cog/Frameworks/GME/gme/Spc_Cpu.cpp

// Core SPC emulation: CPU, timers, SMP registers, memory

// snes_spc $vers. http://www.slack.net/~ant/

#include "Snes_Spc.h"

/* Copyright (C) 2004-2007 Shay Green. This module is free software; you
can redistribute it and/or modify it under the terms of the GNU Lesser
General Public License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version. This
module 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 Lesser General Public License for more
details. You should have received a copy of the GNU Lesser General Public
License along with this module; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */

#include "blargg_source.h"

#define RAM         (m.ram.ram)
#define REGS        (m.smp_regs [0])
#define REGS_IN     (m.smp_regs [1])

// (n ? n : 256)
#define IF_0_THEN_256( n ) ((uint8_t) ((n) - 1) + 1)

// Note: SPC_MORE_ACCURACY exists mainly so I can run my validation tests, which
// do crazy echo buffer accesses.
#ifndef SPC_MORE_ACCURACY
	#define SPC_MORE_ACCURACY 0
#endif


//// Timers

#define TIMER_DIV( t, n ) ((n) / t->prescaler)
#define TIMER_MUL( t, n ) ((n) * t->prescaler)

Snes_Spc::Timer* Snes_Spc::run_timer_( Timer* t, rel_time_t time )
{
	int elapsed = TIMER_DIV( t, time - t->next_time ) + 1;
	t->next_time += TIMER_MUL( t, elapsed );
	
	if ( t->enabled )
	{
		int remain = IF_0_THEN_256( t->period - t->divider );
		int divider = t->divider + elapsed;
		int over = elapsed - remain;
		if ( over >= 0 )
		{
			int n = over / t->period;
			t->counter = (t->counter + 1 + n) & 0x0F;
			divider = over - n * t->period;
		}
		t->divider = (uint8_t) divider;
	}
	return t;
}

inline Snes_Spc::Timer* Snes_Spc::run_timer( Timer* t, rel_time_t time )
{
	if ( time >= t->next_time )
		t = run_timer_( t, time );
	return t;
}


//// ROM

void Snes_Spc::enable_rom( int enable )
{
	if ( m.rom_enabled != enable )
	{
		m.rom_enabled = enable;
		if ( enable )
			memcpy( m.hi_ram, &RAM [rom_addr], sizeof m.hi_ram );
		memcpy( &RAM [rom_addr], (enable ? m.rom : m.hi_ram), rom_size );
		// TODO: ROM can still get overwritten when DSP writes to echo buffer
	}
}


//// DSP

#if SPC_LESS_ACCURATE
	int const max_reg_time = 29;
	
	/* Fast DSP only runs every 32nd clock. By adjusting the end time based
	on which register is being accessed, in most cases the register access
	is emulated at the precise time. */
	signed char const Snes_Spc::reg_times_ [256] =
	{
		 -1,  0,-11,-10,-15,-11, -2, -2,  4,  3, 14, 14, 26, 26, 14, 22,
		  2,  3,  0,  1,-12,  0,  1,  1,  7,  6, 14, 14, 27, 14, 14, 23,
		  5,  6,  3,  4, -1,  3,  4,  4, 10,  9, 14, 14, 26, -5, 14, 23,
		  8,  9,  6,  7,  2,  6,  7,  7, 13, 12, 14, 14, 27, -4, 14, 24,
		 11, 12,  9, 10,  5,  9, 10, 10, 16, 15, 14, 14, -2, -4, 14, 24,
		 14, 15, 12, 13,  8, 12, 13, 13, 19, 18, 14, 14, -2,-36, 14, 24,
		 17, 18, 15, 16, 11, 15, 16, 16, 22, 21, 14, 14, 28, -3, 14, 25,
		 20, 21, 18, 19, 14, 18, 19, 19, 25, 24, 14, 14, 14, 29, 14, 25,
		 
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
		 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
	};
	
