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rockbox/apps/codecs/libgme/nes_cpu_run.h

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// NES 6502 cpu emulator run function
#if 0
/* Define these macros in the source file before #including this file.
- Parameters might be expressions, so they are best evaluated only once,
though they NEVER have side-effects, so multiple evaluation is OK.
- Output parameters might be a multiple-assignment expression like "a=x",
so they must NOT be parenthesized.
- Except where noted, time() and related functions will NOT work
correctly inside a macro. TIME() is always correct, and FLUSH_TIME() and
CACHE_TIME() allow the time changing functions to work.
- Macros "returning" void may use a {} statement block. */
// 0 <= addr <= 0xFFFF + page_size
// time functions can be used
int READ_MEM( addr_t );
void WRITE_MEM( addr_t, int data );
// 0 <= READ_MEM() <= 0xFF
// 0 <= addr <= 0x1FF
int READ_LOW( addr_t );
void WRITE_LOW( addr_t, int data );
// 0 <= READ_LOW() <= 0xFF
// Often-used instructions attempt these before using a normal memory access.
// Optional; defaults to READ_MEM() and WRITE_MEM()
bool CAN_READ_FAST( addr_t ); // if true, uses result of READ_FAST
void READ_FAST( addr_t, int& out ); // ALWAYS called BEFORE CAN_READ_FAST
bool CAN_WRITE_FAST( addr_t ); // if true, uses WRITE_FAST instead of WRITE_MEM
void WRITE_FAST( addr_t, int data );
// Used by instructions most often used to access the NES PPU (LDA abs and BIT abs).
// Optional; defaults to READ_MEM.
void READ_PPU( addr_t, int& out );
// 0 <= out <= 0xFF
// The following can be used within macros:
// Current time
time_t TIME();
// Allows use of time functions
void FLUSH_TIME();
// Must be used before end of macro if FLUSH_TIME() was used earlier
void CACHE_TIME();
// Configuration (optional; commented behavior if defined)
// Emulates dummy reads for indexed instructions
#define NES_CPU_DUMMY_READS 1
// Optimizes as if map_code( 0, 0x10000 + cpu_padding, FLAT_MEM ) is always in effect
#define FLAT_MEM my_mem_array
// Expanded just before beginning of code, to help debugger
#define CPU_BEGIN void my_run_cpu() {
#endif
/* Copyright (C) 2003-2008 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 */
// Allows MWCW debugger to step through code properly
#ifdef CPU_BEGIN
CPU_BEGIN
#endif
// Time
#define TIME() (s_time + s.base)
#define FLUSH_TIME() {s.time = s_time - time_offset;}
#define CACHE_TIME() {s_time = s.time + time_offset;}
// Defaults
#ifndef CAN_WRITE_FAST
#define CAN_WRITE_FAST( addr ) 0
#define WRITE_FAST( addr, data )
#endif
#ifndef CAN_READ_FAST
#define CAN_READ_FAST( addr ) 0
#define READ_FAST( addr, out )
#endif
#ifndef READ_PPU
#define READ_PPU( addr, out )\
{\
FLUSH_TIME();\
out = READ_MEM( addr );\
CACHE_TIME();\
}
#endif
#define READ_STACK READ_LOW
#define WRITE_STACK WRITE_LOW
// Dummy reads
#ifdef NES_CPU_DUMMY_READS
// TODO: optimize time handling
#define DUMMY_READ( addr, idx ) \
if ( (addr & 0xFF) < idx )\
{\
int const time_offset = 1;\
FLUSH_TIME();\
READ_MEM( (addr - 0x100) );\
CACHE_TIME();\
}
#else
#define DUMMY_READ( addr, idx )
#endif
// Code
#ifdef FLAT_MEM
#define CODE_PAGE( addr ) (FLAT_MEM)
#define CODE_OFFSET( addr ) (addr)
#else
#define CODE_PAGE( addr ) (s.code_map [NES_CPU_PAGE( addr )])
#define CODE_OFFSET( addr ) NES_CPU_OFFSET( addr )
#endif
#define READ_CODE( addr ) (CODE_PAGE( addr ) [CODE_OFFSET( addr )])
// Stack
#define SET_SP( v ) (sp = ((v) + 1) | 0x100)
#define GET_SP() ((sp - 1) & 0xFF)
#define SP( o ) ((sp + (o - (o>0)*0x100)) | 0x100)
// Truncation
#define BYTE( n ) ((uint8_t ) (n)) /* (unsigned) n & 0xFF */
#define SBYTE( n ) ((int8_t ) (n)) /* (BYTE( n ) ^ 0x80) - 0x80 */
#define WORD( n ) ((uint16_t) (n)) /* (unsigned) n & 0xFFFF */
// Flags with hex value for clarity when used as mask.
