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small perf fixes and page 0 wrapping fixes from a1
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@davidly
davidly committed Dec 31, 2024
1 parent 922af40 commit f22faa4
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Showing 2 changed files with 23 additions and 24 deletions.
45 changes: 22 additions & 23 deletions mos6502.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@
#include <djltrace.hxx>
#include "mos6502.hxx"

static uint32_t g_State = 0;
static uint8_t g_State = 0;

#define stateTraceInstructions 1
#define stateEndEmulation 2
Expand Down Expand Up @@ -155,8 +155,7 @@ uint8_t MOS_6502::op_rotate( uint8_t op, uint8_t val )

void MOS_6502::op_cmp( uint8_t lhs, uint8_t rhs )
{
uint16_t result = (uint16_t) lhs - (uint16_t) rhs;
set_nz( (uint8_t) result );
set_nz( (uint8_t) ( (uint16_t) lhs - (uint16_t) rhs ) );
fCarry = ( lhs >= rhs );
} //op_cmp

Expand Down Expand Up @@ -283,11 +282,11 @@ void MOS_6502::op_php()
push( pf );
} //op_php

uint64_t MOS_6502::emulate( uint64_t maxcycles )
uint64_t MOS_6502::emulate( uint16_t maxcycles )
{
uint8_t val, *pb;
uint16_t address;
uint64_t cycles = 0;
uint16_t cycles = 0;