	#define RUN_DSP( time, offset ) \
		int count = (time) - (offset) - m.dsp_time;\
		if ( count >= 0 )\
		{\
			int clock_count = (count & ~(clocks_per_sample - 1)) + clocks_per_sample;\
			m.dsp_time += clock_count;\
			dsp.run( clock_count );\
		}
#else
	#define RUN_DSP( time, offset ) \
		{\
			int count = (time) - m.dsp_time;\
			if ( !SPC_MORE_ACCURACY || count )\
			{\
				assert( count > 0 );\
				m.dsp_time = (time);\
				dsp.run( count );\
			}\
		}
#endif

int Snes_Spc::dsp_read( rel_time_t time )
{
	RUN_DSP( time, reg_times [REGS [r_dspaddr] & 0x7F] );
	
	int result = dsp.read( REGS [r_dspaddr] & 0x7F );
	
	#ifdef SPC_DSP_READ_HOOK
		SPC_DSP_READ_HOOK( spc_time + time, (REGS [r_dspaddr] & 0x7F), result );
	#endif
	
	return result;
}

inline void Snes_Spc::dsp_write( int data, rel_time_t time )
{
	RUN_DSP( time, reg_times [REGS [r_dspaddr]] )
	#if SPC_LESS_ACCURATE
		else if ( m.dsp_time == skipping_time )
		{
			int r = REGS [r_dspaddr];
			if ( r == Spc_Dsp::r_kon )
				m.skipped_kon |= data & ~dsp.read( Spc_Dsp::r_koff );
			
			if ( r == Spc_Dsp::r_koff )
			{
				m.skipped_koff |= data;
				m.skipped_kon &= ~data;
			}
		}
	#endif
	
	#ifdef SPC_DSP_WRITE_HOOK
		SPC_DSP_WRITE_HOOK( m.spc_time + time, REGS [r_dspaddr], (uint8_t) data );
	#endif
	
	if ( REGS [r_dspaddr] <= 0x7F )
	{
		if ( REGS [r_dspaddr] != Spc_Dsp::r_flg )
			dsp.write( REGS [r_dspaddr], data );
		else
		{
			int prev = dsp.read( Spc_Dsp::r_flg );
			dsp.write( Spc_Dsp::r_flg, data );
			if ( ( data & 0x20 ) == ( ( data ^ prev ) & 0x20 ) ) clear_echo();
		}
	}
	else if ( !SPC_MORE_ACCURACY )
		dprintf( "SPC wrote to DSP register > $7F\n" );
}


//// Memory access extras

#if SPC_MORE_ACCURACY
	#define MEM_ACCESS( time, addr ) \
	{\
		if ( time >= m.dsp_time )\
		{\
			RUN_DSP( time, max_reg_time );\
		}\
	}
#elif !defined (NDEBUG)
	// Debug-only check for read/write within echo buffer, since this might result in
	// inaccurate emulation due to the DSP not being caught up to the present.
	
	bool Snes_Spc::check_echo_access( int addr )
	{
		if ( !(dsp.read( Spc_Dsp::r_flg ) & 0x20) )
		{
			int start = 0x100 * dsp.read( Spc_Dsp::r_esa );
			int size  = 0x800 * (dsp.read( Spc_Dsp::r_edl ) & 0x0F);
			int end   = start + (size ? size : 4);
			if ( start <= addr && addr < end )
			{
				if ( !m.echo_accessed )
				{
					m.echo_accessed = 1;
					return true;
				}
			}
		}
		return false;
	}
	
	#define MEM_ACCESS( time, addr ) check( !check_echo_access( (uint16_t) addr ) );
#else
	#define MEM_ACCESS( time, addr )
#endif