// Stored in indicated variable during emulation.
int const n80 = 0x80; // nz
int const v40 = 0x40; // flags
int const r20 = 0x20;
int const b10 = 0x10;
int const d08 = 0x08; // flags
int const i04 = 0x04; // flags
int const z02 = 0x02; // nz
int const c01 = 0x01; // c
#define IS_NEG (nz & 0x8080)
#define GET_FLAGS( out ) \
{\
out = flags & (v40 | d08 | i04);\
out += ((nz >> 8) | nz) & n80;\
out += c >> 8 & c01;\
if ( !BYTE( nz ) )\
out += z02;\
}
#define SET_FLAGS( in ) \
{\
flags = in & (v40 | d08 | i04);\
c = nz = in << 8;\
nz += ~in & z02;\
}
{
int const time_offset = 0;
// Local state
struct cpu_state_t s;
#ifdef FLAT_MEM
s.base = cpu->cpu_state_.base;
#else
s = cpu->cpu_state_;
#endif
cpu->cpu_state = &s;
int s_time = cpu->cpu_state_.time; // helps even on x86
// Registers
int pc = cpu->r.pc;
int a = cpu->r.a;
int x = cpu->r.x;
int y = cpu->r.y;
int sp;
SET_SP( cpu->r.sp );
// Flags
int flags;
int c; // carry set if (c & 0x100) != 0
int nz; // Z set if (nz & 0xFF) == 0, N set if (nz & 0x8080) != 0
{
int temp = cpu->r.flags;
SET_FLAGS( temp );
}
loop:
// Check all values
check( (unsigned) sp - 0x100 < 0x100 );
check( (unsigned) pc < 0x10000 );
check( (unsigned) a < 0x100 );
check( (unsigned) x < 0x100 );
check( (unsigned) y < 0x100 );
// Read instruction
byte const* instr = CODE_PAGE( pc );
int opcode;
if ( CODE_OFFSET(~0) == ~0 )
{
opcode = instr [pc];
pc++;
instr += pc;
}
else
{
instr += CODE_OFFSET( pc );
opcode = *instr++;
pc++;
}
// local to function in case it helps optimizer
static byte const clock_table [256] =
{// 0 1 2 3 4 5 6 7 8 9 A B C D E F
0,6,2,8,3,3,5,5,3,2,2,2,4,4,6,6,// 0
2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 1
6,6,0,8,3,3,5,5,4,2,2,2,4,4,6,6,// 2
2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 3
6,6,2,8,3,3,5,5,3,2,2,2,3,4,6,6,// 4
2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 5
6,6,2,8,3,3,5,5,4,2,2,2,5,4,6,6,// 6
2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// 7
2,6,2,6,3,3,3,3,2,2,2,2,4,4,4,4,// 8
2,6,2,6,4,4,4,4,2,5,2,5,5,5,5,5,// 9
2,6,2,6,3,3,3,3,2,2,2,2,4,4,4,4,// A
2,5,2,5,4,4,4,4,2,4,2,4,4,4,4,4,// B
2,6,2,8,3,3,5,5,2,2,2,2,4,4,6,6,// C
2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,// D
2,6,2,8,3,3,5,5,2,2,2,2,4,4,6,6,// E
2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7 // F
}; // 0x00 was 7 and 0x22 was 2
// Update time
if ( s_time >= 0 )
goto out_of_time;
#ifdef CPU_INSTR_HOOK
{ CPU_INSTR_HOOK( (pc-1), (&instr [-1]), a, x, y, GET_SP(), TIME() ); }
#endif
s_time += clock_table [opcode];
int data;
data = *instr;
switch ( opcode )
{
// Macros
#define GET_MSB() (instr [1])
#define ADD_PAGE( out ) (pc++, out = data + 0x100 * GET_MSB())
#define GET_ADDR() GET_LE16( instr )
#define PAGE_PENALTY( lsb ) s_time += (lsb) >> 8;
