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Change from last_opcode/last_operand to opcode/operand 

This change also makes it so that those values are set once they are
known, rather than only at the end of the execute function.
This commit is contained in:
Peter Evans 2018-04-21 23:14:32 -05:00
parent a5947f646e
commit 37f9e627ba
2 changed files with 7 additions and 17 deletions
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5
include/mos6502/mos6502.h
View File

@ -115,9 +115,8 @@ typedef struct {
* executed. Some things (notably soft switches) may need to
* the last opcode.
*/
vm_8bit last_opcode;
vm_8bit last_operand;
vm_16bit last_addr;
vm_8bit opcode;
vm_8bit operand;
/*
* Our program counter register; this is what we'll use to determine

19
src/mos6502/mos6502.c
View File

@ -303,7 +303,7 @@ mos6502_execute(mos6502 *cpu)
mos6502_address_resolver resolver;
mos6502_instruction_handler handler;
opcode = mos6502_get(cpu, cpu->PC);
cpu->opcode = opcode = mos6502_get(cpu, cpu->PC);
cpu->addr_mode = mos6502_addr_mode(opcode);
// The disassembler knows how many bytes each operand requires
@ -328,8 +328,9 @@ mos6502_execute(mos6502 *cpu)
// Note also that resolver may be NULL, as there may not be any
// operand for this instruction! If so, we let the default for
// operand stand, which is zero.
cpu->operand = 0;
if (resolver) {
operand = resolver(cpu);
cpu->operand = operand = resolver(cpu);
}
// Here's where the magic happens. Whatever the instruction does, it
@ -354,12 +355,6 @@ mos6502_execute(mos6502 *cpu)
// something.
//usleep(cycles);
// We need to record the opcode and the effective address for
// anything which might need to reference it.
cpu->last_opcode = opcode;
cpu->last_addr = cpu->eff_addr;
cpu->last_operand = operand;
cpu->P |= MOS_UNUSED | MOS_BREAK;
// Ok -- we're done! This wasn't so hard, was it?
@ -376,15 +371,11 @@ mos6502_last_executed(mos6502 *cpu, vm_8bit *opcode,
vm_8bit *operand, vm_16bit *addr)
{
if (opcode) {
*opcode = cpu->last_opcode;
*opcode = cpu->opcode;
}
if (operand) {
*operand = cpu->last_operand;
}
if (addr) {
*addr = cpu->last_addr;
*operand = cpu->operand;
}
}