//// CPU write

#if SPC_MORE_ACCURACY
static unsigned char const glitch_probs [3] [256] =
{
	0xC3,0x92,0x5B,0x1C,0xD1,0x92,0x5B,0x1C,0xDB,0x9C,0x72,0x18,0xCD,0x5C,0x38,0x0B,
	0xE1,0x9C,0x74,0x17,0xCF,0x75,0x45,0x0C,0xCF,0x6E,0x4A,0x0D,0xA3,0x3A,0x1D,0x08,
	0xDB,0xA0,0x82,0x19,0xD9,0x73,0x3C,0x0E,0xCB,0x76,0x52,0x0B,0xA5,0x46,0x1D,0x09,
	0xDA,0x74,0x55,0x0F,0xA2,0x3F,0x21,0x05,0x9A,0x40,0x20,0x07,0x63,0x1E,0x10,0x01,
	0xDF,0xA9,0x85,0x1D,0xD3,0x84,0x4B,0x0E,0xCF,0x6F,0x49,0x0F,0xB3,0x48,0x1E,0x05,
	0xD8,0x77,0x52,0x12,0xB7,0x49,0x23,0x06,0xAA,0x45,0x28,0x07,0x7D,0x28,0x0F,0x07,
	0xCC,0x7B,0x4A,0x0E,0xB2,0x4F,0x24,0x07,0xAD,0x43,0x2C,0x06,0x86,0x29,0x11,0x07,
	0xAE,0x48,0x1F,0x0A,0x76,0x21,0x19,0x05,0x76,0x21,0x14,0x05,0x44,0x11,0x0B,0x01,
	0xE7,0xAD,0x96,0x23,0xDC,0x86,0x59,0x0E,0xDC,0x7C,0x5F,0x15,0xBB,0x53,0x2E,0x09,
	0xD6,0x7C,0x4A,0x16,0xBB,0x4A,0x25,0x08,0xB3,0x4F,0x28,0x0B,0x8E,0x23,0x15,0x08,
	0xCF,0x7F,0x57,0x11,0xB5,0x4A,0x23,0x0A,0xAA,0x42,0x28,0x05,0x7D,0x22,0x12,0x03,
	0xA6,0x49,0x28,0x09,0x82,0x2B,0x0D,0x04,0x7A,0x20,0x0F,0x04,0x3D,0x0F,0x09,0x03,
	0xD1,0x7C,0x4C,0x0F,0xAF,0x4E,0x21,0x09,0xA8,0x46,0x2A,0x07,0x85,0x1F,0x0E,0x07,
	0xA6,0x3F,0x26,0x07,0x7C,0x24,0x14,0x07,0x78,0x22,0x16,0x04,0x46,0x12,0x0A,0x02,
	0xA6,0x41,0x2C,0x0A,0x7E,0x28,0x11,0x05,0x73,0x1B,0x14,0x05,0x3D,0x11,0x0A,0x02,
	0x70,0x22,0x17,0x05,0x48,0x13,0x08,0x03,0x3C,0x07,0x0D,0x07,0x26,0x07,0x06,0x01,
	
	0xE0,0x9F,0xDA,0x7C,0x4F,0x18,0x28,0x0D,0xE9,0x9F,0xDA,0x7C,0x4F,0x18,0x1F,0x07,
	0xE6,0x97,0xD8,0x72,0x64,0x13,0x26,0x09,0xDC,0x67,0xA9,0x38,0x21,0x07,0x15,0x06,
	0xE9,0x91,0xD2,0x6B,0x63,0x14,0x2B,0x0E,0xD6,0x61,0xB7,0x41,0x2B,0x0E,0x10,0x09,
	0xCF,0x59,0xB0,0x2F,0x35,0x08,0x0F,0x07,0xB6,0x30,0x7A,0x21,0x17,0x07,0x09,0x03,
	0xE7,0xA3,0xE5,0x6B,0x65,0x1F,0x34,0x09,0xD8,0x6B,0xBE,0x45,0x27,0x07,0x10,0x07,
	0xDA,0x54,0xB1,0x39,0x2E,0x0E,0x17,0x08,0xA9,0x3C,0x86,0x22,0x16,0x06,0x07,0x03,
	0xD4,0x51,0xBC,0x3D,0x38,0x0A,0x13,0x06,0xB2,0x37,0x79,0x1C,0x17,0x05,0x0E,0x06,
	0xA7,0x31,0x74,0x1C,0x11,0x06,0x0C,0x02,0x6D,0x1A,0x38,0x10,0x0B,0x05,0x06,0x03,
	0xEB,0x9A,0xE1,0x7A,0x6F,0x13,0x34,0x0E,0xE6,0x75,0xC5,0x45,0x3E,0x0B,0x1A,0x05,
	0xD8,0x63,0xC1,0x40,0x3C,0x1B,0x19,0x06,0xB3,0x42,0x83,0x29,0x18,0x0A,0x08,0x04,
	0xD4,0x58,0xBA,0x43,0x3F,0x0A,0x1F,0x09,0xB1,0x33,0x8A,0x1F,0x1F,0x06,0x0D,0x05,
	0xAF,0x3C,0x7A,0x1F,0x16,0x08,0x0A,0x01,0x72,0x1B,0x52,0x0D,0x0B,0x09,0x06,0x01,
	0xCF,0x63,0xB7,0x47,0x40,0x10,0x14,0x06,0xC0,0x41,0x96,0x20,0x1C,0x09,0x10,0x05,
	0xA6,0x35,0x82,0x1A,0x20,0x0C,0x0E,0x04,0x80,0x1F,0x53,0x0F,0x0B,0x02,0x06,0x01,
	0xA6,0x31,0x81,0x1B,0x1D,0x01,0x08,0x08,0x7B,0x20,0x4D,0x19,0x0E,0x05,0x07,0x03,
	0x6B,0x17,0x49,0x07,0x0E,0x03,0x0A,0x05,0x37,0x0B,0x1F,0x06,0x04,0x02,0x07,0x01,
	