#define INC_DEC( reg, n ) reg = BYTE( nz = reg + n ); goto loop;
#define IND_Y( cross, out ) {\
int temp = READ_LOW( data ) + y;\
out = temp + 0x100 * READ_LOW( BYTE( data + 1 ) );\
cross( temp );\
}
#define IND_X( out ) {\
int temp = data + x;\
out = 0x100 * READ_LOW( BYTE( temp + 1 ) ) + READ_LOW( BYTE( temp ) );\
}
#define ARITH_ADDR_MODES( op )\
case op - 0x04: /* (ind,x) */\
IND_X( data )\
goto ptr##op;\
case op + 0x0C: /* (ind),y */\
IND_Y( PAGE_PENALTY, data )\
goto ptr##op;\
case op + 0x10: /* zp,X */\
data = BYTE( data + x );\
case op + 0x00: /* zp */\
data = READ_LOW( data );\
goto imm##op;\
case op + 0x14: /* abs,Y */\
data += y;\
goto ind##op;\
case op + 0x18: /* abs,X */\
data += x;\
ind##op:\
PAGE_PENALTY( data );\
case op + 0x08: /* abs */\
ADD_PAGE( data );\
ptr##op:\
FLUSH_TIME();\
data = READ_MEM( data );\
CACHE_TIME();\
case op + 0x04: /* imm */\
imm##op:
// TODO: more efficient way to handle negative branch that wraps PC around
#define BRANCH( cond )\
{\
++pc;\
if ( !(cond) ) goto loop;\
s_time++;\
int offset = SBYTE( data );\
s_time += (BYTE(pc) + offset) >> 8 & 1;\
pc = WORD( pc + offset );\
goto loop;\
}
// Often-Used
case 0xB5: // LDA zp,x
a = nz = READ_LOW( BYTE( data + x ) );
pc++;
goto loop;
case 0xA5: // LDA zp
a = nz = READ_LOW( data );
pc++;
goto loop;
case 0xD0: // BNE
BRANCH( BYTE( nz ) );
case 0x20: { // JSR
int temp = pc + 1;
pc = GET_ADDR();
WRITE_STACK( SP( -1 ), temp >> 8 );
sp = SP( -2 );
WRITE_STACK( sp, temp );
goto loop;
}
case 0x4C: // JMP abs
pc = GET_ADDR();
goto loop;
case 0xE8: // INX
INC_DEC( x, 1 )
case 0x10: // BPL
BRANCH( !IS_NEG )
ARITH_ADDR_MODES( 0xC5 ) // CMP
nz = a - data;
pc++;
c = ~nz;
nz &= 0xFF;
goto loop;
case 0x30: // BMI
BRANCH( IS_NEG )
case 0xF0: // BEQ
BRANCH( !BYTE( nz ) );
case 0x95: // STA zp,x
data = BYTE( data + x );
case 0x85: // STA zp
pc++;
WRITE_LOW( data, a );
goto loop;
case 0xC8: // INY
INC_DEC( y, 1 )
case 0xA8: // TAY
y = a;
nz = a;
goto loop;
case 0x98: // TYA
a = y;
nz = y;
goto loop;
case 0xAD:{// LDA abs
int addr = GET_ADDR();
pc += 2;
READ_PPU( addr, a = nz );
goto loop;
}
case 0x60: // RTS
pc = 1 + READ_STACK( sp );
pc += 0x100 * READ_STACK( SP( 1 ) );
sp = SP( 2 );
goto loop;
{
int addr;
case 0x8D: // STA abs
addr = GET_ADDR();
pc += 2;
if ( CAN_WRITE_FAST( addr ) )
{
WRITE_FAST( addr, a );
goto loop;
}
sta_ptr:
FLUSH_TIME();
WRITE_MEM( addr, a );
CACHE_TIME();
goto loop;
case 0x99: // STA abs,Y
addr = y + GET_ADDR();
pc += 2;
if ( CAN_WRITE_FAST( addr ) )
{
WRITE_FAST( addr, a );
goto loop;
}
goto sta_abs_x;
case 0x9D: // STA abs,X (slightly more common than STA abs)
addr = x + GET_ADDR();
pc += 2;
if ( CAN_WRITE_FAST( addr ) )
{
WRITE_FAST( addr, a );
goto loop;
}
DUMMY_READ( addr, x );
sta_abs_x:
FLUSH_TIME();
WRITE_MEM( addr, a );
