void ARMAssembler::epilog(uint32_t touched)
{
touched &= LSAVED;
if (touched) {
// write prolog code
uint32_t* pc = mPC;
mPC = mPrologPC;
STM(AL, FD, SP, 1, touched | LLR);
mPC = pc;
// write epilog code
LDM(AL, FD, SP, 1, touched | LLR);
BX(AL, LR);
} else { // heh, no registers to save!
// write prolog code
uint32_t* pc = mPC;
mPC = mPrologPC;
MOV(AL, 0, R0, R0); // NOP
mPC = pc;
// write epilog code
BX(AL, LR);
}
}
// Execute one instruction cycle
//
void one_instruction_cycle(CPU *cpu) {
// If the CPU isn't running, say so and return.
// If the pc is out of range, complain and stop running the CPU.
//
if ((*cpu).running==0){
printf("The CPU is not running. \n");
return;
}
// Get instruction and increment pc
//
int instr_loc = (*cpu).pc; // Instruction's location (pc before increment)
(*cpu).ir = (*cpu).mem[(*cpu).pc];
(*cpu).pc++;
// Making sure the instruction is
if ((*cpu).reg_R<0 || (*cpu).reg_R>NREG || (*cpu).addr_MM<0 || (*cpu).addr_MM>100 ) {
printf("Error. The register or memory address given in the instruction is out of bounds.\n");
return;
}
//Decode opcode into opcode, reg_r, addr_MM, and instruction sign
(*cpu).opcode = abs((*cpu).mem[instr_loc] / 1000);
(*cpu).reg_R = abs((*cpu).mem[instr_loc] / 100) % 10;
(*cpu).addr_MM = abs((*cpu).mem[instr_loc] % 100);
// In case first instruction stored in memory is a zero, we need to give it a sign of 0.
if((*cpu).mem[instr_loc] != 0) {
(*cpu).instr_sign = (*cpu).mem[instr_loc] / abs((*cpu).mem[instr_loc]);
} else{
(*cpu).instr_sign=0;
}
// Echo instruction
printf("At %02d instr %d %d %02d: ", instr_loc, (*cpu).opcode, (*cpu).reg_R, (*cpu).addr_MM);
switch ((*cpu).opcode) {
case 0: HALT(cpu); break;
case 1: LD(cpu); break;
case 2: ST(cpu); break;
case 3: ADD(cpu); break;
case 4: NEG(cpu); break;
case 5: LDM(cpu); break;
case 6: ADDM(cpu); break;
case 7: BR(cpu); break;
case 8: BRC(cpu); break;
case 9:
switch ((*cpu).reg_R) {
case 0: GETC(cpu); break;
case 1: OUT(cpu); break;
case 2: PUTS(cpu); break;
case 3: dump_CPU(cpu); break;
case 4: dump_memory(cpu); break;
case 5: printf("Ignored"); break;
case 6: printf("Ignored"); break;
case 7: printf("Ignored"); break;
case 8: printf("Ignored"); break;
case 9: printf("Ignored"); break;
}
break;
default: printf("Bad opcode!? %d\n", (*cpu).opcode);
}
}