	0xF0,0xD6,0xED,0xAD,0xEC,0xB1,0xEB,0x79,0xAC,0x22,0x47,0x1E,0x6E,0x1B,0x32,0x0A,
	0xF0,0xD6,0xEA,0xA4,0xED,0xC4,0xDE,0x82,0x98,0x1F,0x50,0x13,0x52,0x15,0x2A,0x0A,
	0xF1,0xD1,0xEB,0xA2,0xEB,0xB7,0xD8,0x69,0xA2,0x1F,0x5B,0x18,0x55,0x18,0x2C,0x0A,
	0xED,0xB5,0xDE,0x7E,0xE6,0x85,0xD3,0x59,0x59,0x0F,0x2C,0x09,0x24,0x07,0x15,0x09,
	0xF1,0xD6,0xEA,0xA0,0xEC,0xBB,0xDA,0x77,0xA9,0x23,0x58,0x14,0x5D,0x12,0x2F,0x09,
	0xF1,0xC1,0xE3,0x86,0xE4,0x87,0xD2,0x4E,0x68,0x15,0x26,0x0B,0x27,0x09,0x15,0x02,
	0xEE,0xA6,0xE0,0x5C,0xE0,0x77,0xC3,0x41,0x67,0x1B,0x3C,0x07,0x2A,0x06,0x19,0x07,
	0xE4,0x75,0xC6,0x43,0xCC,0x50,0x95,0x23,0x35,0x09,0x14,0x04,0x15,0x05,0x0B,0x04,
	0xEE,0xD6,0xED,0xAD,0xEC,0xB1,0xEB,0x79,0xAC,0x22,0x56,0x14,0x5A,0x12,0x26,0x0A,
	0xEE,0xBB,0xE7,0x7E,0xE9,0x8D,0xCB,0x49,0x67,0x11,0x34,0x07,0x2B,0x0B,0x14,0x07,
	0xED,0xA7,0xE5,0x76,0xE3,0x7E,0xC4,0x4B,0x77,0x14,0x34,0x08,0x27,0x07,0x14,0x04,
	0xE7,0x8B,0xD2,0x4C,0xCA,0x56,0x9E,0x31,0x36,0x0C,0x11,0x07,0x14,0x04,0x0A,0x02,
	0xF0,0x9B,0xEA,0x6F,0xE5,0x81,0xC4,0x43,0x74,0x10,0x30,0x0B,0x2D,0x08,0x1B,0x06,
	0xE6,0x83,0xCA,0x48,0xD9,0x56,0xA7,0x23,0x3B,0x09,0x12,0x09,0x15,0x07,0x0A,0x03,
	0xE5,0x5F,0xCB,0x3C,0xCF,0x48,0x91,0x22,0x31,0x0A,0x17,0x08,0x15,0x04,0x0D,0x02,
	0xD1,0x43,0x91,0x20,0xA9,0x2D,0x54,0x12,0x17,0x07,0x09,0x02,0x0C,0x04,0x05,0x03,
};
#endif

// Read/write handlers are divided into multiple functions to keep rarely-used
// functionality separate so often-used functionality can be optimized better
// by compiler.

