond = !armr.v;

	break;

    case 8: /* HI */

	cond = armr.c && !armr.z;

	break;

    case 9: /* LS */

	cond = (!armr.c) || armr.z;

	break;

    case 10: /* GE */

	cond = (armr.n == armr.v);

	break;

    case 11: /* LT */

	cond = (armr.n != armr.v);

	break;

    case 12: /* GT */

	cond = (!armr.z) && (armr.n == armr.v);

	break;

    case 13: /* LE */

	cond = armr.z || (armr.n != armr.v);

	break;

    case 14: /* AL */

	cond = 1;

	break;

    case 15: /* (NV) */

	cond = 0;

	UNDEF(ir);

    }

    if( cond ) {

    /**

     * Condition passed, now for the actual instructions...

     */

    switch( GRP(ir) ) {

    case 0:

	if( (ir & 0x0D900000) == 0x01000000 ) {

	    /* Instructions that aren't actual data processing even though

	     * they sit in the DP instruction block.

	     */

	    switch( ir & 0x0FF000F0 ) {

	    case 0x01200010: /* BX Rd */

		armr.t = ir & 0x01;

		armr.r[15] = RM(ir) & 0xFFFFFFFE;

		break;

	    case 0x01000000: /* MRS Rd, CPSR */

		LRD(ir) = arm_get_cpsr();

		break;

	    case 0x01400000: /* MRS Rd, SPSR */

		LRD(ir) = armr.spsr;

		break;

	    case 0x01200000: /* MSR CPSR, Rd */

		arm_set_cpsr( RM(ir), ir );

		break;

	    case 0x01600000: /* MSR SPSR, Rd */

		arm_set_spsr( RM(ir), ir );

		break;

	    case 0x03200000: /* MSR CPSR, imm */

		arm_set_cpsr( ROTIMM12(ir), ir );

		break;

	    case 0x03600000: /* MSR SPSR, imm */

		arm_set_spsr( ROTIMM12(ir), ir );

		break;

	    default:

		UNIMP(ir);

	    }

	} else if( (ir & 0x0E000090) == 0x00000090 ) {

	    /* Neither are these */

	    switch( (ir>>5)&0x03 ) {

	    case 0:

		/* Arithmetic extension area */

		switch(OPCODE(ir)) {

		case 0: /* MUL */

		    LRN(ir) = RM(ir) * RS(ir);

		    break;

		case 1: /* MULS */

		    tmp = RM(ir) * RS(ir);

		    LRN(ir) = tmp;

		    armr.n = tmp>>31;

		    armr.z = (tmp == 0);

		    break;

		case 2: /* MLA */

		    LRN(ir) = RM(ir) * RS(ir) + RD(ir);

		    break;

		case 3: /* MLAS */

		    tmp = RM(ir) * RS(ir) + RD(ir);

		    LRN(ir) = tmp;

		    armr.n = tmp>>31;

		    armr.z = (tmp == 0);

		    break;

		case 8: /* UMULL */

		case 9: /* UMULLS */

		case 10: /* UMLAL */

		case 11: /* UMLALS */

		case 12: /* SMULL */

		case 13: /* SMULLS */

		case 14: /* SMLAL */

		case 15: /* SMLALS */

		    UNIMP(ir);

		    break;

		case 16: /* SWP */

		    tmp = arm_read_long( RN(ir) );

		    switch( RN(ir) & 0x03 ) {

		    case 1:

			tmp = ROTATE_RIGHT_LONG(tmp, 8);

			break;

		    case 2:

			tmp = ROTATE_RIGHT_LONG(tmp, 16);

			break;

		    case 3:

			tmp = ROTATE_RIGHT_LONG(tmp, 24);

			break;

		    }

		    arm_write_long( RN(ir), RM(ir) );

		    LRD(ir) = tmp;

		    break;

		case 20: /* SWPB */

		    tmp = arm_read_byte( RN(ir) );

		    arm_write_byte( RN(ir), RM(ir) );

		    LRD(ir) = tmp;

		    break;

		default:

		    UNIMP(ir);

		}

		break;

	    case 1:

		if( LFLAG(ir) ) {

		    /* LDRH */

		} else {

		    /* STRH */

		}

		UNIMP(ir);

		break;

	    case 2:

		if( LFLAG(ir) ) {

		    /* LDRSB */

		} else {

		}

		UNIMP(ir);

		break;

	    case 3:

		if( LFLAG(ir) ) {

		    /* LDRSH */

		} else {

		}

		UNIMP(ir);

		break;