CACHE_TIME();
goto loop;
case 0x91: // STA (ind),Y
#define NO_PAGE_PENALTY( lsb )
IND_Y( NO_PAGE_PENALTY, addr )
pc++;
DUMMY_READ( addr, y );
goto sta_ptr;
case 0x81: // STA (ind,X)
IND_X( addr )
pc++;
goto sta_ptr;
}
case 0xA9: // LDA #imm
pc++;
a = data;
nz = data;
goto loop;
// common read instructions
{
int addr;
case 0xA1: // LDA (ind,X)
IND_X( addr )
pc++;
goto a_nz_read_addr;
case 0xB1:// LDA (ind),Y
addr = READ_LOW( data ) + y;
PAGE_PENALTY( addr );
addr += 0x100 * READ_LOW( BYTE( data + 1 ) );
pc++;
READ_FAST( addr, a = nz );
if ( CAN_READ_FAST( addr ) )
goto loop;
DUMMY_READ( addr, y );
goto a_nz_read_addr;
case 0xB9: // LDA abs,Y
PAGE_PENALTY( data + y );
addr = GET_ADDR() + y;
pc += 2;
READ_FAST( addr, a = nz );
if ( CAN_READ_FAST( addr ) )
goto loop;
goto a_nz_read_addr;
case 0xBD: // LDA abs,X
PAGE_PENALTY( data + x );
addr = GET_ADDR() + x;
pc += 2;
READ_FAST( addr, a = nz );
if ( CAN_READ_FAST( addr ) )
goto loop;
DUMMY_READ( addr, x );
a_nz_read_addr:
FLUSH_TIME();
a = nz = READ_MEM( addr );
CACHE_TIME();
goto loop;
}
// Branch
case 0x50: // BVC
BRANCH( !(flags & v40) )
case 0x70: // BVS
BRANCH( flags & v40 )
case 0xB0: // BCS
BRANCH( c & 0x100 )
case 0x90: // BCC
BRANCH( !(c & 0x100) )
// Load/store
case 0x94: // STY zp,x
data = BYTE( data + x );
case 0x84: // STY zp
pc++;
WRITE_LOW( data, y );
goto loop;
case 0x96: // STX zp,y
data = BYTE( data + y );
case 0x86: // STX zp
pc++;
WRITE_LOW( data, x );
goto loop;
case 0xB6: // LDX zp,y
data = BYTE( data + y );
case 0xA6: // LDX zp
data = READ_LOW( data );
case 0xA2: // LDX #imm
pc++;
x = data;
nz = data;
goto loop;
case 0xB4: // LDY zp,x
data = BYTE( data + x );
case 0xA4: // LDY zp
data = READ_LOW( data );
case 0xA0: // LDY #imm
pc++;
y = data;
nz = data;
goto loop;
case 0xBC: // LDY abs,X
data += x;
PAGE_PENALTY( data );
case 0xAC:{// LDY abs
int addr = data + 0x100 * GET_MSB();
pc += 2;
FLUSH_TIME();
y = nz = READ_MEM( addr );
CACHE_TIME();
goto loop;
}
case 0xBE: // LDX abs,y
data += y;
PAGE_PENALTY( data );
case 0xAE:{// LDX abs
int addr = data + 0x100 * GET_MSB();
pc += 2;
FLUSH_TIME();
x = nz = READ_MEM( addr );
CACHE_TIME();
goto loop;
}
{
int temp;
case 0x8C: // STY abs
temp = y;
goto store_abs;
case 0x8E: // STX abs
temp = x;
store_abs:
{
int addr = GET_ADDR();
pc += 2;
if ( CAN_WRITE_FAST( addr ) )
{
WRITE_FAST( addr, temp );
goto loop;
}
FLUSH_TIME();
WRITE_MEM( addr, temp );
CACHE_TIME();
goto loop;
}
}
// Compare
case 0xEC: {// CPX abs
int addr = GET_ADDR();
pc++;
FLUSH_TIME();
data = READ_MEM( addr );
CACHE_TIME();
goto cpx_data;
}
case 0xE4: // CPX zp
data = READ_LOW( data );
case 0xE0: // CPX #imm
cpx_data:
nz = x - data;
pc++;
c = ~nz;
nz &= 0xFF;
goto loop;
case 0xCC:{// CPY abs
int addr = GET_ADDR();
pc++;
FLUSH_TIME();