// If write isn't preceded by read, data has this added to it
int const no_read_before_write = 0x2000;

void Snes_Spc::cpu_write_smp_reg_( int data, rel_time_t time, int addr )
{
	switch ( addr )
	{
	case r_t0target:
	case r_t1target:
	case r_t2target: {
		Timer* t = &m.timers [addr - r_t0target];
		int period = IF_0_THEN_256( data );
		if ( t->period != period )
		{
			t = run_timer( t, time );
			#if SPC_MORE_ACCURACY
				// Insane behavior when target is written just after counter is
				// clocked and counter matches new period and new period isn't 1, 2, 4, or 8
				if ( t->divider == (period & 0xFF) &&
						t->next_time == time + TIMER_MUL( t, 1 ) &&
						((period - 1) | ~0x0F) & period )
				{
					//dprintf( "SPC pathological timer target write\n" );
					
					// If the period is 3, 5, or 9, there's a probability this behavior won't occur,
					// based on the previous period
					int prob = 0xFF;
					int old_period = t->period & 0xFF;
					if ( period == 3 ) prob = glitch_probs [0] [old_period];
					if ( period == 5 ) prob = glitch_probs [1] [old_period];
					if ( period == 9 ) prob = glitch_probs [2] [old_period];
					
					// The glitch suppresses incrementing of one of the counter bits, based on
					// the lowest set bit in the new period
					int b = 1;
					while ( !(period & b) )
						b <<= 1;
					
					if ( (rand() >> 4 & 0xFF) <= prob )
						t->divider = (t->divider - b) & 0xFF;
				}
			#endif
			t->period = period;
		}
		break;
	}
	
	case r_t0out:
	case r_t1out:
	case r_t2out:
		if ( !SPC_MORE_ACCURACY )
			dprintf( "SPC wrote to counter %d\n", (int) addr - r_t0out );
		
		if ( data < no_read_before_write  / 2 )
			run_timer( &m.timers [addr - r_t0out], time - 1 )->counter = 0;
		break;
	
	// Registers that act like RAM
	case 0x8:
	case 0x9:
		REGS_IN [addr] = (uint8_t) data;
		break;
	
	case r_test:
		if ( (uint8_t) data != 0x0A )
			dprintf( "SPC wrote to test register\n" );
		break;
	
	case r_control:
		// port clears
		if ( data & 0x10 )
		{
			REGS_IN [r_cpuio0] = 0;
			REGS_IN [r_cpuio1] = 0;
		}
		if ( data & 0x20 )
		{
			REGS_IN [r_cpuio2] = 0;
			REGS_IN [r_cpuio3] = 0;
		}
		
		// timers
		{
			for ( int i = 0; i < timer_count; i++ )
			{
				Timer* t = &m.timers [i];
				int enabled = data >> i & 1;
				if ( t->enabled != enabled )
				{
					t = run_timer( t, time );
					t->enabled = enabled;
					if ( enabled )
					{
						t->divider = 0;
						t->counter = 0;
					}
				}
			}
		}
		enable_rom( data & 0x80 );
		break;
	}
}

void Snes_Spc::cpu_write_smp_reg( int data, rel_time_t time, int addr )
{
	if ( addr == r_dspdata ) // 99%
		dsp_write( data, time );
	else
		cpu_write_smp_reg_( data, time, addr );
}

void Snes_Spc::cpu_write_high( int data, int i, rel_time_t time )
{
	if ( i < rom_size )
	{
		m.hi_ram [i] = (uint8_t) data;
		if ( m.rom_enabled )
			RAM [i + rom_addr] = m.rom [i]; // restore overwritten ROM
	}
	else
	{
		assert( RAM [i + rom_addr] == (uint8_t) data );
		RAM [i + rom_addr] = cpu_pad_fill; // restore overwritten padding
		cpu_write( data, i + rom_addr - 0x10000, time );
	}
}

int const bits_in_int = CHAR_BIT * sizeof (int);

void Snes_Spc::cpu_write( int data, int addr, rel_time_t time )
{
	MEM_ACCESS( time, addr )
	
	// RAM
	RAM [addr] = (uint8_t) data;
	int reg = addr - 0xF0;
	if ( reg >= 0 ) // 64%
	{
		// $F0-$FF
		if ( reg < reg_count ) // 87%
		{
			REGS [reg] = (uint8_t) data;
			
			// Ports
			#ifdef SPC_PORT_WRITE_HOOK
				if ( (unsigned) (reg - r_cpuio0) < port_count )
					SPC_PORT_WRITE_HOOK( m.spc_time + time, (reg - r_cpuio0),
							(uint8_t) data, &REGS [r_cpuio0] );
			#endif
			