while ( cycles < maxcycles )
{
Expand Down Expand Up @@ -427,14 +426,14 @@ uint64_t MOS_6502::emulate( uint64_t maxcycles )
case 0x6a: case 0x4a: case 0x2a: case 0x0a: { a = op_rotate( op, a ); break; } // asl, rol, lsr, ror
case 0x6c: { pc = get_word( get_word( pc + 1 ) ); continue; } // jmp (a16)
case 0x78: { fInterruptDisable = true; break; } // sei
case 0x81: { address = get_word( 0xff & ( get_byte( cpu.pc + 1 ) + cpu.x ) ); goto _st_complete; } /* stx (a8, x) */
case 0x84: case 0x85: case 0x86: { address = get_byte( cpu.pc + 1 ); goto _st_complete; } /* sty/sta/stx a8 */
case 0x8c: case 0x8d: case 0x8e: { address = get_word( cpu.pc + 1 ); goto _st_complete; } /* sty/sta/stx a16 */
case 0x91: { address = cpu.y + get_word( get_byte( cpu.pc + 1 ) ); goto _st_complete; } /* sta (a8), y */
case 0x94: case 0x95: { address = 0xff & ( get_byte( cpu.pc + 1 ) + cpu.x ); goto _st_complete; } /* sta/sty a8, x */
case 0x96: { address = 0xff & ( get_byte( cpu.pc + 1 ) + cpu.y ); goto _st_complete; } /* stx a8, y */
case 0x99: { address = get_word( cpu.pc + 1 ) + cpu.y; goto _st_complete; } /* sta a16, y */
case 0x9d: /* sta a16, x */
case 0x81: { address = get_word( (uint8_t) ( get_byte( cpu.pc + 1 ) + cpu.x ) ); goto _st_complete; } /* stx (a8, x) */
case 0x84: case 0x85: case 0x86: { address = get_byte( cpu.pc + 1 ); goto _st_complete; } /* sty/sta/stx a8 */
case 0x8c: case 0x8d: case 0x8e: { address = get_word( cpu.pc + 1 ); goto _st_complete; } /* sty/sta/stx a16 */
case 0x91: { address = cpu.y + get_word( get_byte( cpu.pc + 1 ) ); goto _st_complete; } /* sta (a8), y */
case 0x94: case 0x95: { address = (uint8_t) ( get_byte( cpu.pc + 1 ) + cpu.x ); goto _st_complete; } /* sta/sty a8, x */
case 0x96: { address = (uint8_t) ( get_byte( cpu.pc + 1 ) + cpu.y ); goto _st_complete; } /* stx a8, y */
case 0x99: { address = get_word( cpu.pc + 1 ) + cpu.y; goto _st_complete; } /* sta a16, y */
case 0x9d: /* sta a16, x */
{
address = get_word( cpu.pc + 1 ) + cpu.x;
_st_complete:
Expand All @@ -447,15 +446,15 @@ uint64_t MOS_6502::emulate( uint64_t maxcycles )
case 0x8a: { a = x; set_nz( a ); break; } // txa
case 0x98: { a = y; set_nz( a ); break; } // tya
case 0x9a: { sp = x; break; } // txs no flags set
case 0xa0: case 0xa2: case 0xa9: { address = cpu.pc + 1; goto _ld_complete; } /* ldy/ldx/lda #d8 */
case 0xa1: { address = get_word( 0xff & ( get_byte( cpu.pc + 1 ) + cpu.x ) ); goto _ld_complete; } /* lda (a8, x ) */
case 0xa4 : case 0xa5: case 0xa6: { address = get_byte( cpu.pc + 1 ); goto _ld0_complete; } /* ldy/lda/ldx a8 */
case 0xac: case 0xad: case 0xae:{ address = get_word( cpu.pc + 1 ); goto _ld_complete; } /* ldy/lda/ldx a16 */
case 0xb1: { address = cpu.y + get_word( (uint16_t) get_byte( cpu.pc + 1 ) ); goto _ld_complete; } /* lda (a8), y */
case 0xb4: case 0xb5: { address = 0xff & ( get_byte( cpu.pc + 1 ) + cpu.x ); goto _ld0_complete; } /* ldy/lda a8, x */
case 0xb6: { address = 0xff & ( get_byte( cpu.pc + 1 ) + cpu.y ); goto _ld0_complete; } /* ldx a8, y */
case 0xb9 : case 0xbe: { address = get_word( cpu.pc + 1 ) + cpu.y; goto _ld_complete; } /* lda/ldx a16, y */
case 0xbc: case 0xbd: /* ldy/lda a16, x */
case 0xa0: case 0xa2: case 0xa9: { address = cpu.pc + 1; goto _ld_complete; } /* ldy/ldx/lda #d8 */
case 0xa1: { address = get_word( (uint8_t) ( get_byte( cpu.pc + 1 ) + cpu.x ) ); goto _ld_complete; } /* lda (a8, x ) */
case 0xa4 : case 0xa5: case 0xa6: { address = get_byte( cpu.pc + 1 ); goto _ld0_complete; } /* ldy/lda/ldx a8 */
case 0xac: case 0xad: case 0xae:{ address = get_word( cpu.pc + 1 ); goto _ld_complete; } /* ldy/lda/ldx a16 */
case 0xb1: { address = cpu.y + get_word( (uint16_t) get_byte( cpu.pc + 1 ) ); goto _ld_complete; } /* lda (a8), y */
case 0xb4: case 0xb5: { address = (uint8_t) ( get_byte( cpu.pc + 1 ) + cpu.x ); goto _ld0_complete; } /* ldy/lda a8, x */
case 0xb6: { address = (uint8_t) ( get_byte( cpu.pc + 1 ) + cpu.y ); goto _ld0_complete; } /* ldx a8, y */
case 0xb9 : case 0xbe: { address = get_word( cpu.pc + 1 ) + cpu.y; goto _ld_complete; } /* lda/ldx a16, y */
case 0xbc: case 0xbd: /* ldy/lda a16, x */
{
address = get_word( cpu.pc + 1 ) + cpu.x;
_ld_complete: /* load */
Expand All @@ -481,7 +480,7 @@ uint64_t MOS_6502::emulate( uint64_t maxcycles )
case 0xc4: { op_cmp( y, memory[ memory[ pc + 1 ] ] ); break; } // cpy a8
case 0xc6 : case 0xe6: { address = get_byte( cpu.pc + 1 ); goto _crement_complete; } /* inc/dec a8 */
case 0xce : case 0xee: { address = get_word( cpu.pc + 1 ); goto _crement_complete; } /* inc/dec a16 */
case 0xd6 : case 0xf6: { address = cpu.x + get_byte( cpu.pc + 1 ); goto _crement_complete; } /* inc/dec a8, x */
case 0xd6 : case 0xf6: { address = (uint8_t) ( cpu.x + get_byte( cpu.pc + 1 ) ); goto _crement_complete; } /* inc/dec a8, x */
case 0xde : case 0xfe: /* inc/dec a16, x */
{
address = cpu.x + get_word( cpu.pc + 1 );
Expand Down
2 changes: 1 addition & 1 deletion mos6502.hxx
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ struct MOS_6502
{
// emulator API

uint64_t emulate( uint64_t maxcycles ); // execute up to about maxcycles
uint64_t emulate( uint16_t maxcycles ); // execute up to about maxcycles
void trace_instructions( bool trace ); // enable/disable tracing each instruction
void trace_state( void ); // trace the registers
const char * render_operation( uint16_t address ); // return a string with the disassembled instruction at address
Expand Down

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