data = READ_MEM( addr );
CACHE_TIME();
goto cpy_data;
}
case 0xC4: // CPY zp
data = READ_LOW( data );
case 0xC0: // CPY #imm
cpy_data:
nz = y - data;
pc++;
c = ~nz;
nz &= 0xFF;
goto loop;
// Logical
ARITH_ADDR_MODES( 0x25 ) // AND
nz = (a &= data);
pc++;
goto loop;
ARITH_ADDR_MODES( 0x45 ) // EOR
nz = (a ^= data);
pc++;
goto loop;
ARITH_ADDR_MODES( 0x05 ) // ORA
nz = (a |= data);
pc++;
goto loop;
case 0x2C:{// BIT abs
int addr = GET_ADDR();
pc += 2;
READ_PPU( addr, nz );
flags = (flags & ~v40) + (nz & v40);
if ( a & nz )
goto loop;
nz <<= 8; // result must be zero, even if N bit is set
goto loop;
}
case 0x24: // BIT zp
nz = READ_LOW( data );
pc++;
flags = (flags & ~v40) + (nz & v40);
if ( a & nz )
goto loop; // Z should be clear, and nz must be non-zero if nz & a is
nz <<= 8; // set Z flag without affecting N flag
goto loop;
// Add/subtract
ARITH_ADDR_MODES( 0xE5 ) // SBC
case 0xEB: // unofficial equivalent
data ^= 0xFF;
goto adc_imm;
ARITH_ADDR_MODES( 0x65 ) // ADC
adc_imm: {
int carry = c >> 8 & 1;
int ov = (a ^ 0x80) + carry + SBYTE( data );
flags = (flags & ~v40) + (ov >> 2 & v40);
c = nz = a + data + carry;
pc++;
a = BYTE( nz );
goto loop;
}
// Shift/rotate
case 0x4A: // LSR A
c = 0;
case 0x6A: // ROR A
nz = c >> 1 & 0x80;
c = a << 8;
nz += a >> 1;
a = nz;
goto loop;
case 0x0A: // ASL A
nz = a << 1;
c = nz;
a = BYTE( nz );
goto loop;
case 0x2A: { // ROL A
nz = a << 1;
int temp = c >> 8 & 1;
c = nz;
nz += temp;
a = BYTE( nz );
goto loop;
}
case 0x5E: // LSR abs,X
data += x;
case 0x4E: // LSR abs
c = 0;
case 0x6E: // ROR abs
ror_abs: {
ADD_PAGE( data );
FLUSH_TIME();
int temp = READ_MEM( data );
nz = (c >> 1 & 0x80) + (temp >> 1);
c = temp << 8;
goto rotate_common;
}
case 0x3E: // ROL abs,X
data += x;
goto rol_abs;
case 0x1E: // ASL abs,X
data += x;
case 0x0E: // ASL abs
c = 0;
case 0x2E: // ROL abs
rol_abs:
ADD_PAGE( data );
nz = c >> 8 & 1;
FLUSH_TIME();
nz += (c = READ_MEM( data ) << 1);
rotate_common:
pc++;
WRITE_MEM( data, BYTE( nz ) );
CACHE_TIME();
goto loop;
case 0x7E: // ROR abs,X
data += x;
goto ror_abs;
case 0x76: // ROR zp,x
data = BYTE( data + x );
goto ror_zp;
case 0x56: // LSR zp,x
data = BYTE( data + x );
case 0x46: // LSR zp
c = 0;
case 0x66: // ROR zp
ror_zp: {
int temp = READ_LOW( data );
nz = (c >> 1 & 0x80) + (temp >> 1);
c = temp << 8;
goto write_nz_zp;
}
case 0x36: // ROL zp,x
data = BYTE( data + x );
goto rol_zp;
case 0x16: // ASL zp,x
data = BYTE( data + x );
case 0x06: // ASL zp
c = 0;
case 0x26: // ROL zp
rol_zp:
nz = c >> 8 & 1;
nz += (c = READ_LOW( data ) << 1);
goto write_nz_zp;
// Increment/decrement
case 0xCA: // DEX
INC_DEC( x, -1 )
case 0x88: // DEY
INC_DEC( y, -1 )
case 0xF6: // INC zp,x
data = BYTE( data + x );
case 0xE6: // INC zp
nz = 1;
goto add_nz_zp;
case 0xD6: // DEC zp,x
