/* Implements both ID and WB */
void do_id_wb_stages()
{
/* Set up write backs. Don't occur until end of cycle */
wb_destE = gen_w_dstE();
wb_valE = gen_w_valE();
wb_destM = gen_w_dstM();
wb_valM = gen_w_valM();
/* Update processor status */
status = gen_Stat();
id_ex_next->srca = gen_d_srcA();
id_ex_next->srcb = gen_d_srcB();
id_ex_next->deste = gen_d_dstE();
id_ex_next->destm = gen_d_dstM();
/* Read the registers */
d_regvala = get_reg_val(reg, id_ex_next->srca);
d_regvalb = get_reg_val(reg, id_ex_next->srcb);
/* Do forwarding and valA selection */
id_ex_next->vala = gen_d_valA();
id_ex_next->valb = gen_d_valB();
id_ex_next->icode = if_id_curr->icode;
id_ex_next->ifun = if_id_curr->ifun;
id_ex_next->valc = if_id_curr->valc;
id_ex_next->stage_pc = if_id_curr->stage_pc;
id_ex_next->status = if_id_curr->status;
}
/* Return resulting status */
static byte_t sim_step()
{
word_t aluA;
word_t aluB;
word_t alufun;
status = STAT_AOK;
imem_error = dmem_error = FALSE;
update_state(); /* Update state from last cycle */
if (plusmode) {
pc = gen_pc();
}
valp = pc;
instr = HPACK(I_NOP, F_NONE);
imem_error = !get_byte_val(mem, valp, &instr);
if (imem_error) {
sim_log("Couldn't fetch at address 0x%x\n", valp);
}
imem_icode = HI4(instr);
imem_ifun = LO4(instr);
icode = gen_icode();
ifun = gen_ifun();
instr_valid = gen_instr_valid();
valp++;
if (gen_need_regids()) {
byte_t regids;
if (get_byte_val(mem, valp, ®ids)) {
ra = GET_RA(regids);
rb = GET_RB(regids);
} else {
ra = REG_NONE;
rb = REG_NONE;
status = STAT_ADR;
sim_log("Couldn't fetch at address 0x%x\n", valp);
}
valp++;
} else {
ra = REG_NONE;
rb = REG_NONE;
}
if (gen_need_valC()) {
if (get_word_val(mem, valp, &valc)) {
} else {
valc = 0;
status = STAT_ADR;
sim_log("Couldn't fetch at address 0x%x\n", valp);
}
valp+=4;
} else {
valc = 0;
}
sim_log("IF: Fetched %s at 0x%x. ra=%s, rb=%s, valC = 0x%x\n",
iname(HPACK(icode,ifun)), pc, reg_name(ra), reg_name(rb), valc);
if (status == STAT_AOK && icode == I_HALT) {
status = STAT_HLT;
}
srcA = gen_srcA();
if (srcA != REG_NONE) {
vala = get_reg_val(reg, srcA);
} else {
vala = 0;
}
srcB = gen_srcB();
if (srcB != REG_NONE) {
valb = get_reg_val(reg, srcB);
} else {
valb = 0;
}
cond = cond_holds(cc, ifun);
destE = gen_dstE();
destM = gen_dstM();
aluA = gen_aluA();
aluB = gen_aluB();
alufun = gen_alufun();
vale = compute_alu(alufun, aluA, aluB);
cc_in = cc;
if (gen_set_cc())
cc_in = compute_cc(alufun, aluA, aluB);
bcond = cond && (icode == I_JMP);
mem_addr = gen_mem_addr();
mem_data = gen_mem_data();
if (gen_mem_read()) {
dmem_error = dmem_error || !get_word_val(mem, mem_addr, &valm);
if (dmem_error) {
sim_log("Couldn't read at address 0x%x\n", mem_addr);
}
} else
valm = 0;
mem_write = gen_mem_write();
if (mem_write) {
/* Do a test read of the data memory to make sure address is OK */
word_t junk;
dmem_error = dmem_error || !get_word_val(mem, mem_addr, &junk);
}
status = gen_Stat();
if (plusmode) {
prev_icode_in = icode;
prev_ifun_in = ifun;
prev_valc_in = valc;
prev_valm_in = valm;
prev_valp_in = valp;
prev_bcond_in = bcond;
} else {
/* Update PC */
pc_in = gen_new_pc();
}
sim_report();
return status;
}