	    }

	} else {

	    /* Data processing */

	    switch(OPCODE(ir)) {

	    case 0: /* AND Rd, Rn, operand */

		LRD(ir) = RN(ir) & arm_get_shift_operand(ir);

		break;

	    case 1: /* ANDS Rd, Rn, operand */

		operand = arm_get_shift_operand_s(ir) & RN(ir);

		LRD(ir) = operand;

		if( RDn(ir) == 15 ) {

		    arm_restore_cpsr();

		} else {

		    armr.n = operand>>31;

		    armr.z = (operand == 0);

		    armr.c = armr.shift_c;

		}

		break;

	    case 2: /* EOR Rd, Rn, operand */

		LRD(ir) = RN(ir) ^ arm_get_shift_operand(ir);

		break;

	    case 3: /* EORS Rd, Rn, operand */

		operand = arm_get_shift_operand_s(ir) ^ RN(ir);

		LRD(ir) = operand;

		if( RDn(ir) == 15 ) {

		    arm_restore_cpsr();

		} else {

		    armr.n = operand>>31;

		    armr.z = (operand == 0);

		    armr.c = armr.shift_c;

		}

		break;

	    case 4: /* SUB Rd, Rn, operand */

		LRD(ir) = RN(ir) - arm_get_shift_operand(ir);

		break;

	    case 5: /* SUBS Rd, Rn, operand */

		operand = RN(ir);

		operand2 = arm_get_shift_operand(ir);

		tmp = operand - operand2;

		LRD(ir) = tmp;

		if( RDn(ir) == 15 ) {

		    arm_restore_cpsr();

		} else {

		    armr.n = tmp>>31;

		    armr.z = (tmp == 0);

		    armr.c = IS_NOTBORROW(tmp,operand,operand2);

		    armr.v = IS_SUBOVERFLOW(tmp,operand,operand2);

		}

		break;

	    case 6: /* RSB Rd, operand, Rn */

		LRD(ir) = arm_get_shift_operand(ir) - RN(ir);

		break;

	    case 7: /* RSBS Rd, operand, Rn */

		operand = arm_get_shift_operand(ir);

		operand2 = RN(ir);

		tmp = operand - operand2;

		LRD(ir) = tmp;

		if( RDn(ir) == 15 ) {

		    arm_restore_cpsr();

		} else {

		    armr.n = tmp>>31;

		    armr.z = (tmp == 0);

		    armr.c = IS_NOTBORROW(tmp,operand,operand2);

		    armr.v = IS_SUBOVERFLOW(tmp,operand,operand2);

		}

		break;

	    case 8: /* ADD Rd, Rn, operand */

		LRD(ir) = RN(ir) + arm_get_shift_operand(ir);

		break;

	    case 9: /* ADDS Rd, Rn, operand */

		operand = arm_get_shift_operand(ir);

		operand2 = RN(ir);

		tmp = operand + operand2;

		LRD(ir) = tmp;

		if( RDn(ir) == 15 ) {

		    arm_restore_cpsr();

		} else {

		    armr.n = tmp>>31;

		    armr.z = (tmp == 0);

		    armr.c = IS_CARRY(tmp,operand,operand2);

		    armr.v = IS_ADDOVERFLOW(tmp,operand,operand2);

		}

		break;			

	    case 10: /* ADC */

		LRD(ir) = RN(ir) + arm_get_shift_operand(ir) + 

		    (armr.c ? 1 : 0);

		break;

	    case 11: /* ADCS */

		operand = arm_get_shift_operand(ir);

		operand2 = RN(ir);

		tmp = operand + operand2;

		tmp2 = tmp + armr.c ? 1 : 0;

		LRD(ir) = tmp2;

		if( RDn(ir) == 15 ) {

		    arm_restore_cpsr();

		} else {

		    armr.n = tmp >> 31;

		    armr.z = (tmp == 0 );

		    armr.c = IS_CARRY(tmp,operand,operand2) ||

			(tmp2 < tmp);

		    armr.v = IS_ADDOVERFLOW(tmp,operand, operand2) ||

			((tmp&0x80000000) != (tmp2&0x80000000));

		}