data = BYTE( data + x );
case 0xC6: // DEC zp
nz = -1;
add_nz_zp:
nz += READ_LOW( data );
write_nz_zp:
pc++;
WRITE_LOW( data, nz );
goto loop;
case 0xFE: // INC abs,x
data = x + GET_ADDR();
goto inc_ptr;
case 0xEE: // INC abs
data = GET_ADDR();
inc_ptr:
nz = 1;
goto inc_common;
case 0xDE: // DEC abs,x
data = x + GET_ADDR();
goto dec_ptr;
case 0xCE: // DEC abs
data = GET_ADDR();
dec_ptr:
nz = -1;
inc_common:
FLUSH_TIME();
pc += 2;
nz += READ_MEM( data );
WRITE_MEM( data, BYTE( nz ) );
CACHE_TIME();
goto loop;
// Transfer
case 0xAA: // TAX
x = nz = a;
goto loop;
case 0x8A: // TXA
a = nz = x;
goto loop;
case 0x9A: // TXS
SET_SP( x ); // verified (no flag change)
goto loop;
case 0xBA: // TSX
x = nz = GET_SP();
goto loop;
// Stack
case 0x48: // PHA
sp = SP( -1 );
WRITE_STACK( sp, a );
goto loop;
case 0x68: // PLA
a = nz = READ_STACK( sp );
sp = SP( 1 );
goto loop;
case 0x40:{// RTI
pc = READ_STACK( SP( 1 ) );
pc += READ_STACK( SP( 2 ) ) * 0x100;
int temp = READ_STACK( sp );
sp = SP( 3 );
data = flags;
SET_FLAGS( temp );
cpu->r.flags = flags; // update externally-visible I flag
int delta = s.base - cpu->irq_time;
if ( delta <= 0 ) goto loop; // end_time < irq_time
if ( flags & i04 ) goto loop;
s_time += delta;
s.base = cpu->irq_time;
goto loop;
}
case 0x28:{// PLP
int temp = READ_STACK( sp );
sp = SP( 1 );
int changed = flags ^ temp;
SET_FLAGS( temp );
if ( !(changed & i04) )
goto loop; // I flag didn't change
if ( flags & i04 )
goto handle_sei;
goto handle_cli;
}
case 0x08:{// PHP
int temp;
GET_FLAGS( temp );
sp = SP( -1 );
WRITE_STACK( sp, temp | (b10 | r20) );
goto loop;
}
case 0x6C:{// JMP (ind)
data = GET_ADDR();
byte const* page = CODE_PAGE( data );
pc = page [CODE_OFFSET( data )];
data = (data & 0xFF00) + ((data + 1) & 0xFF);
pc += page [CODE_OFFSET( data )] * 0x100;
goto loop;
}
case 0x00: // BRK
goto handle_brk;
// Flags
case 0x38: // SEC
c = 0x100;
goto loop;
case 0x18: // CLC
c = 0;
goto loop;
case 0xB8: // CLV
flags &= ~v40;
goto loop;
case 0xD8: // CLD
flags &= ~d08;
goto loop;
case 0xF8: // SED
flags |= d08;
goto loop;
case 0x58: // CLI
if ( !(flags & i04) )
goto loop;
flags &= ~i04;
handle_cli: {
//dprintf( "CLI at %d\n", TIME );
cpu->r.flags = flags; // update externally-visible I flag
int delta = s.base - cpu->irq_time;
if ( delta <= 0 )
{
if ( TIME() < cpu->irq_time )
goto loop;
goto delayed_cli;
}
s.base = cpu->irq_time;
s_time += delta;
if ( s_time < 0 )
goto loop;
if ( delta >= s_time + 1 )
{
// delayed irq until after next instruction
s.base += s_time + 1;
s_time = -1;
goto loop;
}
// TODO: implement
delayed_cli:
dprintf( "Delayed CLI not emulated\n" );
goto loop;
}
case 0x78: // SEI
if ( flags & i04 )
goto loop;
flags |= i04;
handle_sei: {
cpu->r.flags = flags; // update externally-visible I flag