			// Registers other than $F2 and $F4-$F7
			//if ( reg != 2 && reg != 4 && reg != 5 && reg != 6 && reg != 7 )
			// TODO: this is a bit on the fragile side
			if ( ((~0x2F00 << (bits_in_int - 16)) << reg) < 0 ) // 36%
				cpu_write_smp_reg( data, time, reg );
		}
		// High mem/address wrap-around
		else
		{
			reg -= rom_addr - 0xF0;
			if ( reg >= 0 ) // 1% in IPL ROM area or address wrapped around
				cpu_write_high( data, reg, time );
		}
	}
}


//// CPU read

inline int Snes_Spc::cpu_read_smp_reg( int reg, rel_time_t time )
{
	int result = REGS_IN [reg];
	reg -= r_dspaddr;
	// DSP addr and data
	if ( (unsigned) reg <= 1 ) // 4% 0xF2 and 0xF3
	{
		result = REGS [r_dspaddr];
		if ( (unsigned) reg == 1 )
			result = dsp_read( time ); // 0xF3
	}
    reg -= r_cpuio0 - r_dspaddr;
    if ( (unsigned) reg <= 3 )
    {
        if ( m.sfm_queue && m.sfm_queue < m.sfm_queue_end )
        {
            result = *m.sfm_queue++;
        }
    }
	return result;
}

int Snes_Spc::cpu_read( int addr, rel_time_t time )
{
	MEM_ACCESS( time, addr )
	
	// RAM
	int result = RAM [addr];
	int reg = addr - 0xF0;
	if ( reg >= 0 ) // 40%
	{
		reg -= 0x10;
		if ( (unsigned) reg >= 0xFF00 ) // 21%
		{
			reg += 0x10 - r_t0out;
			
			// Timers
			if ( (unsigned) reg < timer_count ) // 90%
			{
				Timer* t = &m.timers [reg];
				if ( time >= t->next_time )
					t = run_timer_( t, time );
				result = t->counter;
				t->counter = 0;
			}
			// Other registers
			else if ( reg < 0 ) // 10%
			{
				result = cpu_read_smp_reg( reg + r_t0out, time );
			}
			else // 1%
			{
				assert( reg + (r_t0out + 0xF0 - 0x10000) < 0x100 );
				result = cpu_read( reg + (r_t0out + 0xF0 - 0x10000), time );
			}
		}
	}
	
	return result;
}


//// Run

// Prefix and suffix for CPU emulator function
#define SPC_CPU_RUN_FUNC \
BOOST::uint8_t* Snes_Spc::run_until_( time_t end_time )\
{\
	rel_time_t rel_time = m.spc_time - end_time;\
	assert( rel_time <= 0 );\
	m.spc_time = end_time;\
	m.dsp_time += rel_time;\
	m.timers [0].next_time += rel_time;\
	m.timers [1].next_time += rel_time;\
	m.timers [2].next_time += rel_time;

#define SPC_CPU_RUN_FUNC_END \
	m.spc_time += rel_time;\
	m.dsp_time -= rel_time;\
	m.timers [0].next_time -= rel_time;\
	m.timers [1].next_time -= rel_time;\
	m.timers [2].next_time -= rel_time;\
	assert( m.spc_time <= end_time );\
	return &REGS [r_cpuio0];\
}

int const cpu_lag_max = 12 - 1; // DIV YA,X takes 12 clocks

void Snes_Spc::end_frame( time_t end_time )
{
	// Catch CPU up to as close to end as possible. If final instruction
	// would exceed end, does NOT execute it and leaves m.spc_time < end.
	if ( end_time > m.spc_time )
		run_until_( end_time );
	
	m.spc_time     -= end_time;
	m.extra_clocks += end_time;
	
	// Greatest number of clocks early that emulation can stop early due to
	// not being able to execute current instruction without going over
	// allowed time.
	assert( -cpu_lag_max <= m.spc_time && m.spc_time <= 0 );
	
	// Catch timers up to CPU
	for ( int i = 0; i < timer_count; i++ )
		run_timer( &m.timers [i], 0 );
	
	// Catch DSP up to CPU
	if ( m.dsp_time < 0 )
	{
		RUN_DSP( 0, max_reg_time );
	}
	
	// Save any extra samples beyond what should be generated
	if ( m.buf_begin )
		save_extra();
}

// Inclusion here allows static memory access functions and better optimization
#include "Spc_Cpu.h"