int delta = s.base - cpu->end_time;
s.base = cpu->end_time;
s_time += delta;
if ( s_time < 0 )
goto loop;
dprintf( "Delayed SEI not emulated\n" );
goto loop;
}
// Unofficial
// SKW - skip word
case 0x1C: case 0x3C: case 0x5C: case 0x7C: case 0xDC: case 0xFC:
PAGE_PENALTY( data + x );
case 0x0C:
pc++;
// SKB - skip byte
case 0x74: case 0x04: case 0x14: case 0x34: case 0x44: case 0x54: case 0x64:
case 0x80: case 0x82: case 0x89: case 0xC2: case 0xD4: case 0xE2: case 0xF4:
pc++;
goto loop;
// NOP
case 0xEA: case 0x1A: case 0x3A: case 0x5A: case 0x7A: case 0xDA: case 0xFA:
goto loop;
case halt_opcode: // HLT - halt processor
if ( pc-- > 0x10000 )
{
// handle wrap-around (assumes caller has put page of HLT at 0x10000)
pc = WORD( pc );
goto loop;
}
case 0x02: case 0x12: case 0x32: case 0x42: case 0x52:
case 0x62: case 0x72: case 0x92: case 0xB2: case 0xD2: case 0xF2:
goto stop;
// Unimplemented
case 0xFF: // force 256-entry jump table for optimization purposes
c |= 1; // compiler doesn't know that this won't affect anything
default:
check( (unsigned) opcode < 0x100 );
#ifdef UNIMPL_INSTR
UNIMPL_INSTR();
#endif
// At least skip over proper number of bytes instruction uses
static unsigned char const illop_lens [8] = {
0x40, 0x40, 0x40, 0x80, 0x40, 0x40, 0x80, 0xA0
};
int opcode = instr [-1];
int len = illop_lens [opcode >> 2 & 7] >> (opcode << 1 & 6) & 3;
if ( opcode == 0x9C )
len = 2;
pc += len;
// Account for extra clock
if ( (opcode >> 4) == 0x0B )
{
if ( opcode == 0xB3 )
data = READ_LOW( data );
if ( opcode != 0xB7 )
PAGE_PENALTY( data + y );
}
goto loop;
}
assert( false ); // catch missing 'goto loop' or accidental 'break'
int result_;
handle_brk:
pc++;
result_ = b10 | 4;
#ifdef CPU_DONE
interrupt:
#endif
{
s_time += 7;
// Save PC and read vector
WRITE_STACK( SP( -1 ), pc >> 8 );
WRITE_STACK( SP( -2 ), pc );
pc = GET_LE16( &READ_CODE( 0xFFFA ) + (result_ & 4) );
// Save flags
int temp;
GET_FLAGS( temp );
temp |= r20 + (result_ & b10); // B flag set for BRK
sp = SP( -3 );
WRITE_STACK( sp, temp );
// Update I flag in externally-visible flags
cpu->r.flags = (flags |= i04);
// Update time
int delta = s.base - cpu->end_time;
if ( delta >= 0 )
goto loop;
s_time += delta;
s.base = cpu->end_time;
goto loop;
}
out_of_time:
pc--;
// Optional action that triggers interrupt or changes irq/end time
#ifdef CPU_DONE
{
CPU_DONE( result_ );
if ( result_ >= 0 )
goto interrupt;
if ( s_time < 0 )
goto loop;
}
#endif
stop:
// Flush cached state
cpu->r.pc = pc;
cpu->r.sp = GET_SP();
cpu->r.a = a;
cpu->r.x = x;
cpu->r.y = y;
int temp;
GET_FLAGS( temp );
cpu->r.flags = temp;
cpu->cpu_state_.base = s.base;
cpu->cpu_state_.time = s_time;
cpu->cpu_state = &cpu->cpu_state_;
}
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